Abstract 18698: PCBP1 Regulates Alternative Splicing of Aars2 in Congenital Cardiomyopathy

Abstract

Rationale: Alanyl-transfer RNA synthetase 2 (AARS2) is a nuclear encoded mitochondrial tRNA synthetase that is responsible for charging of tRNA-Ala with alanine during mitochondrial translation. Homozygous or compound heterozygous mutations in the Aars2 gene, including those affecting its alternative splicing, are linked to congenital cardiomyopathy in humans. However, the underlying molecular mechanism of how Aars2 regulates heart development remains unknown. Hypothesis: The alternative splicing of Aars2 and its function is essential for cardiac development. Methods and Results: We found that alternative splicing of the Aars2 transcript is mediated by poly(rC) binding protein 1 (PCBP1), an RNA binding protein, through direct interaction. Cardiomyocyte-specific deletion of Pcbp1 in mice resulted in defects in heart development that are reminiscent of human congenital cardiac defects, including noncompaction cardiomyopathy and a disruption of the cardiomyocyte maturation trajectory. Loss of Pcbp1 led to an aberrant alternative splicing and a premature termination of Aars2 in cardiomyocytes. Therefore, Pcbp1 is critical for the expression and function of Aars2. Additionally, Aars2 mutant mice with exon-16 skipping recapitulated heart developmental defects observed in Pcbp1 mutant mice. Mechanistically, we found dysregulated gene and protein expression of the oxidative phosphorylation pathway in both Pcbp1 and Aars2 mutant hearts; these data provide further evidence that the infantile hypertrophic cardiomyopathy associated with the disorder oxidative phosphorylation defect type 8 (COXPD8) is mediated by Aars2. Conclusion: Our study therefore identifies Pcbp1 and Aars2 as critical regulators of heart development and provides important molecular insights into the role of disruptions in metabolism on congenital heart defects.