SEARCH

SEARCH BY CITATION

Keywords:

  • cerebellum;
  • compartmentalization;
  • evolution;
  • granule cells;
  • Purkinje cells

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Regionalization during early development: a set location of the cerebellum on the neural tube
  5. The regional expression of transcription factors in the cerebellar rhombic lip and ventricular zone shapes the cerebellum
  6. Development of cerebellar neurons in zebrafish
  7. The precerebellar nuclei are generated from the hindbrain rhombic lip at rhombomeres 6 to 8
  8. Mediolateral compartmentalization of the mammalian cerebellum
  9. Close correlation between the birthdate of PCs and the mediolateral compartmentalization of the cerebellum
  10. Perspectives
  11. Acknowledgments
  12. References

The cerebellum controls smooth and skillful movements and it is also involved in higher cognitive and emotional functions. The cerebellum is derived from the dorsal part of the anterior hindbrain and contains two groups of cerebellar neurons: glutamatergic and gamma-aminobutyric acid (GABA)ergic neurons. Purkinje cells are GABAergic and granule cells are glutamatergic. Granule and Purkinje cells receive input from outside of the cerebellum from mossy and climbing fibers. Genetic analysis of mice and zebrafish has revealed genetic cascades that control the development of the cerebellum and cerebellar neural circuits. During early neurogenesis, rostrocaudal patterning by intrinsic and extrinsic factors, such as Otx2,Gbx2 and Fgf8, plays an important role in the positioning and formation of the cerebellar primordium. The cerebellar glutamatergic neurons are derived from progenitors in the cerebellar rhombic lip, which express the proneural gene Atoh1. The GABAergic neurons are derived from progenitors in the ventricular zone, which express the proneural gene Ptf1a. The mossy and climbing fiber neurons originate from progenitors in the hindbrain rhombic lip that express Atoh1 or Ptf1a. Purkinje cells exhibit mediolateral compartmentalization determined on the birthdate of Purkinje cells, and linked to the precise neural circuitry formation. Recent studies have shown that anatomy and development of the cerebellum is conserved between mammals and bony fish (teleost species). In this review, we describe the development of cerebellar neurons and neural circuitry, and discuss their evolution by comparing developmental processes of mammalian and teleost cerebellum.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Regionalization during early development: a set location of the cerebellum on the neural tube
  5. The regional expression of transcription factors in the cerebellar rhombic lip and ventricular zone shapes the cerebellum
  6. Development of cerebellar neurons in zebrafish
  7. The precerebellar nuclei are generated from the hindbrain rhombic lip at rhombomeres 6 to 8
  8. Mediolateral compartmentalization of the mammalian cerebellum
  9. Close correlation between the birthdate of PCs and the mediolateral compartmentalization of the cerebellum
  10. Perspectives
  11. Acknowledgments
  12. References

The cerebellum, a structure derived from the dorsal part of the most anterior hindbrain, functions in the control of smooth and skillful movements. It is also implicated in higher cognitive and emotional functions (Ito 2008). The cerebellum integrates sensory and predictive inputs, which include proprioception and information associated with motor commands, to elicit precise motor control and modulate higher cognitive/emotional functions (Ito 2002a,b, 2006, 2008). The functions of the cerebellum rely on its well organized and evolutionarily conserved structure and circuitry.

The cerebellum contains several different types of neurons, which are categorized according to their function as excitatory or inhibitory neurons (Butler & Hodos 1996; Altman & Bayer 1997) (Fig. 1). The excitatory neurons use glutamate as their major neurotransmitter (glutamatergic neurons). They include the granule cells (GCs), unipolar brush cells (UBC), and excitatory projection neurons; that is, large neurons in the deep cerebellar nuclei (DCN) in mammals or eurydendroid cells in teleosts. The inhibitory neurons use gamma-aminobutyric acid (GABA) and/or glycine (GABAergic neurons), and include Purkinje cells (PCs), Golgi cells, Lugaro cells, candelabrum cells, basket cells, stellate cells, and small neurons in the DCN (Laine & Axelrad 1994; Butler & Hodos 1996; Altman & Bayer 1997; Voogd & Glickstein 1998; Sillitoe & Joyner 2007). Additionally, there are astrocytes, Bergmann glia (a specific type of astrocyte in the cerebellum), and oligodendrocytes in the cerebellum. These neurons and glia are arranged in a three-layer structure in the cerebellum, from superficial to deep: the molecular layer (ML), Purkinje cell layer (PCL), and granule cell layer (GCL) (Figs 1, 3). These layers are located over the inner core composed of the white matter and three pairs of the DCN (there is no white matter or DCN in the teleost cerebellum). The ML contains the dendrites of PCs, axons of GCs (parallel fibers), and basket and stellate interneurons in addition to the fibers of Bergmann glia. The PCL contains the somata of PCs, Bergmann glia, and candelabrum interneurons. The GCL contains numerous small GCs, and the somata of Golgi cells, Lugaro cells, and UBCs. Many of these cerebellar neurons and glia are known to be conserved among mammalian species, although the appearance of candelabrum and basket cells in the teleost cerebellum has not been reported (Butler & Hodos 1996; Altman & Bayer 1997). The eurydendroid cells in the teleost cerebellum are located in the GCL near the PCs, and they receive the axons projected from PCs (Murakami & Morita 1987; Ikenaga et al. 2005). Unlike the DCN, the eurydendroid cells extend their dendrites to the ML to receive inputs from GCs via parallel fibers.

image

Figure 1. Structure of cerebellar neural circuits in mouse and zebrafish. Schematic representation of cerebellar neurons and neural circuits in the mouse (A) and zebrafish (B) cerebellum. Ba, basket cell; Ca, candelabrum cell; CF, climbing fiber; Cg, cerebellar glomeruli; DCN, deep cerebellar nuclei (lc, large cell; sc, small cell); EC, eurydendroid cell; ECN, external cuneate nuclei; GCs, granule cells; GCL, granule cell layer; Go, Golgi cell; IO, inferior olive nuclei; Lu, Lugaro cell; LRN, lateral reticular nuclei; MF, mossy fiber; ML, molecular layer; PC, Purkinje cell; PCL, Purkinje cell layer; PG, pontine gray nuclei; PrCN, precerebellar nuclei (except IO); RTN, reticulotegmental nuclei; St, stellate cells; UBC, unipolar brush cell.

Download figure to PowerPoint

The cerebellum of higher vertebrates, including mammalian and avian species, has 10 lobules (I–X), and each lobule contains the three-layer structure (Butler & Hodos 1996; Altman & Bayer 1997). In contrast, the teleost cerebellum is composed of three major lobular structures: the valvula cerebelli (Va, anterior lobe), the corpus cerebelli (CCe, main lobe), and the vestibulo-lateral lobe (caudo-lateral lobe), which consists of the eminentia granularis (EG) and the lobus caudalis cerebelli (LCa) (Butler & Hodos 1996; Wullimann et al. 1996; Altman & Bayer 1997; Bae et al. 2009) (Fig. 3A,B). The anterior and main lobes have the same three-layer structure, whereas the caudo-lateral lobe contains only a GCL in the teleost cerebellum.

The cerebellar neurons receive excitatory input from neurons in the precerebellar nuclei outside the cerebellum. There are two main types of afferent inputs, the climbing fibers (CFs) and mossy fibers (MFs). The CFs originate exclusively from the contralateral side of the inferior olive nuclei (IO) in the caudoventral hindbrain, and innervate the proximal domain of PC dendrites in the ML. The MFs originate from neurons in the precerebellar nuclei, including pontine gray matter nuclei (PG), reticulotegmental nuclei (RTN), the external cuneate nuclei (ECN), and lateral reticulate nuclei (LRN), and synapse with GC dendrites that are in contact with the axons of Golgi cells, to form the cerebellar glomeruli. Information from MFs is conveyed to the dendrites of PCs by the axons of GCs. The information from CFs and MFs is integrated by the PCs. Neural activity of CFs suppresses synaptic transmission from parallel fibers, when the PCs receive these inputs simultaneously, by a mechanism called long-term depression (LTD). LTD is known to play an important role in motor learning (Ito 2002a,b, 2006). PCs send their axons to neurons in the DCN in mammals and eurydendroid cells in teleosts (also to adjacent PCs, at least at early stages) (Alonso et al. 1992; Meek et al. 1992; Butler & Hodos 1996; Altman & Bayer 1997). These projection neurons (DCN and eurydendroid cells) send their axons to other regions of the brain.

Although the cerebellar neural circuits are basically conserved between mammalian and teleost species, there are some differences. The location and cell morphology of the projection neurons (DCN vs. eurydendroid cells) are different (Fig. 1). Furthermore, all parallel fibers of GCs contact the PC dendrites in the mammalian cerebellum, whereas GCs in the caudo-lateral lobe of the teleost cerebellum extend their parallel fibers to the dorsal hindbrain (crista cerebellaris, CC), where the parallel fibers contact the dendrites of crest cells, whose somata are located in the medial octavolateralis nucleus (MON) (Mikami et al. 2004; Bell et al. 2008; Bae et al. 2009) (Fig. 3B,C). This circuit functions as part of the cerebellum (or “cerebellum-like structure”), similar to that found in the flocculonodular lobe in the mammalian cerebellum (Altman & Bayer 1997; Bell et al. 2008).

A cerebellar structure is found in cartilaginous fish, although it is slightly different from the teleost cerebellum. Among agnathans, the lamprey cerebellum contains GCs and cells that are reminiscent of PCs, and the cerebellum appears as a simple bridge of gray matter between the right and left sides of the anterior hindbrain (Nieuwenhuys 1967; Butler & Hodos 1996; Altman & Bayer 1997). Therefore, the cerebellum is an ancient component of the vertebrate brain.

Regionalization during early development: a set location of the cerebellum on the neural tube

  1. Top of page
  2. Abstract
  3. Introduction
  4. Regionalization during early development: a set location of the cerebellum on the neural tube
  5. The regional expression of transcription factors in the cerebellar rhombic lip and ventricular zone shapes the cerebellum
  6. Development of cerebellar neurons in zebrafish
  7. The precerebellar nuclei are generated from the hindbrain rhombic lip at rhombomeres 6 to 8
  8. Mediolateral compartmentalization of the mammalian cerebellum
  9. Close correlation between the birthdate of PCs and the mediolateral compartmentalization of the cerebellum
  10. Perspectives
  11. Acknowledgments
  12. References

The neuroanatomic topography of the developing cerebellum reveals the formation of distinct structural patterns along its dorsoventral and mediolateral (M-L) axes. The complex formation of the central nervous system begins from the formation of the neural tube in the embryo. A portion of this neural tube is specialized during development, and begins to secrete signaling elements along the antero-posterior and dorso-ventral axes of the neural tube. The secretory elements specify positional information along the neural tube. From this nascent positional information, the neural tube establishes the neurodevelopmental regions along the antero-posterior and dorso-ventral axes. For instance, the hindbrain is compartmentalized into rhombomeres, and the telencephalon and diencephalon are compartmentalized into prosomeres. These early compartments ultimately develop into the complex brain. The cerebellum also goes through the process of regionalization during development (Zervas et al. 2005).

Genetic manipulations in mice and analysis of zebrafish mutants have revealed the molecular mechanisms of cerebellar morphogenesis (Wilson et al. 2002; Raible & Brand 2004; Zervas et al. 2005). During cerebellar development, several key molecules are expressed in restricted regions of the embryonic mouse brain and define the midbrain-hindbrain boundary (MHB). First, two homeobox genes, Otx2 and Gbx2, are independently expressed in the neural plate early in development. The expression of Otx2 and Gbx2 is observed in the anterior and posterior regions of the neural plate, respectively (Simeone et al. 1992, 2002; Joyner et al. 2000; Simeone 2000; Liu & Joyner 2001; Wurst & Bally-Cuif 2001; Nakamura et al. 2005). The boundaries of Otx2 and Gbx2 gene expression become clearer by embryonic day (E) 8.5 in mice. They define the future position of the MHB (Bally-Cuif & Wassef 1994; Acampora et al. 1997). In zebrafish, gbx1 is expressed earlier than gbx2, and plays a more important role in positioning the MHB (Rhinn et al. 2009). Subsequently, a set of MHB genes, including Pax2 (pax2a in zebrafish), Engrailed (En) 1/2 (eng2a/2b in zebrafish), and Wnt1 and Fgf8 are expressed in the midbrain and hindbrain domains. Wnt1 and Fgf8 are expressed in the Otx2-positive (+) region (blue region in Fig. 2A) and the Gbx2+ region (green region in Fig. 2A), respectively. In mice, the patterns of Wnt1 gene (red region in Fig. 2A) and Fgf8 gene (yellow region in Fig. 2A) expression tightens at E9.5 when the neural plate closes and forms the neural tube. Wnt1 gene expression (red region in Fig. 2A) is localized to the caudal edge of the mesencephalon (mes). In contrast, Fgf8 gene expression (yellow region in Fig. 2A) is localized to the rostral edge of rhombomere 1 (r1). In addition, Pax5, Pax8, and Fgf17 genes are activated in the MHB, and this activation is dependent on the function of Pax2 (Pax2a in zebrafish) and Fgf8 (Lun & Brand 1998; Pfeffer et al. 1998; Reifers et al. 2000, 1998; Bouchard et al. 2000; Xu et al. 2000). Otx2-driven Wnt1 gene expression and Gbx2-driven Fgf8 gene expression provide positional information in the neural tube along the antero-posterior axis and facilitates regional specification. Consequently, the localized expression of Wnt1 and Fgf8 define the boundary between midbrain and hindbrain. Wnt1 expression probably controls the expression of En 1/2 in the MHB and r1 and the proliferation of the midbrain and anterior hindbrain regions (Dickinson et al. 1994; Danielian & McMahon 1996). In zebrafish, in addition to wnt1, wnt10b and wnt3a are also expressed in overlapping domains across the MHB, and these wnt genes are required for the formation of the MHB constriction and for preventing apoptosis in the MHB region (Buckles et al. 2004). The Otx2+ region (blue region in Fig. 2A) is the future forebrain and midbrain, and the Gbx2+ region (green region in Fig. 2A) is the future hindbrain and spinal cord. Furthermore, the MHB arises from the signaling between Otx2/Wnt1 and Gbx2/Fgf8 gene expression. The Fgf8+ region curves toward the inside of the brain and forms a neck identified as the isthmus. Fgf8 is required for the formation of the isthmic structure and expression of MHB-specific genes (Crossley et al. 1996; Reifers et al. 1998; Liu et al. 1999; Martinez et al. 1999; Picker et al. 1999). The isthmus acts as the organizing center for early development of the midbrain and hindbrain (Brand et al. 1996; Liu & Joyner 2001; Wurst & Bally-Cuif 2001; Sato et al. 2004; Nakamura et al. 2005). The secretory factors from the isthmus regulate morphogenesis of the midbrain and r1 along the anterior-posterior axis and induce cerebellar formation from r1. Consequently, the cerebellar territory in the neural tube is established by the spatial and temporal expression of transcription factors and secreted molecules by E9.5 (Fig. 2A).

image

Figure 2. Cerebellar and precerebellar nuclei development in mice. (A) A schematic view of the mouse embryo at E9.5. The regional expression of transcription factor genes Otx2 (blue), Wnt1 (red), Fgf8 (yellow), and Gbx2 (green) in the E9.5 mouse embryo is shown. The spatial and temporal expression of these transcription factors and morphogens defines the midbrain–hindbrain boundary and induces the isthmus (is) to become the organizing center for early development of the midbrain and hindbrain. Secretory factors from the isthmus induce the formation of the cerebellum (cb) from rhombomere 1 (r1). (B) A schematic view of the posterolateral side of the mouse embryo at E11.5. The cerebellar rhombic lip (CRL) is located at the caudal edge of the cerebellum, the hindbrain rhombic lip (HRL) is located at the dorsal edge of the hindbrain in r2–r8, and the roof plate (rp) is located between CRL and HRL colored with green, red, and yellow, respectively. (C) A schematic view of a sagittal section of the cb along the green plane shown in (B). The ventricular zone (VZ) of the cerebellum, CRL, and rp are colored blue, green, and yellow, respectively. The cerebellum is regionalized into the Ptf1a+VZ of the cb (blue region) and the Atoh1+CRL (green region). Ptf1a+ and Atoh1+ regions generate inhibitory (such as PCs, cerebellar interneurons) and excitatory neurons (such as GCs) in the cerebellum, respectively. Ptf1a+ region is further divided into two regions by a pattern of Neurogenin1 (Ngn1) expression (red dotted region). Progenitor cells in the caudal cerebellar VZ express Ngn1, not those in the rostral cerebellar VZ. Furthermore, the Ptf1a+ and Ngn1+VZ generates Corl2+PCs (orange region). In contrast, the Ptf1a+ and Ngn1VZ generates Pax2+ cerebellar interneurons (purple region). The transcription factor Lmx1a is locally expressed on the rp, and the transforming growth factor (TGF)β family proteins, Gdf7,BMP6, and BMP7 are secreted from the rp. (D) A schematic view of a transversal section of the hindbrain in r7 along the red plane shown in B. HRL is also regionalized into the Atoh1+ (green region), the Ngn1+ (red region), and the Ptf1a+ (blue region) regions. The neurons of the lateral reticular nucleus (LRN) and external cuneate nucleus (ECN) are generated from the Atoh1+ dorsal HRL and migrate from HRL to LRN and ECN along the posterior extramural stream (PES). The inferior olive (IO) neurons are generated from the Ptf1a+ ventral HRL and migrate from HRL to IO nuclei along the intramural migratory stream (IMS). (E) A schematic view of a sagittal section of the mouse cb at E15, P0, and P7. 3v, third ventricle; 4v, fourth ventricle; di, diencephalon; egl, external granular cell layer; hb, hindbrain; igl, internal granular cell layer; mb, midbrain; mes, mesencephalon; pon, pons; pro, prosencephalon; sc, spinal cord; WM, white matter; d, dorsal; v, ventral; r, rostral; c, caudal. Other abbreviations are described in the legend of Figure 1.

Download figure to PowerPoint

Zebrafish fgf8a mutants (acerebellar mutants) lack an MHB organizer and cerebellum (Reifers et al. 1998; Picker et al. 1999), indicating that Fgf8 is a major mediator of the isthmic organizing activity in zebrafish. Zebrafish spiel ohne grenzen (spg) mutants, which have a defective pou5f1 gene, lack the isthmic structure and a cerebellum (Belting et al. 2001; Burgess et al. 2002). The POU domain-containing transcription factor Pou5f1, which is the orthologue of mammalian Oct3/4, confers competence to respond to Fgf8 (Belting et al. 2001; Burgess et al. 2002; Reim & Brand 2002). The importance of Fgf8 signaling in the MHB and cerebellum formation is supported by the identification of Canopy1, which functions as a positive feedback regulator of Fgf signaling involved in MHB formation (Hirate & Okamoto 2006). The roles of Pou5f1 and Canopy1 in MHB formation and in the formation of the mammalian cerebellum await further investigation. Although Fgf8 defects lead to loss of the cerebellum, the co-inhibition of the otx1b/otx2 (which may play an equivalent role to mouse Otx2 gene) and fgf8 genes in zebrafish restores the generation of PCs and GCs to some extent, suggesting that Fgf8 also functions to maintain the cerebellum region by repressing Otx expression (Foucher et al. 2006).

In addition to the patterning genes, the hairy and enhancer of split-related basic helix-loop-helix (bHLH) gene her5 is expressed in the MHB region before MHB establishment in zebrafish, and Her5 with a close homologue, Her11 functions in this region to prevent neuronal differentiation and promote cell proliferation (Geling et al. 2003, 2004; Ninkovic et al. 2005). These genes may be required for the maintenance of the isthmic organizer activity. This is consistent with the finding that the expression of Hes1 and Hes3, which are homologues of her5 and her11, in the mouse MHB region is required for the isthmic organizer activity (Hirata et al. 2001).

The regional expression of transcription factors in the cerebellar rhombic lip and ventricular zone shapes the cerebellum

  1. Top of page
  2. Abstract
  3. Introduction
  4. Regionalization during early development: a set location of the cerebellum on the neural tube
  5. The regional expression of transcription factors in the cerebellar rhombic lip and ventricular zone shapes the cerebellum
  6. Development of cerebellar neurons in zebrafish
  7. The precerebellar nuclei are generated from the hindbrain rhombic lip at rhombomeres 6 to 8
  8. Mediolateral compartmentalization of the mammalian cerebellum
  9. Close correlation between the birthdate of PCs and the mediolateral compartmentalization of the cerebellum
  10. Perspectives
  11. Acknowledgments
  12. References

After E10.5 in mice, the isthmic region narrows, the cerebellar primordium expands laterally, and the wing-like cerebellar shape becomes clearly distinguishable (Fig. 1B). Additionally, the hindbrain that is contiguous to the cerebellum separates into two lateral parts along the dorsal midline, and a thin layer of non-neuronal epithelial cells occupies the area between the cerebellum and the bilaterally separated hindbrain, which is called the roof plate (rp) and the future choroid plexus (yellow region in Fig. 2B–D). The formation of the rp plays an important role in the regionalization of the cerebellum and hindbrain. The rp expresses the LIM homeobox transcription factor Lmx1a and secretes the transforming growth factor (TGF)β family proteins Gdf7, BMP6, and BMP7. These proteins induce the expression of the proneural bHLH factor Atoh1 (mammalian homologue of atonal) in a restricted region adjacent to the rp in the cerebellum (cerebellar rhombic lip: CRL; green region in Fig. 2B) and the hindbrain (dorsal part of hindbrain rhombic lip: HRL; red region in Fig. 2B) (Alder et al. 1999; Chizhikov & Millen 2005; Landsberg et al. 2005; Chizhikov et al. 2006).

Neurons in the cerebellum are generated from two germinal zones: the cerebellar ventricular zone (VZ), which is located at the roof of the fourth ventricle (blue region in Fig. 1C), and the CRL, which is located at the caudal edge of the cerebellar primordium (green region in Fig. 2C,E) (Altman & Bayer 1997; Wingate & Hatten 1999; Wingate 2001; Zervas et al. 2004). The cerebellar VZ adjacent to the Atoh1+ CRL begins to express the proneural gene Ptf1a from E10.5 to E14.5 in mice (Hoshino et al. 2005; Hoshino 2006; Fujiyama et al. 2009). However, it is not clear what molecule induces the Ptf1a+ cerebellar VZ. In addition to Ptf1a, another proneural gene Ascl1, which is a homologue of achaete-scute complex genes, is also expressed in the cerebellar VZ (Grimaldi et al. 2009; Sudarov et al. 2011). The neuroepithelial cells in the Ptf1a+ and Ascl1+ cerebellar VZ produce GABAergic neurons including PCs, Golgi cells, basket cells, stellate cells, candelabrum cells and small neurons in the DCN (Fig. 2E) (Hashimoto & Mikoshiba 2004; Hoshino et al. 2005; Hoshino 2006; Leto et al. 2009, 2006; Grimaldi et al. 2009; Sudarov et al. 2011). Likewise, the neuroepithelial cells from the Atoh1+ CRL give rise to the glutamatergic neurons including cerebellar GCs and large neurons in the DCN (Fig. 2E) (Machold & Fishell 2005; Wang et al. 2005). Accordingly, as the differentially located expression of Ptf1a and Atoh1 structurally regionalizes the cerebellum, Ptf1a+ and Atoh1+ regions generate inhibitory neurons and excitatory neurons, respectively (Fig. 2C,E). PCs are generated from Ptf1a+ neuroepithelial cells from E10.5 to E12.5 in mice (Hashimoto & Mikoshiba 2003; Hoshino et al. 2005). Immature and mature PCs can be distinguished by Corl2 expression (Minaki et al. 2008). The other interneurons including Golgi cells, basket cells, stellate cells, and small neurons in the DCN are generated from Ptf1a+ neuroepithelial cells after E13.5 (Leto et al. 2009, 2006). The interneurons are recognized by Pax2 expression (Maricich & Herrup 1999; Weisheit et al. 2006). The Ptf1a+ region is further divided into the caudal and rostral regions (Zordan et al. 2008). In the Ptf1a+ VZ of E12.5 mice, Neurogenin1 (Ngn1) is expressed in the caudal region (red dotted region in Fig. 2C), but not in the rostral region. Furthermore, the Ptf1+ and Ngn1-negative (−) region (blue region in Fig. 2C) is adjacent to the Pax2+ region (purple region in Fig. 2C). The cell fate mapping of Ngn1+ progenitor cells has been conducted using the BAC-EGFP reporter transgenic mouse (Ngn1-EGFP) (Lundell et al. 2009). The Ngn1+ progenitor cells in a mouse cerebellum generate PCs and Pax2+ cerebellar interneurons excluding small inhibitory neurons in DCN (Golgi, basket, and stellate cells). Similarly, Mizuhara et al. 2010 indicates that the Ptf1a+ VZ in E12.5 mouse cerebellum is divided into two regions by a pattern of E-cadherin (E-cad) expression. E-cad is strongly expressed in the caudal region, which is called the c2d region, whereas E-cad is weakly expressed in the rostral region, which is called the c2v region. The authors suggest that the c2d region generates Corl2+ PCs (orange region in Fig. 2C), whereas the c2v region generates small inhibitory neurons in DCN (Minaki et al. 2008; Mizuhara et al. 2010). The region that expresses E-cad weakly (c2v region) in E12.5 mouse cerebellum seems to be identical to the Ptf1a+ and Ngn1 region (blue region, Fig. 2C), because these regions are similarly adjacent to the Pax2+ region (purple region in Fig. 2C). Furthermore, the c2d region corresponds with the Ptf1a- and Ngn1-double positive region (red dotted region in Fig. 2C), since both of them are the origin of PC's (orange region in Fig. 2C). The cell fate of each subtype of cerebellar GABAergic neuron is individually controlled by the expression of particular molecules.

The PCs migrate from the ventricular side to the surface of the cerebellum and form the PCL (Fig. 2E). Excitatory neurons of the DCN are first generated from Atoh1+ neuroepithelial cells in CRL between E10 and E12 in mice. These cells initially migrate along the outer surface of the cerebellum, and then, eventually migrate into the central part of the cerebellum, which is the location of the DCN (Machold & Fishell 2005; Wang et al. 2005; Fink et al. 2006). Following generation of excitatory neurons of the DCN, Atoh1+ CRL gives rise to the cerebellar GC precursors (GCPs) after E12.5 in mice. The GCPs migrate tangentially over the entire surface of the cerebellum, using a similar route as the excitatory neurons of the DCN, and then form the external granular layer (egl; Fig. 2C,E) (Machold & Fishell 2005; Wang et al. 2005). Thereafter, the GCPs in the egl radially move from egl to the inner granule cell layer (igl) and differentiate into GCs. The cerebellar glial cells, Bergmann glia, astrocytes, and oligodendrocytes are generated from VZ progenitors (Zhang & Goldman 1996a,b; Milosevic & Goldman 2002; Hoshino et al. 2005; Sudarov et al. 2011).

The layer formation of the cerebellum is controlled by various signaling molecules, such as semaphorin (Kerjan et al. 2005; Renaud et al. 2008; Maier et al. 2011) and reelin (Terashima et al. 1985; Miyata et al. 1997, 2010; Takayama et al. 1997). Semaphorin 4C, 4G, and 6A control the radial migration of GCPs (Kerjan et al. 2005; Renaud et al. 2008; Maier et al. 2011). Reelin is highly expressed in GCPs in the egl (Herrup 2000), and it controls positioning of PCs and architectural organization of the cerebellar layers in mice (Goffinet 1983; Terashima et al. 1985; Miyata et al. 1997). PCs are thought to provide trophic support to GCPs in the mammalian cerebellum (Wetts & Herrup 1983; Smeyne et al. 1995). PCs express Sonic hedgehog (Shh), and promote the expansion of GCPs, and thereby control the foliation of the cerebellum in mammals (Dahmane & Ruiz I Altaba 1999; Wallace 1999; Wechsler-Reya & Scott 1999; Lewis et al. 2004; Corrales et al. 2006). Aberrant activation of Shh signaling is known to result in the formation of the malignant tumor, medulloblastoma in human patients (Hatten & Roussel 2011; Roussel & Hatten 2011).

Development of cerebellar neurons in zebrafish

  1. Top of page
  2. Abstract
  3. Introduction
  4. Regionalization during early development: a set location of the cerebellum on the neural tube
  5. The regional expression of transcription factors in the cerebellar rhombic lip and ventricular zone shapes the cerebellum
  6. Development of cerebellar neurons in zebrafish
  7. The precerebellar nuclei are generated from the hindbrain rhombic lip at rhombomeres 6 to 8
  8. Mediolateral compartmentalization of the mammalian cerebellum
  9. Close correlation between the birthdate of PCs and the mediolateral compartmentalization of the cerebellum
  10. Perspectives
  11. Acknowledgments
  12. References

Developmental processes of cerebellar neurons are conserved in teleost species, including zebrafish (Bae et al. 2009; Kani et al. 2010; Hibi & Shimizu 2011). PCs are derived from progenitors in the VZ that express ptf1a, while most of the glutamatergic neurons originate from the atoh1-expressing CRL progenitors (Kani et al. 2010) (Fig. 3D). However, there are teleost-specific features. In contrast to the mouse, the zebrafish has three atoh1 genes, atoh1a/b/c, which show overlapping and distinct expression patterns, and might mark different progenitor populations in the CRL (Kani et al. 2010). Lineage tracing with transgenic zebrafish and birthdate analysis reveal that atoh1-expressing CRL progenitor cells also give rise to GCs in zebrafish (Kani et al. 2010; Wullimann et al. 2011). The anterior CRL progenitors, which preferentially express atoh1a and/or atoh1b, generate GCs in the anterior lobe (Va) and the main lobe (CCe), whereas the caudal and lateral CRL progenitors expressing atoh1b and/or atoh1c give rise to GCs in the caudo-lateral lobe (LCa and EG, Fig. 3A,B,D). As seen in mice, the atoh1-expressing cells are initially located in the superficial layer, which likely corresponds to the egl, and migrate to the inside to form the GCL in the anterior and main lobes (Kani et al. 2010) (Fig. 3D). It is, however, argued that the atoh1-expressing progenitors migrate quickly and do not exhibit a transit amplification of GCs in zebrafish. Furthermore, the atoh1-expressing cells in the caudo-lateral lobe stay and do not migrate inside (Volkmann et al. 2008; Kani et al. 2010). Thus, the zebrafish cerebellum may not have a typical egl (Chaplin et al. 2010). Furthermore, in the mammalian cerebellum, the GCPs in the egl proliferate in response to Shh, which is produced by PCs (Dahmane & Ruiz I Altaba 1999; Wallace 1999; Wechsler-Reya & Scott 1999), whereas PCs in the zebrafish do not express Shh, or GCPs (or immature GCs) do not respond to Shh signaling (Chaplin et al. 2010). Therefore, the atoh1-expressing cells in the superficial domain in zebrafish may not be identical to the cells in the egl. Nevertheless, the atoh1a/b/c-expressing CRL progenitors constitute a population of proliferating cells that are quite similar to the egl progenitor population in mammals. As described above, reelin plays an important role in layer formation in the mouse cerebellum, and is also expressed in both the immature and mature GCs of the zebrafish cerebellum, similar to that in the mouse cerebellum (Carletti et al. 2008). However, it has not been shown whether reelin controls layer formation in the zebrafish cerebellum. During early development of the zebrafish cerebellum, descendant cells from atoh1+ and ptf1a+ progenitors are adjacent to each other (Kani et al. 2010). Deletion of the ptf1a+ lineage led to a strong reduction in the amount of GCs (M. Hibi, unpubl. data, 2008), suggesting that the generation of GCs depends on the presence of the ptf1a+ lineage, such as PCs. Although zebrafish GCPs do not respond to Shh signaling (Chaplin et al. 2010), a trophic role for PCs in GC proliferation may be conserved in zebrafish. Future studies are required to identify the molecules responsible for the interaction between GCs and PCs in teleost species.

image

Figure 3. Anatomy and development of zebrafish cerebellum. (A) Schematic representation of adult zebrafish cerebellar structure. A sagittal section image. (A-a, b) Cross section images at the levels (a, valvula cerebelli, Va; b, corpus cerebelli, CCe) shown in (A). (B) Structure of larval cerebellum (at 5 days postfertilization, dpf). Staining with anti-parvalbumin 7 (Pvalb7, green) and anti-Vglut1 (magenta) antibodies, which recognizes PCs and the axons of GCs, respectively. Dorsal views with anterior to the left. (B-a) Transverse-section image of box a in the merged image. (B-b) High magnification view of box b in the merged image. (C) Schematic representation of parallel fibers in the anterior (Va) and main (CCe) lobes (left panel), and in the caudo-lateral lobes (EG, eminentia granularis and LCa, lobus caudalis cerebelli) and the crista cerebellaris (CC). Parallel fibers of GCs in Va and CCe contact the PC dendrites, whereas parallel fibers in EG and LCa contact the dendrites of crest cells (direction of axons are indicated by arrows in B). (D) Schematic representation of the development of GCs and PCs. MON, medial octavolateralis nucleus; TeO, optic tectum; Vam, medial division of valvula cerebelli; Val, lateral division of the valvula cerebelli. The other abbreviations are described in Figures 1 and 2. This figure is modified from (Bae et al. 2009; Kani et al. 2010; Hibi & Shimizu 2011).

Download figure to PowerPoint

In addition to the GCs and DCN neurons, the Atoh1-expressing CRL progenitors generate tegmental nuclei, including the parabrachial nuclei and parabigeminal nuclei in mice (Machold & Fishell 2005; Wang et al. 2005). The CRL progenitors in zebrafish give rise to the secondary gustatory/viscerosensory nuclei, the nuclei isthmi, and superior reticular nuclei (Kani et al. 2010; Volkmann et al. 2010). The secondary gustatory/viscerosensory nucleus is considered to be homologous to the parabrachial nucleus of mammals (Morita et al. 1980, 1983; Finger 1983, 1987), and the nucleus isthmi is thought to be the homologue of the parabigeminal nucleus in mammals (Clark 1933; Sakamoto et al. 1981; Ito et al. 1982; Volkmann et al. 2010). Thus, the tegmental nuclei from atoh1-expressing progenitors likely have conserved functions in vertebrates.

Eurydendroid cells are teleost-specific cerebellar projection neurons that transmit information from PCs to extracerebellar domains (Ikenaga et al. 2005, 2006; Bae et al. 2009). Although the function of the eurydendroid cells is thought to be equivalent to that of neurons in the DCN of the mammalian cerebellum, the origin of eurydendroid cells has been perplexing. In the mouse cerebellum, there are glutamatergic and GABAergic neurons in the DCN; these neurons originate from Atoh1+ CRL and Ptf1a+ VZ progenitors, respectively (Hoshino et al. 2005; Machold & Fishell 2005; Wang et al. 2005). An analysis of eurydendroid cells in the goldfish cerebellum suggests that there is no GABAergic eurydendroid cell population (Ikenaga et al. 2005). Marker analysis and retrograde labeling experiments with zebrafish revealed two types of eurydendroid cells, olig2-expressing eurydendroid cells and calretinin-immunoreactive (Cr-ir+) eurydendroid cells, in the zebrafish cerebellum (Bae et al. 2009). Lineage tracing with transgenic zebrafish indicated that the majority of the olig2+ eurydendroid cells are derived from ptf1a+ VZ progenitors, and some are derived from atoh1+ CRL progenitors (Bae et al. 2009; Kani et al. 2010). Although Ptf1a+ VZ progenitors generate only GABAergic neurons in the mouse DCN, the olig2+ eurydendroid cells from both ptf1a+ VZ and atoh1+ CRL progenitors are glutamatergic neurons (Bae et al. 2009; Kani et al. 2010). Thus, the development of the olig2+ eurydendroid cells may be different from that of the DCN neurons. Future studies are needed to reveal whether the Cr-ir+ and olig2+ eurydendroid cells have different origins and functions, and whether there are Olig2+ neurons in the mammalian cerebellum.

In contrast to the mammalian cerebellum, the zebrafish cerebellum can be regenerated after its ablation, at least at the early embryonic stage (Koster & Fraser 2006). This regeneration is accompanied by re-patterning of the anterior hindbrain, in which the otx2 and hox r1 identity is re-established, and requires Fgf signaling (Koster & Fraser 2006). Furthermore, cerebellum neurons and glial cells are continuously generated throughout the adult stage (Zupanc et al. 2005; Kaslin et al. 2009; Kani et al. 2010). atoh1a/b/c and ptf1a are expressed in the ML and the VZ, respectively, of adult cerebellum, and the most atoh1a, atoh1b, and/or atoh1c-expressing cells and some ptf1a-expressing cells proliferate in the adult cerebellum (Kani et al. 2010). Bergmann glial cells also proliferate, and Nestin/Sox2/Musashi+ proliferating cell populations have also been found in the adult cerebellum (Kaslin et al. 2009; Kani et al. 2010). These data suggest that there are distinct progenitor populations in the adult cerebellum: proneural gene(s)-expressing progenitors, Bergman glial cells, and Nestin/Sox2/Musashi+ cells. Considering the function of proneural genes, it is likely that atoh1+ or ptf1a+ progenitors generate glutamatergic and GABAergic neurons in the adult cerebellum, as they do in the embryonic/larval stages. It is not yet clear whether Bergmann glial cells or Nestin/Sox2/Musashi+ cells serve as neural stem cells to generate both neurons and glia. Further studies are required to clarify this issue. Although there are different types of proliferating cells in the zebrafish adult cerebellum, the major population is derived from the GC lineage (Zupanc et al. 2005; Kaslin et al. 2009; Kani et al. 2010). Immature GCs in the ML proliferate and migrate rapidly into the GCL within a week. In contrast, turnover of PCs is very slow in the adult cerebellum, indicating that GCs play more important roles in remodeling cerebellar neural circuits in adult zebrafish.

The precerebellar nuclei are generated from the hindbrain rhombic lip at rhombomeres 6 to 8

  1. Top of page
  2. Abstract
  3. Introduction
  4. Regionalization during early development: a set location of the cerebellum on the neural tube
  5. The regional expression of transcription factors in the cerebellar rhombic lip and ventricular zone shapes the cerebellum
  6. Development of cerebellar neurons in zebrafish
  7. The precerebellar nuclei are generated from the hindbrain rhombic lip at rhombomeres 6 to 8
  8. Mediolateral compartmentalization of the mammalian cerebellum
  9. Close correlation between the birthdate of PCs and the mediolateral compartmentalization of the cerebellum
  10. Perspectives
  11. Acknowledgments
  12. References

The cerebellar cortex is innervated by two major afferent inputs, CFs and MFs, which originate from the precerebellar nuclei IO and LRN/ECN/RTN/PG, respectively, in mice (the MF neurons in the hindbrain are not well studied in zebrafish). During development, neurons of the precerebellar nuclei are generated from neuroepithelial cells in HRL, which is located at the dorsal edge of the hindbrain (red region in Fig. 2B) (Bourrat & Sotelo 1988, 1990b; Altman & Bayer 1997; Wingate 2001). In mice, neurons of precerebellar nuclei are generated from HRL in the following order: IO neurons during E10.5–E11.5, LRN and ECN neurons during E11.5–E13.5, and RTN and PG neurons after E12.5. Newborn IO neurons first extend long leading processes to the floor plate (FP) along the surface of the hindbrain, and then, the cell bodies of IO neurons ventrally migrate from the HRL to the FP through the intramural migratory stream (IMS; Fig. 2D) (Bourrat & Sotelo 1990b; Altman & Bayer 1997). The long leading processes of IO neurons (which later become CFs) go through the FP, whereas the cell bodies of IO neurons cease migrating before the FP and form immature IO nuclei in the caudoventral hindbrain at E14.5 in mice (Bourrat & Sotelo 1988, 1990a,b; Altman & Bayer 1997). Consequently, IO neurons develop a specific projection only to the contralateral side of the cerebellar cortex. The arrest of IO neurons before the FP is essential for establishment of the contralateral olivocerebellar projection. LCN and ECN neurons ventrally migrate from HRL to their destinations through the posterior extramural stream (PES; Fig. 2D), which is more superficial than the IMS (Bourrat & Sotelo 1990b; Altman & Bayer 1997). In contrast to IO neurons, LCN and ECN neurons cross the midline of the FP, and therefore settle in the contralateral side to their origin in HRL and project their axons to the ipsilateral side of the cerebellum as the MFs. Therefore, IO neurons and LCN/ECN neurons are different in their developmental processes and neuronal projections. IO, LCN, and ECN neurons express the Netrin receptor DCC (Deleted in Colorectal Cancer) and Slit receptor roundabout (Robo)1/2/3, and respond to Netrin-1 and Slit1/2/3 generated by the FP, which act as short- and long-range chemoattractants and chemorepellents (Bloch-Gallego et al. 1999; Causeret et al. 2002; Marillat et al. 2004; Di Meglio et al. 2008). In addition, IO neurons express a tyrosine kinase receptor, EphA4, whereas the FP expresses EphrinB3, which is a ligand for EphA4. The Netrin/DCC, Slit/Robo, and Ephrin/Eph signaling between the FP and IO/LCN/ECN neurons is involved in the guidance of neuronal migration and controls the midline crossing of these neurons (Bloch-Gallego et al. 1999; Causeret et al. 2002; Marillat et al. 2004; Di Meglio et al. 2008; Hashimoto et al. 2011).

Previous studies indicate that neurons of precerebellar nuclei are derived from the neuroepithelial cells in HRL at rhombomeres 6 to 8 (Cambronero & Puelles 2000; Landsberg et al. 2005; Farago et al. 2006; Kawauchi et al. 2006; Yamada et al. 2007; Liu et al. 2008; Ray & Dymecki 2009). Furthermore, genetic studies indicate that HRL in rhombomeres 6–8 is regionalized by the patterns of Atoh1, bHLH gene Neurogenin1 (Ngn1), and Ptf1a expression (Fig. 2D), as well as the cerebellum. The Atoh1+ region is located on the dorsal part of HRL (green region in Fig. 2D), and the Ngn1+ region is contiguous to this Atoh1+ region (red region in Fig. 2D) (Landsberg et al. 2005). The Ptf1a+ region is located on the ventral part of HRL (blue region in Fig. 2D). In addition, Wnt1 and bHLH gene Olig3 are expressed in the entire HRL in a dorsoventral gradient (Rodriguez & Dymecki 2000; Landsberg et al. 2005; Liu et al. 2008; Ray & Dymecki 2009; Storm et al. 2009). Using Cre-loxP, Flp-FTR, and ligand-inducible Cre recombinase (CreER) systems, temporal fate maps of the Atoh1-, Ptf1a-, Wnt1-, and Olig3+ neuroepithelial cells in HRL have been constructed (Rodriguez & Dymecki 2000; Hoshino et al. 2005; Landsberg et al. 2005; Yamada et al. 2007; Liu et al. 2008; Ray & Dymecki 2009; Storm et al. 2009). The Atoh1+ neuroepithelial cells in HRL at rhombomeres 6–8 generate neurons of PG, LRN, and ECN (Rodriguez & Dymecki 2000; Landsberg et al. 2005). In contrast, the Ptf1a+ neuroepithelial cells in HRL at rhombomeres 6–8 generate IO neurons in mice (Hoshino et al. 2005; Yamada et al. 2007) as well as in zebrafish (Bae et al. 2009). Accordingly, the differentially located expression of Ptf1a and Atoh1 in HRL at rhombomeres 6–8 is important to determine the cell fate of precerebellar nuclei. Furthermore, the gradual expression of Olig3 in HRL is involved in the regional specification in HRL because Olig3 knockout mice are associated with a reduction of the Atoh1+ and Ngn1+ domains in HRL, and dorsal expansion of the Ptf1a+ domain (Liu et al. 2008; Storm et al. 2009). However, both Olig3 and Ptf1a are required for the generation of IO neurons (Yamada et al. 2007; Liu et al. 2008; Storm et al. 2009). Consequently, the neurogenesis of precerebellar nuclei is closely regulated by the spatial and temporal expression of Atoh1, Ptf1a, and Olig3 in HRL (Fig. 2D).

Mediolateral compartmentalization of the mammalian cerebellum

  1. Top of page
  2. Abstract
  3. Introduction
  4. Regionalization during early development: a set location of the cerebellum on the neural tube
  5. The regional expression of transcription factors in the cerebellar rhombic lip and ventricular zone shapes the cerebellum
  6. Development of cerebellar neurons in zebrafish
  7. The precerebellar nuclei are generated from the hindbrain rhombic lip at rhombomeres 6 to 8
  8. Mediolateral compartmentalization of the mammalian cerebellum
  9. Close correlation between the birthdate of PCs and the mediolateral compartmentalization of the cerebellum
  10. Perspectives
  11. Acknowledgments
  12. References

The mammalian cerebellar cortex is organized into a series of longitudinal compartments along the M-L axis (for reviews, see Apps & Garwicz 2005; Apps & Hawkes 2009; Ito 2001, 2005; Voogd & Glickstein 1998). PCs in each compartment are innervated by a specific subarea of IO through CFs (olivocerebellar projections) and project their axons to a specific region in the DCN or vestibular nuclei (corticonuclear projections). Therefore, the olivo-cortico-nuclear circuit shows modular formation and compartmentalizes the cerebellum along the M-L axis. Remarkably, CFs projected from the subset of neurons in a sub-nucleus of the IO form specific striped compartments in the cerebellum, which show a bilateral symmetrical distribution (Fig. 4).

image

Figure 4. Mediolateral compartmentalization of the cerebellar neural projections. A specific subnucleus of inferior olive nuclei (IO) nuclei projects its axons (climbing fibers [CFs]) into the contralateral cerebellar cortex. CFs organize into striped, compartmentalized regions within the cerebellum along the mediolateral (M-L) axis (M-L compartments 1–4). Additionally, the Purkinje cells (PCs) within each M-L compartment project their axons into a particular region of the deep cerebellar and vestibular nuclei. The olivo-cortico-nuclear circuit shows modular formation and compartmentalizes the cerebellum along the M-L axis.

Download figure to PowerPoint

Molecular studies indicate that the cerebellar compartments are identified by the expression of a variety of marker genes (for reviews, see Hawkes & Eisenman 1997; Herrup & Kuemerle 1997; Oberdick et al. 1998; Larouche & Hawkes 2006; Sillitoe & Joyner 2007; Apps & Hawkes 2009 ). For instance, gene expression of L7/pcp2 (a genetic marker of cerebellar PCs), En1, En2, Pax2, and Wnt7B appears in specific striped-regions. In addition, the expression of zebrin II (aldolase C) also shows a specific striped-pattern in the adult cerebellum. Interestingly, En2-deficient mice show an abnormal morphology of the cerebellum (Kuemerle et al. 1997), and the striped pattern of zebrin II is closely correlated to the striped region formed by the olivocerebellar and corticonuclear projections (Gravel et al., 1987, Gravel & Hawkes, 1990, Voogd et al., 2003, Sugihara & Shinoda, 2004, Voogd & Ruigrok, 2004, Odeh et al., 2005, Sugihara & Quy 2007; Ruigrok et al., 2008), and to physiological activity in the adult cerebellum (Chen et al. 1996; Apps & Garwicz 2005; Gao et al. 2006; Sugihara & Quy 2007; Pijpers et al. 2008). However, the striped pattern of expression is not stable. The striped-patterns of L7/pcp2, En1, En2, Pax2, and Wnt7B gene expression initially appear from E15.5, but then disappear shortly after birth; therefore, the striped-pattern of gene expression is referred to as an early-onset pattern. In addition, all PCs express zebrin II by the first week after birth, but the expression of zebrin II gradually changes to a striped-pattern within the cerebellum until 20 days after birth; thus, the striped-pattern of zebrin II expression is referred to as a late-onset pattern (Leclerc et al. 1988). Furthermore, the striped pattern of zebrin II (late-onset) is entirely different from the L7/pcp2, En1, En2, Pax2, and Wnt7B gene expression patterns (early-onset). Consequently, the difference between the embryonic and adult compartments and the transient disappearance of the cerebellar compartments have made it difficult to determine how striped compartments are established, and how the embryonic compartments (early-onset pattern) and the adult compartments (late-onset pattern) are related, despite several studies having addressed this issue (Larouche & Hawkes 2006; Marzban et al. 2007; Sillitoe & Joyner 2007). In any case, the striped cerebellar compartments are thought to be the basic modular structures from which cerebellar functions are performed, because the striped compartments are observed not only at the neural circuit and neurophysiologic level, but also at the cellular and molecular levels.

In a teleost cerebellum, zebrin II is expressed in most if not all PCs and does not show compartment-specific expression (Brochu et al. 1990; Lannoo et al. 1991a,b; Meek et al. 1992; Bae et al. 2009). For instance, in zebrafish cerebellum, anti-zebrin II antibody stains the same population of PCs as the anti-parvalbumin and anti-carbonic anhydrase 8 (Ca8) antibodies (Bae et al. 2009). Parvalbumin and Ca8 are expressed in all PCs of the mammalian cerebellum (Celio & Heizmann 1981; Celio 1990; Kato 1990; Nogradi et al. 1997; Hirota et al. 2003). These data indicate that zebrin II, parvalbumin, and Ca8-expressing PCs are the sole PCs in the zebrafish cerebellum. Currently, there is no compartment-specific expression of any PC genes reported for the teleost cerebellum (Nieuwenhuys & Nicholson 1967; Meek 1992; Altman & Bayer 1997; Meek et al. 2008). Thus, the teleost cerebellum does not exhibit clear M-L compartmentalization marked by the gene expression that distinguishes the compartments in the mammalian cerebellum. M-L compartmentalization may have arisen during evolution as the cerebellar neural circuits became more complex. The present data, however, do not exclude the possibility that the M-L compartmentalization of the cerebellum is present in teleosts and may be detected by different genes from mammals.

Close correlation between the birthdate of PCs and the mediolateral compartmentalization of the cerebellum

  1. Top of page
  2. Abstract
  3. Introduction
  4. Regionalization during early development: a set location of the cerebellum on the neural tube
  5. The regional expression of transcription factors in the cerebellar rhombic lip and ventricular zone shapes the cerebellum
  6. Development of cerebellar neurons in zebrafish
  7. The precerebellar nuclei are generated from the hindbrain rhombic lip at rhombomeres 6 to 8
  8. Mediolateral compartmentalization of the mammalian cerebellum
  9. Close correlation between the birthdate of PCs and the mediolateral compartmentalization of the cerebellum
  10. Perspectives
  11. Acknowledgments
  12. References

Using replication-defective adenoviral vectors, we have successfully performed a “pulse gene transfer” approach to deliver an exogenous gene into restricted sub-populations of neuronal progenitor cells in a birthdate specific manner (Hashimoto & Mikoshiba 2004). The adenoviral vector system is very useful for the examination of neuronal development and function because we can genetically manipulate each subset of neurons that share the same neuronal birthdate and can examine the native behavior of each such neuronal subset.

The timed adenovirus gene transfer approach can be applied to the study of cerebellar development and regionalization (Hashimoto & Mikoshiba 2003). When AdexCAG-NL-LacZ, a viral vector designed for nucleus-targeted β-galactosidase (βgal) expression, is injected into the midbrain ventricle of the mouse embryo, it also infects the progenitor cells on the surface of the fourth ventricle and effectively transfers the nuclear-targeted βgal into the progenitor cells. Interestingly, the injection of AdexCAG-NL-LacZ into embryos at E10.5, E11.5, and E12.5 reveals that successfully infected βgal+ progenitor cells develop normally and differentiate into cerebellar PCs. This result is consistent with a report indicating that cerebellar PCs are generated from Ptf1a+ progenitor cells (blue region in Fig. 1C) on the surface of the fourth ventricle (Hoshino et al. 2005). By using adenoviral vectors, we can efficiently transfer a foreign gene into the progenitor cells of PCs in a neuronal birthdate-specific manner and observe the native behavior of each cohort of PCs that share the same neuronal birthdate. Remarkably, PCs that shared the same birthdate formed specific subsets of M-L compartments in the cerebellum (Fig. 5). PCs born on E10.5 (Fig. 5B,E), E11.5 (Fig. 5C,F), and E12.5 (Fig. 5D,G) are respectively labeled with nuclear-targeted βgal by the injection of the adenoviral vector AdexCAG-NL-LacZ into the midbrain ventricle of mouse embryos at E10.5, E11.5, and E12.5. We found that PCs that are generated at E10.5, E11.5, and E12.5 form distinct subsets of compartments, which are arranged mediolaterally (designated PC birthdate compartments, BC1–BC8) in the E18.5 cerebellum (Fig. 5). The PC precursors that share the same birthdate seem to migrate tangentially from the cerebellar VZ to their fated position (Hashimoto & Mikoshiba 2003). However, details about the developmental processes involved in forming the PC birthdate compartments are still unclear. The patterns of PC birthdate compartments in the embryonic cerebellum are similar to the expression patterns of several early-onset markers (Fig. 5A, En2, Wnt7b) (Hashimoto & Mikoshiba 2003). In contrast to these early- but also to late-onset markers such as zebrin II, the adenoviral labeling of PCs is stable from embryo until adult (at least until 1.5 years of age, data not shown). Furthermore, there is a close correlation between the patterns of PC birthdate compartments and the striped expression of zebrin II in the adult mouse cerebellum (Namba et al. 2011). Consequently, PCs are already predestined to form specific subsets of M-L compartments on their neuronal birthdates between E10.5 and E12.5, and the M-L compartments determined by the birthdate of PCs are unchangeable structures from embryo until adult. This is supported by another study showing a correlation between birthdates of PCs, as determined by using BrdU and striped expression of zebrin II in the adult cerebellum (Larouche & Hawkes 2006). It is possible that each subset of PCs that share the same birthdate acquires distinct characteristics by expressing particular genes based on PC birthdate. For instance, early B-cell factor 2 (Ebf2), a member of the atypical helix-loop-helix transcription factor family Collier/Olf1/EBF, is a candidate for cell fate determination of PCs (Croci et al. 2006; Chung et al. 2008). The expression of Ebf2 shows a striped-pattern in the adult mouse cerebellum (Croci et al. 2006). Deficiency of Ebf2 results in a small cerebellum and abnormal foliation, particularly in the anterior vermis. Additionally, zebrin II-immunonegative stripes disappear in Ebf2 knockout mice (Croci et al. 2006). Detailed analysis of gene expression in Ebf2 knockout mice suggests that Ebf2 contributes to cell fate determination of the zebrin II-immunopositive PC population (Chung et al. 2008). The striped expression of Ebf2 appears to be similar to the striped distribution of E11.5-born PCs in the adult mouse cerebellum, but the relationship between them is unclear.

image

Figure 5. Mediolateral compartments formed by the birthdate-related Purkinje cells (PCs) in E18.5. (A) The distribution of PCs born on E10.5 (green), E11.5 (blue), and E12.5 (red) in E18.5 cerebella are illustrated. At E18.5, cohorts of PCs born on E10.5, E11.5, and E12.5 form eight longitudinal compartments along the mediolateral axis (designated PC birthdate compartments, BC1–BC8). Each cohort of birthdate-related PCs is located to a specific subset of compartments displaying nested and, in part, mutual complementarity. PCs born on E10.5 form BC3, BC6, and BC8 (green, A, B), PCs born on E11.5 form BC2, BC4, BC5, and BC8 (blue, A, C), and PCs born on E12.5 form BC1, BC2, BC5, and BC7 (red, A, D). AdexCAG-NL-LacZ was injected into embryos at E10.5, E11.5, and E12.5, and then each cerebellum was whole mount stained for β-gal (blue color) at E18.5. The dorsal views of the E18.5 cerebella are shown (E–G). In (A), expression patterns of Wnt7b and En2 (Millen et al. 1995; Hashimoto & Mikoshiba 2003), early-onset markers, are also shown. Scale bar, 1 mm.

Download figure to PowerPoint

Perspectives

  1. Top of page
  2. Abstract
  3. Introduction
  4. Regionalization during early development: a set location of the cerebellum on the neural tube
  5. The regional expression of transcription factors in the cerebellar rhombic lip and ventricular zone shapes the cerebellum
  6. Development of cerebellar neurons in zebrafish
  7. The precerebellar nuclei are generated from the hindbrain rhombic lip at rhombomeres 6 to 8
  8. Mediolateral compartmentalization of the mammalian cerebellum
  9. Close correlation between the birthdate of PCs and the mediolateral compartmentalization of the cerebellum
  10. Perspectives
  11. Acknowledgments
  12. References

Studies have revealed that development of cerebellar neural circuits is mainly controlled by molecular mechanisms that are conserved among vertebrates. However, many questions still remain to be elucidated. Glutamatergic and GABAergic cerebellar neurons are generated from Atoh1 and Ptf1a (Ascl1a)-expressing neuronal progenitors. It is not known what mechanisms underlie generation of a diverse set of glutamatergic and GABAergic neurons. Which molecules control differentiation and migration of cerebellar neurons? What mechanisms regulate and coordinate the formation of axons and dendrites of cerebellar neurons and CF/MF neurons?

There are variations in the structure of the cerebellum and cerebellar neural circuits between mammals and teleosts (e.g. mice vs. zebrafish), and among the same species (e.g. the cerebellum of mormyrid fish has a more complex structure than that of the zebrafish). What accounts for such differences? The teleost cerebellum contains eurydendroid cells, and the location, morphology, and possibly the origin of eurydendroid cells are different from that of DCN neurons. It would be intriguing to know how eurydendroid cells and DCN neurons arise during evolution. The teleost cerebellum exhibits adult neurogenesis; GCs are generated during remodeling of adult cerebellar neural circuits. How neuronal progenitors and neural stem cells are maintained in the adult teleost cerebellum is not currently known. Knowledge on adult neurogenesis and regeneration in teleost species may potentially lead to treatments of disorders of the cerebellum, such as spinocerebellar ataxia.

M-L compartmentalization is a prerequisite for formation and function of cerebellar neural circuits as it is linked to formation of the topographic map of olivocerebellar and corticonuclear connections. The birthdate of PCs determines which compartment individual PCs belong to. It is not known what mechanism gives PCs different identities during differentiation; how PCs having the same birthdate are segregated into compartments, and how PCs in each compartment control the formation of the topographic map is also unknown. What is the physiological meaning of the compartmentalization of the cerebellum? Future studies with transgenic and mutant mice and zebrafish are needed to shed light on the development and function of the cerebellum.

Acknowledgments

  1. Top of page
  2. Abstract
  3. Introduction
  4. Regionalization during early development: a set location of the cerebellum on the neural tube
  5. The regional expression of transcription factors in the cerebellar rhombic lip and ventricular zone shapes the cerebellum
  6. Development of cerebellar neurons in zebrafish
  7. The precerebellar nuclei are generated from the hindbrain rhombic lip at rhombomeres 6 to 8
  8. Mediolateral compartmentalization of the mammalian cerebellum
  9. Close correlation between the birthdate of PCs and the mediolateral compartmentalization of the cerebellum
  10. Perspectives
  11. Acknowledgments
  12. References

The authors thank past and current members of the Hashimoto and Hibi laboratories for their contribution to the works cited here. They are grateful to Dr Takaki Miyata for advice and discussion. The studies conducted in the Hashimoto laboratory were supported by grants from RIKEN. The studies conducted in the Hibi laboratory were supported by grants from the Uehara Memorial Foundation, Takeda Science Foundation, and RIKEN.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Regionalization during early development: a set location of the cerebellum on the neural tube
  5. The regional expression of transcription factors in the cerebellar rhombic lip and ventricular zone shapes the cerebellum
  6. Development of cerebellar neurons in zebrafish
  7. The precerebellar nuclei are generated from the hindbrain rhombic lip at rhombomeres 6 to 8
  8. Mediolateral compartmentalization of the mammalian cerebellum
  9. Close correlation between the birthdate of PCs and the mediolateral compartmentalization of the cerebellum
  10. Perspectives
  11. Acknowledgments
  12. References
  • Acampora, D., Avantaggiato, V., Tuorto, F. & Simeone, A. 1997. Genetic control of brain morphogenesis through Otx gene dosage requirement. Development 124, 36393650.
  • Alder, J., Lee, K. J., Jessell, T. M. & Hatten, M. E. 1999. Generation of cerebellar granule neurons in vivo by transplantation of BMP-treated neural progenitor cells. Nat. Neurosci. 2, 535540.
  • Alonso, J. R., Arevalo, R., Brinon, J. G., Lara, J., Weruaga, E. & Aijon, J. 1992. Parvalbumin immunoreactive neurons and fibres in the teleost cerebellum. Anat. Embryol. 185, 355361.
  • Altman, J. & Bayer, S. A. 1997. Developmentof the Cerebellar System in Relation to Its Evolution, Structure, and Function. CRC Press, Inc., Boca Raton, FL.
  • Apps, R. & Garwicz, M. 2005. Anatomical and physiological foundations of cerebellar information processing. Nat. Rev. Neurosci. 6, 297311.
  • Apps, R. & Hawkes, R. 2009. Cerebellar cortical organization: a one-map hypothesis. Nat. Rev. Neurosci. 10, 670681.
  • Bae, Y. K., Kani, S., Shimizu, T., Tanabe, K., Nojima, H., Kimura, Y., Higashijima, S. & Hibi, M. 2009. Anatomy of zebrafish cerebellum and screen for mutations affecting its development. Dev. Biol. 330, 406426.
  • Bally-Cuif, L. & Wassef, M. 1994. Ectopic induction and reorganization of Wnt-1 expression in quail/chick chimeras. Development 120, 33793394.
  • Bell, C. C., Han, V. & Sawtell, N. B. 2008. Cerebellum-like structures and their implications for cerebellar function. Annu. Rev. Neurosci. 31, 124.
  • Belting, H. G., Hauptmann, G., Meyer, D., Abdelilah-Seyfried, S., Chitnis, A., Eschbach, C., Soll, I., Thisse, C., Thisse, B., Artinger, K. B., Lunde, K. & Driever, W. 2001. spiel ohne grenzen/pou2 is required during establishment of the zebrafish midbrain-hindbrain boundary organizer. Development 128, 41654176.
  • Bloch-Gallego, E., Ezan, F., Tessier-Lavigne, M. & Sotelo, C. 1999. Floor plate and netrin-1 are involved in the migration and survival of inferior olivary neurons. J. Neurosci. 19, 44074420.
  • Bouchard, M., Pfeffer, P. & Busslinger, M. 2000. Functional equivalence of the transcription factors Pax2 and Pax5 in mouse development. Development 127, 37033713.
  • Bourrat, F. & Sotelo, C. 1988. Migratory pathways and neuritic differentiation of inferior olivary neurons in the rat embryo. Axonal tracing study using the in vitro slab technique. Brain Res. 467, 1937.
  • Bourrat, F. & Sotelo, C. 1990a. Early development of the rat precerebellar system: migratory routes, selective aggregation and neuritic differentiation of the inferior olive and lateral reticular nucleus neurons. An overview. Arch. Ital. Biol. 128, 151170.
  • Bourrat, F. & Sotelo, C. 1990b. Migratory pathways and selective aggregation of the lateral reticular neurons in the rat embryo: a horseradish peroxidase in vitro study, with special reference to migration patterns of the precerebellar nuclei. J. Comp. Neurol. 294, 113.
  • Brand, M., Heisenberg, C. P., Jiang, Y. J., Beuchle, D., Lun, K., Furutani-Seiki, M., Granato, M., Haffter, P., Hammerschmidt, M., Kane, D. A., Kelsh, R. N., Mullins, M. C., Odenthal, J., Van Eeden, F. J. & Nusslein-Volhard, C. 1996. Mutations in zebrafish genes affecting the formation of the boundary between midbrain and hindbrain. Development 123, 179190.
  • Brochu, G., Maler, L. & Hawkes, R. 1990. Zebrin II: a polypeptide antigen expressed selectively by Purkinje cells reveals compartments in rat and fish cerebellum. J. Comp. Neurol. 291, 538552.
  • Buckles, G. R., Thorpe, C. J., Ramel, M. C. & Lekven, A. C. 2004. Combinatorial Wnt control of zebrafish midbrain-hindbrain boundary formation. Mech. Dev. 121, 437447.
  • Burgess, S., Reim, G., Chen, W., Hopkins, N. & Brand, M. 2002. The zebrafish spiel-ohne-grenzen (spg) gene encodes the POU domain protein Pou2 related to mammalian Oct4 and is essential for formation of the midbrain and hindbrain, and for pre-gastrula morphogenesis. Development 129, 905916.
  • Butler, A. B. & Hodos, H. 1996. Comparative Vertebrate Neuroanatomy: Evolution and Adaptation, Wiley-Liss, New York, NY.
  • Cambronero, F. & Puelles, L. 2000. Rostrocaudal nuclear relationships in the avian medulla oblongata: a fate map with quail chick chimeras. J. Comp. Neurol. 427, 522545.
  • Carletti, B., Williams, I. M., Leto, K., Nakajima, K., Magrassi, L. & Rossi, F. 2008. Time constraints and positional cues in the developing cerebellum regulate Purkinje cell placement in the cortical architecture. Dev. Biol. 317, 147160.
  • Causeret, F., Danne, F., Ezan, F., Sotelo, C. & Bloch-Gallego, E. 2002. Slit antagonizes netrin-1 attractive effects during the migration of inferior olivary neurons. Dev. Biol. 246, 429440.
  • Celio, M. R. 1990. Calbindin D-28k and parvalbumin in the rat nervous system. Neuroscience 35, 375475.
  • Celio, M. R. & Heizmann, C. W. 1981. Calcium-binding protein parvalbumin as a neuronal marker. Nature 293, 300302.
  • Chaplin, N., Tendeng, C. & Wingate, R. J. 2010. Absence of an external germinal layer in zebrafish and shark reveals a distinct, anamniote ground plan of cerebellum development. J. Neurosci. 30, 30483057.
  • Chen, G., Hanson, C. L. & Ebner, T. J. 1996. Functional parasagittal compartments in the rat cerebellar cortex: an in vivo optical imaging study using neutral red. J. Neurophysiol. 76, 41694174.
  • Chizhikov, V. V., Lindgren, A. G., Currle, D. S., Rose, M. F., Monuki, E. S. & Millen, K. J. 2006. The roof plate regulates cerebellar cell-type specification and proliferation. Development 133, 27932804.
  • Chizhikov, V. V. & Millen, K. J. 2005. Roof plate-dependent patterning of the vertebrate dorsal central nervous system. Dev. Biol. 277, 287295.
  • Chung, S. H., Marzban, H., Croci, L., Consalez, G. G. & Hawkes, R. 2008. Purkinje cell subtype specification in the cerebellar cortex: early B-cell factor 2 acts to repress the zebrin II-positive Purkinje cell phenotype. Neuroscience 153, 721732.
  • Clark, W. E. 1933. The medical geniculate body and the nucleus isthmi. J. Anat. 67, 536548 531.
  • Corrales, J. D., Blaess, S., Mahoney, E. M. & Joyner, A. L. 2006. The level of sonic hedgehog signaling regulates the complexity of cerebellar foliation. Development 133, 18111821.
  • Croci, L., Chung, S. H., Masserdotti, G., Gianola, S., Bizzoca, A., Gennarini, G., Corradi, A., Rossi, F., Hawkes, R. & Consalez, G. G. 2006. A key role for the HLH transcription factor EBF2COE2,O/E-3 in Purkinje neuron migration and cerebellar cortical topography. Development 133, 27192729.
  • Crossley, P. H., Martinez, S. & Martin, G. R. 1996. Midbrain development induced by FGF8 in the chick embryo. Nature 380, 6668.
  • Dahmane, N. & Ruiz I Altaba, A. 1999. Sonic hedgehog regulates the growth and patterning of the cerebellum. Development 126, 30893100.
  • Danielian, P. S. & McMahon, A. P. 1996. Engrailed-1 as a target of the Wnt-1 signalling pathway in vertebrate midbrain development. Nature 383, 332334.
  • Di Meglio, T., Nguyen-Ba-Charvet, K. T., Tessier-Lavigne, M., Sotelo, C. & Chedotal, A. 2008. Molecular mechanisms controlling midline crossing by precerebellar neurons. J. Neurosci. 28, 62856294.
  • Dickinson, M. E., Krumlauf, R. & Mcmahon, A. P. 1994. Evidence for a mitogenic effect of Wnt-1 in the developing mammalian central nervous system. Development 120, 14531471.
  • Farago, A. F., Awatramani, R. B. & Dymecki, S. M. 2006. Assembly of the brainstem cochlear nuclear complex is revealed by intersectional and subtractive genetic fate maps. Neuron 50, 205218.
  • Finger, T. E. 1983. The gustatory system in teleost fish. In: Fish Neurobiology (eds R. G. Northcutt & R. E. Davis), pp. 285319. University of Michigan Press, Ann Arbor.
  • Finger, T. E. 1987. Gustatory nuclei and pathways in the central nervous system. In: Neurobiology of Taste and Smell (eds T. E. Finger & W. L. Silver), pp. 331354. John Wiley & Sons, New York, NY.
  • Fink, A. J., Englund, C., Daza, R. A., Pham, D., Lau, C., Nivison, M., Kowalczyk, T. & Hevner, R. F. 2006. Development of the deep cerebellar nuclei: transcription factors and cell migration from the rhombic lip. J. Neurosci. 26, 30663076.
  • Foucher, I., Mione, M., Simeone, A., Acampora, D., Bally-Cuif, L. & Houart, C. 2006. Differentiation of cerebellar cell identities in absence of Fgf signalling in zebrafish Otx morphants. Development 133, 18911900.
  • Fujiyama, T., Yamada, M., Terao, M., Terashima, T., Hioki, H., Inoue, Y. U., Inoue, T., Masuyama, N., Obata, K., Yanagawa, Y., Kawaguchi, Y., Nabeshima, Y. & Hoshino, M. 2009. Inhibitory and excitatory subtypes of cochlear nucleus neurons are defined by distinct bHLH transcription factors, Ptf1a and Atoh1. Development 136, 20492058.
  • Gao, W., Chen, G., Reinert, K. C. & Ebner, T. J. 2006. Cerebellar cortical molecular layer inhibition is organized in parasagittal zones. J. Neurosci. 26, 83778387.
  • Geling, A., Itoh, M., Tallafuss, A., Chapouton, P., Tannhauser, B., Kuwada, J. Y., Chitnis, A. B. & Bally-Cuif, L. 2003. bHLH transcription factor Her5 links patterning to regional inhibition of neurogenesis at the midbrain-hindbrain boundary. Development 130, 15911604.
  • Geling, A., Plessy, C., Rastegar, S., Strahle, U. & Bally-Cuif, L. 2004. Her5 acts as a prepattern factor that blocks neurogenin1 and coe2 expression upstream of Notch to inhibit neurogenesis at the midbrain-hindbrain boundary. Development 131, 19932006.
  • Goffinet, A. M. 1983. The embryonic development of the cerebellum in normal and reeler mutant mice. Anat. Embryol. 168, 7386.
  • Gravel, C., Eisenman, L. M., Sasseville, R. & Hawkes, R. 1987. Parasagittal organization of the rat cerebellar cortex: direct correlation between antigenic Purkinje cell bands revealed by mabQ113 and the organization of the olivocerebellar projection. The Journal of comparative neurology 265, 294310.
  • Gravel, C. & Hawkes, R. 1990. Parasagittal organization of the rat cerebellar cortex: direct comparison of Purkinje cell compartments and the organization of the spinocerebellar projection. The Journal of comparative neurology 291, 79102.
  • Grimaldi, P., Parras, C., Guillemot, F., Rossi, F. & Wassef, M. 2009. Origins and control of the differentiation of inhibitory interneurons and glia in the cerebellum. Dev. Biol. 328, 422433.
  • Hashimoto, M., Ito, R., Kitamura, N., Namba, K. & Hisano, Y. 2011. EphA4 controls the midline crossing and contralateral axonal projections of inferior olive neurons. J. Comp. Neurol. doi: 10.1002/cne.23008
  • Hashimoto, M. & Mikoshiba, K. 2003. Mediolateral compartmentalization of the cerebellum is determined on the “birth date” of Purkinje cells. J. Neurosci. 23, 1134211351.
  • Hashimoto, M. & Mikoshiba, K. 2004. Neuronal birthdate-specific gene transfer with adenoviral vectors. J. Neurosci. 24, 286296.
  • Hatten, M. E. & Roussel, M. F. 2011. Development and cancer of the cerebellum. Trends Neurosci. 34, 134142.
  • Hawkes, R. & Eisenman, L. M. 1997. Stripes and zones: the origins of regionalization of the adult cerebellum. Perspect. Dev. Neurobiol. 5, 95105.
  • Herrup, K. 2000. Thoughts on the cerebellum as a model for cerebral cortical development and evolution. Novartis Found. Symp. 224, 1524, discussion 24–19, 46–52.
  • Herrup, K. & Kuemerle, B. 1997. The compartmentalization of the cerebellum. Annu. Rev. Neurosci. 20, 6190.
  • Hibi, M. & Shimizu, T. 2011. Development of the cerebellum and cerebellar neural circuits. Dev. Neurobiol. doi: 10.1002/dneu.20875
  • Hirata, H., Tomita, K., Bessho, Y. & Kageyama, R. 2001. Hes1 and Hes3 regulate maintenance of the isthmic organizer and development of the mid/hindbrain. EMBO J. 20, 44544466.
  • Hirate, Y. & Okamoto, H. 2006. Canopy1, a novel regulator of FGF signaling around the midbrain-hindbrain boundary in zebrafish. Curr. Biol. 16, 421427.
  • Hirota, J., Ando, H., Hamada, K. & Mikoshiba, K. 2003. Carbonic anhydrase-related protein is a novel binding protein for inositol 1,4,5-trisphosphate receptor type 1. Biochem. J. 372, 435441.
  • Hoshino, M. 2006. Molecular machinery governing GABAergic neuron specification in the cerebellum. Cerebellum 5, 193198.
  • Hoshino, M., Nakamura, S., Mori, K., Kawauchi, T., Terao, M., Nishimura, Y. V., Fukuda, A., Fuse, T., Matsuo, N., Sone, M., Watanabe, M., Bito, H., Terashima, T., Wright, C. V., Kawaguchi, Y., Nakao, K. & Nabeshima, Y. 2005. Ptf1a, a bHLH transcriptional gene, defines GABAergic neuronal fates in cerebellum. Neuron 47, 201213.
  • Ikenaga, T., Yoshida, M. & Uematsu, K. 2005. Morphology and immunohistochemistry of efferent neurons of the goldfish corpus cerebelli. J. Comp. Neurol. 487, 300311.
  • Ikenaga, T., Yoshida, M. & Uematsu, K. 2006. Cerebellar efferent neurons in teleost fish. Cerebellum 5, 268274.
  • Ito, H., Sakamoto, N. & Takatsuji, K. 1982. Cytoarchitecture, fiber connections, and ultrastructure of nucleus isthmi in a teleost (Navodon modestus) with a special reference to degenerating isthmic afferents from optic tectum and nucleus pretectalis. J. Comp. Neurol. 205, 299311.
  • Ito, M. 2001. Cerebellar long-term depression: characterization, signal transduction, and functional roles. Physiol. Rev. 81, 11431195.
  • Ito, M. 2002a. Historical review of the significance of the cerebellum and the role of Purkinje cells in motor learning. Ann. N. Y. Acad. Sci. 978, 273288.
  • Ito, M. 2002b. The molecular organization of cerebellar long-term depression. Nat. Rev. Neurosci. 3, 896902.
  • Ito, M. 2005. Bases and implications of learning in the cerebellum–adaptive control and internal model mechanism. Prog. Brain Res. 148, 95109.
  • Ito, M. 2006. Cerebellar circuitry as a neuronal machine. Prog. Neurobiol. 78, 272303.
  • Ito, M. 2008. Control of mental activities by internal models in the cerebellum. Nat. Rev. Neurosci. 9, 304313.
  • Joyner, A. L., Liu, A. & Millet, S. 2000. Otx2, Gbx2 and Fgf8 interact to position and maintain a mid-hindbrain organizer. Curr. Opin. Cell Biol. 12, 736741.
  • Kani, S., Bae, Y. K., Shimizu, T., Tanabe, K., Satou, C., Parsons, M. J., Scott, E., Higashijima, S. & Hibi, M. 2010. Proneural gene-linked neurogenesis in zebrafish cerebellum. Dev. Biol. 343, 117.
  • Kaslin, J., Ganz, J., Geffarth, M., Grandel, H., Hans, S. & Brand, M. 2009. Stem cells in the adult zebrafish cerebellum: initiation and maintenance of a novel stem cell niche. J. Neurosci. 29, 61426153.
  • Kato, K. 1990. Sequence of a novel carbonic anhydrase-related polypeptide and its exclusive presence in Purkinje cells. FEBS Lett. 271, 137140.
  • Kawauchi, D., Taniguchi, H., Watanabe, H., Saito, T. & Murakami, F. 2006. Direct visualization of nucleogenesis by precerebellar neurons: involvement of ventricle-directed, radial fibre-associated migration. Development 133, 11131123.
  • Kerjan, G., Dolan, J., Haumaitre, C., Schneider-Maunoury, S., Fujisawa, H., Mitchell, K. J. & Chedotal, A. 2005. The transmembrane semaphorin Sema6A controls cerebellar granule cell migration. Nat. Neurosci. 8, 15161524.
  • Koster, R. W. & Fraser, S. E. 2006. FGF signaling mediates regeneration of the differentiating cerebellum through repatterning of the anterior hindbrain and reinitiation of neuronal migration. J. Neurosci. 26, 72937304.
  • Kuemerle, B., Zanjani, H., Joyner, A. & Herrup, K. 1997. Pattern deformities and cell loss in Engrailed-2 mutant mice suggest two separate patterning events during cerebellar development. J. Neurosci. 17, 78817889.
  • Laine, J. & Axelrad, H. 1994. The candelabrum cell: a new interneuron in the cerebellar cortex. J. Comp. Neurol. 339, 159173.
  • Landsberg, R. L., Awatramani, R. B., Hunter, N. L., Farago, A. F., Dipietrantonio, H. J., Rodriguez, C. I. & Dymecki, S. M. 2005. Hindbrain rhombic lip is comprised of discrete progenitor cell populations allocated by Pax6. Neuron 48, 933947.
  • Lannoo, M. J., Brochu, G., Maler, L. & Hawkes, R. 1991a. Zebrin II immunoreactivity in the rat and in the weakly electric teleost Eigenmannia (gymnotiformes) reveals three modes of Purkinje cell development. J. Comp. Neurol. 310, 215233.
  • Lannoo, M. J., Ross, L., Maler, L. & Hawkes, R. 1991b. Development of the cerebellum and its extracerebellar Purkinje cell projection in teleost fishes as determined by zebrin II immunocytochemistry. Prog. Neurobiol. 37, 329363.
  • Larouche, M. & Hawkes, R. 2006. From clusters to stripes: the developmental origins of adult cerebellar compartmentation. Cerebellum 5, 7788.
  • Leclerc, N., Gravel, C. & Hawkes, R. 1988. Development of parasagittal zonation in the rat cerebellar cortex: MabQ113 antigenic bands are created postnatally by the suppression of antigen expression in a subset of Purkinje cells. J. Comp. Neurol. 273, 399420.
  • Leto, K., Bartolini, A., Yanagawa, Y., Obata, K., Magrassi, L., Schilling, K. & Rossi, F. 2009. Laminar fate and phenotype specification of cerebellar GABAergic interneurons. J. Neurosci. 29, 70797091.
  • Leto, K., Carletti, B., Williams, I. M., Magrassi, L. & Rossi, F. 2006. Different types of cerebellar GABAergic interneurons originate from a common pool of multipotent progenitor cells. J. Neurosci. 26, 1168211694.
  • Lewis, P. M., Gritli-Linde, A., Smeyne, R., Kottmann, A. & Mcmahon, A. P. 2004. Sonic hedgehog signaling is required for expansion of granule neuron precursors and patterning of the mouse cerebellum. Developmental biology, 270, 393410.
  • Liu, A. & Joyner, A. L. 2001. Early anterior/posterior patterning of the midbrain and cerebellum. Annu. Rev. Neurosci. 24, 869896.
  • Liu, A., Losos, K. & Joyner, A. L. 1999. FGF8 can activate Gbx2 and transform regions of the rostral mouse brain into a hindbrain fate. Development 126, 48274838.
  • Liu, Z., Li, H., Hu, X., Yu, L., Liu, H., Han, R., Colella, R., Mower, G. D., Chen, Y. & Qiu, M. 2008. Control of precerebellar neuron development by Olig3 bHLH transcription factor. J. Neurosci. 28, 1012410133.
  • Lun, K. & Brand, M. 1998. A series of no isthmus (noi) alleles of the zebrafish pax2.1 gene reveals multiple signaling events in development of the midbrain-hindbrain boundary. Development 125, 30493062.
  • Lundell, T. G., Zhou, Q. & Doughty, M. L. 2009. Neurogenin1 expression in cell lineages of the cerebellar cortex in embryonic and postnatal mice. Dev. Dyn. 238, 33103325.
  • Machold, R. & Fishell, G. 2005. Math1 is expressed in temporally discrete pools of cerebellar rhombic-lip neural progenitors. Neuron 48, 1724.
  • Maier, V., Jolicoeur, C., Rayburn, H., Takegahara, N., Kumanogoh, A., Kikutani, H., Tessier-Lavigne, M., Wurst, W. & Friedel, R. H. 2011. Semaphorin 4C and 4G are ligands of Plexin-B2 required in cerebellar development. Mol. Cell. Neurosci. 46, 419431.
  • Maricich, S. M. & Herrup, K. 1999. Pax-2 expression defines a subset of GABAergic interneurons and their precursors in the developing murine cerebellum. J. Neurobiol. 41, 281294.
  • Marillat, V., Sabatier, C., Failli, V., Matsunaga, E., Sotelo, C., Tessier-Lavigne, M. & Chedotal, A. 2004. The slit receptor Rig-1/Robo3 controls midline crossing by hindbrain precerebellar neurons and axons. Neuron 43, 6979.
  • Martinez, S., Crossley, P. H., Cobos, I., Rubenstein, J. L. & Martin, G. R. 1999. FGF8 induces formation of an ectopic isthmic organizer and isthmocerebellar development via a repressive effect on Otx2 expression. Development 126, 11891200.
  • Marzban, H., Chung, S., Watanabe, M. & Hawkes, R. 2007. Phospholipase Cbeta4 expression reveals the continuity of cerebellar topography through development. J. Comp. Neurol. 502, 857871.
  • Meek, J. 1992. Comparative aspects of cerebellar organization. From mormyrids to mammals. Eur. J. Morphol. 30, 3751.
  • Meek, J., Hafmans, T. G., Maler, L. & Hawkes, R. 1992. Distribution of zebrin II in the gigantocerebellum of the mormyrid fish Gnathonemus petersii compared with other teleosts. J. Comp. Neurol. 316, 1731.
  • Meek, J., Yang, J. Y., Han, V. Z. & Bell, C. C. 2008. Morphological analysis of the mormyrid cerebellum using immunohistochemistry, with emphasis on the unusual neuronal organization of the valvula. J. Comp. Neurol. 510, 396421.
  • Mikami, Y., Yoshida, T., Matsuda, N. & Mishina, M. 2004. Expression of zebrafish glutamate receptor delta2 in neurons with cerebellum-like wiring. Biochem. Biophys. Res. Commun. 322, 168176.
  • Millen, K. J., Hui, C. C. & Joyner, A. L. 1995. A role for En-2 and other murine homologues of Drosophila segment polarity genes in regulating positional information in the developing cerebellum. Development 121, 39353945.
  • Milosevic, A. & Goldman, J. E. 2002. Progenitors in the postnatal cerebellar white matter are antigenically heterogeneous. J. Comp. Neurol. 452, 192203.
  • Minaki, Y., Nakatani, T., Mizuhara, E., Inoue, T. & Ono, Y. 2008. Identification of a novel transcriptional corepressor, Corl2, as a cerebellar Purkinje cell-selective marker. Gene Expr. Patterns 8, 418423.
  • Miyata, T., Nakajima, K., Mikoshiba, K. & Ogawa, M. 1997. Regulation of Purkinje cell alignment by reelin as revealed with CR-50 antibody. J. Neurosci. 17, 35993609.
  • Miyata, T., Ono, Y., Okamoto, M., Masaoka, M., Sakakibara, A., Kawaguchi, A., Hashimoto, M. & Ogawa, M. 2010. Migration, early axonogenesis, and Reelin-dependent layer-forming behavior of early/posterior-born Purkinje cells in the developing mouse lateral cerebellum. Neural Dev. 5, 23.
  • Mizuhara, E., Minaki, Y., Nakatani, T., Kumai, M., Inoue, T., Muguruma, K., Sasai, Y. & Ono, Y. 2010. Purkinje cells originate from cerebellar ventricular zone progenitors positive for Neph3 and E-cadherin. Dev. Biol. 338, 202214.
  • Morita, Y., Ito, H. & Masai, H. 1980. Central gustatory paths in the crucian carp, Carassius carassius. J. Comp. Neurol. 191, 119132.
  • Morita, Y., Murakami, T. & Ito, H. 1983. Cytoarchitecture and topographic projections of the gustatory centers in a teleost, Carassius carassius. J. Comp. Neurol. 218, 378394.
  • Murakami, T. & Morita, Y. 1987. Morphology and distribution of the projection neurons in the cerebellum in a teleost, Sebastiscus marmoratus. J. Comp. Neurol. 256, 607623.
  • Nakamura, H., Katahira, T., Matsunaga, E. & Sato, T. 2005. Isthmus organizer for midbrain and hindbrain development. Brain Res. Brain Res. Rev. 49, 120126.
  • Namba, K., Sugihara, I. & Hashimoto, M. 2011. Close correlation between the birth date of Purkinje cells and the longitudinal compartmentalization of the mouse adult cerebellum. J. Comp. Neurol. 519, 25942614.
  • Nieuwenhuys, R. 1967. Comparative anatomy of the cerebellum. Prog. Brain Res. 25, 193.
  • Nieuwenhuys, R. & Nicholson, C. 1967. Cerebellum of mormyrids. Nature 215, 764765.
  • Ninkovic, J., Tallafuss, A., Leucht, C., Topczewski, J., Tannhauser, B., Solnica-Krezel, L. & Bally-Cuif, L. 2005. Inhibition of neurogenesis at the zebrafish midbrain-hindbrain boundary by the combined and dose-dependent activity of a new hairy/E(spl) gene pair. Development 132, 7588.
  • Nogradi, A., Jonsson, N., Walker, R., Caddy, K., Carter, N. & Kelly, C. 1997. Carbonic anhydrase II and carbonic anhydrase-related protein in the cerebellar cortex of normal and lurcher mice. Brain Res. Dev. Brain Res. 98, 91101.
  • Oberdick, J., Baader, S. L. & Schilling, K. 1998. From zebra stripes to postal zones: deciphering patterns of gene expression in the cerebellum. Trends Neurosci. 21, 383390.
  • Odeh, F., Ackerley, R., Bjaalie, J. G. & Apps, R. 2005. Pontine maps linking somatosensory and cerebellar cortices are in register with climbing fiber somatotopy. The Journal of neuroscience : the official journal of the Society for Neuroscience 25, 56805690.
  • Pfeffer, P. L., Gerster, T., Lun, K., Brand, M. & Busslinger, M. 1998. Characterization of three novel members of the zebrafish Pax2/5/8 family: dependency of Pax5 and Pax8 expression on the Pax2.1 (noi) function. Development 125, 30633074.
  • Picker, A., Brennan, C., Reifers, F., Clarke, J. D., Holder, N. & Brand, M. 1999. Requirement for the zebrafish mid-hindbrain boundary in midbrain polarisation, mapping and confinement of the retinotectal projection. Development 126, 29672978.
  • Pijpers, A., Winkelman, B. H., Bronsing, R. & Ruigrok, T. J. 2008. Selective impairment of the cerebellar C1 module involved in rat hind limb control reduces step-dependent modulation of cutaneous reflexes. J. Neurosci. 28, 21792189.
  • Raible, F. & Brand, M. 2004. Divide et Impera–the midbrain-hindbrain boundary and its organizer. Trends Neurosci. 27, 727734.
  • Ray, R. S. & Dymecki, S. M. 2009. Rautenlippe Redux – toward a unified view of the precerebellar rhombic lip. Curr. Opin. Cell Biol. 21, 741747.
  • Reifers, F., Adams, J., Mason, I. J., Schulte-Merker, S. & Brand, M. 2000. Overlapping and distinct functions provided by fgf17, a new zebrafish member of the Fgf8/17/18 subgroup of Fgfs. Mech. Dev. 99, 3949.
  • Reifers, F., Bohli, H., Walsh, E. C., Crossley, P. H., Stainier, D. Y. & Brand, M. 1998. Fgf8 is mutated in zebrafish acerebellar (ace) mutants and is required for maintenance of midbrain-hindbrain boundary development and somitogenesis. Development 125, 23812395.
  • Reim, G. & Brand, M. 2002. Spiel-ohne-grenzen/pou2 mediates regional competence to respond to Fgf8 during zebrafish early neural development. Development 129, 917933.
  • Renaud, J., Kerjan, G., Sumita, I., Zagar, Y., Georget, V., Kim, D., Fouquet, C., Suda, K., Sanbo, M., Suto, F., Ackerman, S. L., Mitchell, K. J., Fujisawa, H. & Chedotal, A. 2008. Plexin-A2 and its ligand, Sema6A, control nucleus-centrosome coupling in migrating granule cells. Nat. Neurosci. 11, 440449.
  • Rhinn, M., Lun, K., Ahrendt, R., Geffarth, M. & Brand, M. 2009. Zebrafish gbx1 refines the midbrain-hindbrain boundary border and mediates the Wnt8 posteriorization signal. Neural Dev. 4, 12.
  • Rodriguez, C. I. & Dymecki, S. M. 2000. Origin of the precerebellar system. Neuron 27, 475486.
  • Roussel, M. F. & Hatten, M. E. 2011. Cerebellum development and medulloblastoma. Curr. Top. Dev. Biol. 94, 235282.
  • Ruigrok, T. J., Pijpers, A., Goedknegt-Sabel, E. & Coulon, P. 2008. Multiple cerebellar zones are involved in the control of individual muscles: a retrograde transneuronal tracing study with rabies virus in the rat. Eur. J. Neurosci. 28, 181200.
  • Sakamoto, N., Ito, H. & Ueda, S. 1981. Topographic projections between the nucleus isthmi and the optic tectum in a teleost. Navodon modestus. Brain Res. 224, 225234.
  • Sato, T., Joyner, A. L. & Nakamura, H. 2004. How does Fgf signaling from the isthmic organizer induce midbrain and cerebellum development? Dev. Growth Differ. 46, 487494.
  • Sillitoe, R. V. & Joyner, A. L. 2007. Morphology, molecular codes, and circuitry produce the three-dimensional complexity of the cerebellum. Annu. Rev. Cell Dev. Biol. 23, 549577.
  • Simeone, A. 2000. Positioning the isthmic organizer where Otx2 and Gbx2meet. Trends Genet. 16, 237240.
  • Simeone, A., Acampora, D., Gulisano, M., Stornaiuolo, A. & Boncinelli, E. 1992. Nested expression domains of four homeobox genes in developing rostral brain. Nature 358, 687690.
  • Simeone, A., Puelles, E. & Acampora, D. 2002. The Otx family. Curr. Opin. Genet. Dev. 12, 409415.
  • Smeyne, R. J., Chu, T., Lewin, A., Bian, F., Sanlioglu, S., Kunsch, C., Lira, S. A. & Oberdick, J. 1995. Local control of granule cell generation by cerebellar Purkinje cells. Mol. Cell Neurosci. 6, 230251.
  • Storm, R., Cholewa-Waclaw, J., Reuter, K., Brohl, D., Sieber, M., Treier, M., Muller, T. & Birchmeier, C. 2009. The bHLH transcription factor Olig3 marks the dorsal neuroepithelium of the hindbrain and is essential for the development of brainstem nuclei. Development 136, 295305.
  • Sudarov, A., Turnbull, R. K., Kim, E. J., Lebel-Potter, M., Guillemot, F. & Joyner, A. L. 2011. Ascl1 genetics reveals insights into cerebellum local circuit assembly. J. Neurosci. 31, 1105511069.
  • Sugihara, I. & Quy, P. N. 2007. Identification of aldolase C compartments in the mouse cerebellar cortex by olivocerebellar labeling. J. Comp. Neurol. 500, 10761092.
  • Sugihara, I. & Shinoda, Y. 2004. Molecular, topographic, and functional organization of the cerebellar cortex: a study with combined aldolase C and olivocerebellar labeling. The Journal of neuroscience : the official journal of the Society for Neuroscience 24, 87718785.
  • Takayama, C., Nakagawa, S., Watanabe, M., Kurihara, H., Mishina, M. & Inoue, Y. 1997. Altered intracellular localization of the glutamate receptor channel delta 2 subunit in weaver and reeler Purkinje cells. Brain Res. 745, 231242.
  • Terashima, T., Inoue, K., Inoue, Y., Mikoshiba, K. & Tsukada, Y. 1985. Observations on Golgi epithelial cells and granule cells in the cerebellum of the reeler mutant mouse. Brain Res. 350, 103112.
  • Volkmann, K., Chen, Y. Y., Harris, M. P., Wullimann, M. F. & Koster, R. W. 2010. The zebrafish cerebellar upper rhombic lip generates tegmental hindbrain nuclei by long-distance migration in an evolutionary conserved manner. J. Comp. Neurol. 518, 27942817.
  • Volkmann, K., Rieger, S., Babaryka, A. & Koster, R. W. 2008. The zebrafish cerebellar rhombic lip is spatially patterned in producing granule cell populations of different functional compartments. Dev. Biol. 313, 167180.
  • Voogd, J. & Glickstein, M. 1998. The anatomy of the cerebellum. Trends Neurosci. 21, 370375.
  • Voogd, J., Pardoe, J., Ruigrok, T. J. & Apps, R. 2003. The distribution of climbing and mossy fiber collateral branches from the copula pyramidis and the paramedian lobule: congruence of climbing fiber cortical zones and the pattern of zebrin banding within the rat cerebellum. The Journal of neuroscience : the official journal of the Society for Neuroscience 23, 46454656.
  • Voogd, J. & Ruigrok, T. J. 2004. The organization of the corticonuclear and olivocerebellar climbing fiber projections to the rat cerebellar vermis: the congruence of projection zones and the zebrin pattern. J. Neurocytol. 33, 521.
  • Wallace, V. A. 1999. Purkinje-cell-derived Sonic hedgehog regulates granule neuron precursor cell proliferation in the developing mouse cerebellum. Curr. Biol. 9, 445448.
  • Wang, V. Y., Rose, M. F. & Zoghbi, H. Y. 2005. Math1 expression redefines the rhombic lip derivatives and reveals novel lineages within the brainstem and cerebellum. Neuron 48, 3143.
  • Wechsler-Reya, R. J. & Scott, M. P. 1999. Control of neuronal precursor proliferation in the cerebellum by Sonic Hedgehog. Neuron 22, 103114.
  • Weisheit, G., Gliem, M., Endl, E., Pfeffer, P. L., Busslinger, M. & Schilling, K. 2006. Postnatal development of the murine cerebellar cortex: formation and early dispersal of basket, stellate and Golgi neurons. Eur. J. Neurosci. 24, 466478.
  • Wetts, R. & Herrup, K. 1983. Direct correlation between Purkinje and granule cell number in the cerebella of lurcher chimeras and wild-type mice. Brain Res. 312, 4147.
  • Wilson, S. W., Brand, M. & Eisen, J. S. 2002. Patterning the zebrafish central nervous system. Results Probl. Cell Differ. 40, 181215.
  • Wingate, R. J. 2001. The rhombic lip and early cerebellar development. Curr. Opin. Neurobiol. 11, 8288.
  • Wingate, R. J. & Hatten, M. E. 1999. The role of the rhombic lip in avian cerebellum development. Development 126, 43954404.
  • Wullimann, M. F., Mueller, T., Distel, M., Babaryka, A., Grothe, B. & Koster, R. W. 2011. The long adventurous journey of rhombic lip cells in jawed vertebrates: a comparative developmental analysis. Front Neuroanat. 5, 27.
  • Wullimann, M. F., Rupp, B. & Reichert, H. 1996. Neuroanatomy of the Zebrafish Brain: A Topological Atlas. Birkhäuser Verlag, Basel.
  • Wurst, W. & Bally-Cuif, L. 2001. Neural plate patterning: upstream and downstream of the isthmic organizer. Nat. Rev. Neurosci. 2, 99108.
  • Xu, J., Liu, Z. & Ornitz, D. M. 2000. Temporal and spatial gradients of Fgf8 and Fgf17 regulate proliferation and differentiation of midline cerebellar structures. Development 127, 18331843.
  • Yamada, M., Terao, M., Terashima, T., Fujiyama, T., Kawaguchi, Y., Nabeshima, Y. & Hoshino, M. 2007. Origin of climbing fiber neurons and their developmental dependence on Ptf1a. J. Neurosci. 27, 1092410934.
  • Zervas, M., Blaess, S. & Joyner, A. L. 2005. Classical embryological studies and modern genetic analysis of midbrain and cerebellum development. Curr. Top. Dev. Biol. 69, 101138.
  • Zervas, M., Millet, S., Ahn, S. & Joyner, A. L. 2004. Cell behaviors and genetic lineages of the mesencephalon and rhombomere 1. Neuron 43, 345357.
  • Zhang, L. & Goldman, J. E. 1996a. Developmental fates and migratory pathways of dividing progenitors in the postnatal rat cerebellum. J. Comp. Neurol. 370, 536550.
  • Zhang, L. & Goldman, J. E. 1996b. Generation of cerebellar interneurons from dividing progenitors in white matter. Neuron 16, 4754.
  • Zordan, P., Croci, L., Hawkes, R. & Consalez, G. G. 2008. Comparative analysis of proneural gene expression in the embryonic cerebellum. Dev. Dyn. 237, 17261735.
  • Zupanc, G. K., Hinsch, K. & Gage, F. H. 2005. Proliferation, migration, neuronal differentiation, and long-term survival of new cells in the adult zebrafish brain. J. Comp. Neurol. 488, 290319.