Laminin α5 guides tissue patterning and organogenesis

Laminins (LM) are extracellular matrix molecules that contribute to and are required for the formation of basement membranes. They participate in the modulation of epithelial/mesenchymal interactions and are implicated in organogenesis and maintenance of organ homeostasis. Among the LM molecules, the LM α5 chain (LMα5) is one of the most widely distributed LM in the developing and mature organism. Its presence in some basement membranes during embryogenesis is absolutely required for maintenance of basement membrane integrity and thus for proper organogenesis. LMα5 also regulates the expression of genes important for major biological processes, in part by repressing or activating signaling pathways, depending upon the physiological context

Quantitative proteomics identify Tenascin-C as a promoter of lung cancer progression and contributor to a signature prognostic of patient survival

The extracellular microenvironment is an integral component of normal and diseased tissues that is poorly understood owing to its complexity. To investigate the contribution of the microenvironment to lung fibrosis and adenocarcinoma progression, two pathologies characterized by excessive stromal expansion, we used mouse models to characterize the extracellular matrix (ECM) composition of normal lung, fibrotic lung, lung tumors, and metastases. Using quantitative proteomics, we identified and assayed the abundance of 113 ECM proteins, which revealed robust ECM protein signatures unique to fibrosis, primary tumors, or metastases. These analyses indicated significantly increased abundance of several S100 proteins, including Fibronectin and Tenascin-C (Tnc), in primary lung tumors and associated lymph node metastases compared with normal tissue. We further showed that Tnc expression is repressed by the transcription factor Nkx2-1, a well-established suppressor of metastatic progression. We found that increasing the levels of Tnc, via CRISPR-mediated transcriptional activation of the endogenous gene, enhanced the metastatic dissemination of lung adenocarcinoma cells. Interrogation of human cancer gene expression data revealed that high TNC expression correlates with worse prognosis for lung adenocarcinoma, and that a three-gene expression signature comprising TNC, S100A10, and S100A11 is a robust predictor of patient survival independent of age, sex, smoking history, and mutational load. Our findings suggest that the poorly understood ECM composition of the fibrotic and tumor microenvironment is an underexplored source of diagnostic markers and potential therapeutic targets for cancer patients

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

laminin-511, actor of inflammation and of tumoral progression in the intestine?

La laminine-511 (a5b1y1), élément de la matrice extracellulaire, fait partie des molécules médiatrices des interactions épithélio-mésenchymateuses qui contrôlent le développement intestinal puis le renouvellement cellulaire dans l'organe mature. Une rupture de l'homéostasie de l'ensemble de ces mécanismes est centrale dans les maladies inflammatoires chroniques de l'intestin (MICI) qui, dans une certaine proportion, peuvent dégénérer en cancer colorectal. Ce travail de thèse a permis de démontrer que la chaîne a5 de laminine, caractéristique de la laminine-511, pouvait d'une part réguler l'expression de gènes cibles importants dans les fonctions biologiques majeures des cellules intestinales et d'autre part était capable de réprimer ou d'activer deux voies de signalisation, Wnt et PI3K/Akt, suivant le contexte physiologique. Dans le contexte pathologique particulier des MICI, j ai pu définir la composition en laminines de la lame basale dans des segments pathologiques issus d'exérèses chirurgicales de côlons de patients atteints de maladie de Crohn ou de rectocolite hémorragique. De façon très intéressante, des glandes atypiques y ont été trouvées, délimitées par une lame basale enrichie en chaînes a1 et a5 de laminines et caractérisées par une accumulation nucléaire de la protéine p53, suppresseur de tumeur. J ai pu définir, par des expériences in vitro, une chronologie d'activation montrant que la protéine p53 était capable de stimuler l'expression endogène de la chaîne a1 de laminine. J ai également pu modéliser les résultats obtenus chez l'humain par des inductions chimiques d'inflammation et de tumorigenèse associée grâce à des modèles de souris transgéniques sur-exprimant soit la chaîne a1 soit la chaîne a5 dans l'épithélium intestinal, modèles établis par l'équipe. Les dérégulations des laminines qui ont été observées peuvent jouer un rôle important dans la rupture de l'épithélium, l'inflammation et les mécanismes de réparation qui leur sont inhérents ou dans la progression des MICI en cancer.The laminin-511 (a5b1y1), key element of the extracellular matrix, mediates the epithelialmesenchymal interactions controlling the intestinal development and the cell renewal in the mature organ. A deregulation of the mechanisms implied in the homeostasis is obvious in inflammatory bowel diseases (IBD). IBD can in some cases degenerate into colorectal cancer. My present work demonstrates that the a5 chain, characteristic of the laminin-511 molecule, regulates the expression of target genes important for major biological functions of the intestinal cells as well as is able to repress or activate two signaling pathways, Wnt and PI3K/Akt, according to the physiological context. In the particular context of IBD, I could define the laminin composition of the basement membrane in pathological samples from surgical resection of colon from patients with Crohn s disease or Ulcerative colitis. Interestingly, atypical glands are also found in these samples. These glands are encircled with a basement membrane enriched in laminin a1 and a5 chains and are characterized by a nuclear accumulation of p53, a tumor suppressor. By in vitro experiments, I have defined a chronology of activation showing that the p53 protein is able to stimulate the endogenous expression of the laminin a1 chain. I could mimic the results obtained in humans by triggering inflammation and inflammation-associated tumorigenesis chemically to transgenic murine models overexpressing either the laminin a1 or a5 chain, models that were previously established in the team. The laminin-observed deregulations could play an important role in the epithelium rupture, the inflammation and the inherent repair mechanisms, as well as in the progression of IBD into cancer

Autonomous Extracellular Matrix Remodeling Controls a Progressive Adaptation in Muscle Stem Cell Regenerative Capacity during Development.

Muscle stem cells (MuSCs) exhibit distinct behavior during successive phases of developmental myogenesis. However, how their transition to adulthood is regulated is poorly understood. Here, we show that fetal MuSCs resist progenitor specification and exhibit altered division dynamics, intrinsic features that are progressively lost postnatally. After transplantation, fetal MuSCs expand more efficiently and contribute to muscle repair. Conversely, niche colonization efficiency increases in adulthood, indicating a balance between muscle growth and stem cell pool repopulation. Gene expression profiling identified several extracellular matrix (ECM) molecules preferentially expressed in fetal MuSCs, including tenascin-C, fibronectin, and collagen VI. Loss-of-function experiments confirmed their essential and stage-specific role in regulating MuSC function. Finally, fetal-derived paracrine factors were able to enhance adult MuSC regenerative potential. Together, these findings demonstrate that MuSCs change the way in which they remodel their microenvironment to direct stem cell behavior and support the unique demands of muscle development or repair

Autonomous Extracellular Matrix Remodeling Controls a Progressive Adaptation in Muscle Stem Cell Regenerative Capacity during Development

Muscle stem cells (MuSCs) exhibit distinct behavior during successive phases of developmental myogenesis. However, how their transition to adulthood is regulated is poorly understood. Here, we show that fetal MuSCs resist progenitor specification and exhibit altered division dynamics, intrinsic features that are progressively lost postnatally. After transplantation, fetal MuSCs expand more efficiently and contribute to muscle repair. Conversely, niche colonization efficiency increases in adulthood, indicating a balance between muscle growth and stem cell pool repopulation. Gene expression profiling identified several extracellular matrix (ECM) molecules preferentially expressed in fetal MuSCs, including tenascin-C, fibronectin, and collagen VI. Loss-of-function experiments confirmed their essential and stage-specific role in regulating MuSC function. Finally, fetal-derived paracrine factors were able to enhance adult MuSC regenerative potential. Together, these findings demonstrate that MuSCs change the way in which they remodel their microenvironment to direct stem cell behavior and support the unique demands of muscle development or repair

Toward a Combination of Biomarkers for Molecular Characterization of Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disease affecting the central nervous system associated with chronic inflammation, demyelination, and axonal damage. MS is a highly heterogeneous disease that leads to discrepancies regarding the clinical appearance, progression, and therapy response of patients. Therefore, there is a strong unmet need for clinically relevant biomarkers capable of recapitulating the features of the disease. Experimental autoimmune encephalomyelitis (EAE) is a valuable model for studying the pathophysiology of MS as it recapitulates the main hallmarks of the disease: inflammation, blood-brain barrier (BBB) disruption, gliosis, myelin damage, and repair mechanisms. In this study, we used the EAE-PLP animal model and established a molecular RNA signature for each phase of the disease (onset, peak, remission). We compared variances of expression of known biomarkers by RT-qPCR in the brain and spinal cord of sham and EAE animals monitoring each of the five hallmarks of the disease. Using magnetic cell isolation technology, we isolated microglia and oligodendrocytes of mice of each category, and we compared the RNA expression variations. We identify genes deregulated during a restricted time frame, and we provide insight into the timing and interrelationships of pathological disease processes at the organ and cell levels

Functionalized Tobacco Mosaic Virus Coat Protein Monomers and Oligomers as Nanocarriers for Anti-Cancer Peptides

Coralie Gamper, Caroline Spenlé and Sonia Boscá contributed equally to the study.International audienceComponents with self-assembly properties derived from plant viruses provide the opportunity to design biological nanoscaffolds for the ordered display of agents of diverse nature and with complementing functions. With the aim of designing a functionalized nanoscaffold to target cancer, the coat protein (CP) of Tobacco mosaic virus (TMV) was tested as nanocarrier for an insoluble, highly hydrophobic peptide that targets the transmembrane domain of the Neuropilin-1 (NRP1) receptor in cancer cells. The resulting construct CPL-K (CP-linker-"Kill") binds to NRP1 in cancer cells and disrupts NRP1 complex formation with PlexA1 as well as downstream Akt survival signaling. The application of CPL-K also inhibits angiogenesis and cell migration. CP was also fused to a peptide that targets the extracellular domain of NRP1 and this fusion protein (CPL-F, CP-Linker-"Find") is shown to bind to cultured cancer cells and to inhibit NRP1-dependent angiogenesis as well. CPL-K and CPL-F maintain their anti-angiogenic properties upon co-assembly to oligomers/nanoparticles together with CPL. The observations show that the CP of TMV can be employed to generate a functionalized nanoparticle with biological activity. Remarkably, fusion to CPL allowed us to solubilize the highly insoluble transmembrane NRP1 peptide and to retain its anti-angiogenic effect