Characterization of a zebrafish (Danio rerio) desmin cDNA: an early molecular marker of myogenesis

Desmin is a muscle-specific protein and a constitutive subunit of the inter mediate filaments (IF) in skeletal, cardiac and smooth muscles. It is an ea rly marker of skeletal muscle myogenesis. We have characterized a clone of desmin cDNA from an embryonic zebrafish (Danio rerio) cDNA library. The ful l-length cDNA comprised 1798 nucleotides, encoding a protein of 473 amino a cids. The predicted amino acid sequence of the zebrafish desmin shares a hi gh degree of similarity to other vertebrate desmins, but also contains a se quence at the carboxyl terminal of the tail domain that is unique to the ze brafish. It carries many features which are distinctive of IF subunit prote ins. These include the T/SSYRRXF/Y motif in the head domain, and the interm ediate filament signature consensus, [I/V]-X-[T/A/C/I]-Y-[R/K/H]-X-[L/M]-L- [D/E], located in the carboxyl terminus of the central helical rod. Unlike other 3' UTR sequences, the 3' UTR of the zebrafish cDNA sequence has two C AYUG elements flanking a single polyadenylation site. The temporal and spat ial expression patterns of desmin mRNA during early zebrafish development w ere studied. The onset of desmin expression occurred at the 1-3 somite stag e (11 hpf). It increased throughout somitogenesis, with maximum expression at the Prim-6 stage (25 hpf), and decreasing expression towards the protrud ing-mouth stage (72 hpf). Desmin mRNA was initially localised exclusively t o the somites, but was subsequently also detected in other musculature in t he developing heart and fins. The onset of expression and the spatial local ization of desmin mRNA in the zebrafish coincides with that reported for My oD and myogenin.