A targeting vector was designed to insert a loxP upstream of exon 2 (containing the start codon), and an FRT-flanked neomycin resistance (neo) cassette, followed by a second loxP site, downstream of exon 2. Cre-mediated recombination removed exon 2 and the selection cassette. Immunoblot analysis of brain, spleen, liver and thymus indicate the presence of an N-terminally truncated protein. (J:231724)