Characterization of the myostatin gene and a linked microsatellite marker in shi drum ( Umbrina cirrosa, Sciaenidae)

We report the characterisation of the gene coding for myostatin (or growth differentiation factor 8, GDF8) in the shi drum, Umbrina cirrosa. Because of its relevant role in muscle growth regulation, GDF8 is an important candidate locus for improvement of animal production. RT-PCR and RACE protocols were used to obtain the full-length GDF8 cDNA sequence. The complete cDNA was 2086-bp long, containing an open reading frame of 376 amino acids. Similarity searches on protein databases give highest values with zebrafish GDF8 (291 identical residues over 376 compared amino acid positions), and other vertebrate GDF8s. This evidence suggests that the putative protein isolated is the GDF8 homologue in the shi drum. At the genomic level, the position and complete sequence was determined for two introns. While intron–exon boundaries were conserved compared to mammalian GDF8 genes, both introns were considerably smaller, of 342 and 735 bp, respectively. In the 3′ noncoding region of the cDNA, a microsatellite repeat (AC 29) was present. This repeat region was examined at the genomic level, and its size polymorphism assessed in a preliminary way, revealing four distinct alleles. This microsatellite locus might represent a useful polymorphic marker for studying phenotype/genotype association. We also examined the pattern of expression of sdGDF8, which is wider in the shi drum compared to other vertebrates, suggesting possible additional functions of myostatin in the teleost fish. These results should be taken into account if null mutants for GDF8 in this species are to be produced, as they might have a more severe phenotype than observed in mammals.