Enhanced gliogenesis and delayed maturation underpin the neurodevelopmental defects in Lowe syndrome

The activity of signaling pathways is required for coordinated cellular and physiological processes that lead to the normal development of brain structure and function. Mutations in OCRL, a phosphatidylinositol 4,5-bisphosphate (PIP₂) 5-phosphatase, lead to the neurodevelopmental disorder Lowe Syndrome (LS). However, the mechanism by which mutations in OCRL lead to the brain phenotypes observed in LS remains unclear.We found that LS patient-derived induced pluripotent stem cells (iPSCs), when differentiated into neural cultures, exhibited significantly reduced neuronal excitability along with increased expression of the astrocytic marker GFAP. Multiomic single-nucleus RNA and ATAC sequencing revealed an early fate switch of LS patient-derived neural stem cells (LSP-NSCs) toward gliogenesis. Pseudobulk analysis of snRNA-seq data showed increased levels of DLK1, a non-canonical Notch ligand, in LS patient NSCs. This was associated with elevated levels of cleaved Notch protein and increased expression of its transcriptional target HES5, indicating upregulated Notch signaling. Treatment of iPSC-derived brain organoids with an inhibitor of PIP5K1C, the lipid kinase responsible for synthesizing PIP₂, restored neuronal excitability and rescued Notch signaling defects in LS patient-derived organoid cultures. Overall, our results demonstrate a role for PIP₂-dependent regulation of Notch signaling, cell fate specification, and the development of neuronal excitability mediated by OCRL activity.