A to T transversions in the sequences corresponding to codons 739 and 750 were introduced that altered the corresponding amino acids from tyrosine to phenylalanine (Y739F, Y750F). In addition, a mutation was introduced that altered the sequences of the codon corresponding to amino-acid 1020 from a tyrosine to an isoleucine (Y1020I) (DNA alteration not specified). These mutations are predicted to disrupt the PI3-K and PLC-gamma binding sites in the protein. A loxP flanked neomycin cassette was inserted into an adjacent intron. Removal of this neomycin cassette had no effect on the phenotype, and analysis of mice with or without the neomycin casstte was not distinguished in the paper.