A bacterial lacZ gene and neomycin resistance cassette was inserted to replace a 52 bp segment within the coding portion of exon 1 such that the endogenous gene promoter drives expression of beta-galactosidase. While RT-PCR analysis detects high levels of RNA transcripts in the kidney and very low levels in the brain, beta-galactosidase expression from this allele is detectable in brain and kidney. (J:108655)