Fig. 1. Fgf10 is expressed in the pancreatic mesenchyme during the early stages of pancreatic organogenesis. (A,B,E) Whole-mount in situ hybridisation on dissected gastrointestinal tracts (dorsal is to the right) showing (A) Fgf10 expression in the gut dissected from an E9.5 embryo. The first signs of Fgf10 expression in the posterior foregut were two distinct stripes where the dorsal and ventral pancreatic buds emerge. Expression of Fgf10 in the foregut anterior to the pancreas was also observed in the lung buds. (B) By E10.5, the dorsal epithelial bud was clearly visible and Fgf10 was expressed broadly in the surrounding mesenchyme. Expression of Fgf10 also extended into the posterior stomach mesenchyme. (C,D) Vibratome sections (20 µm) of the gut from the E10.5 embryo shown in B demonstrates that Fgf10 expression is confined to the mesenchyme adjacent to the dorsal (C) and ventral (D) bud. (E) Fgf10 continued to be expressed at E11.5 in a restricted area in the dorsal mesenchyme (indicated by an arrow). The uniform weak staining observed in the stomach epithelium was due to the trapping of the in situ probe in the lumen of the stomach. d, dorsal; v, ventral; db, dorsal bud; vb, ventral bud; lb, lung bud; st, stomach.
