A mini cDNA consisting of exon 15 with an ACG to ATC change resulting in a threonine to isoleucine substitution at amino acid 985 (T985I), a loxP site, an FRT-flanked PGK-neo, a terminating STOP codon, exons 15-23, and a loxP site replaced exon 15. The PGK-neo selection cassette was removed via Flp-mediated recombination. (J:266704)