Fig. 1. Gastrointestinal homeosis in the absence of Barx1. (A) Comparison of the differences in size and morphology of normal (left) and Barx1^-/- (right) neonatal stomach, as observed in dozens of embryos and newborn mice. Es, esophagus; St, stomach; Du, duodenum. (B,D) Mucosal differences between normal (D) and Barx1^-/- neonatal (B) stomach, revealing a crowded villiform epithelium in the latter. (C) Low-magnification micrograph of PAS staining of Barx1^-/- neonatal stomach, shown to reveal the boundary within the stomach (dotted line) of strongly PAS⁺ gastric mucosa proximally and largely PAS^- intestinal epithelium distally. (E-G) Normal epithelial histology (H&E stain) from the neonatal mouse forestomach (E), corpus (F) and antrum (G). (H,I) Gross architectural disorganization typifies the abnormal epithelium (H&E stain) of Barx1^-/- neonatal mid-stomach. (J-O) Histochemical (PAS and Alcian Blue) and molecular [Pdx1, Cdx2, gastric intrinsic factor (If) and trefoil factor 3 (Tff3)] stains highlight the sharp boundary (dotted line) between epithelia of the gastric (top in J-M, left in N,O) and intestinal (bottom in J-M, right in N,O) types in Barx1^-/- stomach. J-M represent consecutive tissue sections, and N-O are consecutive to each other but not to the others.