Recruitment of coactivators is required for ligand-induced transcriptional activation of gene expression by nuclear receptors.Thyroid hormone receptor associated protein complex(TRAP)is the most important coactivator of thyroid hormone receptors(TRs)and enhance gene transcription regulated by TRs.TRAP150 has been identified as a subunit of TRAP and activate mRNA splicing in vivo.However,the function of TRAP150 in development is still unclear.Zebrafish TRAP150 was specific expressed in muscle during early embryonic development.Moreover,TRAP150 and MyoD are co-expressed in the myotomes with overlap patterns.Over-expressed TRAP150 can up-regulate MyoD expression,while knock-down can down-regulate MyoD expression in fast muscle.Also knock-down TRAP150 affected the organization of fast muscle fibers.So,the TRAP150 might be a positive upstream regulator of MyoD during fast muscle development.