Figure 4.

Ventral pituitary cell types are increased in the absence of Pax6. (A) Newborn Pax6 mutant mice are characterized by increased GH, TSH, and αGSU as well as by down-regulation of LH but not by a difference in POMC levels. (B) Very few dorsal GH- and PRL-positive cells are detected in mutant mice. (C) Pax6 establishes the boundary along the dorsoventral pituitary axis as early as e10 in response to the inhibitory Shh gradient and maybe the BMP2 from the ventral Rathke’s pouch and oral ectoderm. In the absence of Pax6, there is a dorsal shift of the boundary, with up-regulation of the transcription factors determining the most ventral cell types, the gonadotropes and thyrotropes. M, melanotropes; other abbreviations are defined in the legend to Fig. 1.