We have used in situ hybridization to localize expression of the cystic fibrosis transmembrane conductance regulator (CFTR) gene in the human gastrointestinal tract and associated organs. The stomach exhibits a low level of CFTR expression throughout gastric mucosa. In the small intestine, expression is relatively high in the mucosal epithelium, with a decreasing gradient of expression along the crypt to tip axis. The cells of the Brunner's glands express high levels of CFTR mRNA. In addition, there is a small subpopulation of highly positive cells scattered along the epithelium in the duodenum and jejunum, but not in the ileum. These cells do not represent endocrine cells, as determined by lack of colocalization with an endocrine-specific marker. The distribution of CFTR mRNA in the colon is similar to the small intestine, with highest level of expression in the epithelial cells at the base of the crypts. In the pancreas, CFIR is expressed at high levels in the small, intercalated ducts and at lower levels in the interlobular ducts. CFI'R transcripts are expressed at uniformly high levels in the epithelium of the gallbladder. Throughout the gastrointestinal tract, CFTR expression is increased in mucosal epithelial cells that are near lymph nodules. (J. Clin. Invest. 1994. 93:347-354.)

We have used RNA in situ hybridization to study the regional expression of the Huntington's disease gene (HD) and its rat homologue in brain and selected nonneural tissues. The HD transcript was expressed throughout the brain in both rat and human, especially in the neurons of the dentate gyrus and pyramidal neurons of the hippocampal formation, cerebellar granule cell layer, cerebellar Purkinje cells and pontine nuclei. Other brain areas expressed lower levels of the HD transcript without pronounced regional differences. Neuronal expression predominated over glial expression in all regions. HD mRNA was also expressed in colon, liver, pancreas and testes. The regional specificity of neuropathology in HD, which is most prominent in the basal ganglia, thus cannot be accounted for by the pattern of expression of HD.