Too light to be essential? Insights from FHC-related mutations in essential myosin light chains

This editorial refers to ‘Mutations of ventricular essential myosin light chain disturb myosin binding and sarcomeric sorting’ by J. Lossie et al ., pp. 390–396, this issue. Familial hypertrophic cardiomyopathy (FHC) is an autosomal dominant disease affecting one in 500 individuals that is characterized by left ventricular hypertrophy, interstitial fibrosis, and myocyte disarray. Moreover, the disease is associated with arrhythmias and may progress to heart failure or sudden cardiac death, especially in young adults.1 Clinical diagnosis and genetic analysis of FHC have been performed over the past two decades, but the underlying pathomechanisms are still not entirely understood. FHC is a disease of the sarcomere caused by numerous mutations in proteins of the contractile machinery. Among them are the thin filament proteins troponin I and T; yet, the majority of FHC-related mutations have been identified in the genes of myosin heavy chain (MYH or MHC) and MHC-associated proteins such as myosin-binding protein C or myosin light chains.1,2While the role of MHC in driving muscle contraction is well established, less is known about the physiological role of MHC-associated proteins. Studying FHC-related mutations in myosin-binding proteins therefore provides a chance to not only unravel the pathomechanisms of inherited cardiomyopathies but also to improve our basic understanding of the functional role of these proteins in the sarcomeric setting.Lossie et al. …