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Dynamic patterning at the pylorus: formation of an epithelial intestine-stomach boundary in late fetal life

ABSTRACT: In the adult mouse, distinct morphological and transcriptional differences separate stomach from intestinal epithelium. Remarkably, the epithelial boundary between these two organs is literally one cell thick. This discrete junction is established suddenly and precisely at embryonic day (E) 16.5, by sharpening a previously diffuse intermediate zone. In the present study, we define the dynamic transcriptome of stomach, pylorus and intestinal tissues between E14.5 and E16.5. We show that establishment of this boundary is concomitant with the induction of over a thousand genes in intestinal epithelium, and these gene products provide intestinal character. Hence, we call this process intestinalization. We identify specific transcription factors (Hnf4g, Creb3l3 and Tcfec) and examine signaling pathways (Hedgehog and Wnt) that may play a role in this process. Finally, we define a unique expression domain at the pylorus itself and detect novel pylorus-specific patterns for the transcription factor Gata3 and the secreted protein nephrocan.

ORGANISM(S): Mus musculus

PROVIDER: GSE15872 | GEO | 2009/10/01

SECONDARY ACCESSION(S): PRJNA117023

REPOSITORIES: GEO

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Project description:Diverse functions of the homeodomain transcription factor BARX1 include Wnt-dependent, non-cell autonomous specification of the stomach epithelium, tracheo-bronchial septation, and Wnt-independent expansion of the spleen primordium. Tight spatio-temporal regulation of Barx1 levels in the mesentery and stomach mesenchyme suggests additional roles. To determine these functions, we forced constitutive BARX1 expression in the Bapx1 expression domain, which includes the mesentery and intestinal mesenchyme, and also examined Barx1-/- embryos in further detail. Transgenic embryos invariably showed intestinal truncation and malrotation, in part reflecting abnormal left-right patterning. Ectopic BARX1 expression did not affect intestinal epithelium, but intestinal smooth muscle developed with features typical of the stomach wall. BARX1, which is normally restricted to the developing stomach, drives robust smooth muscle expansion in this organ by promoting proliferation of myogenic progenitors at the expense of other sub-epithelial cells. Undifferentiated embryonic stomach and intestinal mesenchyme showed modest differences in mRNA expression and BARX1 was sufficient to induce much of the stomach profile in intestinal cells. However, limited binding at cis-regulatory sites implies that BARX1 may act principally through other transcription factors. Genes expressed ectopically in BARX1+ intestinal mesenchyme and reduced in Barx1-/- stomach mesenchyme include Isl1, Pitx1, Six2 and Pitx2, transcription factors known to control left-right patterning and influence smooth muscle development. The sum of evidence suggests that potent BARX1 functions in intestinal rotation and stomach myogenesis occur through this small group of intermediary transcription factors. To investigate how Barx1 regulates gut smooth muscle development in a cell-autonomous manner, we used Affymetrix arrays to profile genes enriched in wild-type stomach and BARX1-overexpressing intestinal mesenchyme, compared to wild-type intestinal mesenchyme.

Project description:The endodermal lining of the adult gastro-intestinal tract harbors stem cells that are responsible for the day-to-day regeneration of the epithelium. Stem cells residing in the pyloric glands of the stomach and in the small intestinal crypts differ in their differentiation program and in the gene repertoire that they express. Both types of stem cells have been shown to grow from single cells into 3D structures (organoids) in vitro. We show that single adult Lgr5-positive stem cells, isolated from small intestinal organoids, require Cdx2 to maintain their intestinal identity and are converted cell-autonomously into pyloric stem cells in the absence of this transcription factor. Clonal descendants of Cdx2null small intestinal stem cells enter the gastric differentiation program instead of producing intestinal derivatives. Conversely, forced expression of Cdx2 in gastric organoids results in their intestinalization. The intestinal genetic program is thus critically dependent on the single transcription factor encoding gene Cdx2. Small intestinal crypts and stomach glands were isolated from Cdx2-/fl / Lgr5-EGFP-CreERT2 mice and cultured for a week in order to generate small intestinal (SI) and stomach (Sto) in vitro organoids. The Lgr5-CreERT2 enzyme activity has been induced by overnight 4-hydroxytamoxifen induction. Tamoxifen treated and untreated Lgr5-EGFPhi SI and Sto stem cells were FACS sorted and seeded back into ENRWfg (Sto med) culture conditions in order to generate Cdx2-/fl small intestinal (Control SI), Cdx2null small intestinal (Cdx2null SI) and Cdx2-/fl stomach (Control Sto) clonal organoids. Cdx2-/fl SI organoids and Cdx2-/fl Sto organoids have been also cultured in ENR (SI med) to induce differentiation. After some passages of clonal organoid expansion, RNA was isolated from Control SI, Cdx2null SI and Control Sto Lgr5-EGFPhi FACS sorted stem cell populations and from smal intestinal and stomach organoids cultured in different conditions and hybridized on Affymetrix Mouse Gene ST 1.1 arrays.

Project description:The small intestinal epithelium mediates vital functions of nutrient absorption and host defense. The spatial organization of the epithelial cells along the crypt-villus axis segregates them into regions of specialized function. However, many of the mechanisms governing intestinal epithelial cell migration and the coordination of interactions with adjacent cells and the extracellular matrix are not fully understood. We have evaluated in vivo gene expression patterns of ileal epithelial cells in healthy human subjects, isolated by laser capture microdissection from either the villus epithelial or crypt cell regions of the small intestinal mucosa. Expression profiles in villus epithelium and Paneth cell lineages were determined by quantitative real-time PCR, DNA microarray, and immunohistochemistry based methods. Relative expression levels of selected epithelial biomarkers were compared between the ileum, jejunum, duodenum, colon, stomach, and esophagus. Previously established biomarkers as well as a novel and distinct set of genes believed to be linked to epithelial cell motility, adhesion, and differentiation were found to be enriched in each of the two corresponding cell populations. Additionally, high baseline expression levels of innate antimicrobials, alpha defensin 5 (HD5) and regenerating islet-derived 3 alpha (Reg3A), were detected exclusively within the small bowel, most notably in the ileum, in comparison to other sites along the gastrointestinal tract. Our findings provide new and important insights regarding the molecular machinery employed by small intestinal epithelial cells to mediate their function and spatial organization in vivo. Experiment Overall Design: Surgical specimens of human intestinal mucosa were obtained from 4 individuals undergoing surgery for colon cancer, bowel obstruction, or other non-inflammatory conditions. The samples were fixed overnight in 4% (w/v) paraformaldehyde, dehydrated in a graded alcohol series and paraffin-embedded. At least 500 epithelial cells from the crypt or upper villus regions were then captured by LCMD from unstained 6Âµm thick sections using a PALM MicroLaser System Total RNA was extracted for microarray-based gene expression analysis.

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Dynamic patterning at the pylorus: formation of an epithelial intestine-stomach boundary in late fetal life

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