A ~1 kb genomic fragment containing intron 10, and the first 44 bp of exon 11 was replaced with a neomycin selection cassette. Northern blot analysis on colon and kidney RNA demonstrated that a 1.1 kb aberrant transcript was produced from this allele. Western blot analysis on kidney, stomach or colon tissue lysates derived from homozygous mice confirmed that no detectable protein is produced from this allele, and additional western blots on proteins derived from LPS-induced macrophages derived from homozygous mice demonstrated that no encoded protein was present.