Developmental Expression and Cellular Origin of the Laminin α2, α4, and α5 Chains in the Intestine

AbstractLaminins are extracellular matrix glycoproteins that are involved in various cellular functions, including adhesion, proliferation, and differentiation. In this study, we examine the expression patterns and the cellular origins of the laminin α2, α4, and α5 chains in the developing mouse intestine and inin vitromouse/chick or chick/mouse interspecies hybrid intestines.In situhybridization and Northern blot analysis revealed that mRNA levels for all three laminin α chains are highest in the fetal intestine undergoing intense morphogenetic movements. Laminin α4 mRNA and polypeptide are associated with mesenchyme-derived cell populations such as endothelium and smooth muscle. In contrast, laminin α2 and α5 chains participate in the structural organization of the subepithelial basement membrane and, in the mature intestine, show a complementary pattern of expression. All three laminin α chains occur in the smooth muscle basement membrane, with a differential expression of laminin α5 chain in the circular and longitudinal smooth muscle layers. The cellular origin of laminin α2 and α5 chains found in the subepithelial cell basement membrane was studied by immunocytochemical analysis of mouse/chick or chick/mouse interspecies hybrid intestines at various stages of development using mouse-specific antibodies. Laminin α2 was found to be deposited into the basement membrane exclusively by mesenchymal cells, while the laminin α5 chain was deposited by both epithelial and mesenchymal cells in an apparently developmentally regulated pattern. We conclude that (1) multiple laminin α chains are expressed in the intestine, implying specific roles for individual laminin isoforms during intestinal development, and (2) reciprocal epithelial/mesenchymal interactions are essential for the formation of a structured subepithelial basement membrane

Functional interaction between the homeoprotein CDX1 and the transcriptional machinery containing the TATA-binding protein

We have previously reported that the CDX1 homeoprotein interacts with the TATA-box binding protein (TBP) on the promoter of the glucose-6-phosphatase (G6Pase) gene. We show here that CDX1 interacts with TBP via the homeodomain and that the transcriptional activity additionally requires the N-terminal domain upstream of the homeodomain. CDX1 interacting with TBP is connected to members of the TFIID and Mediator complexes, two major elements of the general transcriptional machinery. Transcription luciferase assays performed using an altered-specificity mutant of TBP provide evidence for the functionality of the interaction between CDX1 and TBP. Unlike CDX1, CDX2 does not interact with TBP nor does it transactivate the G6Pase promoter. Swapping experiments between the domains of CDX1 and CDX2 indicate that, despite opposite functional effects of the homeoproteins on the G6Pase promoter, the N-terminal domains and homeodomains of both CDX1 and CDX2 have the intrinsic ability to activate transcription and to interact with TBP. However, the carboxy domains define the specificity of CDX1 and CDX2. Thus, intra-molecular interactions control the activity and partner recruitment of CDX1 and CDX2, leading to different molecular functions

Abnormal Wnt and PI3Kinase Signaling in the Malformed Intestine of lama5 Deficient Mice

Laminins are major constituents of basement membranes and are essential for tissue homeostasis. Laminin-511 is highly expressed in the intestine and its absence causes severe malformation of the intestine and embryonic lethality. To understand the mechanistic role of laminin-511 in tissue homeostasis, we used RNA profiling of embryonic intestinal tissue of lama5 knockout mice and identified a lama5 specific gene expression signature. By combining cell culture experiments with mediated knockdown approaches, we provide a mechanistic link between laminin α5 gene deficiency and the physiological phenotype. We show that laminin α5 plays a crucial role in both epithelial and mesenchymal cell behavior by inhibiting Wnt and activating PI3K signaling. We conclude that conflicting signals are elicited in the absence of lama5, which alter cell adhesion, migration as well as epithelial and muscle differentiation. Conversely, adhesion to laminin-511 may serve as a potent regulator of known interconnected PI3K/Akt and Wnt signaling pathways. Thus deregulated adhesion to laminin-511 may be instrumental in diseases such as human pathologies of the gut where laminin-511 is abnormally expressed as it is shown here

Hemidesmosome integrity protects the colon against colitis and colorectal cancer

OBJECTIVE: Epidemiological and clinical data indicate that patients suffering from IBD with long-standing colitis display a higher risk to develop colorectal high-grade dysplasia. Whereas carcinoma invasion and metastasis rely on basement membrane (BM) disruption, experimental evidence is lacking regarding the potential contribution of epithelial cell/BM anchorage on inflammation onset and subsequent neoplastic transformation of inflammatory lesions. Herein, we analyse the role of the alpha6beta4 integrin receptor found in hemidesmosomes that attach intestinal epithelial cells (IECs) to the laminin-containing BM. DESIGN: We developed new mouse models inducing IEC-specific ablation of alpha6 integrin either during development (alpha6DeltaIEC) or in adults (alpha6DeltaIEC-TAM). RESULTS: Strikingly, all alpha6DeltaIEC mutant mice spontaneously developed long-standing colitis, which degenerated overtime into infiltrating adenocarcinoma. The sequence of events leading to disease onset entails hemidesmosome disruption, BM detachment, IL-18 overproduction by IECs, hyperplasia and enhanced intestinal permeability. Likewise, IEC-specific ablation of alpha6 integrin induced in adult mice (alpha6DeltaIEC-TAM) resulted in fully penetrant colitis and tumour progression. Whereas broad-spectrum antibiotic treatment lowered tissue pathology and IL-1beta secretion from infiltrating myeloid cells, it failed to reduce Th1 and Th17 response. Interestingly, while the initial intestinal inflammation occurred independently of the adaptive immune system, tumourigenesis required B and T lymphocyte activation. CONCLUSIONS: We provide for the first time evidence that loss of IECs/BM interactions triggered by hemidesmosome disruption initiates the development of inflammatory lesions that progress into high-grade dysplasia and carcinoma. Colorectal neoplasia in our mouse models resemble that seen in patients with IBD, making them highly attractive for discovering more efficient therapies.PMC559510

Optimisation de la revascularisation des îlots pancréatiques au cours de la transplantation (Approche génétique ou pharmacologique?)

Une revascularisation rapide et efficace des îlots pancréatiques au cours de la transplantation est essentielle pour la survie et la fonctionnalité du greffon à long terme. Le Vascular Endothelial Growth Factor (VEGF), un puissant facteur de croissance vasculaire, pourrait être un facteur clé dans la modulation de la revascularisation des îlots après la transplantation. Le but de ce travail était d'étudier l'effet de l infection adénovirale ou de la déferoxamine (DFO), un chélateur du fer, sur la viabilité, la fonctionnalité et l expression du VEGF sur les cellules b et les îlots pancréatiques in vitro et sur la revascularisation des îlots et le contrôle métabolique de rats diabétiques après transplantation. In vitro, la DFO et l infection adénovirale induisent une surexpression du VEGF qui dure respectivement 3 et 14 jours. La DFO pour une concentration de 10 mol/L permet une préservation de la viabilité, une stimulation de la fonctionnalité et est anti-apoptotique sur les cellules b et les îlots pancréatiques. Par contre, l infection adénovirale est pro-apoptotique et induit une diminution de la fonctionnalité et de l expression de l ARNm de l insuline dans les cellules b et les îlots pancréatiques. Finalement, l étude in vivo confirment les données in vitro, montrant une stimulation de la revascularisation des îlots et une amélioration du contrôle métabolique chez le rat diabétique pour une pré-incubation des îlots pendant 3 jours en présence de DFO. De même, l étude in vivo confirme l effet délétère de l infection adénovirale sur le contrôle métabolique par rapport à une transplantation classique malgré une stimulation de la revascularisation. En conclusion, l approche pharmacologique de surexpression du VEGF par la DFO semble être un outil plus prometteur qu une infection adénovirale du gène du VEGF pour améliorer la viabilité du greffon après transplantation.Rapid and adequate revascularisation of transplanted islets is important for islet survival and function during transplantation.Vascular Endothelial Growth Factor (VEGF), a major angiogenic growth factor, may be a key factor in modulating the revascularization of islets after transplantation. The aim of this work was to study the effect of adenoviral infection or deferoxamine (DFO), an iron chelator, on b cells and pancreatic islets viability, functionality and VEGF expression in vitro and on islets revascularisation and on metabolic control of diabetics rats after transplantation. In vitro, DFO and adenoviral infection induce VEGF overexpression during respectively 3 and 14 days. DFO, for a concentration of 10 mol/L, allows a preservation of b cells and pancreatic islets viability, a stimulation of functionality and present an anti-apoptotic effect. Adenoviral infection is pro-apoptotique and induces a reduction of functionality and expression of insulin mRNA in b cells and islets. Finally, the in vivo study confirms the in vitro data, showing a stimulation of islets revascularization and an improvement of metabolic control of diabetics rats for a pre-incubation of islets during 3 days in the presence of DFO. Also, the in vivo study confirms the deleterious effect of adenoviral infection on metabolic control in comparison with a classical transplantation, despite a stimulation of islets revascularisation. In conclusion, the pharmacological approach of VEGF overexpression using DFO seemed more promising to improve islets vascularization after transplantation than adenoviral infection with human VEGF 165 gene.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Rôle des plastines/fimbrines dans l'assemblage du cytosquelette d'actine et le mouvement cellulaire

STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Biosynthesis and turn-over of human intestinal brush border glycoproteins during organ culture

International audienc

Développement de la fonction digestive : régulation de la maturation des enzymes de la bordure en brosse intestinale

International audienc