Journal
ANNALS OF NEUROLOGY
Volume 61, Issue 6, Pages 552-561Publisher
WILEY-LISS
DOI: 10.1002/ana.21112
Keywords
-
Categories
Ask authors/readers for more resources
Objective: Mutations in ACTAI have been associated with a variety of changes in muscle histology that likely result from fundamental differences in the way that ACTAI mutations disrupt muscle function. Recently, we reported three patients with congenital fiber type disproportion (CFTD) caused by novel heterozygous missense mutations in ACTAI (D292V, L221P, P332S) with marked type I Fiber hypotrophy as the only pathological finding on muscle biopsy. We have investigated the basis for the histological differences between these CFTD patients and patients with ACTAI nernaline myopathy (NM). Methods and Results: Mass spectrometry and two-dimensional gel electrophoresis demonstrate that mutant actin accounts for 25 and 50% of alpha-skeletal actin in the skeletal muscle of patients with the P332S and D292V mutations, respectively, consistent with a dominan t- negative disease mechanism. In vitro motility studies indicate that abnormal interactions between actin and tropomyosin are the likely principal cause of muscle weakness for D292V, with tropomyosin stabilized in the switched off' position. Both the D292V and P322S CFTD mutations are associated with normal sarcomeric structure on electron microscopy, which is atypical for severe NM. In contrast, we found no clear difference between ACTAI mutations associated with NM and CFTD in tendency to polymerize or aggregate in C2C12 expression models. Interpretation: These data suggest that ACTAI CFTD mutations cause weakness by disrupting sarcomere function rather than structure. We raise the possibility that the presence or absence of structural disorganization when mutant actin incorporates into sarcomeres may be an important determinant of whether the histological patterns of CFTD or NM develop in ACTAI myopathy.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available