Fig. 2.
Fgf8 expression in normal genital tubercles is restricted to Shh-expressing cloacal endoderm. (A) Fgf8 expression (red arrow) in a section of an E11.5 normal embryo is localized exclusively to the cloacal endoderm (ENDO) and is excluded from the ectoderm (ECTO; dotted lines). (B) X-Gal-stained ShhGFPcre;R26R cells are restricted to the cloacal endoderm. (C) In situ hybridization and X-Gal staining of an E11.5 genital tubercle shows that Fgf8 expression (red bracket) is restricted to ShhGFPcre-expressing cloacal endodermal cells. Black bracket marks X-Gal-stained endoderm. (D-F) Dynamics of Fgf8 expression during initiation of genital outgrowth. (D) Fgf8 is not expressed in the cloacal endoderm at E10 (dotted circle), before initiation of genital outgrowth. Expression is detected in the tailbud (inset; position of section indicated by dotted line), where it localizes to the chordoneural hinge (CNH) and tailgut. NT, neural tube. (E,F) Fgf8 is expressed during initiation (E) and early outgrowth (F) of the genital swellings (red arrows).