The homozygous variant c.245G > A/p.G82D in PNPLA2 is associated with arrhythmogenic cardiomyopathy phenotypic manifestations

Arrhythmogenic cardiomyopathy (ACM) is a familial cardiomyopathy featured by fibrofatty replacement of cardiomyocytes. Responsible genetic factors are not discernible in approximately one-third of ACM probands. To investigate this further, we performed whole genome sequencing in 14 mutation-negative ACM probands who underwent cardiac transplantation, and we identified one ACM proband with a rare homozygous missense variant in PNPLA2 (c.245G > A, p.G82D), a rate-limiting enzyme that hydrolyzes triglycerides into fatty acids and diacylglycerol. Bioinformatic analysis suggested that this missense variant may lead to loss of function and therefore impair lipid catabolism. Genetic screening in this proband's family also inferred that the homozygous variant cosegregated with disease. To validate the pathogenicity of this variant and confirm its association with ACM, we established a knockin mouse model carrying the orthologous human homozygous PNPLA2 variant. Interestingly, mice with the homozygous variant presented with arrhythmias and significant cardiac dysfunction at 12 weeks, whereas heterozygous mice were not affected. Moreover, those homozygous mice suffered sudden death and/or heart failure by the age of 14 weeks. Pathological examination showed that extensive lipogenesis in cardiomyocytes and cardiac fibrosis were prominent in the myocardium. Herein, our data demonstrated that the homozygous missense variant PNPLA2 (c.245G > A, p.G82D) associated with a recessive form of ACM.