Ectodysplasin A: role of N-glycosylation and structural impact of pathogenic mutations

Ectodysplasin A (EDA) is a TNF family member produced in several splice variants, the longest of which encodes EDA1, a ligand for EDA1 receptor (EDAR). EDA1-EDAR interactions are critical for the intrauterine development of skin appendages, including hair, teeth and eccrine sweat glands. EDA or EDAR mutations cause hypohidrotic ectodermal dysplasia characterized by hypotrichosis, hypodontia and insufficient ability to perspire. In affected patients, prenatal treatment with a recombinant EDA1 molecule, delivered intra-amniotically to stimulate EDAR, resulted in long-term sweat gland function in children and fully corrected the heat intolerance phenotype. Recombinant EDA1 is a fusion protein between the Fc fragment of an IgGl and the receptor binding domain of EDA1 (amino acids 239-245) (Fc-EDA1). Both the Fc and EDA1 portions are N-glycosylated. N-linked glycans are heterogenous in nature, making it difficult to manufacture the protein in a reproducible manner with regards to glycans. A better understanding of the function (or lack of function) of N-linked glycans in the activity of Fc-EDA1 is needed to determine the extent of care required for batch-to-batch reproducibility of N-linked glycans.