Kinetics of neurotensin gene expression in the developing gut

Background: Expression of the gene encoding neurotensin (NT/N) is regulated in a strict temporal- and spatial-specific pattern during gut development; the mechanisms (that is, transcriptional versus posttransciptional) responsible for this expression pattern are not known. The purpose of this study was to determine whether developmental changes in NT/N expression reflect alternations in gene transcription. Methods. Sensitive ribonuclease protection assays were performed with a rat NT/N genomic probe containing the entire sequence of both exon 1 and intron 1 hybridized with RNA from fetal (day 19) and postnatal (days 14, 28, and 60) rat jejunum and ileum; signals were quantitated densitometrically. Results. Mature (exon 1) and precursor (exon 1 + intron 1) NT/N RNA, initially low in the fetus, increased dramatically by postnatal day 14 and attained maximal levels by day 28. NT/N RNA levels remained stable in the ileum of the 60- day-old rat but decreased in the jejunum, consistent with the typical expression pattern in the gut. Conclusions. Concomitant changes in expression of precursor and mature NT/N RNA suggest that NT/N gene regulation occurs at the level of transcription in the gut during development. Identifying the factors that regulate NT/N gene transcription is crucial to our understanding of how neurotensin functions in the gut.