EDA-A2

Ectodysplasin-A2 (EDA-A2) is the short splice variant of ectodysplasin-A, distinguished from EDA-A1 by a distinct C-terminal region that redirects its receptor specificity: instead of EDAR, EDA-A2 binds XEDAR (X-linked ectodysplasin receptor, TNFRSF27). EDA-A2 arises from alternative splicing that replaces the final two exons, producing a 156-amino-acid mature protein containing a short collagen-like repeat and a death domain-like region. Signaling through XEDAR recruits TRAF3, TRAF6 and caspase pathways, activating NF-κB and JNK, and in ectoderm-related developmental contexts overlaps partially with EDA-A1 function in appendage formation. However, EDA-A2-XEDAR also has a distinctive role in immunity and cancer: XEDAR is expressed in melanocytes and melanoma, where EDA-A2 acts as a pro-apoptotic ligand inducing tumor-cell death, and the axis contributes to osteoblast differentiation and bone development. X-chromosome-linked EDA-A2 has been implicated as a candidate gene in immunodeficiency associated with ectodermal dysplasia, reflecting collateral roles beyond skin appendages.