A bacterial lacZ gene was inserted into the gene such that the endogenous gene promoter drives expression of beta-galactosidase. RT-PCR analysis detects a high level of gene transcript in the whole brain, cortex, subcortical region, pancreas, pituitary gland and adrenal gland, moderate levels in cerebellum, olfactory bulb, eye, heart, liver, thymus, lymph nodes, skin, salivary gland, large intestine and prostate gland and low levels in kidney, spleen, testis and seminal vesicle. Beta-galactosidase expression from this allele is detectable in brain, eyes and pituitary gland. Strong expression was detected in several regions of the brain, including the caudate putamen, cortex, thalamus and hippocampus. Moderate expression was detected in some cells in the inner nuclear layer of the retina. In the pituitary gland, moderate staining was observed in many cells of the pars intermedia.