The LMNA p.R541C mutation causes dilated cardiomyopathy in human and mice.

Dilated cardiomyopathy (DCM) is a major cause of heart failure. LMNA variants contribute to 6-10% DCM cases, but the underlying mechanisms remain incompletely understood. Here, we reported two patients carrying the LMNA c.1621C > T/ p.R541C variant and generated a knock-in mouse model (LmnaRC) to study the role of this variant in DCM pathogenesis. We found LmnaRC/RC mice exhibited ventricular dilation and reduced systolic functions at 6 months after birth. The LmnaRC/RC cardiomyocytes increased in size but no nuclear morphology defects were detected. Transcriptomic and microscopic analyses revealed suppressed gene expression and perturbed ultrastructure in LmnaRC/RC mitochondria. These defects were associated with increased heterochromatin structures and epigenetic markers including H3K9me2/3. Together, these data implied that the LMNA c.1621C > T/ p.R541C variant enhanced heterochromatic gene suppression and disrupted mitochondria functions as a cause of DCM.