 Basic helix-loop-helix (bHLH) transcription factors, MyoD, Myf5, myogenin, and MRF4 are critical to its formation.MyoD and Myf5 enable the differentiation of myogenic progenitors into myoblasts, followed by myogenin, which differentiates the myoblast into myotubes.MRF4 is important for blocking the transcription of muscle-specific promoters, enabling skeletal muscle progenitors to grow and proliferate before differentiating.