Genes regulating the growth of myotomal muscle in teleost fish.

Postembryonic muscle growth in fish differs from that in mammals in that new muscle fibres continue to be produced throughout much of the life cycle. Growth involves the proliferation of a population of myogenic progenitor cells showing varying degrees of commitment to terminal differentiation. Muscle fibre recruitment and hypertrophy are independently regulated during growth by a wide range of extrinsic (temperature, photoperiod, feeding regime) and intrinsic factors (genotype, sexual maturation state). In some species egg incubation temperature has long lasting effects on the number of muscle fibres recruited during subsequent stages of the life cycle. This suggests that the commitment of the myogenic progenitor cells destined to participate in fibre recruitment and hypertrophy is decided relatively early in development. Current knowledge about the structure and function of genes regulating postembryonic muscle growth in teleosts is reviewed.