Restoration of normal ultrastructure after expression of the alpha 1 subunit of the L-type Ca2+ channel in dysgenic myotubes.
Muscular dysgenesis (mdg) is a spontaneous mutation affecting the alpha 1 subunit of the skeletal L-type Ca2+ channel. mdg/mdg mice suffer from a skeletal muscle disease characterised by low levels of the slow Ca2+ current, lack of contractile activity, and immature organisation of skeletal muscle. Microinjections of a cDNA encoding alpha 1 into mutant myotubes restore excitation-contraction coupling. We checked here that dysgenic myotubes transfected with expression vectors, including a full-length alpha 1 cDNA, also recover normal ultrastructural features. Transfection of alpha 1 cDNA partially deleted on the 5' end leads to the recovery of a good structural organisation without any improvement in the mutant physiological phenotype. These results suggest that: (i) the proper expression of alpha 1 is required for the full muscle differentiation of muscular dysgenesis myotubes, and (ii) portions of the alpha 1 molecule may be involved in the structural organisation of a muscle fiber, independent of its known functional properties.
Seigneurin-Venin
S
S
Groupe de Biologie Developpement et Pathologie Neuromusculaire, U 153 INSERM, Paris, France.
Song
M
M
Pinçon-Raymond
M
M
Rieger
F
F
Garcia
L
L
D000818:Animals; D015220:Calcium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000235:genetics; D004558:Electric Stimulation; D015870:Gene Expression; D005822:Genetic Vectors; D051379:Mice; D008817:Mice, Mutant Strains; D008854:Microscopy, Electron; D009119:Muscle Contraction / Q000235:genetics / Q000502:physiology; D024510:Muscle Development; D009132:Muscles / Q000378:metabolism / Q000648:ultrastructure; D009135:Muscular Diseases / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D011487:Protein Conformation; D011817:Rabbits; D014162:Transfection
D015220:Calcium Channels; D018076:DNA, Complementary