Fig. 4. Reduced Pitx2 causes decreased expression of lineage-specific transcription factors. In situ hybridization or immunohistochemistry was performed to examine the change of transcription factor expression in Pitx2^neo/neo mice and wild-type littermates at E12.5 and P1. Gata2 expression initiates normally at early stages (A,B), but fails to be maintained (C,D). The expression of Egr1 (E,F) and SF1 (G,H) is nearly undetectable in Pitx2^neo/neo animals. PITX1 (I,J and K,L) and PROP1 (M,N) expression was unchanged in homozygotes for Pitx2^neo. Pit1 in situ hybridization shows a reduction in the number of Pit1-producing cells (O,P). Note Gata2 (A,B), PITX1 (I,J) and PROP1 (M,N) expression at E12.5. Arrowhead, rostral tip of pituitary gland; the brackets in C-F indicate the ventral and caudomedial aspect of the pituitary gland.