PhD candidate The Hebrew University of Jerusalem Jerusalem, United States
Abstract: Fragile X syndrome (FXS) is the most prevalent form of inherited intellectual disability and is one of the leading causes of autism spectrum disorders. FXS is caused by a trinucleotide repeat (CGG) expansion located at the 5' untranslated region (5' UTR) of the fragile X messenger ribonucleoprotein 1 (FMR1) gene, leading to its inactivation. To identify genes involved in regulating FMR1 silencing, we have previously conducted a genome-wide screen using human embryonic stem cells. Among the candidate genes identified, SDHAF4 emerged as a key regulator. This gene encodes an assembly factor of the succinate dehydrogenase (SDH) enzyme. Knocking out SDHAF4 reactivated the FMR1 gene in FXS-induced pluripotent stem cells (iPSCs). We further explored small molecule treatments to inhibit screen candidate genes, focusing on oxaloacetic acid (OAA), a known allosteric inhibitor of SDH. Treatment of FXS iPSCs with OAA for 10 days significantly reactivated FMR1 expression. Remarkably, combining OAA with ascorbic acid (vitamin C) resulted in even greater FMR1 reactivation. Furthermore, in pre-clinical experiments with humanized mouse model, human FXS-iPSCs were transplanted into immunodeficient mice. Treatment with intra-peritoneal injection of OAA resulted in significant FMR1 reactivation within the human cells. Further analysis revealed that this treatment caused massive demethylation of the FMR1 promoter region in a subset of the cells. Additional metabolic modulators, including malonate and α-ketoglutarate, also demonstrated strong potential to reactivate FMR1. This study provides novel insights highlighting metabolic pathways as promising therapeutic targets for FXS. These findings open new avenues for the development of effective treatments for this challenging condition.
