ARHGAP35 and coloboma: Mice homozygous for a loss-of-function Arhgap35 allele display highly penetrant early lethality, structural brain anomalies, cystic glomeruli, and optic cup anomalies including coloboma and microphthalmia while heterozygous mice are unaffected; a subset of homozygous animals also display neural tube closure defects, particularly exencephaly [7, 8].