Ectodysplasin-A (EDA) is a trimeric type II membrane protein whose sequence includes an interrupted collagenous domain of 19 Gly-X-Y repeats and a motif conserved in the tumor necrosis factor (TNF)-related ligand family. EDA regulates ectodermal appendage formation by colocalising with cytoskeletal structures on cell surfaces (Ezer et al. 1999). Activation of the NF-kappaB pathway by the tumor necrosis factor receptor superfamily member EDAR (EDAR) and its downstream adaptator EDAR-associated death domain (EDARADD) is essential for the development of hair follicles, teeth, exocrine glands and other ectodermal structures. EDA isoform 3 specifically binds tumor necrosis factor receptor superfamily member 27 (EDA2R aka XEDAR) whilst EDA isoform 1 specifcally binds EDAR (Hymowitz et al. 2003).