ARF1 and periventricular nodular heterotopia: The identification of ARF1 variants here suggests an effect in brain development and further extends the FLNA-associated pathway in periventricular heterotopia.28–30 Interestingly, mutations in ARFGEF2 encoding BIG2 has been associated with recessive periventricular heterotopia, and these predict loss of ARF-activation in the disorder.