Fiber type composition of the sternomastoid and diaphragm muscles of dystrophin-deficient mdx mice.
The muscle fiber phenotype is mainly determined by motoneuron innervation and changes in neuromuscular interaction alter the muscle fiber type. In dystrophin-deficient mdx mice, changes in the molecular assembly of the neuromuscular junction and in nerve terminal sprouting occur in the sternomastoid (STN) muscle during early stages of the disease. In this study, we were interested to see whether early changes in neuromuscular assembly are correlated with alterations in fiber type in dystrophic STN at 2 months of age. A predominance of hybrid fast myofibers (about 52% type IIDB) was observed in control (C57Bl/10) STN. In mdx muscle, the lack of dystrophin did not change this profile (about 54% hybrid type IIDB). Pure fast type IID fibers predominated in normal and dystrophic diaphragm (DIA; about 39% in control and 30% in mdx muscle) and a population of slow Type I fibers was also present (about 10% in control and 13% in mdx muscle). In conclusion, early changes in neuromuscular assembly do not affect the fiber type composition of dystrophic STN. In contrast to the pure fast fibers of the more affected DIA, the hybrid phenotype of the STN may permit dynamic adaptations during progression of the disease.
Guido
Anderson Neri
AN
Departamento de Anatomia, Biologia Celular, Fisiologia e Biofísica, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, São Paulo, Brazil.
Campos
Gerson Eduardo Rocha
GE
Neto
Humberto Santo
HS
Marques
Maria Julia
MJ
Minatel
Elaine
E
D000222:Adaptation, Physiological; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D003964:Diaphragm / Q000166:cytology; D016189:Dystrophin / Q000172:deficiency* / Q000235:genetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018656:Muscle Fibers, Fast-Twitch / Q000166:cytology* / Q000201:enzymology; D018657:Muscle Fibers, Slow-Twitch / Q000166:cytology* / Q000201:enzymology
D016189:Dystrophin; D000251:Adenosine Triphosphatases