Developmental Dynamics

Key findings:

• Specification of epibranchial placode-derived nodose ganglion requires both Neurog1 and Neurog2.

• Specification of neural crest-derived parasympathetic otic ganglion requires both Neurog1 and Neurog2.

• Loss of Neurog genes associated with the complementary loss of visceral sensory (nodose) and parasympathetic (otic) ganglia due to apoptosis.

• Neurog1 and Neurog2 are transiently expressed in the neural crest fated for the parasympathetic otic ganglion lineage.

Key findings:

• Elevating the level of active β-catenin in the anterior neural plate leads to a loss of the telencephalon.

• Instead, high levels of β-catenin in the anterior neural plate leads to mid-hindbrain characteristics.

• β-catenin levels may regulate a telencephalic versus mid-hindbrain fate by regulating levels of FGF signaling.

Key findings:

• SHH can rescue facial malformations after blocking SHH signaling in the brain.

• Induction of Shh expression in the FEZ requires SHH signaling from the brain.

• 3D geometric morphometrics can be used to quantify malformation and rescue.

Key findings:

• ΔNp63 expression is regulated by BMP signaling.

• Gain- and loss-of-function experiments show that ΔNp63 is essential since the earliest steps of epidermis induction for the proper development of this tissue.

• ΔNp63 participates in epidermal development regulating the expression of some components of the apoptotic pathway.

Key findings:

• The posterior epiblast of the murine embryo does not display convergence and extension behavior, coordinated cell migration, or large-scale cell rearrangements prior to or during primitive streak formation.

• The murine primitive streak develops in situ by initiation of epithelial to mesenchymal transition (EMT) in the posterior-most epiblast, and elongates by anterior progression of this EMT.

• Loss of basal lamina (BL) precedes other steps of EMT at the primitive streak, and is tightly correlated with the ingression of nascent mesoderm.

• Cells leave the epiblast and enter the primitive streak by apical constriction and somal translocation.

Key findings:

• Myocardial progenitors from the secondary heart field (SHF) and anterior heart field (AHF) contribute to distinct conotruncal regions.

• Progenitor cells from the right and left SHF migrate rotationally to form left dorsal wall of the OFT and right ventral wall of the OFT, respectively.

• Progenitors from the AHF migrate non-rotationally and contribute to ventral wall of the OFT.

Key findings:

• Cranial NCC migrate throughout a hyaluronan rich extracellular matrix

• Hyaluronan synthases 1 and 2 activity is necessary to maintain the migratory behaviour of cranial NCC

• After NCC migration, the presence of Hyaluronan in the extracellular matrix is necessary for the survival of pre-chondrogenic cranial NCC.

• CD44, a Hyaluronan receptor, is required for cranial NCC migration but not for their survival.

• In Xenopus, the craniofacial skeleton formation is deeply influenced by the composition of the extracellular matrix during cranial NCC migration and differentiation.

Key findings:

• Fibulin-1 promotes ADAMTS1-mediated cleavage of versican.

• Fibulin-1 deficient embryonic cardiac ventricles have reduced levels of the 70-kDa amino-terminal fragment of versican V1 containing a carboxy terminal DPEAAE sequence.

• Fibulin-1 deficient embryonic cardiac ventricles have increased trabecular cardiomyocyte proliferation.

• Fibulin-1 deficient embryonic cardiac ventricles have increased levels of ErbB2 and Erk1/2 activation.

• Hearts from versican^hdf/hdf embryos lack versican V0/V1 and show a lack of trabeculae.

Key findings:

• Hindbrain cells along the pathway of migrating facial motor neurons express olig2.

• Loss of olig2 function disrupts facial motor neuron migration through the hindbrain.

• olig2-expressing hindbrain cells might be intermediate targets from migrating facial motor neurons.

Key findings:

• The mnr2b/hlxb9lb enhancer trap line marks spinal and abducens motor neurons during embryonic and larval stages.

• A Gal4FF transgenic line that labels the extraocular muscles, including the lateral rectus muscle, was established.

• By combining these transgenic constructs, the innervation of the lateral rectus by the abducens motor neurons can be visualized in intact animals.

Key findings:

• Insect resilins are rubber-like proteins laid down in cuticle that confer extreme flexibility and energy storage.

• An antibody to the Drosophila Rec-1 resilin is used to explore the expression of resilin in Drosophila and other species.

• In Drosophila embryos, expression is seen in the epidermis in repeated segmental patterns.

• In Drosophila adults, expression is seen at the wing bases and the bases of sense organs.

• The antibody cross-reacts, binding to well-characterised resilin sites in the dragonfly and flea.

Key findings:

• MCS9.7 activity is highly associated with endogenous expression of IRF6 in most embryonic murine tissues.

• MCS9.7 is not sufficient to recapitulate the expression of IRF6 in the medial edge epithelium at E14.5.

• MCS9.7 activity and IRF6 expression are highly colocalized in periderm where p63 is absent in orofacial epithelium.

Key findings:

• Four stages of dermomyotome/myotome development are defined.

• The interstitial matrix around thde dermomyotome and myotome is rich in fibronectin.

• Fibronectin and tenascin are enriched at intersegmental borders and penetrate into the myotome.

• Laminin matrices line the dermomyotome and myotome.

• These laminin matrices are disassembled as the dermomyotome dissociates and the myotome transforms into the epaxial muscle masses.

Key findings:

• This is the first study to characterize the expression of multiple T-box genes, the four closely related members of the Tbx2 subfamily, in both the internal and external reproductive systems of males and females.

• We show that Tbx2 and Tbx3 have both unique and overlapping expression domains in the internal reproductive system during initial stages of gonad and genital duct formation, after establishment of sexual dimorphism and at postnatal, pre-pubertal stages.

• β-Tbx4 is expressed in embryonic male and female germ cells and postnatal oocytes.

• All four Tbx2 subfamily genes, Tbx2, Tbx3, Tbx4, and Tbx5, are expressed in mesenchyme in external genitalia, with Tbx3 and Tbx5 expression in the epithelium as well.

Key findings:

• Altered Notch signaling in neural crest cells results in neurocristopathies.

• Manipulation of Notch signaling results in defective neural crest cell migration.

• Notch signaling promotes neural crest cell proliferation.

• Notch signaling regulates pharyngeal arch artery smooth muscle differentiation.

• Notch signaling promotes gliogenesis while inhibiting neurogenesis.

Key findings:

• NO is endogenously synthesized in all developmental stages of the cuttlefish Sepia officinalis.

• The spatial pattern of NO and NOS is very dynamic and concerns both superficial and internal structures.

• NO could be involved in important functional processes providing new insights in this emerging model for developmental studies.

Key findings:

• Ptc-1, Smo, Gli1, Gli2 and Gli3 are up-regulated in the mesenchymal tissues of the Xenopus laevis intestine during natural and TH-induced metamorphosis.

• Gli2 is a direct TH response gene.

• The expression of Ptc-1, Smo, Gli1, Gli2 and Gli3 are also regulated by Shh itself.

Key findings:

• Isolation of appa and aplp2 Tol2 gene trap alleles; appa and aplp2 expression in neuronal tissues during embryogenesis.

• Secretion of predicted appa-RFP and aplp2-RFP fusion proteins.

• Accumulation of appa-RFP and aplp2-RFP in living embryos at veinous vasculature.