Molecular characterization and expression patterns of myogenin in compensatory growth of Megalobrama amblycephala

Abstract Myogenin (myog) is a muscle-specific basic helix–loop–helix (bHLH) transcription factor that plays an essential role in regulating skeletal muscle development and growth. To investigate molecular characterization of myog and the effect of starvation/refeeding on the gene expression, we isolated the myog cDNA sequence and analyzed the expression patterns using quantitative real-time polymerase chain reaction in Megalobrama amblycephala . Sequence analysis indicated that M. amblycephala myog shared an analogous structure with the highly conserved His/Cys-rich, bHLH and C-terminal helix III domains with other vertebrates. Sequence alignment and phylogenetic tree showed that M. amblycephala myog had the highest identity with the homologues of Ctenopharyngodon idella and Cyprinus carpio . Spatio-temporal expression patterns revealed that myog mRNA levels at the segmentation period and 12 h post-hatching (hph) were significantly higher than at other development stages ( P myog expression level was predominantly observed in white muscle compared with the other types of muscle. Fish body weight continuously decreased during 21-day starvation and then significantly increased after 7 days of refeeding and reached the similar level to the control at 21 days of refeeding, indicating that the pattern of complete compensatory growth possibly occurred in M. amblycephala ; meanwhile, the relative somatic growth rate after refeeding was also dramatically higher than the control group. In addition, the myog expression decreased during 21 days of starvation and then exhibited a strong rebound effect after 7 days of refeeding and subsequently declined gradually to the control level by 21 days of refeeding.