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 liver, gallbladder, urinary bladder, pituitary gland, adrenal gland, testis, coagulating gland, prostate gland, ovary, whole brain, cortex, subcortical region, cerebellum, brainstem, olfactory bulb, spinal cord, eye, Harderian glands, heart, lung, pancreas, kidney, spleen, thymus, lymph nodes, bone marrow, skin, salivary gland, skeletal muscle, tongue, stomach, small intestine, cecum, colon, epididymis, seminal vesicle, uterus and white fat. LacZ expression was detected in testis with moderate staining observed in some spermatogenic cells of the seminiferous tubules.