In more detail, in extreme fatal primary human microcephaly, due to a deleterious variant in megakaryoblastic leukemia 2 (MKL2) [23] and in MKL1/MKL2 double knockout mice with defective neuronal migration and neurite outgrowth during brain development, PCTAIRE-1 expression is decreased [7]. Here, MRTFB is linked to microcephaly.