Développement Normal et Pathologique des Mélanocytes

Publications de l’équipe

Année de publication : 2013

Jacky Bonaventure, Melanie J Domingues, Lionel Larue (2013 Feb 26)

Cellular and molecular mechanisms controlling the migration of melanocytes and melanoma cells.

Pigment cell & melanoma research : 316-25 : DOI : 10.1111/pcmr.12080 En savoir plus
Résumé

During embryonic development in vertebrates, the neural crest-derived melanoblasts migrate along the dorsolateral axis and cross the basal membrane separating the dermis from the epidermis to reach their final location in the interfollicular epidermis and epidermal hair follicles. Neoplastic transformation converts melanocytes into highly invasive and metastatic melanoma cells. In vitro, these cells extend various types of protrusions and adopt two interconvertible modes of migration, mesenchymal and amoeboid, driven by different signalling molecules. In this review, we describe the major contributions of natural mouse mutants, mouse models generated by genetic engineering and in vitro culture systems, to identification of the genes, signalling pathways and mechanisms regulating the migration of normal and pathological cells of the melanocyte lineage, at both the cellular and molecular levels.

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Ichiro Yajima, Sophie Colombo, Isabel Puig, Delphine Champeval, Mayuko Kumasaka, Elodie Belloir, Jacky Bonaventure, Manuel Mark, Hiroaki Yamamoto, Mark M Taketo, Philippe Choquet, Heather C Etchevers, Friedrich Beermann, Véronique Delmas, Laurent Monassier, Lionel Larue (2013 Feb 6)

A subpopulation of smooth muscle cells, derived from melanocyte-competent precursors, prevents patent ductus arteriosus.

PloS one : e53183 : DOI : 10.1371/journal.pone.0053183 En savoir plus
Résumé

Patent ductus arteriosus is a life-threatening condition frequent in premature newborns but also present in some term infants. Current mouse models of this malformation generally lead to perinatal death, not reproducing the full phenotypic spectrum in humans, in whom genetic inheritance appears complex. The ductus arteriosus (DA), a temporary fetal vessel that bypasses the lungs by shunting the aortic arch to the pulmonary artery, is constituted by smooth muscle cells of distinct origins (SMC1 and SMC2) and many fewer melanocytes. To understand novel mechanisms preventing DA closure at birth, we evaluated the importance of cell fate specification in SMC that form the DA during embryonic development. Upon specific Tyr::Cre-driven activation of Wnt/β-catenin signaling at the time of cell fate specification, melanocytes replaced the SMC2 population of the DA, suggesting that SMC2 and melanocytes have a common precursor. The number of SMC1 in the DA remained similar to that in controls, but insufficient to allow full DA closure at birth. Thus, there was no cellular compensation by SMC1 for the loss of SMC2. Mice in which only melanocytes were genetically ablated after specification from their potential common precursor with SMC2, demonstrated that differentiated melanocytes themselves do not affect DA closure. Loss of the SMC2 population, independent of the presence of melanocytes, is therefore a cause of patent ductus arteriosus and premature death in the first months of life. Our results indicate that patent ductus arteriosus can result from the insufficient differentiation, proliferation, or contractility of a specific smooth muscle subpopulation that shares a common neural crest precursor with cardiovascular melanocytes.

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Année de publication : 2012

Alejandro Conde-Perez, Lionel Larue (2012 Oct 4)

PTEN and melanomagenesis.

Future oncology (London, England) : 1109-20 : DOI : 10.2217/fon.12.106 En savoir plus
Résumé

The PI3K-PTEN-AKT signaling pathway is involved in various cellular activities, including proliferation, migration, cell growth, cell survival and differentiation during adult homeostasis as well as in tumorigenesis. It has been suggested that the constitutive activation of PI3K/AKT signaling with concurrent loss of function of the tumor suppressor molecule PTEN contributes to cancer formation. Members of the PI3K-PTEN-AKT pathway, including these proteins and mTOR, are altered in melanoma tumors and cell lines. A hallmark of activation of the pathway is the loss of function of PTEN. Indeed, loss of heterozygosity of PTEN has been observed in approximately 30% of human melanomas, implicating this signaling pathway in this cancer. PI3K signaling activation, via loss of PTEN function, can inhibit proapoptotic genes such as the FoxO family of transcription factors, while inducing cell growth- and cell survival-related elements such as p70S6K and AKT. Determining how the PI3K-PTEN-AKT signaling pathway, alone or in cooperation with other pathways, orchestrates the induction of target genes involved in a diverse range of activities is a major challenge in research into melanoma initiation and progression. Moreover, the acquisition of basic knowledge will help patient management with appropriate therapies that are already, or will shortly be, on the market.

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Samira Makhzami, Florian Rambow, Veronique Delmas, Lionel Larue (2012 Sep 1)

Efficient gene expression profiling of laser-microdissected melanoma metastases.

Pigment cell & melanoma research : 783-91 : DOI : 10.1111/pcmr.12013 En savoir plus
Résumé

Comparing the transcriptomes of primary and metastatic tumour tissues is a useful strategy for studying tumour progression. One factor limiting the interpretation of tissue-based transcriptomic data is the lack of cell-type purity. Laser capture microdissection (LCM) has been shown to be useful for overcoming this limitation. We established an efficient protocol for gene expression profiling of LCM and matched metastatic melanomas using a transgenic mouse model. This optimized workflow combines microsurgical recovery of mouse lungs, appropriate tissue freezing, laser microdissection of homogeneous tumour cell populations from cryosections, isolation of high-quality RNA and gene expression analysis. The RNA isolated from laser-microdissected material was not contaminated by stroma cells, was of excellent quality, and the synthesis of cDNAs was homogeneous and highly reproducible. Subsequent custom-based Taqman-low-density-array (TLDA)-based gene expression profiling identified stronger expression of five genes (M-MITF, TYR, STAT3, CCND1 and PAX3) in primary than metastatic melanoma. We detected only minor transcriptomic differences between primary and metastatic melanoma tissue. This optimized workflow could be very valuable for various studies requiring cell type-specific transcriptomic analysis.

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Lionel Larue, Florian de Vuyst, Véronique Delmas (2012 Aug 24)

Modeling melanoblast development.

Cellular and molecular life sciences : CMLS : 1067-79 : DOI : 10.1007/s00018-012-1112-4 En savoir plus
Résumé

Melanoblasts are a particular type of cell that displays extensive cellular proliferation during development to contribute to the skin. There are only a few melanoblast founders, initially located just dorsal to the neural tube, and they sequentially colonize the dermis, epidermis, and hair follicles. In each compartment, melanoblasts are exposed to a wide variety of developmental cues that regulate their expansion. The colonization of the dermis and epidermis by melanoblasts involves substantial proliferation to generate thousands of cells or more from a few founders within a week of development. This review addresses the cellular and molecular events occurring during melanoblast development. We focus on intrinsic and extrinsic factors that control melanoblast proliferation. We also present a robust mathematical model for estimating the doubling-time of dermal and epidermal melanoblasts for all coat color phenotypes from black to white.

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Lionel Larue (2012 Aug 17)

Origin of mouse melanomas.

The Journal of investigative dermatology : 2135-6 : DOI : 10.1038/jid.2012.221 En savoir plus
Résumé

In humans, melanomas are found mostly in the epidermis, whereas mouse melanomas are found in the dermis. It is, however, possible to force mouse melanomas to develop more efficiently in the epidermis. The histological location of a melanoma when discovered, whether in the epidermis or dermis, does not necessarily reflect the location of the original cell.

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Irina Berlin, Laurence Denat, Anne-Lise Steunou, Isabel Puig, Delphine Champeval, Sophie Colombo, Karen Roberts, Elise Bonvin, Yveline Bourgeois, Irwin Davidson, Véronique Delmas, Laurence Nieto, Colin R Goding, Lionel Larue (2012 Jan 30)

Phosphorylation of BRN2 modulates its interaction with the Pax3 promoter to control melanocyte migration and proliferation.

Molecular and cellular biology : 1237-47 : DOI : 10.1128/MCB.06257-11 En savoir plus
Résumé

MITF-M and PAX3 are proteins central to the establishment and transformation of the melanocyte lineage. They control various cellular mechanisms, including migration and proliferation. BRN2 is a POU domain transcription factor expressed in melanoma cell lines and is involved in proliferation and invasion, at least in part by regulating the expression of MITF-M and PAX3. The T361 and S362 residues of BRN2, both in the POU domain, are conserved throughout the POU protein family and are targets for phosphorylation, but their roles in vivo remain unknown. To examine the role of this phosphorylation, we generated mutant BRN2 in which these two residues were replaced with alanines (BRN2TS→BRN2AA). When expressed in melanocytes in vitro or in the melanocyte lineage in transgenic mice, BRN2TS induced proliferation and repressed migration, whereas BRN2AA repressed both proliferation and migration. BRN2TS and BRN2AA bound and repressed the MITF-M promoter, whereas PAX3 transcription was induced by BRN2TS but repressed by BRN2AA. Expression of the BRN2AA transgene in a Mitf heterozygous background and in a Pax3 mutant background enhanced the coat color phenotype. Our findings show that melanocyte migration and proliferation are controlled both through the regulation of PAX3 by nonphosphorylated BRN2 and through the regulation of MITF-M by the overall BRN2 level.

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Année de publication : 2011

Irina Berlin, Flavie Luciani, Stuart J Gallagher, Florian Rambow, Alejandro Conde-Perez, Sophie Colombo, Delphine Champeval, Véronique Delmas, Lionel Larue (2011 Nov 17)

General strategy to analyse coat colour phenotypes in mice.

Pigment cell & melanoma research : 117-9 : DOI : 10.1111/j.1755-148X.2011.00912.x En savoir plus
Résumé

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Christine Longvert, Gwendoline Gros, Friedrich Beermann, Richard Marais, Véronique Delmas, Lionel Larue (2011 Nov 8)

[Murine cutaneous melanoma models. Importance of the genetic background].

Annales de pathologie : S70-3 : DOI : 10.1016/j.annpat.2011.09.002 En savoir plus
Résumé

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Stuart J Gallagher, Flavie Luciani, Irina Berlin, Florian Rambow, Gwendoline Gros, Delphine Champeval, Véronique Delmas, Lionel Larue (2011 Sep 30)

General strategy to analyse melanoma in mice.

Pigment cell & melanoma research : 987-8 : DOI : 10.1111/j.1755-148X.2011.00907.x En savoir plus
Résumé

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Lionel Larue, Irwin Davidson (2011 Sep 14)

Front seat and back seat drivers of melanoma metastasis.

Pigment cell & melanoma research : 898-901 : DOI : 10.1111/j.1755-148X.2011.00905.x En savoir plus
Résumé

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Flavie Luciani, Delphine Champeval, Aurélie Herbette, Laurence Denat, Bouchra Aylaj, Silvia Martinozzi, Robert Ballotti, Rolf Kemler, Colin R Goding, Florian De Vuyst, Lionel Larue, Véronique Delmas (2011 Aug 25)

Biological and mathematical modeling of melanocyte development.

Development (Cambridge, England) : 3943-54 : DOI : 10.1242/dev.067447 En savoir plus
Résumé

We aim to evaluate environmental and genetic effects on the expansion/proliferation of committed single cells during embryonic development, using melanoblasts as a paradigm to model this phenomenon. Melanoblasts are a specific type of cell that display extensive cellular proliferation during development. However, the events controlling melanoblast expansion are still poorly understood due to insufficient knowledge concerning their number and distribution in the various skin compartments. We show that melanoblast expansion is tightly controlled both spatially and temporally, with little variation between embryos. We established a mathematical model reflecting the main cellular mechanisms involved in melanoblast expansion, including proliferation and migration from the dermis to epidermis. In association with biological information, the model allows the calculation of doubling times for melanoblasts, revealing that dermal and epidermal melanoblasts have short but different doubling times. Moreover, the number of trunk founder melanoblasts at E8.5 was estimated to be 16, a population impossible to count by classical biological approaches. We also assessed the importance of the genetic background by studying gain- and loss-of-function β-catenin mutants in the melanocyte lineage. We found that any alteration of β-catenin activity, whether positive or negative, reduced both dermal and epidermal melanoblast proliferation. Finally, we determined that the pool of dermal melanoblasts remains constant in wild-type and mutant embryos during development, implying that specific control mechanisms associated with cell division ensure half of the cells at each cell division to migrate from the dermis to the epidermis. Modeling melanoblast expansion revealed novel links between cell division, cell localization within the embryo and appropriate feedback control through β-catenin.

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Sophie Colombo, Delphine Champeval, Florian Rambow, Lionel Larue (2011 Aug 19)

Transcriptomic analysis of mouse embryonic skin cells reveals previously unreported genes expressed in melanoblasts.

The Journal of investigative dermatology : 170-8 : DOI : 10.1038/jid.2011.252 En savoir plus
Résumé

Studying the development of melanoblasts, precursors of melanocytes, is challenging owing to their scarcity and dispersion in the skin embryo. However, this is an important subject because diverse diseases are associated with defective melanoblast development. Consequently, characterizing patterns of expression in melanoblasts during normal development is an important issue. This requires isolating enough melanoblasts during embryonic development to obtain sufficient RNA to study their transcriptome. ZEG reporter mouse line crossed with Tyr::Cre mouse line was used to label melanoblasts by enhanced green fluorescent protein (EGFP) autofluorescence. We isolated melanoblasts by FACS from the skin of E14.5-E16.5 embryos, and obtained sufficient cells for large-scale transcriptomic analysis after RNA isolation and amplification. We confirmed our array-based data for various genes of interest by standard quantitative real-time RT-PCR. We demonstrated that phosphatase and tensin homolog was expressed in melanoblasts but BRN2 was not, although both are involved in melanomagenesis. We also revealed the potential contribution of genes not previously implicated in any function in melanocytes or even in neural crest derivatives. Finally, the Schwann cell markers, PLP1 and FABP7, were significantly expressed in melanoblasts, melanocytes, and melanoma. This study demonstrates the feasibility of the transcriptomic analysis of purified melanoblasts at different embryonic stages and reveals the involvement of previously unreported genes in melanoblast development.

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Salvatore Cortellino, Jinfei Xu, Mara Sannai, Robert Moore, Elena Caretti, Antonio Cigliano, Madeleine Le Coz, Karthik Devarajan, Andy Wessels, Dianne Soprano, Lara K Abramowitz, Marisa S Bartolomei, Florian Rambow, Maria Rosaria Bassi, Tiziana Bruno, Maurizio Fanciulli, Catherine Renner, Andres J Klein-Szanto, Yoshihiro Matsumoto, Dominique Kobi, Irwin Davidson, Christophe Alberti, Lionel Larue, Alfonso Bellacosa (2011 Feb 18)

Thymine DNA glycosylase is essential for active DNA demethylation by linked deamination-base excision repair.

Cell : 67-79 : DOI : 10.1016/j.cell.2011.06.020 En savoir plus
Résumé

DNA methylation is a major epigenetic mechanism for gene silencing. Whereas methyltransferases mediate cytosine methylation, it is less clear how unmethylated regions in mammalian genomes are protected from de novo methylation and whether an active demethylating activity is involved. Here, we show that either knockout or catalytic inactivation of the DNA repair enzyme thymine DNA glycosylase (TDG) leads to embryonic lethality in mice. TDG is necessary for recruiting p300 to retinoic acid (RA)-regulated promoters, protection of CpG islands from hypermethylation, and active demethylation of tissue-specific developmentally and hormonally regulated promoters and enhancers. TDG interacts with the deaminase AID and the damage response protein GADD45a. These findings highlight a dual role for TDG in promoting proper epigenetic states during development and suggest a two-step mechanism for DNA demethylation in mammals, whereby 5-methylcytosine and 5-hydroxymethylcytosine are first deaminated by AID to thymine and 5-hydroxymethyluracil, respectively, followed by TDG-mediated thymine and 5-hydroxymethyluracil excision repair.

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Année de publication : 2010

Lionel Larue (2010 Jun 4)

Richard Marais.

Pigment cell & melanoma research : 448 : DOI : 10.1111/j.1755-148X.2010.00708.x En savoir plus
Résumé

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