Exons 6 through 8 and the first 6 bases of exon 9 were replaced by a lacZ-neomycin cassette. RT-PCR analysis detected a gene transcript in most tissues analyzed except for Harderian glands, liver, lymph nodes, bone marrow and skeletal muscle. Beta-galactosidase expression from this allele was detectable in brain, spinal cord, eyes, heart, pancreas, kidney, urinary bladder, pituitary gland, adrenal glands, testis, prostate gland, ovary and cervix. Western blot analysis of brain and spinal cord homogenates failed to detect any protein product.