Alcohol use disorder–associated gene FNDC4 alters glutamatergic and GABAergic neurogenesis in neural organoids

Large-cohort GWAS for alcohol use disorder (AUD) drug treatment outcomes and AUD risk have repeatedly identified genetic loci that are splicing quantitative trait loci for the fibronectin III domain containing 4 (FNDC4) gene in the brain. However, FNDC4 function in the brain and how it might contribute to AUD pathophysiology remain unclear. In the present study, we characterized GWAS loci-associated FNDC4 splice isoforms and demonstrated that FNDC4 alternative splicing results in loss of function for FNDC4. We also investigated FNDC4 function using CRISPR/Cas9 editing and the creation of human induced pluripotent stem cell-derived (iPSC-derived) neural organoids joined with single-nucleus RNA sequencing, a series of studies that showed that FNDC4 KO resulted in a striking shift in the relative proportions of glutamatergic and GABAergic neurons in iPSC-derived forebrain organoids as well as changes in their electrical activity. We further explored a potential mechanism(s) of FNDC4-dependent neurogenesis, and the results suggested a role for FNDC4 in mediating neural cell surface interactions. In summary, this series of experiments indicates that FNDC4 plays a role in regulating cerebral cortical neurogenesis in the brain. This regulation may contribute to the response to AUD pharmacotherapy as well as the effects of alcohol on the brain.