Loss of the mitochondrial citrate carrier,Slc25a1/CICdisrupts embryogenesisvia2-Hydroxyglutarate

ABSTRACT Biallelic germline mutations in the SLC25A1 gene lead to combined D/L-2-hydroxyglutaric aciduria (D/L-2HGA), a fatal systemic disease uniquely characterized by the accumulation of both enantiomers of 2-hydroxyglutaric acid (2HG). How SLC25A1 deficiency contributes to D/L-2HGA and the role played by 2HG is unclear and no therapy exists. Both enantiomers act as oncometabolites, but their activities in normal tissues remain understudied. Here we show that mice lacking both SLC25A1 alleles exhibit developmental abnormalities that mirror human D/L-2HGA. SLC25A1 deficient cells undergo premature mitochondrial dysfunction associated senescence, suggesting that loss of proliferative capacity underlies the pathogenesis of D/L-2HGA. Remarkably, D- and L-2HG directly induce mitochondrial respiratory deficit and treatment of zebrafish embryos with the combination of D- and L-2HG phenocopies SLC25A1 loss, leading to developmental abnormalities in an additive fashion relative to either enantiomer alone. Metabolic analyses demonstrated that loss of SLC25A1 leads to global remodeling towards glutamine metabolism, with glutamine serving as a source for 2HG synthesis. Therefore, we explored the pre-clinical relevance of phenylbutyrate, an FDA-approved drug that reduces the blood glutamine levels, and found that it reduces 2HG accumulation reversing metabolic abnormalities in patients affected by D/L-2HGA. These results reveal pathogenic and growth suppressive activities of 2HG in the context of SLC25A1 deficiency and expose metabolic vulnerabilities for the clinical management of this disease.