A bacterial lacZ gene was inserted into the gene such that the endogenous gene promoter drives expression of beta-galactosidase. RNA transcripts are detectable in salivary gland, subcortical region of the brain, cerebellum, brainstem, olfactory bulb, spinal cord, eye, Harderian glands, lung, liver, pancreas, kidney, spleen, thymus, bone marrow, skin, gallbladder, urinary bladder, stomach, large intestine, cecum, epididymis, seminal vesicle, coagulating gland, prostate gland, ovaries and uterus. Striking lacZ (beta-galactosidase) expression is detectable in brain, spinal cord and ganglia. Other tissues displaying X-Gal staining are kidney, urinary bladder, salivary glands, and male reproductive system.