Fig. 1.

Development of the anterior pituitary requires both Hes1 and Prop1. Embryos were sectioned sagittally at e12.5, e13.5, e14.5, and e16.5 and stained for morphology with hematoxylin and eosin. At e12.5 the wild type consists of an anterior lobe (AL), posterior lobe (PL), and Rathke’s pouch (RP) (A, arrows). In panel A, arrows point to D, V, R, and C which correspond to the directions of dorsal, ventral, rostral, and caudal, respectively. The anterior lobe at e13.5 has grown and Rathke’s pouch has begun to elongate (E). This trend continues with the e14.5 (I) and e16.5 (M) wildtype pituitaries. At e12.5 the Hes1 mutant lacks a distinct anterior lobe and the posterior lobe is noticeably smaller (B). The anterior lobe gets larger at e13.5 (F), e14.5 (J), and e16.5 (N) while Rathke’s pouch gets smaller. At e12.5 the Prop1 mutant (C) is nearly indistinguishable from the wild type, however the anterior lobe doesn’t enlarge much by e13.5 (G). By e14.5 (K) and e16.5 (O) of the Prop1 mutant, Rathke’s pouch is abnormally branched and elongated while the anterior lobe is much smaller than the wildtype anterior lobe. The double mutant at e12.5 (D) and e13.5 (H) has a morphology very similar to the Hes1 mutant at those ages. However, at e14.5 the anterior lobe is forming along the sides of Rathke’s pouch (L, arrows). By e16.5 the Rathke’s pouch is difficult to distinguish from the anterior lobe however, some anterior lobe cells do appear to be located more dorsally than ventrally (P). n=3 Magnification: 200X