Développement Normal et Pathologique des Mélanocytes

Publications de l’équipe

Année de publication : 2017

Emma F Woodham, Nikki R Paul, Benjamin Tyrrell, Heather J Spence, Karthic Swaminathan, Michelle R Scribner, Evangelos Giampazolias, Ann Hedley, William Clark, Frieda Kage, Daniel J Marston, Klaus M Hahn, Stephen W G Tait, Lionel Larue, Cord H Brakebusch, Robert H Insall, Laura M Machesky (2017 Feb 28)

Coordination by Cdc42 of Actin, Contractility, and Adhesion for Melanoblast Movement in Mouse Skin.

Current biology : CB : DOI : S0960-9822(17)30065-9 En savoir plus
Résumé

The individual molecular pathways downstream of Cdc42, Rac, and Rho GTPases are well documented, but we know surprisingly little about how these pathways are coordinated when cells move in a complex environment in vivo. In the developing embryo, melanoblasts originating from the neural crest must traverse the dermis to reach the epidermis of the skin and hair follicles. We previously established that Rac1 signals via Scar/WAVE and Arp2/3 to effect pseudopod extension and migration of melanoblasts in skin. Here we show that RhoA is redundant in the melanocyte lineage but that Cdc42 coordinates multiple motility systems independent of Rac1. Similar to Rac1 knockouts, Cdc42 null mice displayed a severe loss of pigmentation, and melanoblasts showed cell-cycle progression, migration, and cytokinesis defects. However, unlike Rac1 knockouts, Cdc42 null melanoblasts were elongated and displayed large, bulky pseudopods with dynamic actin bursts. Despite assuming an elongated shape usually associated with fast mesenchymal motility, Cdc42 knockout melanoblasts migrated slowly and inefficiently in the epidermis, with nearly static pseudopods. Although much of the basic actin machinery was intact, Cdc42 null cells lacked the ability to polarize their Golgi and coordinate motility systems for efficient movement. Loss of Cdc42 de-coupled three main systems: actin assembly via the formin FMNL2 and Arp2/3, active myosin-II localization, and integrin-based adhesion dynamics.

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Juliette U Bertrand, Valérie Petit, Elke Hacker, Irina Berlin, Nicholas K Hayward, Marie Pouteaux, Evelyne Sage, David C Whiteman, Lionel Larue (2017 Feb 14)

UVB represses melanocyte cell migration and acts through β-catenin.

Experimental dermatology : DOI : 10.1111/exd.13318 En savoir plus
Résumé

The exposure of skin to ultraviolet (UV) radiation can have both beneficial and deleterious effects: it can lead, for instance, to increased pigmentation and vitamin D synthesis but also to inflammation and skin cancer. UVB may induce genetic and epigenetic alterations, and have reversible effects associated with post-translational and gene regulation modifications. β-catenin is a main driver in melanocyte development; although infrequently mutated in melanoma, its cellular localization and activity is frequently altered. Here, we evaluate the consequence of UVB on β-catenin in the melanocyte lineage. We report that in vivo, UVB induces cytoplasmic/nuclear relocalization of β-catenin in melanocytes of newborn mice and adult human skin. In mouse melanocyte and human melanoma cell lines in vitro, UVB increases β-catenin stability, accumulation in the nucleus, and co-transcriptional activity, leading to the repression of cell motility and velocity. The activation of the β-catenin signaling pathway and its effect on migration by UVB are increased by an inhibitor of GSK3β, and decreased by an inhibitor of β-catenin. In conclusion, UVB represses melanocyte migration and does so by acting through the GSK3-β-catenin axis. This article is protected by copyright. All rights reserved.

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Année de publication : 2016

Chunya Ni, Marie-Sophie Narzt, Ionela-Mariana Nagelreiter, Cheng Feng Zhang, Lionel Larue, Heidemarie Rossiter, Johannes Grillari, Erwin Tschachler, Florian Gruber (2016 Oct 13)

Autophagy deficient melanocytes display a senescence associated secretory phenotype that includes oxidized lipid mediators.

The international journal of biochemistry & cell biology : DOI : S1357-2725(16)30305-3 En savoir plus
Résumé

Autophagy is a recycling program which allows cells to adapt to metabolic needs and to stress. Defects in autophagy can affect metabolism, aging, proteostasis and inflammation. Autophagy pathway genes, including autophagy related 7 (Atg7), have been associated with the regulation of skin pigmentation, and autophagy defects disturb the biogenesis and transport of melanosomes in melanocytes as well as transfer and processing of melanin into keratinocytes. We have previously shown that mice whose melanocytes or keratinocytes lack Atg7 (and thus autophagy) as a result of specific gene knockout still retained functioning melanosome synthesis and transfer, and displayed only moderate reduction of pigmentation. In cell culture the Atg7 deficient melanocytes were prone to premature senescence and dysregulation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) signaling. To elucidate the biochemical basis of this phenotype, we performed a study on global gene expression, protein secretion and phospholipid composition in Atg7 deficient versus Atg7 expressing melanocytes. In cell culture Atg7 deficient melanocytes showed a pro-inflammatory gene expression signature and secreted higher levels of C-X-C motif chemokine ligand -1,-2,-10 and -12 (Cxcl1, Cxcl2, Cxcl10, Cxcl12), which are implicated in the pathogenesis of pigmentary disorders and expressed higher amounts of matrix metalloproteinases -3 and -13 (Mmp3, Mmp13). The analysis of membrane phospholipid composition identified an increase in the arachidonic- to linoleic acid ratio in the autophagy deficient cells, as well as an increase in oxidized phospholipid species that act as danger associated molecular patterns (DAMPs). The secretion of inflammation related factors suggests that autophagy deficient melanocytes display a senescence associated secretory phenotype (SASP), and we propose oxidized lipid mediators as novel components of this SASP.

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Christine Grill, Lionel Larue (2016 Sep 25)

NRAS, NRAS, Which Mutation Is Fairest of Them All?

The Journal of investigative dermatology : 1936-8 : DOI : 10.1016/j.jid.2016.06.011 En savoir plus
Résumé

In 28% of melanomas, NRAS is mutated in one of two hotspots: G12 or Q61. Phosphoproteomic analysis of primary human melanocytes transduced with G12 and Q61 showed different phosphorylation events in the phosphoinositide 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathways. Surprisingly, NRAS(G12) modulates the PI3K pathway and overexpresses the kinase PIM2, whereas NRAS(Q61) is associated with the MAPK pathway and overexpression of CK2α.

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Supawadee Sukseree, Ying-Ting Chen, Maria Laggner, Florian Gruber, Valérie Petit, Ionela-Mariana Nagelreiter, Veronika Mlitz, Heidemarie Rossiter, Andreas Pollreisz, Ursula Schmidt-Erfurth, Lionel Larue, Erwin Tschachler, Leopold Eckhart (2016 Aug 19)

Tyrosinase-Cre-Mediated Deletion of the Autophagy Gene Atg7 Leads to Accumulation of the RPE65 Variant M450 in the Retinal Pigment Epithelium of C57BL/6 Mice.

PloS one : e0161640 : DOI : 10.1371/journal.pone.0161640 En savoir plus
Résumé

Targeted gene knockout mouse models have helped to identify roles of autophagy in many tissues. Here, we investigated the retinal pigment epithelium (RPE) of Atg7f/f Tyr-Cre mice (on a C57BL/6 background), in which Cre recombinase is expressed under the control of the tyrosinase promoter to delete the autophagy gene Atg7. In line with pigment cell-directed blockade of autophagy, the RPE and the melanocytes of the choroid showed strong accumulation of the autophagy adaptor and substrate, sequestosome 1 (Sqstm1)/p62, relative to the levels in control mice. Immunofluorescence and Western blot analysis demonstrated that the RPE, but not the choroid melanocytes, of Atg7f/f Tyr-Cre mice also had strongly increased levels of retinoid isomerohydrolase RPE65, a pivotal enzyme for the maintenance of visual perception. In contrast to Sqstm1, genes involved in retinal regeneration, i.e. Lrat, Rdh5, Rgr, and Rpe65, were expressed at higher mRNA levels. Sequencing of the Rpe65 gene showed that Atg7f/f and Atg7f/f Tyr-Cre mice carry a point mutation (L450M) that is characteristic for the C57BL/6 mouse strain and reportedly causes enhanced degradation of the RPE65 protein by an as-yet unknown mechanism. These results suggest that the increased abundance of RPE65 M450 in the RPE of Atg7f/f Tyr-Cre mice is, at least partly, mediated by upregulation of Rpe65 transcription; however, our data are also compatible with the hypothesis that the RPE65 M450 protein is degraded by Atg7-dependent autophagy in Atg7f/f mice. Further studies in mice of different genetic backgrounds are necessary to determine the relative contributions of these mechanisms.

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Valérie Petit, Lionel Larue (2016 Apr 28)

Any route for melanoblasts to colonize the skin !

Experimental dermatology : DOI : 10.1111/exd.13061 En savoir plus
Résumé

Melanocytes arise from the fourth embryonic layer, the neural crest. They emerge from the roof plate of the neural tube and migrate throughout the body. In mammals, these cells have the capacity to migrate in any type of environment and use various pathways and mechanisms to colonize the skin and hair, and for their maintenance throughout the life of the animal. This article is protected by copyright. All rights reserved.

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Année de publication : 2015

F Rambow, A Bechadergue, F Luciani, G Gros, M Domingues, J Bonaventure, G Meurice, J-C Marine, L Larue (2015 Dec 16)

Regulation of melanoma progression through the TCF4/miR-125b/NEDD9 cascade.

The Journal of investigative dermatology : DOI : 10.1016/j.jid.2016.02.803 En savoir plus
Résumé

Melanoma progression from a primary lesion to a distant metastasis is a complex process associated with genetic alterations, epigenetic modifications and phenotypic switches. Elucidation of these phenomena may indicate how to interfere with this fatal disease. The role of microRNAs (miRNAs) as key negative regulators of gene expression, controlling all cellular processes including cell migration and invasion, is now being recognized. Here we show from in silico analysis of miRNA expression profiles of primary and metastatic melanomas, and from functional experiments that miR-125b is a determinant candidate of melanoma progression: (i) miR-125b is more strongly expressed in aggressive metastatic than primary melanomas, (ii) there is an inverse correlation between the amount of miR-125b and overall patient survival, (iii) invasion/migration potentials in vitro are inversely correlated with the amount of miR-125b in a series of human melanoma cell lines and (iv) inhibition of miR-125b reduces migratory and invasive potentials without affecting cell proliferation in vitro. Furthermore, we show that NEDD9 is a direct target of miR-125b and is involved in modulating melanoma cell migration and invasion. Also, TCF4, associated with EMT, and invasion, induces the transcription of mir-125b-1. In conclusion, the TCF4/miR-125b/NEDD9 cascade promotes melanoma cell migration/invasion.

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Stefán A H Gudjohnsen, Diahann A M Atacho, Franck Gesbert, Graca Raposo, Ilse Hurbain, Lionel Larue, Eirikur Steingrimsson, Petur Henry Petersen (2015 Dec 5)

Meningeal Melanocytes in the Mouse: Distribution and Dependence on Mitf.

Frontiers in neuroanatomy : 149 : DOI : 10.3389/fnana.2015.00149 En savoir plus
Résumé

Melanocytes are pigment producing cells derived from the neural crest. They are primarily found in the skin and hair follicles, but can also be found in other tissues including the eye, ear and heart. Here, we describe the distribution of pigmented cells in C57BL/6J mouse meninges, the membranes that envelope the brain. These cells contain melanosomes of all four stages of development and they depend on Microphthalmia associated transcription factor (MITF), the master regulator of melanocyte development, suggesting that they are bona-fide melanocytes. The location of these pigmented cells is consistent with the location of meningeal melanomas in humans and animal models.

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Florian Rambow, Bastien Job, Valérie Petit, Franck Gesbert, Véronique Delmas, Hannah Seberg, Guillaume Meurice, Eric Van Otterloo, Philippe Dessen, Caroline Robert, Daniel Gautheret, Robert A Cornell, Alain Sarasin, Lionel Larue (2015 Oct 23)

New Functional Signatures for Understanding Melanoma Biology from Tumor Cell Lineage-Specific Analysis.

Cell reports : 840-53 : DOI : 10.1016/j.celrep.2015.09.037 En savoir plus
Résumé

Molecular signatures specific to particular tumor types are required to design treatments for resistant tumors. However, it remains unclear whether tumors and corresponding cell lines used for drug development share such signatures. We developed similarity core analysis (SCA), a universal and unsupervised computational framework for extracting core molecular features common to tumors and cell lines. We applied SCA to mRNA/miRNA expression data from various sources, comparing melanoma cell lines and metastases. The signature obtained was associated with phenotypic characteristics in vitro, and the core genes CAPN3 and TRIM63 were implicated in melanoma cell migration/invasion. About 90% of the melanoma signature genes belong to an intrinsic network of transcription factors governing neural development (TFAP2A, DLX2, ALX1, MITF, PAX3, SOX10, LEF1, and GAS7) and miRNAs (211-5p, 221-3p, and 10a-5p). The SCA signature effectively discriminated between two subpopulations of melanoma patients differing in overall survival, and classified MEKi/BRAFi-resistant and -sensitive melanoma cell lines.

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Céline Loriot, Mélanie Domingues, Adeline Berger, Mélanie Menara, Maëva Ruel, Aurélie Morin, Luis-Jaime Castro-Vega, Éric Letouzé, Cosimo Martinelli, Alexis-Pierre Bemelmans, Lionel Larue, Anne-Paule Gimenez-Roqueplo, Judith Favier (2015 Oct 14)

Deciphering the molecular basis of invasiveness in Sdhb-deficient cells.

Oncotarget : 32955-65 : DOI : 10.18632/oncotarget.5106 En savoir plus
Résumé

Metastatic pheochromocytomas and paragangliomas (PPGL) are malignant neuroendocrine tumors frequently associated with germline mutations in the SDHB gene. SDHB-mutated PPGL display a hypermethylator phenotype associated with hallmarks of epithelial-to-mesenchymal transition (EMT). In the present study, we report the characterization of a unique model of Sdhb knockout in mouse chromaffin cells. Sdhb deficient cells exhibit a metastatic phenotype as highlighted by increased individual cell migration (characterized by faster motility and increased persistence) as well as high invasive and adhesion abilities. This phenotype is associated with the modulation of Twist1, Twist2, Tcf3, Snai1, N-cadherin or Krt19 expression, reflecting an EMT-like reprogramming of cells. Krt19 is epigenetically silenced in Sdhb-deficient cells and re-expressed after treatment by the demethylating agent decitabine. Krt19 rescue by lentiviral transduction in Sdhb-deficient cells and Krt19 inhibition by RNA interference in wild-type cells were performed. Both studies revealed the involvement of KRT19 in the invasive phenotype by modulating collective and individual migration and cell/extra-cellular matrix adhesion properties. These findings underline the role of hypermethylation and EMT in the in vitro acquisition of metastatic properties, following SDHB loss of function.

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Dana Koludrovic, Patrick Laurette, Thomas Strub, Céline Keime, Madeleine Le Coz, Sebastien Coassolo, Gabrielle Mengus, Lionel Larue, Irwin Davidson (2015 Oct 7)

Chromatin-Remodelling Complex NURF Is Essential for Differentiation of Adult Melanocyte Stem Cells.

PLoS genetics : e1005555 : DOI : 10.1371/journal.pgen.1005555 En savoir plus
Résumé

MIcrophthalmia-associated Transcription Factor (MITF) regulates melanocyte and melanoma physiology. We show that MITF associates the NURF chromatin-remodelling factor in melanoma cells. ShRNA-mediated silencing of the NURF subunit BPTF revealed its essential role in several melanoma cell lines and in untransformed melanocytes in vitro. Comparative RNA-seq shows that MITF and BPTF co-regulate overlapping gene expression programs in cell lines in vitro. Somatic and specific inactivation of Bptf in developing murine melanoblasts in vivo shows that Bptf regulates their proliferation, migration and morphology. Once born, Bptf-mutant mice display premature greying where the second post-natal coat is white. This second coat is normally pigmented by differentiated melanocytes derived from the adult melanocyte stem cell (MSC) population that is stimulated to proliferate and differentiate at anagen. An MSC population is established and maintained throughout the life of the Bptf-mutant mice, but these MSCs are abnormal and at anagen, give rise to reduced numbers of transient amplifying cells (TACs) that do not express melanocyte markers and fail to differentiate into mature melanin producing melanocytes. MSCs display a transcriptionally repressed chromatin state and Bptf is essential for reactivation of the melanocyte gene expression program at anagen, the subsequent normal proliferation of TACs and their differentiation into mature melanocytes.

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Alejandro Conde-Perez, Gwendoline Gros, Christine Longvert, Malin Pedersen, Valérie Petit, Zackie Aktary, Amaya Viros, Franck Gesbert, Véronique Delmas, Florian Rambow, Boris C Bastian, Andrew D Campbell, Sophie Colombo, Isabel Puig, Alfonso Bellacosa, Owen Sansom, Richard Marais, Leon C L T Van Kempen, Lionel Larue (2015 Aug 27)

A caveolin-dependent and PI3K/AKT-independent role of PTEN in β-catenin transcriptional activity.

Nature communications : 6 : 8093 : DOI : 10.1038/ncomms9093 En savoir plus
Résumé

Loss of the tumour suppressor PTEN is frequent in human melanoma, results in MAPK activation, suppresses senescence and mediates metastatic behaviour. How PTEN loss mediates these effects is unknown. Here we show that loss of PTEN in epithelial and melanocytic cell lines induces the nuclear localization and transcriptional activation of β-catenin independent of the PI3K-AKT-GSK3β axis. The absence of PTEN leads to caveolin-1 (CAV1)-dependent β-catenin transcriptional modulation in vitro, cooperates with NRAS(Q61K) to initiate melanomagenesis in vivo and induces efficient metastasis formation associated with E-cadherin internalization. The CAV1-β-catenin axis is mediated by a feedback loop in which β-catenin represses transcription of miR-199a-5p and miR-203, which suppress the levels of CAV1 mRNA in melanoma cells. These data reveal a mechanism by which loss of PTEN increases CAV1-mediated dissociation of β-catenin from membranous E-cadherin, which may promote senescence bypass and metastasis.

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Manfred Schartl, Lionel Larue, Makoto Goda, Marcus W Bosenberg, Hisashi Hashimoto, Robert N Kelsh (2015 Aug 7)

What is a vertebrate pigment cell?

Pigment cell & melanoma research : 8-14 : DOI : 10.1111/pcmr.12409 En savoir plus
Résumé

On the basis of discussions emerging from a workshop and discussions at the 7th meeting of the European Society for Pigment Cell Research in Geneva in 2012, this manuscript outlines useful criteria for defining the bona fide pigment cells as a functional entity of the vertebrate body plan and differentiating them from ‘pigmented’ cells in general. It also proposes a nomenclature for various types of pigment cells of vertebrates.

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David J Huels, Rachel A Ridgway, Sorina Radulescu, Marc Leushacke, Andrew D Campbell, Sujata Biswas, Simon Leedham, Stefano Serra, Runjan Chetty, Guenievre Moreaux, Lee Parry, James Matthews, Fei Song, Ann Hedley, Gabriela Kalna, Fatih Ceteci, Karen R Reed, Valerie S Meniel, Aoife Maguire, Brendan Doyle, Ola Söderberg, Nick Barker, Alastair Watson, Lionel Larue, Alan R Clarke, Owen J Sansom (2015 Aug 5)

E-cadherin can limit the transforming properties of activating β-catenin mutations.

The EMBO journal : 2321-33 : DOI : 10.15252/embj.201591739 En savoir plus
Résumé

Wnt pathway deregulation is a common characteristic of many cancers. Only colorectal cancer predominantly harbours mutations in APC, whereas other cancer types (hepatocellular carcinoma, solid pseudopapillary tumours of the pancreas) have activating mutations in β-catenin (CTNNB1). We have compared the dynamics and the potency of β-catenin mutations in vivo. Within the murine small intestine (SI), an activating mutation of β-catenin took much longer to achieve Wnt deregulation and acquire a crypt-progenitor cell (CPC) phenotype than Apc or Gsk3 loss. Within the colon, a single activating mutation of β-catenin was unable to drive Wnt deregulation or induce the CPC phenotype. This ability of β-catenin mutation to differentially transform the SI versus the colon correlated with higher expression of E-cadherin and a higher number of E-cadherin:β-catenin complexes at the membrane. Reduction in E-cadherin synergised with an activating mutation of β-catenin resulting in a rapid CPC phenotype within the SI and colon. Thus, there is a threshold of β-catenin that is required to drive transformation, and E-cadherin can act as a buffer to sequester mutated β-catenin.

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Tianyi Zhang, Qingxiang Zhou, Margret Helga Ogmundsdottir, Katrin Möller, Robert Siddaway, Lionel Larue, Michael Hsing, Sek Won Kong, Colin Ronald Goding, Arnar Palsson, Eirikur Steingrimsson, Francesca Pignoni (2015 Jun 21)

Mitf is a master regulator of the v-ATPase, forming a control module for cellular homeostasis with v-ATPase and TORC1.

Journal of cell science : 2938-50 : DOI : 10.1242/jcs.173807 En savoir plus
Résumé

The v-ATPase is a fundamental eukaryotic enzyme that is central to cellular homeostasis. Although its impact on key metabolic regulators such as TORC1 is well documented, our knowledge of mechanisms that regulate v-ATPase activity is limited. Here, we report that the Drosophila transcription factor Mitf is a master regulator of this holoenzyme. Mitf directly controls transcription of all 15 v-ATPase components through M-box cis-sites and this coordinated regulation affects holoenzyme activity in vivo. In addition, through the v-ATPase, Mitf promotes the activity of TORC1, which in turn negatively regulates Mitf. We provide evidence that Mitf, v-ATPase and TORC1 form a negative regulatory loop that maintains each of these important metabolic regulators in relative balance. Interestingly, direct regulation of v-ATPase genes by human MITF also occurs in cells of the melanocytic lineage, showing mechanistic conservation in the regulation of the v-ATPase by MITF family proteins in fly and mammals. Collectively, this evidence points to an ancient module comprising Mitf, v-ATPase and TORC1 that serves as a dynamic modulator of metabolism for cellular homeostasis.

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