Fig. 3. Analysis of Pbx1 and Nkx2.5 gene expression during early spleen organogenesis. In situ hybridization was performed on frozen sagittal sections of E12-12.5 embryonic upper abdominal organs. (A-F) Normal expression of Pbx1 within the developing splenic anlage of Hox11^-/-, Pod1^-/- and Nkx3.2^-/- embryos. (G-L) Perturbed expression of Nkx2.5 in Pod1^-/- and Pbx1^-/- embryos. Nkx2.5 expression is unperturbed in the developing splenic anlage of Hox11^-/- embryos (H), while it is absent in Pod1^-/- (J) and Pbx1^-/- (L) embryos, compared with their wild-type littermates (G,I,K). L, liver; Sp, spleen; St, stomach.