PubMed Health⌕ Search

PubMed · 10708521

Multiple potential intragenic regulatory elements in the CFTR gene.

Abstract

The CFTR gene exhibits a complex pattern of expression that shows temporal and spatial regulation though the control mechanisms have not been fully elucidated. We have mapped DNase I hypersensitive sites (DHS) flanking the CFTR gene to identify potential regulatory elements. We previously characterized DHS at -79.5 and -20.9 kb with respect to the CFTR translational start site, DHS 3' to the gene at 4574 + 5.4-7.4 and 4574 + 15.6 kb, and a regulatory element in the first intron of the gene at 185 + 10 kb. We generated a cosmid contig to provide probes to evaluate the whole of the CFTR gene for DHS and have now mapped novel sites in introns 2, 3, 10, 16, 17a, 18, 20, and 21. These DHS show different patterns of cell-specific expression.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

D J Smith, H N Nuthall, M E Majetti, A Harris. 2000-02-15. Multiple potential intragenic regulatory elements in the CFTR gene.. https://doi.org/10.1006/geno.1999.6086

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

Supplementation of test meals with fat-free phytosterol products can reduce cholesterol micellarization during simulated digestion and cholesterol accumulation by Caco-2 cells.

Phytosterols have been shown to reduce cholesterol absorption in humans. Supplementing phytosterols in fat-free formulations, however, has yielded controversial results. In the present study, we investigated the effect of supplementing test meals with different fat-free phytosterol products on cholesterol incorporation into mixed micelles during simulated digestion and accumulation of micellar cholesterol by Caco-2 cells: control orange juice (OJ), orange juice supplemented with either multivitamin/multimineral tablets (MVT), multivitamin/multimineral tablets containing phytosterols (MVT+P), and phytosterol powder (PP). These combinations were added to Ensure-based test meals and spiked with cholesterol of natural isotopic composition or 13C2-cholesterol to differentiate external from endogenous cholesterol. After simulated gastric/small intestinal digestion, micelle fractions were analyzed for cholesterol enzymatically (n = 6-20/product) and by high-performance liquid chromatography-tandem mass spectrometry (n = 12/product) and added to Caco-2 cells to determine the accumulation of 13C2-cholesterol (n = 10-24/product). As compared to OJ, PP and MVT+P significantly decreased cholesterol micellarization (determined enzymatically) by 70 +/- 39 (mean +/- SD) and 70 +/- 39%, respectively (P < 0.001, Bonferroni). The stable isotope experiments revealed that both PP and MVT+P reduced cholesterol micellarization [by 25 +/- 12 (P = 0.055) and 21 +/- 8% (P = 0.020), respectively, Fisher's protected LSD test] and Caco-2 cell accumulation (by 28 +/- 8 and 10 +/- 8%, respectively; P < 0.010, Bonferroni). OJ+P did not inhibit micellarization or accumulation of cholesterol by Caco-2 cells. This study shows that fat-free phytosterol-containing products can significantly inhibit cholesterol micellarization and Caco-2 cell bioaccessibility, albeit to different extents depending on individual formulations. This is most likely explained by inhibition of cholesterol micellarization.

Caco-2 Cells↗

Heat shock stress ameliorates cytokine mixture-induced permeability by downregulating the nitric oxide and signal transducer and activator of transcription pathways in Caco-2 cells.

Proinflammatory cytokines are known to impair intestinal barrier function and to activate signaling pathways, whereas heat shock responses prevent cytokine-induced mucosal damage. We hypothesized that heat shock response blocks the effects of proinflammatory cytokines by regulating nitric oxide (NO) production and the activities of the Janus kinase/signal transducer and activator of transcription (STAT) pathway. A monolayer of Caco-2 cells were pretreated with sodium arsenite (SA, 500 micromol/L) for 1 h, followed by a 1-h recovery, and then stimulated with a cytokine mixture (cytomix: tumor necrosis factor alpha [10 ng/mL], interferon beta [1000 U/mL], and interleukin [IL] 1beta [1 ng/mL]) for 24 h. The permeability of horseradish peroxidase and fluorescein isothiocyanate-conjugated Dextran and transepithelial resistance and potential difference were measured in Ussing chambers. Interleukin-6, IL-8, NO, inducible NO synthase mRNA, STAT activity, and suppressor of cytokine signaling (SOCS) expression were measured in medium or cell lysates. Cytomix resulted in increased epithelial permeability of both fluorescein isothiocyanate-conjugated Dextran and horseradish peroxidase; whereas treatment of Caco-2 cells with SA 500 micromol/L blocked the cytomix-induced permeability changes. In addition, SA treatment decreased cytomix-induced NO production and inducible NO synthase mRNA expression and decreased the levels of STAT1, STAT3, SOCS1, and SOCS3. The SA treatment also decreased cytomix-induced IL-6 and IL-8 production in a dose-dependent manner. In conclusion, cytomix increased epithelial permeability, which is associated with increased NO and STAT activities. The SA treatment ameliorated cytomix-induced permeability, possibly through the downregulation of the NO and Janus kinase/STAT pathways.

Caco-2 Cells↗