A bacterial lacZ gene was inserted into the gene such that the endogenous gene promoter drives expression of beta-galactosidase. RNA transcripts are detectable exclusively in whole brain, cortex, subcortical region, cerebellum, brainstem and olfactory bulb. LacZ expression was detected: brain, spinal cord, sciatic nerve, eyes, spleen, heart, lung, liver, pancreas, kidney, urinary bladder, thyroid gland, trachea, pituitary gland, adrenal glands, skeletal muscle, skin, testis, prostate gland and ovary.