CRISPR-Engineered hiPSC-derived Cardiomyocytes Reveal Divergent Responses to Loss and Defective Processing of A-type Lamins
A-type lamins are critical for nuclear integrity and mechanotransduction in cardiomyocytes, and their disruption is a major cause of inherited cardiomyopathy. To compare the consequences of lamin A/C loss versus defective lamin A maturation, we generated CRISPR/Cas9-edited hiPSC lines lacking LMNA or ZMPSTE24 and differentiated them into iPSC-derived cardiomyocytes. LMNA knockout caused progressive nuclear deformation, loss of culture stability, and contractile vulnerability in iCM. ZMPSTE24 knockout led to subtler nuclear abnormalities and reduced calcium transient activity, temporally correlating with prelamin A accrual. Transcriptomics profiling revealed aberrant mechanical responses in both LMNA and ZMPSTE24 bi-allelic knockouts as well as unique perturbations in inflammatory signaling and epigenetic pathways. Interestingly, both knockout models shared a marked defect in proteostasis, as confirmed by reduced proteasome activity. Together, these results show that loss of lamin A/C and accumulation of prelamin A trigger both converging and distinct cardiomyocyte stress responses. In addition, the newly generated models offer an attractive platform to study lamin-associated cardiomyopathy and its therapeutic targeting.