Use of transgenic mice to map cis-acting elements in the intestinal fatty acid binding protein gene (Fabpi) that control its cell lineage-specific and regional patterns of expression along the duodenal-colonic and crypt-villus axes of the gut epithelium.

Abstract

Abstract. The mouse intestinal epithelium is able to establish and maintain complex lineage-specific, spatial, and temporal patterns of gene expression despite its rapid and continuous renewal. A multipotent stem cell located near the base of each intestinal crypt gives rise to progeny which undergo amplification and allocation to either enterocytic, Paneth cell, goblet cell, or enteroendocrine cell lineages. Differentiation of these four lineages occurs during their geographically ordered migration along the crypt-villus axis. Gut stem cells appear to have a "positional address" which is manifested by differences in the differentiation programs of their lineal descendants along the duodenalcolonic (cephalocaudal) axis. We have used the intestinal fatty acid binding protein gene (Fabpi) as a model to identify cis-acting elements which regulate cell-and region-specific patterns of gene expression in the gut.Nucleotides -1178 to +28 of rat Fabpi direct a pattern of expression of a reporter (human growth hormone [hGH]) which mimics that of mouse Fabpi (a) steady-state levels of hGH mRNA are highest in the distal jejunum of adult transgenic mice and fall progressively toward both the duodenum and the midcolon; and (b) hGH is confined to the enterocytic lineage and first appears as postmitotic, differentiating cells exit the crypt and migrate to the base of small intestinal villi or their colonic homologs, the surface epithelial cuffs. Nucleotides -103 to +28, which are highly conserved in rat, mouse and human Fabpi, are able to correctly initiate transgene expression in late fetal life, restrict hGH to the enterocytic lineage, and establish an appropriate cephalocaudal gradient of reporter expression. This cephalocaudal gradient is also influenced by cis-acting elements located between nucleotides -1178 and -278, and -277 and -185 that enhance and suppress (respectively) expression in the ileum and colon and by element(s) located upstream of nucleotide -277 that are needed to sustain high levels of hGH production after weaning. Nucleotides -277 to -185 contain part of a domain conserved between the three orthologous Fabpi genes (nucleotides -240 to -159), a 24-bp element (nucleotides -212 to -188) that binds nuclear factors present in colonic but not small intestinal epithelial cells, and a portion of a CCAAT/enhancer binding protein footprint (C/EBPa, nucleotides -188 to -167). Removal of nucleotides -277 to -185 (yielding i_FABP-lS4 to +2S/hGH+3) results in inappropriate expression of hGH in proliferating and nonproliferating epithelial cells located in the mid and upper portions of duodenal, jejunal, ileal, and colonic crypts without affecting the "shape" of the cephalocaudal gradient of transgene expression. Despite this precocious induction of hGH production, the hGH reporter remains restricted to the enterocytic lineage in both the small intestine and colon suggesting that these replicating crypt epithelial cells may already be allocated to this lineage at the point of induction of transgene expression. Alt...

Prosurvival and antiapoptotic effects of PGE2in radiation injury are mediated by EP2receptor in intestine

“…Mice were irradiated at 12-14 wk of age in a Gamacel 40 cesium irradiator (Atomic Energy of Canada, Ottawa, Canada) at 0.96 cGy/min. Animals were killed at specified times after irradiation and were rapidly dissected as described previously (11). The proximal jejunum was fixed in Bouin's solution and divided into at least 8-to 5-mm segments before paraffin embedding and immunohistochemical analysis.…”

Evidence for a Role of the Gut Hormone PYY in the Regulation of Intestinal Fatty Acid-binding Protein Transcripts in Differentiated Subpopulations of Intestinal Epithelial Cell Hybrids

“…The proposed "programming" of I-FABP expression at the level of the progenitor cell has been based on data derived from transgenic mice. In these studies, the Ϫ1178 to 28 nt of the rat I-FABP gene was used to identify specific patterns of gene expression in the gut (51). A number of elements within this region have been identified as potential targets for regulation by both hormonal and unidentified intestine-specific nuclear factors (51)(52)(53).…”

“…In these studies, the Ϫ1178 to 28 nt of the rat I-FABP gene was used to identify specific patterns of gene expression in the gut (51). A number of elements within this region have been identified as potential targets for regulation by both hormonal and unidentified intestine-specific nuclear factors (51)(52)(53). One of these sequences was a potential CCAAT/enhancer-binding protein element, and specific isoforms of CCAAT/enhancerbinding protein have been proposed to play a role in the differentiation of enterocytes (54).…”

Diverse developing mouse lineages exhibit high-level c-Myb expression in immature cells and loss of expression upon differentiation

“…The maturation of intestinal cells follows a highly proscribed course; proliferating stem cells in the lower crypt region continuously give rise to post-mitotic cells that migrate up the crypt, past the neck, and up the villous. No expression of terminal di erentiation villous epithelial markers such as sucrase/isomaltase (Chandrasena et al, 1992;Tung et al, 1997), fatty acid binding protein (Cohn et al, 1992;Rottman and Gordon, 1993), and adenosine deaminase (Witte et al, 1991) occurs until the cells cross the neck of the crypt. This is exactly the stage at which c-Myb expression is extinguished.…”