ARF1 and periventricular nodular heterotopia: Lastly, mutations in the human genes for ARFGEF2 and ARF1 have been associated with cortical malformations, including periventricular nodular heterotopia and microcephaly, indicating that the ARFGEF2-Arf1 pathway is critical for cerebral cortical development (Sheen et al., 2004; Gana et al., 2022).