FMRP regulates mitotic progression in many tissues, as loss of Fmr1 leads to elevated rates of neural stem cell proliferation, resulting in impaired neurogenesis in Drosophila and, remarkably, in induced pluripotent stem cells (iPSCs) derived from FXS patients (Callan et al., 2010; Raj et al., 2021). This evidence concerns the gene FMR1 and fragile X syndrome.