Table 1.

Muscle-specific factors during myogenic process

	Proliferation	Differentiation
Myogenic factors	PAX3/7, HDAC4, MEF2, IGFI	MRF (MyoD, MRF4, Myf5), MEF2, IGFII, Myogenin (MyoG), MHC, M-CK
Signaling pathway	MEK/ERK pathway	mTOR/PI3K/AKT pathway

Transition from proliferation to differentiation, which is accompanied by the down-regulation of Pax-7 and up-regulation of Myogenin and MRF-4 is dependent on both MyoD and the mTOR/PI3K/AKT pathway. MyoD and Myf5 are both considered markers of terminal com- mitment to muscle fate. Muscle-specific genes such as myosin heavy chain genes (MHC genes) and muscle creatine kinase (M-CK) are expressed in the last phase of this multi-regulated program.

AKT; RAC-beta serine/threonine-protein kinase, ERK; Extracellular-signal-regulated kinases, IGF; Insulin-like growth factor, IRS; Insulin receptor substrates, MEF2; Myocyte enhancer factor2, MEK; Mitogen/extracellular signal-regulated Kinase, MRF; Myogenic regulatory factors, mTOR; Mammalian target of rapamycin, MyoD; Myogenic differentiation, HDAC4; Histone deacetylase 4 and PI3K; Phospho- inositide 3-kinase.