The Basis of Muscle Regeneration

Table 1

Gene-targeting of factors involved in muscle development.

Gene knockout	Phenotype	References
Pax3	Absence of the limb and diaphragm muscles	[11–13]
Pax7	(i) Normal muscle development; (ii) Satellite cells are progressively lost postnatally because of apoptosis accompanied by cell cycle defects	[15, 16, 140]
MyoD	(i) Viable without obvious defects; (ii) Increased expression of myf-5; (iii) Normal expression of myogenin; (iv) Impaired regeneration	[182–184]
Myf5	(i) Muscle develops relatively normally; (ii) Normal expression of myogenin; (iii) Hypertrophy and fibrosis in adult life	[21, 29, 185–187]
Myogenin	(i) Die perinatally; (ii) Prevents muscle differentiation (despite the continued expression of MyoD); (iii) Reduced muscle	[19, 27, 28, 188, 189]
MRF4	(i) Variable viability dependent on targeting construct; (ii) No obvious muscle defects	[19, 20, 29, 190, 191]
MyoD and Myf5	(i) Die perinatally; (ii) Absence of skeletal muscle cells; (iii) Absence of myogenin; (iv) No markers of differentiation	[19, 26]