Generation of a mef2aa:EGFP transgenic zebrafish line that expresses EGFP in muscle cells.

Transgenesis is an important tool for exploring gene expression and function. The myocyte enhancer factor 2a (mef2a) gene encodes a member of the Mef2 protein family that is involved in vertebrate skeletal, cardiac, and smooth muscle development and differentiation during myogenesis. According to studies on human and animal models, mef2a is highly expressed in the heart and somites. To explore the potential of mef2a as a tool for selective labeling of muscle cells in living zebrafish embryos, we constructed a transgene mef2aa:EGFP to induce the expression of green fluorescent protein (GFP) under the control of mef2a promoter. A ~2-kb DNA fragment, upstream of the translational start site of mef2aa, was identified to drive muscle-specific expression of EGFP in zebrafish embryos. Interestingly, the cranial muscles, abductor muscle, and adductor muscle were clearly labeled with EGFP in the established line Tg(mef2aa:EGFP) ntu803 . In addition, we showed that mef2aa mRNA was highly present in adult zebrafish heart, but not the skeleton muscle, whereas it was expressed in both embryonic heart and myotome, suggesting that mef2a is vital to the function of adult heart in vertebrates.