Fig. 3. Noggin partially restores hair placode formation in Eda-deficient skin. E13 skin explants were cultured for 1 day and hair placode induction was detected by expression of placode marker Shh. (A) Eda-deficient explants cultured in the control medium lack the primary hair follicles. (B,C) Explants cultured in the presence of 0.5 µg/ml exogenous noggin (B) partially restored hair placode induction, whereas a more prominent rescue was seen with 2 µg/ml of noggin (C). (D,E) Eda-A1 at 0.1 µg/ml restored the expression of Shh (D), whereas 2 µg/ml Eda-A1 caused a prominent enlargement of placodes in Eda^-/- skin (E). (F,G) noggin at 2 µg/ml caused enlargement of hair placodes in wild-type skin (G) compared with untreated explants (F).