Front cover:

Cover image: Transverse section cut through a mouse epitrochleoanconeus muscle and stained for myosin heavy chain type I, type IIa and type IIb, as well as laminin to distinguish fibre borders. See D. Villarroel-Campos and colleagues, ‘Dissection, in vivo imaging and analysis of the mouse epitrochleoanconeus muscle’, this issue.

Special issue on Peripheral nerve anatomy in health and disease

Summary of neuromuscular junction (NMJ) changes across ALS mouse models. ALS mouse models show different levels of NMJ pathology depending on gene targets: SOD1, TDP-43 and FUS models all show initial NMJ dysfunction prior to motor neuron death (arrows), supporting a ‘dying-back’ theory, while C9orf72 NMJ pathology is less clear. Terminal Schwann cells (tSCs) are lost in the SOD1 model. Dark red regions on the muscle fibre represent the endplate, which is smaller and fragmented in some C9orf72, TDP-43 and FUS models.

The mouse epitrochleoanconeus (ETA) is a thin and flat muscle located in the upper forelimb. Aided by step-by-step images and videos, we describe a simple method for its rapid isolation to analyse muscle fibre types and neuromuscular junctions (NMJs). We also outline how the ETA can be imaged in live, anaesthetised mice to enable examination of dynamic cellular processes occurring at the NMJ and within intramuscular axons.

The role of the neuromuscular junction in neuromuscular disorders is not fully understood. Naturally occurring neuromuscular diseases in large animals might offer translational benefits over lab rodent studies.

This equine NMJ method paper tackles the staining and analysis of large mammalian muscles. Equine NMJ morphology is revealed to be similar to other vertebrates. Clear differences exist between the equine soleus and other equine pelvic limb muscle NMJs.

We integrate evidence of key processes and crucial molecules that have shed light on our current understanding of neuromuscular junction (NMJ) maturation. The molecular mechanisms that assemble podosomes-like structures in vitro could be involved in the maturation of the NMJ postsynaptic apparatus in vivo. We propose that members of the small Rho GTPases drive the formation of synaptic podosomes by modulating actin dynamics during postsynaptic maturation of the vertebrate NMJ.

In this study, Kissane et al performed parallel analyses of central (motoneurons) and peripheral (muscles) adaptations to chronic functional overload of extensor digitorum longus motor units in rats. They show that a functional shift to a slower phenotype in the muscle is reflected by a corresponding reduction in motoneuron size, while modulatory C-bouton synapses remain unaltered. These results provide a greater understanding of neuromuscular plasticity in response to increased functional demands.

Intraepidermal nerve fiber density in wild type and Sptlc1-C133W knockin mice, modeling hereditary sensory and autonomic neuropathy type 1.

Like most neurons, sensory afferents are highly compartmentalised. In this review we will discuss the structure of distinct compartments within sensory neurons, how they relate to normal sensory function and highlight anatomical changes which occur to these compartments following nerve injury and their relationship to neuropathic pain.

Here we report the generation of primary neuronal dorsal root ganglia (DRG) cultures from adult horses, containing neurons and glial cells. Cultured neurons varied in size, and they developed long neurites. The mitochondrial movement was detected in cultured cells and was significantly slower in glial cells compared to DRG-derived neurons. In addition, mitochondria were more elongated in glial cells than those in neurons.

Glia found in the peripheral nervous system are anatomically, morphologically, and functionally diverse. They include: myelinating Schwann cells, Remak Schwann cells, repair Schwann cells, satellite glia, boundary cap-derived glia, perineurial glia, terminal Schwann cells, glia found in the skin, olfactory ensheathing cells, and enteric glia. The morphological and functional heterogeneity of glia found in the periphery reflects the diverse roles the nervous system performs throughout the body.

Schwann cells (SCs) are fundamental components of the peripheral nervous system of all vertebrates, where they play an essential role in nerve function, development, maturation, in regeneration after injury and in varied pathophysiological processes and disease. We present here a revision of methodological approaches to study and manipulate SCs, to provide researchers approaching this field with a general overview of the experimental possibilities currently available for these cells.

Gangliosides are a family of sialic acid containing glycosphingolipids highly enriched in the vertebrate nervous system and associated with nervous system integrity and maintenance. In this review we discuss results from the culmination of a series of studies on transgenic mice with varying deficiencies in glycolipids used to dissect the contribution of complex gangliosides and sulfatides to the organisation of the node of Ranvier. This figure shows the likely impact of increasing glycolipid deficiency on paranodal arrangement at nodes of Ranvier based on known data from the peripheral and central nervous systems of transgenic mice.