IL2RG cDNA map showing exons, cDNA numbers corresponding to the first coding nucleotide of each exon, protein domains, and sites of mutations found in unrelated patients with X-linked SCID in our series. Identical mutations found in unrelated patients are surrounded by shaded boxes. For IL2RG domains: (▨) signal peptide; C, conserved cysteine; W, WSEWS box; TM, transmembrane; B, box1-box2 domain; () 3′ untranslated. For X-linked SCID mutations: (•) point mutation, nonsense; (○) point mutation, missense; (▪) insertion, frame shift; (□) insertion, in frame; (▴) deletion, frame shift; (▵) deletion, in frame; (*) splice site; () site of recurrent mutation.