Exon 1 was replaced with one in which a C to T transition results in an amino acid substitution of tryptophan for arginine at position 93 (R93W). A self-excising neo cassette was inserted downstream of exon 1 and was subsequently removed. This amino acid substitution mimic the one identified in human SCID patients that abrogates store-operated calcium entry and calcium release-activated channel currents. (J:144861)