DIFFERENCES IN EXPRESSION OF HOMEOBOX TRANSCRIPTION FACTORS IN PROXIMAL AND DISTAL HUMAN SMALL-INTESTINE

Background & Aims: Different digestive enzymes and transporters are pr esent in the duodenum, jejunum, and ileum, but the factors determining region-specific gene expression are not yet understood. Homeobox tran scription factors are important in defining gradients of cellular diff erentiation. The aim of this study was to investigate whether their ex pression differs between proximal (duodenal) and distal (ileal) region s of human small intestine. Methods: Intestinal RNA was prepared from surgical patients, and reverse-transcription polymerase chain reaction s (PCRs) performed with mixed sequence oligonucleotide primers based o n conserved regions. PCR products were identified by cloning and seque ncing. Transcript abundance was determined by Northern blotting. Resul ts: The human homologues were identified as Cdx-1, Cdx-2 (or Cdx-3), P dx-1 (previously named islet/duodenal homeobox [Idx]-1, Ipf-1, or Stf- 1), and 13 human homeodomain cluster genes, including HOXB3, ROXB4, an d HOXA6. The relative abundance of some of these differed between duod enum and ileum. Pdx-1 transcripts were found only in duodenum. Cdx-2, Cdx-1, and HOXB3 were readily detectable in both regions, with Cdx-1 h aving a more marked distal expression. Conclusions: Many homeobox gene s are expressed in human adult small intestinal mucosa, and some are f ound predominantly in one region.