Abstract Body: Background: Congenital heart defects (CHDs) are the most common type of birth defect, yet the etiology of most CHDs are unknown. A major genetic risk factor for CHD is 22q11.2 deletion syndrome (22q11.2DS), a multisystem chromosomal microdeletion disorder where ~75% of patients present with CHD. SLC25A1 is a gene found within the 22q11.2DS microdeletion region that encodes for the mitochondrial citrate carrier, an inner membrane transporter that regulates intracellular citrate compartmentalization. Through this role, SLC25A1 is thought to contribute to cytosolic acetyl-CoA availability, and processes like protein acetylation and the epigenetic regulation of gene expression. We have previously found that SLC25A1 is a central gene contributing to the neurodevelopmental presentation of 22q11.2DS and importantly, neuronal mitochondrial function. Because the heart, like the brain, is highly reliant on energy derived from mitochondria, and the developing heart must undergo metabolic maturation whereby metabolism is reprogrammed from primary reliance on glycolysis towards mitochondrial oxidative metabolism, we hypothesized that SLC25A1 plays a key role in the metabolic maturation that is required for proper cardiac development.

Objective: Here, we studied the role of Slc25a1 in the developing heart to examine the link between mitochondria and cardiac morphogenesis.

Methods and Results: By studying mice with the systemic knockout of SLC25A1, we discovered that Slc25a1 null embryos displayed impaired growth, cardiac malformations, mitochondrial ultrastructural defects and impaired mitochondrial oxygen consumption. Transcriptomics analyses of metabolism-related genes revealed that Slc25a1deletion causes widespread alterations in metabolic gene expression. Further, metabolic modelling predicted that loss of SLC25A1 downregulates oxidative phosphorylation, while increasing reliance on glucose. Finally, we found that loss of SLC25A1 decreases cardiac H3K9 acetylation levels at promoter regions of dysregulated metabolic genes. Mechanistically, SLC25A1 may regulating mitochondrial function and metabolism through epigenetic control of gene expression to promote metabolic remodeling in the developing heart.

Conclusions: Our work suggests that SLC25A1 as an an important mitochondrial regulator of gene expression in the developing heart. Importantly, it positions SLC25A1 as a novel mitochondrial regulator of ventricular morphogenesis as well as cardiac metabolic maturation.