EDAR

Edar, written as EDAR in genetic nomenclature, refers to the Ectodysplasin A receptor gene in humans. It encodes a transmembrane receptor in the tumor necrosis factor (TNF) receptor superfamily that binds the EDA ligand (ectodysplasin A). Engagement of EDAR by EDA-A1 activates downstream signaling, including the NF-κB pathway, and regulates the development of ectodermal derivatives such as hair follicles, teeth, and sweat glands during embryogenesis. The gene is located on chromosome 2 (2q12).

Genetic variants in EDAR can disrupt ectodermal development and contribute to hypohidrotic ectodermal dysplasia (HED) in autosomal modes of inheritance (autosomal dominant or recessive), distinct from the X-linked form caused by EDA mutations. Common clinical features include sparse hair, abnormal or missing teeth, and reduced sweating; severity varies by mutation and zygosity. EDAR also interacts with EDARADD, another component of the same signaling pathway, to regulate ectodermal organ formation.

An ancestral EDAR allele, EDAR V370A, is notably frequent in some East Asian populations and has been associated with phenotypic differences such as thicker hair shafts and increased sweat gland density in some studies. The interpretation of these associations is complex and may reflect historical selection along with other genetic factors. See also hypohidrotic ectodermal dysplasia for related conditions.