Multiple transcription factors mediating the expressional regulation of myosin heavy chain gene involved in the indeterminate muscle growth of fish

Torafugu myosin heavy chain gene, MYHM2528–1, is specifically expressed in neonatal slow and fast muscle fibers, suggesting its functional role in indeterminate muscle growth in fish. However, the transcriptional regulatory mechanisms of MYHM2528–1 involved in indeterminate muscle growth in fish remained unknown. We previously isolated a 2100 bp 5′- flanking sequence of torafugu MYHM2528–1 that showed sufficient promoter activity to allow specific gene expression in neonatal muscle fibers of zebrafish. Here, we examined the cis-regulatory mechanism of 2100 bp 5′-flanking region of torafugu MYHM2528–1 using deletion-mutation analysis in zebrafish embryo. We discovered that myoblast determining factor (MyoD) binding elements play a key role and participate in the transcriptional regulation of MYHM2528–1 expression in zebrafish embryos. We further discovered that paired box protein (Pax3) are required for promoting MYHM2528–1 expression and myocyte enhancer factor-2 (MEF2) binding sites participate in the transcriptional regulation of MYHM2528–1 expression in slow/fast skeletal muscles. Our study also confirmed that the nuclear factor of activated T-cell (NFAT) binding sites take part in the transcriptional regulation of MYHM2528–1 expression in slow and fast muscles fiber in relation to indeterminate muscle growth. These results obviously confirmed that multiple cis-elements in the 5′-flanking region of MYHM2528–1 function in the transcriptional regulation of its expression. •In vivo reporter assay was used to discover the transcriptional regulation of torafugu MYHM2528-1 in indeterminate growth in fish•2.1 kb of MYHM2528-1 contained the essential cis-elements required for the neonatal muscle-fiber specific expression•Our study confirmed that MyoD and MEF2 binding sites participate in the transcriptional regulation of MYHM2528-1 expression•Study also confirmed that Pax3 and NFAT binding sites involved in the transcriptional regulation of MYHM2528-1 in indeterminate growth of fish.