The R120G Knock-in Mutation in αB-Crystallin is Insufficient to Induce Cardiomyopathy in Mice

Abstract

Alpha B-crystallin (CryAB) is a small heat-shock protein highly expressed in cardiac tissue, where it functions as a molecular chaperone that helps prevent protein aggregation, particularly under stress conditions. A missense mutation in CryAB (R120G) causes autosomal dominant cardiomyopathy in humans and is characterized by extensive protein aggregation in cardiomyocytes. To better understand the pathogenic mechanisms underlying CryABR120G-associated cardiomyopathy, appropriate in vivo models are essential. Genetic mouse models are valuable tools for investigating disease pathogenesis and evaluating potential therapeutic strategies. In this study, we characterized a homozygous CryABR120G knock-in (KI) mouse model to assess the impact of this mutation on cardiac function. CryABR120G KI mice exhibited no overt changes in cardiac structure and function up to 12 months of age, with minimal changes in cardiac and proteotoxic stress markers, except for an increased atrial natriuretic peptide expression at 12 months. Protein quality control pathways remained largely unchanged. Although mitochondrial respiration was normal in young CryABR120G KI mice, it was reduced at 12 months of age. Despite the presence of insoluble protein aggregates, homozygous CryABR120G KI mice did not develop overt structural or functional cardiomyopathy through 12 months of age. These findings indicate that, within the age range examined, the CryABR120G KI model does not reproduce the overt cardiomyopathic phenotype associated with the CRYABR120G mutation in patients.