ORAI1 mutations abolishing store-operated Ca2+ entry cause anhidrotic ectodermal dysplasia with immunodeficiency (EDA-ID).
BACKGROUND: Store-operated Ca2+ entry (SOCE) through Ca2+ release-activated Ca2+ (CRAC) channels is an essential signaling pathway in many cell types. CRAC channels are formed by ORAI1, ORAI2 and ORAI3 proteins and activated by stromal interaction molecule 1 (STIM1) and STIM2. Mutations in ORAI1 and STIM1 genes that abolish SOCE cause a combined immunodeficiency (CID) syndrome that is accompanied by autoimmunity and non-immunological symptoms.
OBJECTIVE: Molecular and immunological analysis of patients with CID, anhidrosis and ectodermal dysplasia of unknown etiology.
METHODS: DNA sequencing of ORAI1 gene, modeling of mutations on ORAI1 crystal structure, analysis of ORAI1 mRNA and protein expression, measurements of SOCE, immunological analysis of peripheral blood lymphocyte populations by flow cytometry, histological and ultrastructural analysis of patient tissues.
RESULTS: We identified 3 novel autosomal recessive mutations in ORAI1 in unrelated kindreds with CID, autoimmunity, ectodermal dysplasia with anhidrosis (EDA) and muscular dysplasia. The patients were homozygous for p.V181SfsX8, p.L194P and p.G98R mutations in the ORAI1 gene that suppressed ORAI1 protein expression and SOCE in the patients' lymphocytes and fibroblasts. Besides impaired T cell cytokine production, ORAI1 mutations were associated with strongly reduced numbers of invariant natural killer (iNKT) and regulatory T (Treg) cells, and altered composition of γδ T cell and NK cell subsets.
CONCLUSION: ORAI1 null mutations are associated with reduced numbers of iNKT and Treg cells that likely contribute to the patients' immunodeficiency and autoimmunity. ORAI1 deficient patients suffer from dental enamel defects and anhidrosis representing a new form of anhidrotic ectodermal dysplasia with immunodeficiency (EDA-ID) that is distinct from previously reported patients with EDA-ID due to mutations in the NF-kB signaling pathway (IKBKG and NFKBIA).