Fig. 4. Edar (dl) expression and hair placode formation in E15.5 embryos of c^IBN and wild-type mice. Increased apoptosis in hair follicles of c^IBN embryos at day E17.5. (A) In situ hybridization (ISH) was used to assess Edar (dl) expression at E15.5. Panels dl-w.t.1 and dl-N1 show skin of whole mount embryos. dl-w.t.2 and dl-N2 show plastic sections of the same. At E15.5, Edar (dl) expression (arrow in dl-w.t.2) and concomitant hair placode formation is observed in torso skin of only wild-type mice. (B) Plastic sections of vibrissal follicles at E15.5, after ISH using a probe for Edar (dl). In follicles of vibrissae, Edar expression is observed in wild-type and c^IBN mice (arrows). (C) Increased apoptosis is seen in hair follicles of pelage hair (right panel N1) and vibrissae (right panel N2) in c^IBN mice at E17.5. Left panels show nuclear DAPI stain, right panels show the in situ TUNEL assay. White arrows in wild-type point to two pelage hair follicles.