MyoD

MyoD is a protein with a key role in regulating muscle differentiation. MyoD belongs to a family of proteins known as myogenic regulatory factors (MRFs). These bHLH (basic helix loop helix) transcription factors act sequentially in myogenic differentiation. MRF family members include MyoD, Myf5, myogenin, and MRF4 (Myf6).

MyoD is one of the earliest markers of myogenic commitment. MyoD is expressed in activated satellite cells, but not in quiescent satellite cells. Although MyoD marks myoblast commitment, muscle development is not dramatically ablated in mouse mutants lacking the MyoD gene. This is likely to be due to functional redundancy from Myf5.