Abstract

Desmin is a muscle-specific intermediate filament protein that has fundamental role in muscle structure and force transmission. Whereas human desmin protein is encoded by a single gene, two desmin paralogs (desma and desmb) exist in zebrafish. Desma and desmb show differential spatiotemporal expression during zebrafish embryonic and larval development, being similarly expressed in skeletal muscle until hatching, after which expression of desmb shifts to gut smooth muscle. We generated knockout (KO) mutant lines carrying loss-of-function mutations for each gene by using CRISPR/Cas9. Mutants are viable and fertile, and lack obvious skeletal muscle, heart or intestinal defects. In contrast to morphants, knockout of each gene did not cause any overt muscular phenotype, but did alter calcium flux in myofibres. These results point to a possible compensation mechanism in these mutant lines generated by targeting nonsense mutations to the first coding exon.

Highlights

  • Desmin is a muscle-specific intermediate filament protein that has fundamental role in muscle structure and force transmission

  • Altered calcium flux was observed in desma-KO myofibres. These results show that loss-of-function of desmin genes by mutations in the first coding exon result in a mild phenotype with no visible muscle degeneration but altered calcium flux, in contrast to morpholino-mediated knockdown models and the desmasa[5] allele

  • A single transcript is known to be encoded by human DES gene, in ENSEMBL two isoforms are predicted to be transcribed from zebrafish desma; desma-1 mRNA coding for a 488 amino acid protein and desma-2 mRNA coding for a 473 amino acid protein

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Summary

Introduction

Desmin is a muscle-specific intermediate filament protein that has fundamental role in muscle structure and force transmission. Knockout of each gene did not cause any overt muscular phenotype, but did alter calcium flux in myofibres These results point to a possible compensation mechanism in these mutant lines generated by targeting nonsense mutations to the first coding exon. Desmin is a type III intermediate filament protein that is expressed in skeletal, cardiac and smooth muscles. In addition to their fundamental role in maintaining the structural integrity of the sarcomere, desmin intermediate filaments are involved in mechanotransduction and organelle positioning. Ramspacher et al studied a desmin mutant line (desmasa5) generated by ENU mutagenesis, which causes a truncation mutation approximately half way along the molecule, that presented with skeletal and cardiac muscle p­ henotype[14]. Previous work has not established the tissue specific distribution and role of these two desmin paralogs

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