Nearly two decades ago, Feske and his colleagues by applying two unbiased genetic methods reported a modified linkage analysis to categorize the gene mutated in the severe combined immune deficiency (SCID) patients, and a genome-wide RNA interference (RNAi) screen identified that a mutation in Orai1, R91W, produces immune deficiency by abolishing CRAC channel function [30]. Here, ORAI1 is linked to Immunodeficiency.