Table 2.

Protein and mRNA expression of conventional MHC isoforms in young (8 month) and old (26 month) muscles with different origins and functions. Extraocular (EOM); Masseter (M); Posterior digastric (PD); Geniohyoid (GH); Styloglossus (SG) and Biceps brachii (BB).

Function	BRANCHIAL ARCH						SOMITIC
	Eye		Mastication				Mastication				Locomotion
	EOM		M		PD		GH		SG		BB		P
	Vision		Jaw Closer		Jaw Opener		Hyoid Elevation		Tongue Retrusion		Stability/Locomotion		Stability/Locomotion
MHC composition by protein analysis
	EOM		M		PD		GH		SG		BB		P
	Y	O	Y	O	Y	O	Y	O	Y	O	Y	O	Y	O
IIb	47%±5%	56%±7%	51%±14%	48%±9%	35%±10%	33%±5%	49%±5%	50%±7%	29%±5%	25%±6%	61%±7%	53%±12%	60%±13%	62%±11%
IIx	27%±3%	27%±6%	35%±8%	37%±5%	39%±5%	41%±3%	34%±4%	34%±5%	43%±6%	43%±4%	26%±4%	31%±7%	29%±8%	24%±6%
IIa	17%±4%	12%±3%	13%±7%	14%±5%	20%±6%	23%±3%	15%±2%	16%±3%	27%±4%	32%±2%	10%±4%	13%±5%	9%±5%	10%±5%
I	9%±5%	6%±4%	1%±1%	1%±1%	6%±3%	3%±2%	2%±2%	0%±1%	1%±2%	1%±1%	3%±1%	3%±1%	2%±2%	3%±2%
“Fast”			0.63	0.26	−0.26	−0.65	0.67	0.23	−1.27	−1.36	1.22	0.62
Factor Score			0.457		−0.466		0.448		−1.309		0.922
MHC composition by mRNA analysis
	EOM		M		PD		GH		SG		BB
	Y(n=1)	O(n=1)	Y	O	Y	O	Y	O	Y	O	Y	O
IIb	46%	59%	59%±16%	62%±6%	36%±6%	26%±9%	69%±12%	63%±6%	33%±10%	44%±12%	71%±9%	68%24%
IIx	30%	21%	39%±14%	37%±7%	46%±6%	42%±9%	24%±10%	27%±14%	52%±10%	42%±9%	21%±5%	28%±19%
IIa	12%	5%	2%±2%	1%±1%	11%±5%	13%±4%	8%±2%	8%±2%	14%±2%	13%±2%	5%±3%	3%±3%
I	12%	15%	0%±0%	0%±1%	7%±3%	20%±13%	0%±0%	2%±1%	2%±2%	2%±2%	3%±2%	2%±2%