Nuclear damage in mutant iPSC-derived cardiomyocytes is associated with impaired lamin localization to the nuclear envelope.

The gene encodes the nuclear envelope proteins Lamins A and C, which comprise a major part of the nuclear lamina, provide mechanical support to the nucleus, and participate in diverse intracellular signaling. mutations give rise to a collection of diseases called laminopathies, including dilated cardiomyopathy (-DCM) and muscular dystrophies. Although nuclear deformities are a hallmark of -DCM, the role of nuclear abnormalities in the pathogenesis of -DCM remains incompletely understood. Using induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) from mutant patients and healthy controls, we show that mutant iPSC-CM nuclei have altered shape or increased size compared to healthy control iPSC-CM nuclei. The mutation exhibiting the most severe nuclear deformities, R249Q, additionally caused reduced nuclear stiffness and increased nuclear fragility. Importantly, for all cell lines, the degree of nuclear abnormalities corresponded to the degree of Lamin A/C and Lamin B1 mislocalization from the nuclear envelope. The mislocalization was likely due to altered assembly of Lamin A/C. Collectively, these results point to the importance of correct lamin assembly at the nuclear envelope in providing mechanical stability to the nucleus and suggest that defects in nuclear lamina organization may contribute to the nuclear and cellular dysfunction in -DCM.