ARFGEF2 and microcephaly: Mutations in the human FILAMIN-A (FLNA) gene have been identified in inherited and sporadic periventricular heterotopia (Fox et al., 1998; Sheen and Sheen, 2014), whereas periventricular heterotopia can occur with or without microcephaly in patients carrying mutations in the ARFGEF2 gene which encodes BIG2, a guanine nucleotide exchange factor (Sheen et al., 2003).