TY - JOUR
T1 - Altered myofilament function depresses force generation in patients with nebulin-based nemaline myopathy (NEM2)
AU - Ottenheijm, Coen A.C.
AU - Hooijman, Pleuni
AU - DeChene, Elizabeth T.
AU - Stienen, Ger J.
AU - Beggs, Alan H.
AU - Granzier, Henk
N1 - Funding Information:
Thanks to Danielle Pier and Hal Schneider for nebulin gene mutation detection and for Eric Rogers for gel and Western blot analysis. Special thanks to all the patients, their family members, and referring physicians and health care providers, particularly genetic counselor Joanne Taylor, MS CGC, without whom this study would not have been possible. This work was supported by a VENI grant from the Dutch Organization for Scientific Research to C.A.C.O, NIH RO1 AR053897 to H.G., NIH R01 AR044345, MDA3971 from the Muscular Dystrophy Association (USA) , the Lee and Penny Anderson Family Foundation , and the Joshua Frase Foundation to A.H.B. DNA sequencing was performed in the MRDDRC Molecular Genetics Core Facility at Children’s Hospital Boston supported by NIH-P30-HD18655.
PY - 2010/5
Y1 - 2010/5
N2 - Nemaline myopathy (NM), the most common non-dystrophic congenital myopathy, is clinically characterized by muscle weakness. However, the mechanisms underlying this weakness are poorly understood. Here, we studied the contractile phenotype of skeletal muscle from NM patients with nebulin mutations (NEM2). SDS-PAGE and Western blotting studies revealed markedly reduced nebulin protein levels in muscle from NM patients, whereas levels of other thin filament-based proteins were not significantly altered. Muscle mechanics studies indicated significantly reduced calcium sensitivity of force generation in NM muscle fibers compared to control fibers. In addition, we found slower rate constant of force redevelopment, as well as increased tension cost, in NM compared to control fibers, indicating that in NM muscle the rate of cross-bridge attachment is reduced, whereas the rate of cross-bridge detachment is increased. The resulting reduced fraction of force generating cross-bridges is expected to greatly impair the force generating capacity of muscle from NM patients. Thus, the present study provides important novel insights into the pathogenesis of muscle weakness in nebulin-based NM.
AB - Nemaline myopathy (NM), the most common non-dystrophic congenital myopathy, is clinically characterized by muscle weakness. However, the mechanisms underlying this weakness are poorly understood. Here, we studied the contractile phenotype of skeletal muscle from NM patients with nebulin mutations (NEM2). SDS-PAGE and Western blotting studies revealed markedly reduced nebulin protein levels in muscle from NM patients, whereas levels of other thin filament-based proteins were not significantly altered. Muscle mechanics studies indicated significantly reduced calcium sensitivity of force generation in NM muscle fibers compared to control fibers. In addition, we found slower rate constant of force redevelopment, as well as increased tension cost, in NM compared to control fibers, indicating that in NM muscle the rate of cross-bridge attachment is reduced, whereas the rate of cross-bridge detachment is increased. The resulting reduced fraction of force generating cross-bridges is expected to greatly impair the force generating capacity of muscle from NM patients. Thus, the present study provides important novel insights into the pathogenesis of muscle weakness in nebulin-based NM.
KW - Cross-bridge cycling
KW - Muscle weakness
KW - Nebulin
KW - Nemaline myopathy
KW - Thin filament length
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U2 - 10.1016/j.jsb.2009.11.013
DO - 10.1016/j.jsb.2009.11.013
M3 - Article
C2 - 19944167
AN - SCOPUS:77951974414
SN - 1047-8477
VL - 170
SP - 334
EP - 343
JO - Journal of Structural Biology
JF - Journal of Structural Biology
IS - 2
ER -