Fig. 1. Hoxa5 expression in the developing stomach. In situ hybridization was performed on sections of E10.5 (A,B) and E12.5 (C,D) mouse embryos, and E15.5 (E), E17.5 (F-H) and P15 (I,J) stomachs. At E10.5, a widespread distribution of Hoxa5 transcripts was observed in the gastric mesenchyme (A,B). A gradient had formed by E12.5, with Hoxa5 being more expressed in the hindstomach (arrowheads; C,D). This gradient persisted at E15.5 (E). By E17.5, Hoxa5 transcripts were redistributed accompanying the formation of the infoldings (F-H). The signal became mainly confined to the submucosal cells underlying the epithelium and expression was observed in the muscular layer (G,H). Hoxa5 expression stopped around P15 (I,J). e, epithelium; f, forestomach; h, hindstomach; m, muscular layer; me, mesenchyme; s, submucosal layer. Scale bars: 100 µm.