| 1. |
- Ochala, Julien, et al.
(författare)
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Disrupted myosin cross-bridge cycling kinetics triggers muscle weakness in nebulin-related myopathy
- 2011
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Ingår i: The FASEB Journal. - : Wiley. - 0892-6638 .- 1530-6860. ; 25:6, s. 1903-1913
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Tidskriftsartikel (refereegranskat)abstract
- Nebulin is a giant protein expressed at high levels in skeletal muscle. Mutations in the nebulin gene (NEB) lead to muscle weakness and various congenital myopathies. Despite increasing clinical and scientific interest, the pathogenesis of weakness remains unknown. The present study, therefore, aims at unraveling the underlying molecular mechanisms. Hence, we recorded and analyzed the mechanics as well as the X-ray diffraction patterns of human membrane-permeabilized single muscle fibers expressing nebulin mutations. Results demonstrated that, during contraction, the cycling rate of myosin heads attaching to actin is dramatically perturbed, causing a reduction in the fraction of myosin-actin interactions in the strong binding state. This phenomenon prevents complete thin-filament activation, more especially proper and full tropomyosin movement, further limiting additional binding of myosin cross-bridges. At the cell level, this reduces the force-generating capacity and, overall, provokes muscle weakness. To reverse such a negative cascade of events, future potential therapeutic interventions should, therefore, focus on the triggering component, the altered myosin cross-bridge cycling kinetics.
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| 2. |
- Wallgren-Pettersson, Carina, et al.
(författare)
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Distal myopathy caused by homozygous missense mutations in the nebulin gene
- 2007
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Ingår i: Brain. - : Oxford University Press (OUP). - 0006-8950 .- 1460-2156. ; 130:Pt 6, s. 1465-1476
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Tidskriftsartikel (refereegranskat)abstract
- We describe a novel, recessively inherited distal myopathy caused by homozygous missense mutations in the nebulin gene (NEB), in which other combinations of mutations are known to cause nemaline (rod) myopathy (NM). Two different missense mutations were identified in homozygous form in seven Finnish patients from four unrelated families with childhood or adult-onset foot drop. Both mutations, when combined in compound heterozygous form with more disruptive mutations in NEB, are known to cause NM. Hitherto, no patients with NM have been found to have two missense mutations in NEB. Muscle weakness predominantly affected ankle dorsiflexors, finger extensors and neck flexors, a distribution different both from the patterns of weakness seen in NM caused by NEB mutations, and those of the known recessively inherited distal myopathies. Singleton cases need to be distinguished from the Laing type of distal myopathy. Histologically, this myopathy differs from NM in that nemaline bodies were not detectable with routine light microscopy, and they were inconspicuous or absent even with electron microscopy. Rimmed vacuoles, commonly seen in other distal myopathies, were not a feature. We conclude that homozygous missense mutations in NEB cause a novel distal myopathy, predominantly involving lower leg extensor muscles, finger extensors and neck flexors.
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