Whole exome sequencing in Dandy-Walker variant with intellectual disability reveals an activating CIP2A mutation as novel genetic cause

Dandy-Walker malformation (DWM) has been reported to have heterogeneous causes, including mutations in genes of fibroblast growth factors and in genes in the sonic hedgehog (Shh) signaling pathway. Here, we identified an activatin g cancerous inhibitor of protein phosphatase 2A (CIP2A) p.D269V mutation, located at the predicted protein-protein interaction groove, as a novel genetic cause of Dandy-Walker variant (DWV). CIP2A has been reported as an oncoprotein promoting tumor survival via inhibition of protein phosphatase 2A (PP2A). However, the impact of human germline CIP2A mutation is unknown. We report a novel heterozygous CIP2A p. D269V mutation via whole exome sequencing in two siblings with DWV and severe intellectual disability who were born to non-consanguineous parents. Only the older brother developed a slow-growing sacral leiomyoma in his teens. The CIP2A p. D269V mutation is associated with increased PP2A, mTOR, and c-Myc protein levels in peripheral blood mononuclear cells (PBMCs). The PP2A phosphatase activity, however, was not suppressed. Deep sequencing revealed that the father carries 16% of somatic CIP2A p.D269V mutation, suggesting potential inheritance from the mosaic sperm populations. Our study is the first to describe a pathogenic CIP2A mutation in humans, which might disrupt neuronal development via enhancing mTOR and c-Myc protein expressions, shedding light in mechanisms of DWV pathogenesis.