Fig. 5. Expression of Fgf3 and Fgf10 in early feather development. Detection of Fgf3 (A-C) or Fgf10 (D-F,J-L) expression by whole-mount RNA in situ hybridization of embryos at HH28, before the onset of feather placode development, and at HH30. (C,F) Expression of Fgf3 and Fgf10 in embryos infected with RCAS-FGFR1-Fc and RCAS-FGFR2-Fc at HH18. The nude region devoid of Fgf3 and Fgf10 expression is included with a bracket. (G-I) Vibratome sections, at the indicated positions, through the embryos shown in B, D and E, respectively. Arrowheads in D indicate the stripes of Fgf10 expression in the region where bud development will be initiated. (J-L) Expression of Fgf10 in the alar (J), pectoral (K) and tail tract (L). Arrows indicate the feather tract, delineated by Fgf10 expression. nt, neural tube.