Most of the exon 1 coding region and the exon 1 to intron 1 junction is replaced by an in-frame EGFP-bGH-pA-FRT-neo-FRT cassette via homologous recombination. Flp-mediated recombination removed the FRT-flanked neo cassette. Although predicted to be a loss-of-function allele, both heterozygous and homozygous mice exhibit no obvious phenotypic abnormalities. (J:229960)