ATRX and spina bifida: Several mouse and human studies have proven that consumption of VPA during pregnancy causes spina bifida and exencephaly, both representing neural tube defects.23, 35, 36 Many signaling pathways such as the sonic hedgehog, WNT pathways and epigenetic transcriptional regulators, such as PAX3, CITED1, SUZ12, ATRX, PTCH1 and GLI2 are essential for neural tube closure (reviewed in Copp and Greene50).