B. Lefeuvre et al., INNERVATION REGULATES MYOSIN HEAVY-CHAIN ISOFORM EXPRESSION IN DEVELOPING SKELETAL-MUSCLE FIBERS, Mechanisms of development, 58(1-2), 1996, pp. 115-127
The influence of innervation on primary and secondary myogenesis and i
ts relation to fiber type diversity were investigated in two specific
wing muscles of quail embryo, the posterior (PLD) and anterior latissi
mus dorsi (ALD). In the adult, these muscles are composed almost exclu
sively of pure populations of fast and slow fibers, respectively. When
slow ALD and fast PLD muscles developed in ovo in an aneurogenic envi
ronment induced after neural tube ablation, the cardiac ventricular my
osin heavy chain (MHC) isoform was not expressed. The adult slow MHC i
soform, SM2, appeared by embryonic day 7 (ED 7) in normal innervated s
low ALD but was not expressed in denervated muscle. Analysis of in vit
ro differentiation of myoblasts from fast PLD and slow ALD muscles iso
lated from ED 7 control and neuralectomized quail embryos showed no fu
ndamental differences in the pattern of MHC isoform expression. Newly
differentiated fibers accumulated cardiac ventricular, embryonic fast,
slow SM1 and SM3 MHC isoforms. Nevertheless, the expression of slow S
M2 isoform in myotubes formed from slow ALD myoblasts only occurred wh
en myoblasts were cultured in the presence of embryonic spinal cord. O
ur studies demonstrate that the neural tube influences primary as well
as secondary myotube differentiation in avian forelimb and facilitate
s the expression of different MHC, particularly slow SM2 MHC gene expr
ession in slow myoblasts.