The MADS domain containing transcription factor cMef2a is expressed in heart and skeletal muscle during embryonic chick development

Muscle enhancer factor 2 (MEF2) proteins are important transcription factor s for muscle-specific gene activation. Four family members are known in mam mals, referred to as MEF2A, MEF2B, MEF2C, and MEF2D. Here we report the iso lation and expression pattern of the chick Mef2a gene (cMef2a). cMef2a expr ession starts in precardiac mesoderm of HH stage 8 embryos. During further embryonic development expression continues in the heart tube and later in a trium and ventricle. A second cMef2a expression domain appears in somites o f stage 13 embryos. Semitic cMef2a expression is limited to the myotome and is not found in newly formed somites until the muscle-specific transcripti on factors MyoD and myogenein are present. This suggests that activation of the cMef2a gene in skeletal muscle is dependent on these basic helix-loop- helix transcription factors. cMcf2a expression in heart and skeletal muscle continues into adulthood when it is also seen in intestinal mesenchyme and in brain.