Distinct hyperactive RAS/MAPK alleles converge on common GABAergic interneuron core programs.

RAS/MAPK gene dysfunction underlies various cancers and neurocognitive disorders. While the role of RAS/MAPK genes have been well studied in cancer, less is known about their function during neurodevelopment. There are many genes that work in concert to regulate RAS/MAPK signaling, suggesting that if common brain phenotypes could be discovered they could have a broad impact on the many other disorders caused by distinct RAS/MAPK genes. We assessed the cellular and molecular consequences of hyperactivating the RAS/MAPK pathway using two distinct genes in a cell type previously implicated in RAS/MAPK-mediated cognitive changes, cortical GABAergic interneurons. We uncovered some GABAergic core programs that are commonly altered in each of the mutants. Notably, hyperactive RAS/MAPK mutants bias developing cortical interneurons towards those that are somatostatin+. The increase in somatostatin+ interneurons could also be induced by elevated neural activity and we show the core RAS/MAPK signaling pathway is one mechanism by which this occurs. Overall, these findings present new insights into how different RAS/MAPK mutations can converge on GABAergic interneurons, which may be important for other RAS/MAPK genes/disorders.