ORCID Profile
0000-0001-9130-9174
Current Organisation
INSERM U1109
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Publisher: Elsevier BV
Date: 1999
Abstract: Laminins 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 alpha2, alpha4, and alpha5 chains in the developing mouse intestine and in in vitro mouse/chick or chick/mouse interspecies hybrid intestines. In situ hybridization and Northern blot analysis revealed that mRNA levels for all three laminin alpha chains are highest in the fetal intestine undergoing intense morphogenetic movements. Laminin alpha4 mRNA and polypeptide are associated with mesenchyme-derived cell populations such as endothelium and smooth muscle. In contrast, laminin alpha2 and alpha5 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 alpha chains occur in the smooth muscle basement membrane, with a differential expression of laminin alpha5 chain in the circular and longitudinal smooth muscle layers. The cellular origin of laminin alpha2 and alpha5 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 alpha2 was found to be deposited into the basement membrane exclusively by mesenchymal cells, while the laminin alpha5 chain was deposited by both epithelial and mesenchymal cells in an apparently developmentally regulated pattern. We conclude that (1) multiple laminin alpha chains are expressed in the intestine, implying specific roles for in idual laminin isoforms during intestinal development, and (2) reciprocal epithelial/mesenchymal interactions are essential for the formation of a structured subepithelial basement membrane.
Publisher: Elsevier BV
Date: 08-2003
DOI: 10.1016/S0012-1606(03)00254-9
Abstract: Laminins (comprised of alpha, beta, and gamma chains) are heterotrimeric glycoproteins integral to all basement membranes. The function of the laminin alpha5 chain in the developing intestine was defined by analysing laminin alpha5(-/-) mutants and by grafting experiments. We show that laminin alpha5 plays a major role in smooth muscle organisation and differentiation, as excessive folding of intestinal loops and delay in the expression of specific markers are observed in laminin alpha5(-/-) mice. In the subepithelial basement membrane, loss of alpha5 expression was paralleled by ectopic or accelerated deposition of laminin alpha2 and alpha4 chains this may explain why no obvious defects were observed in the villous form and enterocytic differentiation. This compensation process is attributable to mesenchyme-derived molecules as assessed by chick/mouse alpha5(-/-) grafted associations. Lack of the laminin alpha5 chain was accompanied by a decrease in epithelial alpha3beta1 integrin receptor expression adjacent to the epithelial basement membrane and of Lutheran blood group glycoprotein in the smooth muscle cells, indicating that these receptors are likely mediating interactions with laminin alpha5-containing molecules. Taken together, the data indicate that the laminin alpha5 chain is essential for normal development of the intestinal smooth muscle and point to possible mesenchyme-derived compensation to promote normal intestinal morphogenesis when laminin alpha5 is absent.
Publisher: Wiley
Date: 2005
DOI: 10.1002/GENE.20154
Abstract: Laminins are heterotrimeric glycoproteins of the basement membranes. Laminin 1 (alpha1, beta1, gamma1) is the major laminin expressed during early mouse embryogenesis. To gain access to the physiological function of laminin alpha1 chain, we developed a conditionally null allele of its encoding gene (Lama1) using the cre/loxP system. Floxed-allele-carrying mice (Lama1(flox/flox)) display no overt phenotype. Lama1(flox/flox) mice were crossed with transgenic deleter mice (CMV-Cre) to generate Lama1-deficient mice (Lama1(Delta/Delta)). Lama1(Delta/Delta) embryos die during the early postimplantation period after embryonic day 6.5. They lack Reichert's membrane, an extraembryonic basement membrane in which laminin alpha1 is normally highly expressed. In parallel, Lama1(Delta/Delta) embryos display 1) parietal and visceral endoderm differentiation defects with altered expression of cytokeratin 19 and GATA4, respectively, and 2) an induction of apoptosis. This new mouse model is of particular interest as it will allow time- and tissue-specific inactivation of the Lama1 gene in various organs.
Publisher: eLife Sciences Publications, Ltd
Date: 06-01-2021
DOI: 10.7554/ELIFE.61539
Abstract: Cancer extracellular vesicles (EVs) shuttle at distance and fertilize pre-metastatic niches facilitating subsequent seeding by tumor cells. However, the link between EV secretion mechanisms and their capacity to form pre-metastatic niches remains obscure. Using mouse models, we show that GTPases of the Ral family control, through the phospholipase D1, multi-vesicular bodies homeostasis and tune the biogenesis and secretion of pro-metastatic EVs. Importantly, EVs from RalA or RalB depleted cells have limited organotropic capacities in vivo and are less efficient in promoting metastasis. RalA and RalB reduce the EV levels of the adhesion molecule MCAM/CD146, which favors EV-mediated metastasis by allowing EVs targeting to the lungs. Finally, RalA, RalB, and MCAM/CD146, are factors of poor prognosis in breast cancer patients. Altogether, our study identifies RalGTPases as central molecules linking the mechanisms of EVs secretion and cargo loading to their capacity to disseminate and induce pre-metastatic niches in a CD146-dependent manner.
Publisher: Cold Spring Harbor Laboratory
Date: 10-07-2020
DOI: 10.1101/2020.07.10.196691
Abstract: Cancer extracellular vesicles (EVs) mainly exert pro-tumoral functions by changing the phenotypes of stromal cells to the benefit of tumor growth and metastasis. They shuttle to distant organs and fertilize pre-metastatic niches facilitating subsequent seeding by circulating tumor cells. The levels of tumor secreted EVs correlate with tumor aggressiveness, however, the link between EV secretion mechanisms and their capacity to form pre-metastatic niches remains obscure. Here, we show that GTPases of the Ral family control, through the phospholipase D1, multi-vesicular bodies homeostasis and thereby tune the biogenesis and secretion of pro-metastatic EVs. RalA and RalB promote lung metastasis in a syngeneic mouse model. Importantly, EVs from RalA or RalB depleted cells have limited organotropic capacities in vivo and, as a consequence, are less efficient in promoting lung metastasis. RalA or RalB modulate the EV levels of the adhesion molecule MCAM/CD146, which mediates lung colonization. Finally, RalA and RalB, but also MCAM/CD146, are factors of poor prognosis in human breast cancer patients. Altogether, our study identifies Ral GTPases as central molecules linking the mechanisms of EVs secretion, cargo loading to their capacity to disseminate and induce pre-metastatic niches.
Publisher: Elsevier BV
Date: 10-2005
DOI: 10.1016/J.HUMPATH.2005.07.013
Abstract: Hirschsprung disease (HD), a developmental disorder, is associated with failure of enteric ganglia formation. Signaling molecules, including secreted basement membrane molecules, derived from the mesenchyme of the gut wall play an important role in the colonization and/or differentiation of the enteric nervous system. The current study aims to define the possible alterations of laminins involved in the pathogenesis of HD. Expression of the various laminin alpha, beta, and gamma chains, was assessed in the aganglionic, transitional, and ganglionic bowel segments of patients with HD or with other motor disorders. Cytoskeletal, neuronal, and glial markers were also included in this study. The major finding highlighted by the present work concerns the clear identification and location of myenteric aganglionic plexuses in HD with some of the laminin antibodies, which reveal a peripheral nerve type of differentiation. Furthermore, we could show an increase of laminin alpha5 chain immunostaining in the dilated muscle of the ganglionic bowel upstream the distal aganglionic region in a subgroup of patients with HD, as well as a relocalization of laminin alpha2 chain in the subepithelial basement membrane. Overall, these basement membrane molecules could provide useful markers for diagnosis of aganglionosis or hypoganglionosis.
Publisher: Public Library of Science (PLoS)
Date: 27-10-2014
No related grants have been discovered for Olivier Lefebvre.