Table 1.

Summary of studies on ERK1/2 signaling and myofiber size and specification discussed in this review^a.

Study [Reference]	Experimental Model	Manipulation of ERK1/2 pathway	Major Findings
[5]	C2C12 cells	Pharmacological block of ERK1/2 activation	Reduced myotube size
[6]	Mouse	Muscle conditional, loss-of-function Erk1/2 mutant. Focus on slow fibers	Dramatic fiber loss and atrophy. Marginal effect on fiber identity
[7]	Mouse	Muscle conditional, loss-of-function Erk1/2 mutant. Focus on fast fibers	Mild muscle fiber loss and atrophy. Marginal effect on fiber identity
[8]	Mouse	Muscle conditional, gain-of-function Mek1 mutant	No effect on fiber size. Fast-to-slow fiber switch
[9]	Rat	Electroporation of Ras constitutively-active (CA) & dominant-negative (DN) mutants Electrical stimulation of denervated SOL with slow/fast patterns	No effect on fiber size. MyHC-β/ slow expression: Induced with CARas; suppressed with DNRas ERK activation: strong with slow stimulation; weak with fast stimulation
[13]	C2C12 cells and mouse SOL	How ERK1/2 activation and calcineurin-NFATc1 regulate MyHC-β/ slow transcription	pERK1/2 enhances NFATc1 transcriptional activity
[10]	Rat and mouse	Electroporation of: CAERK2 MKP-1	Slow-to-fast fiber switch Fast-to-slow fiber switch
[12]	Rat	pERK1/2 levels vis-a-vis fiber type	High pERK1/2 linked to fast fibers

^aFor abbreviations see text