Figure 2. Sprouty and FGF pathway genes are expressed in the embryonic GT.

In situ hybridization was used to determine expression patterns of Sprouty and FGF pathway genes in sagittal sections of E14.5 male mouse GTs. Spry1, Spry2, and Spry4 mRNA transcripts primarily aggregate in the urethral epithelium, with higher levels of Spry1 and Spry2 expression relative to Spry4 (A-C′). Spry1, but not Spry2, is detected in a small mesenchymal region on the dorsal region of the distal GT (A, B), while low levels of Spry4 are diffusely distributed throughout the GT mesenchyme (C). Quantitative PCR detection of Spry1, Spry2, and Spry4 transcripts in the male GT at E14.5 show higher expression levels for Spry1 and Spry2 in comparison to Spry4 (D). Both Fgf10 and Fgfr1 are expressed in the GT mesenchyme adjacent to the urethral epithelium, while Fgfr2 expression overlaps with Sprouty in the urothelium (E-G’). Etv4 and Etv5 expression is also restricted to the epithelium (H-I’). Black boxes in low-magnification images (A-C, E-I) represent regions shown under high magnification (A’-C′, E’-I’). Urethral epithelium is outlined with black dots in high-magnification panels (A’- C′, E’-I’). Scale bars, 400 µm (A-C, E-I), 50 µm (A’-C’, E’-I’). D, dorsal; V, ventral; epi, epithelium; mes, mesenchyme.