TUBB4A and schizencephaly: Consequently, variants in the genes encoding alpha-tubulin (ɑ-tubulin; TUBA1A), beta-tubulin (β-tubulin; TUBB2A, TUBB2B, TUBB3, TUBB4A, and TUBB), and gamma-tubulin (γ-tubulin; TUBG1) may affect MT function, leading to brain malformations including LIS, schizencephaly, polymicrocerebellar disease, cerebellar disease, and simplified cyclotorsion (8).