Oxysterol-liver X receptor signaling mediates CYFIP1 regulation of cortical neurogenesis

Dysregulation in neural progenitor proliferation and neuronal differentiation has been increasingly recognised as a common pathology in neural cells harboring genetic risks to neuropsychiatric and neurodevelopmental disorders, yet the underlying molecular mechanisms remains largely unknown. Deletions and duplications of the 15q11.2 region containing the CYFIP1 gene have been associated with autism and schizophrenia. Using patient-derived iPSCs carrying 15q11.2 deletion and genetically manipulated hESCs with CYFIP1 gain- and loss-of-function (GoF and LoF), we show that 15q11.2 deletion and CYFIP1-LoF leads to premature neuronal differentiation while CYFIP1-GoF favours neural progenitor maintenance. We identified cholesterol biosynthesis and metabolism as a biological process disturbed by CYFIP1 dosage change, leading to altered neuro-oxysterol profiles. 24S,25-epoxycholesterol, which was decreased in CYFIP1-GoF and increased in CYFIP1-LoF and 15q11.2del neural cells, can mimic the 15q11.2del and CYFIP1-LoF phenotype by promoting cortical neuronal differentiation and restore the impaired neuronal differentiation of CYFIP1-GoF neural progenitors. Moreover, the neurogenic activity of 24S,25-epoxycholesterol is lost following genetic deletion of the brain expressed isoform of the liver X receptor LXRb while compound deletion of LXRb in CYFIP1-/- background rescued their premature neurogenesis. This work delineates LXR mediated oxysterol regulation of neurogenesis as a novel pathological mechanism in neural cells carrying 15q11.2CNV and provides a potential target for therapeutic strategies for genetic disorders associated with this risk locus.