Slow Muscle Precursors Lay Down a Collagen XV Matrix Fingerprint to Guide Motor Axon Navigation

Abstract

The extracellular matrix (ECM) provides local positional information to guide motoneuron axons toward their muscle target. Collagen XV is a basement membrane component mainly expressed in skeletal muscle. We have identified two zebrafish paralogs of the human COL15A1 gene, col15a1aandcol15a1b,whichdisplaydistinctexpressionpatterns.Hereweshowthatcol15a1bisexpressedanddepositedinthemotorpathECM by slow muscle precursors also called adaxial cells. We further demonstrate that collagen XV-B deposition is both temporally and spatially regulated before motor axon extension from the spinal cord in such a way that it remains in this region after the adaxial cells have migrated toward the periphery of the myotome. Loss-and gain-of-function experiments in zebrafish embryos demonstrate that col15a1b expression and subsequent collagen XV-B deposition and organization in the motor path ECM depend on a previously undescribed two-step mechanism involving Hedgehog/Gli and unplugged/MuSK signaling pathways. In silico analysis predicts a putative Gli binding site in the col15a1b proximal promoter. Using col15a1b promoter-reporter constructs, we demonstrate that col15a1b participates in the slow muscle genetic program as a direct target of Hedgehog/Gli signaling. Loss and gain of col15a1b function provoke pathfinding errors in primary and secondary motoneuron axons both at and beyond the choice point where axon pathway selection takes place. These defects result in muscle atrophy and compromised swimming behavior, a phenotype partially rescued by injection of a smyhc1:col15a1b construct. These reveal an unexpected and novel role for collagen XV in motor axon pathfinding and neuromuscular development.

Genetic Diversity and Selection Signatures Within Diannan Small-Ear Pigs Revealed by Next-Generation Sequencing

“…Twenty potential genes were annotated according to these SNPs, and those specific trait-associated genes that we showed were paid more attention to. For example, there was a study that showed the loss of COL15A1 provoked muscle atrophy (Guillon et al, 2016). Another study showed that overexpression of RPL3L impaired the growth and myogenic fusion of myotubes (Chaillou, 2019).…”

Collagen type XV and the ‘osteogenic status’

“…Its expression is associated with vascular, neuronal, mesenchymal and some epithelial basement membrane (BM) in many tissues, indicating a probable function in the adhesion between BM and the underlying connective tissue stroma . Its precise functions remain to be fully elucidated, even if evidence so far suggests that ColXV is involved in more sophisticated roles than just the molecular architecture of BM, particularly in the context of ECM organization and degradation .…”

Interaction of Axonal Chondrolectin with Collagen XIXa1 Is Necessary for Precise Neuromuscular Junction Formation

“…Immuno-precipitations show that the C-type lectin domain of Chodl binds the collagenous domains of ColXIXa1 but does not bind ColXIIa1a. However, other collagens could also act as a ligand, such as ColXV, which possesses collagenous domains (Eklund et al, 2000) and for which the mutant phenotype is also similar to that of chodl mutants in zebrafish (Guillon et al, 2016). Cell transfection assays indicate that binding of extracellular ColXIXa1 by the extracellular C-type lectin domains of Chodl occurs at the plasma membrane.…”

“…The horizontal myoseptum in zebrafish is rich in ECM factors, such as Tenascin-C (Schweitzer et al, 2005), Chondroitin sulfates (Zhang et al, 2004), and collagens (Guillon et al, 2016), which are likely to take part in synaptogenesis. The fact that ColXIXa1 is produced by muscle cells (Hilario et al, 2010) and Chodl by motor neurons (Zhong et al, 2012) makes it probable that these factors interact at the horizontal myoseptum synapses.…”