Ketogenic supplementations for AGC1 deficiency: investigating epigenetic and metabolic paths to recover proliferation and differentiation of OPCs and NSCs in vitro models

AGC1 deficiency is an ultra-rare demyelinating disease caused by mutations in the SLC25A12 gene, which encodes for isoform 1 of the mitochondrial aspartate-glutamate carrier (AGC1). The main pathological features are brain atrophy, growth retardation and secondary hypomyelination, along with impaired proliferation of brain cells. As demonstrated in patients, the abnormal myelin production is due to a reduced synthesis of N-acetyl-aspartate (NAA), from which the acetyl groups mainly derive. This, in turn, leads to epigenetic alterations in the brain precursor cells and resulting in transcriptional dysregulation, causing proliferation and differentiation defects, as demonstrated by previous data on our in vitro AGC1 deficiency models of our laboratory (precursor cells of mouse oligodendrocytes -OPCs- where SLC25A12 is silenced by a shRNA and neurospheres by mouse model of AGC1 deficiency). Along with epigenetic alterations, lower production of NAA leads specifically to reduced levels of acetyl-CoA, involved in many biological activities, including the synthesis of fatty acids, major components of the myelin sheath. Thus, an alteration of their production causes hypomyelination. This is confirmed by RNA-seq analysis and in vitro validation on OPCs and on neural stem cells model, which show altered expression of transcriptional factors and enzymes involved in the fatty acid synthesis pathway. Meanwhile, metabolomics analysis shows altered concentrations of many metabolites, as TCA cycle intermediates, amino acids and cofactors (NAD+, CoA); whereas ATAC-seq confirmed the presence of abnormal epigenetic landscape, which could affect genes involved in many biological pathways. To try to rebalance the epigenetic and metabolic alterations, supplementations with ketogenic compounds, as branched-chain amino acids and ketone bodies, will be carried out on OPCs and neurospheres, to induce a potential recovery of differentiation/proliferation defects, through epigenetic modifications restoration.