Journal
MUSCLE & NERVE
Volume 46, Issue 4, Pages 588-591Publisher
WILEY
DOI: 10.1002/mus.23463
Keywords
function; muscle damage; myotubular myopathy; myotubularin; strength; stretch
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Funding
- NIAMS NIH HHS [R01 AR044345] Funding Source: Medline
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Introduction: We established a colony of dogs that harbor an X-linked MTM1 missense mutation. Muscle from affected male dogs exhibits reduction and altered localization of the MTM1 gene product, myotubularin, and provides a model analogous to X-linked myotubular myopathy (XLMTM). Methods: We studied hindlimb muscle function in age-matched canine XLMTM genotypes between ages 9 and 18 weeks. Results: By the end of the study, affected dogs produce only similar to 15% of the torque generated by normals or carriers (0.023 +/- 0.005 vs. 0.152 +/- 0.007 and 0.154 +/- 0.003 N-m/kg body mass, respectively, P < 0.05) and are too weak to stand unassisted. At this age, XLMTM dogs also demonstrate an abnormally low twitch: tetanus ratio, a right-shifted torque-frequency relationship and an increase in torque during repetitive stimulation (P < 0.05). Conclusions: We hypothesize that muscle weakness results from impaired excitation-contraction (E-C) coupling. Interventions that improve E-C coupling might be translated from the XLMTM dog model to patients. Muscle Nerve 46: 588-591, 2012
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