Background & Aims: Although total proctocolectomy (TPC) followed by ileoanal anastomosis has been established as a surgical treatment for ulcerative colitis and familial adenomatous polyposis, almost all patients suffer from persistent diarrhea and chronic electrolyte imbalance due to the lack of colon (CL). We demonstrated that 11beta hydroxysteroid dehydrogenase type 2 and amiloride-sensitive Na channel mRNAs, which are expressed in the colon, were induced in EC the remnant small intestine (SI) after TPC (GE:116:A1349,1999). We hypothesized that EC of SI may express additional molecules, which are constitutively expressed in the CL following TPC. The aim of the present study was to identify genes that are selectively expressed in EC either SI or CL and possibly contribute to accelerate adaptation of the remnant SI following TPC.
Methods: We isolated intestinal and EC of CL from ICR mice and extracted RNA. Differential expression of EC RNA was investigated by differential displays. Bands of interest were selected subcloned, sequenced and identified by computer search using BLSTN program. Differential expression was confirmed by northern blotting using EC RNAs from three different strains.
Results: In total 180 displays, we selected 26 bands and successfully subcloned 20 bands. In them, 8 clones were expressed only in EC of SI but not in CL. Sequence of 5 clones was identical to down regulated in adenoma protein, fatty acid binding protein, ornithine aminotransferase, or thymus-expressed chemokine, respectively. Three clones appeared to be new genes. In contrast, 12 clones were preferentially expressed in the CL. Sequencing revealed that 10 out of 12 clones were known genes including actin depolimerizing factor, carbonic anhydrase I, IgE-binding lectin gene, lamin A, 14-3-3 zeta tyrosine 3-monooxygenase phospholipase and alpha 1,2-fucosyl transferase. Two are probably new genes. Differential expression was confirmed in 10 clones by northern blotting so far.
Conclusions: We successfully compared epithelial gene expression between SI and CL and identified selectively expressed genes including candidates of new genes. The present approach enables us to understand functional difference between SI and CL based on gene expression and may lead to discovery of essential molecules for adaptive response in EC of the remnant SI following TPC.