Dynamic expression of tgf-β2, tgf-β3 and inhibin βA during muscle growth resumption and satellite cell differentiation in rainbow trout (Oncorhynchus mykiss)

Members of the TGF-beta superfamily are involved in numerous cell functions; however, except for myostatin, their roles in the regulation of muscle growth in fish are completely unknown. We measured tgf-beta 1, tgf-beta 2, tgf-beta 3, inhibin beta A (inh) and follistatin (fst) gene expression during muscle growth recovery following a fasting period. We observed that tgf-beta 1a and tgf-beta 2 expression were quickly down-regulated after refeeding and that tgf-beta 3 reached its highest level of expression 7 days post-refeeding, mirroring myogenin expression. Inh beta A1 mRNA levels decreased sharply after refeeding, in contrast to fst b2 expression, which peaked at day 2. No significant modification of expression was observed for tgf-beta 1a, tgf-beta 1b, tgf-beta 1c and tgf-beta 6 during refeeding. In vitro, tgf-beta 2 and inh beta A1 expression decreased during the differentiation of satellite cells, whereas tgf-beta 3 expression increased following the same pattern as myogenin. Surprisingly, fst b1 and fst b2 expression decreased during differentiation, whereas no variation was observed in 1st a1 and fst a2 expression levels. In vitro analyses also indicated that IGF1 treatment up-regulated tgf-beta 3, inh beta A1 and myogenin expression, and that MSTN treatment increased fst b1 and fst b2 expression. In conclusion, we showed that the expression of tgf-beta 2, tgf-beta 3 and inh beta A1 is dynamically regulated during muscle growth resumption and satellite cell differentiation, strongly suggesting that these genes have a role in the regulation of muscle growth. (C) 2014 Elsevier Inc. All rights reserved.