Ventral markers are overexpressed in the absence of Pax6 in the early stage of pituitary development. At e12 in Rathke’s pouch, the ventral markers αGSU, GATA2, Brn4, Isl-1, and Prop-1 are overexpressed in the Pax6 mutant mice. No difference has been observed for the POMC and Nkx3.1 levels. Pitx1, a uniformly expressed pituitary marker, showed an up-regulation at the ventral site of the pouch.