Furthermore, this role of FMRP during neurodevelopment is highlighted by one of the most characteristic neuronal phenotypes found in FXS: an abundance of hyper elongated and immature dendritic spines observed in both animal models (Zito and Svoboda, 2002; Kang et al., 2021) and human cortical brain regions (Irwin et al., 2000, 2001). The gene discussed is FMR1; the disease is fragile X syndrome.