A loxP site was inserted into exon 1 upstream of the initiation codon, and an frt-flanked neomycin resistance cassette with a 3' loxP site, followed by an internal ribosomal entry site (IRES) and the coding sequence for green fluorescent protein (GFP), was inserted into the second exon downstream of the stop codon. The neo cassette was removed by germ line, flp-mediated recombination. This is a conditional knockout (floxed) allele and a reporter allele.