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The gut endocrine gene, neurotensin (NT/N), isexpressed in a strict temporally and spatially specificpattern. Utilizing a sensitive reversetranscription-polymerase chain reaction procedure, weanalyzed foregut and midgut organs for NT/N expression,determined the earliest apparent time point that NT/N isexpressed in the gastrointestinal tract and compared thetemporal relationship of NT/N with other genes. NT/N expression was detected in thefetal and early postnatal stomach. In the small bowel,NT/N was expressed at the earliest fetal time (14 days)that the small bowel could be reliably delineated from other gut organs; in contrast, expressionof sucrase-isomaltase was only apparent at 28 days afterbirth. NT/N was expressed in the fetal (12, 14 and 16days) liver and then again on days 3 and 7 after birth; however, NT/N was detected only in thefetal (14 and 16 days) pancreas. Finally, NT/Nexpression was first detected at ~12 days gestation inthe primitive foregut and midgut, thus occurringsignificantly earlier than actual intestinalcytodifferentiation. NT/N is widely expressed in thegastrointestinal tract during fetal development,suggesting the presence of a shared ancestral stem cell;NT/N expression is then restricted to the small bowel of theadult. The determination of the cellular factorsregulating the expression of NT/N will provide a betterunderstanding of the mechanisms responsible for the strict patterning of gene expression in thegastrointestinal tract and possibly gutdifferentiation. |
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