NKX2-2 and spina bifida: Therefore, to assess the impact of RA-induced spina bifida on NPC differentiation, we characterized Pax6, Olig2, and Nkx2.2 expression in fetal spinal cords during gestation because in spina bifida the spinal cord is open and unfolded exposing the VZ and the progenitor cells to the amniotic fluid.