2 research outputs found
Human skeletal myopathy myosin mutations disrupt myosin head sequestration
Myosin heavy chains encoded by MYH7 and MYH2 are abundant in human skeletal muscle and important for muscle contraction. However, it is unclear how mutations in these genes disrupt myosin structure and function leading to skeletal muscle myopathies termed myosinopathies. Here, we used multiple approaches to analyze the effects of common MYH7 and MYH2 mutations in the light meromyosin (LMM) region of myosin. Analyses of expressed and purified MYH7 and MYH2 LMM mutant proteins combined with in silico modeling showed that myosin coiled coil structure and packing of filaments in vitro are commonly disrupted. Using muscle biopsies from patients and fluorescent ATP analog chase protocols to estimate the proportion of myosin heads that were super-relaxed, together with x-ray diffraction measurements to estimate myosin head order, we found that basal myosin ATP consumption was increased and the myosin super-relaxed state was decreased in vivo. In addition, myofiber mechanics experiments to investigate contractile function showed that myofiber contractility was not affected. These findings indicate that the structural remodeling associated with LMM mutations induces a pathogenic state in which formation of shutdown heads is impaired, thus increasing myosin head ATP demand in the filaments, rather than affecting contractility. These key findings will help design future therapies for myosinopathies.</p
Immunohistochemical analysis of Tuba8 knockout.
<p><b>A,B.</b> Cerebellum, stained using the Tuba8 monoclonal (Bioserv). (A, control animal; B, knockout animal) Scale bar = 200 μm. Arrow in part A indicates stronger labelling of dendrites in control tissue. <b>C-E.</b> Testis stained using the Tuba8 monoclonal (Bioserv). (C, D, wild-type control, low and higher magnification respectively: C, scale bar = 200 μm; D, scale bar = 100 μm. E, knockout at low magnification. Arrow indicates strong Tuba8 presence peripheral to the nucleus. <b>F,G.</b> Staining for tyrosinated alpha tubulin. Control (F) and knockout (G) testis. Scale bar = 100 μm. <b>H,I.</b> Staining for acetylated alpha tubulin. Control (H) and knockout (I) testis. Scale bar = 100 μm</p