Fig. 10. The regulation of hair follicle formation by the TNF signal ectodysplasin [encoded by Eda (Ta) gene] and its receptor Edar [encoded by Edar (dl) gene], and integration with other signaling pathways. Ectodysplasin is expressed in the interfollicular ectoderm and induced by WNT signals, which are transduced by LEF1. Edar is expressed in the placodes and stimulated by activin signals from the underlying mesenchyme. Ectodysplasin is shed (secreted) and binds as a trimer to the trimerized Edar receptor. This TNF signaling is transduced by the NF-B transcription factor.