Myopathy-causing Actin Mutations Promote Defects in Serum Response Factor Signaling
Résumé
Mutations in the gene encoding alpha skeletal muscle actin (ACTA1) account for around 20% of patients with the muscular disorder nemaline myopathy. Nemaline myopathy is a muscular wasting disease similar to muscular dystrophy, but distinguished by deposits of actin and actin-associated proteins near the z-line of the sarcomere. Around 1/3 of the over 140 myopathy actin mutations have been characterized either biochemically or in cultured cells to determine their effects on the actin cytoskeleton. However, the actin defects causing myopathy are likely to be heterogeneous, with only a few common trends observed among the actin mutants, such as reduced polymerization capacity or inability to fold properly. Notably, the transcriptional programme regulated by serum-response factor, which is instrumental in muscle development and maintenance, is directly controlled by the balance of actin assembly and disassembly in cells. We explore the impact of myopathy mutations in actin on the control of the transcriptional response by serum response factor and we find that the majority of mutants examined have altered serum response factor signaling. We propose that altered serum response factor signaling could be a major factor in actin-based nemaline myopathy and that this area could be exploited to develop therapies for sufferers.
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