Cloning and characterization of myogenic regulatory genes in three Ictalurid species

We report sequence, tissue expression and map-position data for myogenin, MYOD1, myostatin and follistatin in three Ictalurid catfish species: channel catfish (Ictalurus punctatus), blue catfish (I. furcatus) and white catfish (Ameiurus catus). These genes are involved in muscle growth and development in mammals and may play similar roles in catfish. Amino acid sequences were highly conserved among the three Ictalurid species (>95% identity), moderately conserved among catfish and zebrafish (approximately 80% identity), and less conserved among catfish and humans (approximately 40-60% identity) for all four genes. Gene structure (number of exons and introns and exon-intron boundaries) was conserved between catfish and other species for all genes. Myogenin and MYOD1 expression was limited to skeletal muscle in juvenile channel catfish, similar to expression patterns for these genes in other fish and mammalian species. Myostatin was expressed in a variety of tissues in juvenile channel catfish, a pattern common in other fish species but contrasting with data from mammals where myostatin is primarily expressed in skeletal muscle. Follistatin was expressed in juvenile catfish heart, testes and spleen. All four genes contained polymorphic microsatellite repeats in non-coding regions and linkage analysis based on inheritance of these microsatellite loci was used to place the genes on the channel catfish linkage map. Information provided in this study will be useful in further studies to determine the role these genes play in muscle growth and development in catfish.