Functional characterization of a newly identified LMNA mutant in HL-1 cardiomyocytes

A novel mutation in the Lamin A/C gene (LMNA c.418_438dup) was detected in the index patient and in additional family members with diagnosis of arrhythmogenic right ventricular cardiomyopathy (ARVC) and history of sudden cardiac death. The functional characterization of this LMNA mutant was performed in cultured HL-1 cardiomyocytes expressing EGFP-tagged wild-type and mutated LMNA constructs and subjected to confocal microscopy analysis and hypoxic stress conditions in 100% N2 for 8h. Mutated LMNA was clearly expressed in aggregates of different sizes and not uniformly distributed along the nuclear envelope as WT LMNA. Moreover, the mutated LMNA variant causes perturbation in nuclear shape and Nuclear Pore Complexes organization. Of note, we observed that under hypoxic conditions nuclear envelopes expressing mutated LMNA become leaky, leading a nuclear fluorescent marker to escape into the cytoplasm. This indicates that, under cell stressing conditions, the nucleo-cytoplasmic compartmentalization is affected in cardiomyocytes expressing this LMNA mutation, inducing, as final fatal consequence, cell apoptosis. In conclusion, we not only open new avenues to gain more insights in the pathogenesis of ARVC and to conceive novel therapeutic strategies but we also shed lights on the role of nuclear Lamin A in the physio-pathology of cardiomyocytes.