Mutations in dock1 disrupt early Schwann cell development

Rebecca L Cunningham,Breanne L Harty,Sarah D Ackerman,Amy L Herbert,Kelly R Monk

doi:10.1186/s13064-018-0114-9

Abstract

BackgroundIn the peripheral nervous system (PNS), specialized glial cells called Schwann cells produce myelin, a lipid-rich insulating sheath that surrounds axons and promotes rapid action potential propagation. During development, Schwann cells must undergo extensive cytoskeletal rearrangements in order to become mature, myelinating Schwann cells. The intracellular mechanisms that drive Schwann cell development, myelination, and accompanying cell shape changes are poorly understood.MethodsThrough a forward genetic screen in zebrafish, we identified a mutation in the atypical guanine nucleotide exchange factor, dock1, that results in decreased myelination of peripheral axons. Rescue experiments and complementation tests with newly engineered alleles confirmed that mutations in dock1 cause defects in myelination of the PNS. Whole mount in situ hybridization, transmission electron microscopy, and live imaging were used to fully define mutant phenotypes.ResultsWe show that Schwann cells in dock1 mutants can appropriately migrate and are not decreased in number, but exhibit delayed radial sorting and decreased myelination during early stages of development.ConclusionsTogether, our results demonstrate that mutations in dock1 result in defects in Schwann cell development and myelination. Specifically, loss of dock1 delays radial sorting and myelination of peripheral axons in zebrafish.

Highlights

In the peripheral nervous system (PNS), specialized glial cells called Schwann cells produce myelin, a lipid-rich insulating sheath that surrounds axons and promotes rapid action potential propagation
The DHR-1 domain interacts with PtdIns(3,4,5)P3 and the DHR-2 domain is the catalytic domain can that catalyzes the exchange of Guanosine diphosphate (GDP) for Guanosine triphosphate (GTP) in Rac1. h-i) Quantification of Whole mount in situ hybridization (WISH) for mbp at 3 dpf (h) and 5 dpf (i), respectively, based on phenotypic classes and genotypes for the stl145 lesion. **** p < 0.0001, Chi-squared analysis. j) Genotyping assay for the stl145 lesion
To confirm that dock1 is expressed in Schwann cells of zebrafish in addition to mammalian Schwann cells [20], RT-Polymerase chain reaction (PCR) for dock1 was performed on cDNA from adult Posterior lateral line nerve (PLLn), which is enriched in Schwann cell nuclei

Summary

Introduction

In the peripheral nervous system (PNS), specialized glial cells called Schwann cells produce myelin, a lipid-rich insulating sheath that surrounds axons and promotes rapid action potential propagation. Schwann cells are the myelinating glia of the peripheral nervous system (PNS), and one Schwann cell myelinates one axonal segment. Schwann cells are derived from the neural crest and undergo a distinct series of developmental stages [1, 2]. These developmental stages of Schwann cells require migration as well as unique and substantial changes in cell shape. SCPs develop into immature Schwann cells, which undergo a unique process called radial sorting in which Schwann cells extend processes into axon bundles and select an

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