A portion of exon 1 and all of exons 2 through 6 were replaced with a cassette containing IRES-NLS-lacZ and floxed neo. While transcript containing the targeted exons was undetected, RT-PCR analysis of homozygous mutant mice revealed transcript that included exons 14 through 18. A C-terminal antibody was not available to determine if protein was produced from the detected message. (J:85108)