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William J Pavan - One of the best experts on this subject based on the ideXlab platform.
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The Secreted Metalloprotease ADAMTS20 Is Required for Melanoblast Survival
2013Co-Authors: Debra L. Silver, Ling Hou, Robert Somerville, Mary E. Young, Suneel S. Apte, William J PavanAbstract:ADAMTS20 (A disintegrin-like and metalloprotease domain with thrombospondin type-1 motifs) is a member of a family of secreted metalloproteases that can process a variety of extracellular matrix (ECM) components and secreted molecules. Adamts20 mutations in belted (bt) mice cause white spotting of the dorsal and ventral torso, indicative of defective neural crest (NC)-derived Melanoblast development. The expression pattern of Adamts20 in dermal mesenchymal cells adjacent to migrating Melanoblasts led us to initially propose that Adamts20 regulated Melanoblast migration. However, using a Dct-LacZ transgene to track Melanoblast development, we determined that Melanoblasts were distributed normally in whole mount E12.5 bt/bt embryos, but were specifically reduced in the trunk of E13.5 bt/bt embryos due to a seven-fold higher rate of apoptosis. The Melanoblast defect was exacerbated in newborn skin and embryos from bt/bt animals that were also haploinsufficient for Adamts9, a close homolog of Adamts20, indicating that these metalloproteases functionally overlap in Melanoblast development. We identified two potential mechanisms by which Adamts20 may regulate Melanoblast survival. First, skin explant cultures demonstrated that Adamts20 was required for Melanoblasts to respond to soluble Kit ligand (sKitl). In support of this requirement, bt/bt;Kit tm1Alf /+ and bt/bt;Kitl Sl /+ mice exhibited synergistically increased spotting. Second, ADAMTS20 cleaved the aggregating proteoglycan versican in vitro and was necessary for versican processing in vivo, raising the possibility that versican can participate in Melanoblast development. These findings reveal previousl
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A sensitized mutagenesis screen identifies Gli3 as a modifier of Sox10 neurocristopathy
Human molecular genetics, 2008Co-Authors: Ivana Matera, Stacie K. Loftus, Laura L. Baxter, Arturo Incao, Dawn E. Watkins-chow, Ling Hou, Debra L. Silver, Cecelia Rivas, Eugene C. Elliott, William J PavanAbstract:Haploinsufficiency for the transcription factor SOX10 is associated with the pigmentary deficiencies of Waardenburg syndrome (WS) and is modeled in Sox10 haploinsufficient mice (Sox10(LacZ/+)). As genetic background affects WS severity in both humans and mice, we established an N-ethyl-N-nitrosourea (ENU) mutagenesis screen to identify modifiers that increase the phenotypic severity of Sox10(LacZ/+) mice. Analysis of 230 pedigrees identified three modifiers, named modifier of Sox10 neurocristopathies (Mos1, Mos2 and Mos3). Linkage analysis confirmed their locations on mouse chromosomes 13, 4 and 3, respectively, within regions distinct from previously identified WS loci. Positional candidate analysis of Mos1 identified a truncation mutation in a hedgehog(HH)-signaling mediator, GLI-Kruppel family member 3 (Gli3). Complementation tests using a second allele of Gli3 (Gli3(Xt-J)) confirmed that a null mutation of Gli3 causes the increased hypopigmentation in Sox10(LacZ/+);Gli3(Mos1/)(+) double heterozygotes. Early Melanoblast markers (Mitf, Sox10, Dct, and Si) are reduced in Gli3(Mos1/)(Mos1) embryos, indicating that loss of GLI3 signaling disrupts Melanoblast specification. In contrast, mice expressing only the GLI3 repressor have normal Melanoblast specification, indicating that the full-length GLI3 activator is not required for specification of neural crest to the melanocyte lineage. This study demonstrates the feasibility of sensitized screens to identify disease modifier loci and implicates GLI3 and other HH signaling components as modifiers of human neurocristopathies.
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The secreted metalloprotease ADAMTS20 is required for Melanoblast survival.
Public Library of Science (PLoS), 2008Co-Authors: Debra L. Silver, Ling Hou, Robert Somerville, Mary E. Young, Suneel S. Apte, William J PavanAbstract:ADAMTS20 (Adisintegrin-like and metalloprotease domain with thrombospondin type-1 motifs) is a member of a family of secreted metalloproteases that can process a variety of extracellular matrix (ECM) components and secreted molecules. Adamts20 mutations in belted (bt) mice cause white spotting of the dorsal and ventral torso, indicative of defective neural crest (NC)-derived Melanoblast development. The expression pattern of Adamts20 in dermal mesenchymal cells adjacent to migrating Melanoblasts led us to initially propose that Adamts20 regulated Melanoblast migration. However, using a Dct-LacZ transgene to track Melanoblast development, we determined that Melanoblasts were distributed normally in whole mount E12.5 bt/bt embryos, but were specifically reduced in the trunk of E13.5 bt/bt embryos due to a seven-fold higher rate of apoptosis. The Melanoblast defect was exacerbated in newborn skin and embryos from bt/bt animals that were also haploinsufficient for Adamts9, a close homolog of Adamts20, indicating that these metalloproteases functionally overlap in Melanoblast development. We identified two potential mechanisms by which Adamts20 may regulate Melanoblast survival. First, skin explant cultures demonstrated that Adamts20 was required for Melanoblasts to respond to soluble Kit ligand (sKitl). In support of this requirement, bt/bt;Kit(tm1Alf)/+ and bt/bt;Kitl(Sl)/+ mice exhibited synergistically increased spotting. Second, ADAMTS20 cleaved the aggregating proteoglycan versican in vitro and was necessary for versican processing in vivo, raising the possibility that versican can participate in Melanoblast development. These findings reveal previously unrecognized roles for Adamts proteases in cell survival and in mediating Kit signaling during Melanoblast colonization of the skin. Our results have implications not only for understanding mechanisms of NC-derived Melanoblast development but also provide insights on novel biological functions of secreted metalloproteases
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wnt1 and wnt3a promote expansion of melanocytes through distinct modes of action
Pigment Cell Research, 2004Co-Authors: Karen J Dunn, Matthew J Brady, Christina Ochsenbauerjambor, Sara K Snyder, Arturo Incao, William J PavanAbstract:Summary WNT1 and WNT3a have been described as having redundant roles in promoting the development of neural crest-derived melanocytes (NC-Ms). We used cell lineage restricted retroviral infections to examine the effects of WNT signaling on defined cell types in neural crest cultures. RCAS retroviral infections were targeted to Melanoblasts (NC-M precursor cells) derived from transgenic mice that express the virus receptor, TVA, under the control of a Melanoblast promoter (DCT). As expected, over 90% of DCT-TVA+ cells expressed early Melanoblast markers MITF and KIT. However, by following the fate of infected cells in standard culture conditions, we find that only 5% of descendents were NC-Ms. The majority of the descendents were not NC-Ms, but expressed smooth muscle cell markers, demonstrating that mammalian Melanoblasts are not committed to the NC-M lineage. RCAS infection of DCT-TVA+ cells demonstrated that overexpression of canonical WNT signaling genes (betaCAT, WNT3a or WNT1) can increase NC-M numbers in an endothelin dependent manner. However, WNT1 and WNT3a have different modes of action with respect to Melanoblast fate. Intrinsic over-expression of betaCAT or WNT3a can increase NC-M numbers by biasing the fate of DCT-TVA+ cells to NC-Ms. In contrast, the DCT-TVA+ Melanoblasts cannot respond to WNT1 signaling and do not alter their fate towards NC-M. Instead, WNT1 only increases NC-M numbers through paracrine signaling on Melanoblast precursors to increase the numbers of neural crest cells that become NC-Ms.
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analysis of sox10 function in neural crest derived melanocyte development sox10 dependent transcriptional control of dopachrome tautomerase
Developmental Biology, 2001Co-Authors: Brian S Potterf, Ling Hou, Ramin Mollaaghababa, Michelle E Southardsmith, Thomas J Hornyak, Heinz Arnheiter, William J PavanAbstract:SOX10 is a high-mobility-group transcription factor that plays a critical role in the development of neural crest-derived melanocytes. At E11.5, mouse embryos homozygous for the Sox10(Dom) mutation entirely lack neural crest-derived cells expressing the lineage marker KIT, MITF, or DCT. Moreover, neural crest cell cultures derived from homozygous embryos do not give rise to pigmented cells. In contrast, in Sox10(Dom) heterozygous embryos, Melanoblasts expressing KIT and MITF do occur, albeit in reduced numbers, and pigmented cells eventually develop in nearly normal numbers both in culture and in vivo. Intriguingly, however, Sox10(Dom)/+ Melanoblasts transiently lack Dct expression both in culture and in vivo, suggesting that during a critical developmental period SOX10 may serve as a transcriptional activator of Dct. Indeed, we found that SOX10 and DCT colocalized in early Melanoblasts and that SOX10 is capable of transactivating the Dct promoter in vitro. Our data suggest that during early Melanoblast development SOX10 acts as a critical transactivator of Dct, that MITF, on its own, is insufficient to stimulate Dct expression, and that delayed onset of Dct expression is not deleterious to the melanocyte lineage.
Paul D Henion - One of the best experts on this subject based on the ideXlab platform.
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colgate hdac1 repression of foxd3 expression is required to permit mitfa dependent melanogenesis
Developmental Biology, 2008Co-Authors: Myron S Ignatius, Holly E Moose, Heithem M Elhodiri, Paul D HenionAbstract:Neural crest-derived pigment cell development has been used extensively to study cell fate specification, migration, proliferation, survival and differentiation. Many of the genes and regulatory mechanisms required for pigment cell development are conserved across vertebrates. The zebrafish mutant colgate (col)/histone deacetylase1 (hdac1) has reduced numbers, delayed differentiation and decreased migration of neural crest-derived melanophores and their precursors. In hdac1(col) mutants normal numbers of premigratory neural crest cells are induced. Later, while there is only a slight reduction in the number of neural crest cells in hdac1(col) mutants, there is a severe reduction in the number of mitfa-positive Melanoblasts suggesting that hdac1 is required for Melanoblast specification. Concomitantly, there is a significant increase in and prolonged expression of foxd3 in neural crest cells in hdac1(col) mutants. We found that partially reducing Foxd3 expression in hdac1(col) mutants rescues mitfa expression and the melanophore defects in hdac1(col) mutants. Furthermore, we demonstrate the ability of Foxd3 to physically interact at the mitfa promoter. Because mitfa is required for Melanoblast specification and development, our results suggest that hdac1 is normally required to suppress neural crest foxd3 expression thus de-repressing mitfa resulting in melanogenesis by a subset of neural crest-derived cells.
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colgate/hdac1 Repression of foxd3 expression is required to permit mitfa-dependent melanogenesis.
Developmental biology, 2007Co-Authors: Myron S Ignatius, Holly E Moose, Heithem M. El-hodiri, Paul D HenionAbstract:Neural crest-derived pigment cell development has been used extensively to study cell fate specification, migration, proliferation, survival and differentiation. Many of the genes and regulatory mechanisms required for pigment cell development are conserved across vertebrates. The zebrafish mutant colgate (col)/histone deacetylase1 (hdac1) has reduced numbers, delayed differentiation and decreased migration of neural crest-derived melanophores and their precursors. In hdac1(col) mutants normal numbers of premigratory neural crest cells are induced. Later, while there is only a slight reduction in the number of neural crest cells in hdac1(col) mutants, there is a severe reduction in the number of mitfa-positive Melanoblasts suggesting that hdac1 is required for Melanoblast specification. Concomitantly, there is a significant increase in and prolonged expression of foxd3 in neural crest cells in hdac1(col) mutants. We found that partially reducing Foxd3 expression in hdac1(col) mutants rescues mitfa expression and the melanophore defects in hdac1(col) mutants. Furthermore, we demonstrate the ability of Foxd3 to physically interact at the mitfa promoter. Because mitfa is required for Melanoblast specification and development, our results suggest that hdac1 is normally required to suppress neural crest foxd3 expression thus de-repressing mitfa resulting in melanogenesis by a subset of neural crest-derived cells.
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melanophore sublineage specific requirement for zebrafish touchtone during neural crest development
Mechanisms of Development, 2004Co-Authors: Brigitte L Arduini, Paul D HenionAbstract:The specification, differentiation and maintenance of diverse cell types are of central importance to the development of multicellular organisms. The neural crest of vertebrate animals gives rise to many derivatives, including pigment cells, peripheral neurons, glia and elements of the craniofacial skeleton. The development of neural crest-derived pigment cells has been studied extensively to elucidate mechanisms involved in cell fate specification, differentiation, migration and survival. This analysis has been advanced considerably by the availability of large numbers of mouse and, more recently, zebrafish mutants with defects in pigment cell development. We have identified the zebrafish mutant touchtone (tct), which is characterized by the selective absence of most neural crest-derived melanophores. We find that although wild-type numbers of melanophore precursors are generated in the first day of development and migrate normally in tct mutants, most differentiated melanophores subsequently fail to appear. We demonstrate that the failure in melanophore differentiation in tct mutant embryos is due at least in part to the death of Melanoblasts and that tct function is required cell autonomously by Melanoblasts. The tct locus is located on chromosome 18 in a genomic region apparently devoid of genes known to be involved in melanophore development. Thus, zebrafish tct may represent a novel as well as selective regulator of Melanoblast development within the neural crest lineage. Further, our results suggest that, like other neural crest-derived sublineages, melanogenic precursors constitute a heterogeneous population with respect to genetic requirements for development.
Owen J. Sansom - One of the best experts on this subject based on the ideXlab platform.
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Activated mutant NRas(Q61K) drives aberrant melanocyte signaling, survival, and invasiveness via a Rac1-dependent mechanism. J Invest Dermatol. 2012; 132:2610–2621. [PubMed: 22718121
2016Co-Authors: Meng Jin, Richard L. Mort, Owen J. Sansom, Lionel Larue, Susan Mason, Karen Blyth, Laura M. MacheskyAbstract:Around a fifth of melanomas exhibit an activating mutation in the oncogene NRas that confers constitutive signaling to proliferation and promotes tumor initiation. NRas signals downstream of the major melanocyte tyrosine kinase receptor c-kit and activated NRas results in increased signaling via the extracellular signal–regulated kinase (ERK)/MAPK/ERK kinase/mitogen-activated protein kinase (MAPK) pathways to enhance proliferation. The Ras oncogene also activates signaling via the related Rho GTPase Rac1, which can mediate growth, survival, and motility signaling. We tested the effects of activated NRasQ61K on the proliferation, motility, and invasiveness of Melanoblasts and melanocytes in the developing mouse and ex vivo explant culture as well as in a melanoma transplant model. We find an important role for Rac1 downstream of NRasQ61K in mediating dermal melanocyte survival in vivo in mouse, but surprisingly NRasQ61K does not appear to affect Melanoblast motility or proliferation during mouse embryogenesis. We also show that genetic deletion or pharmacological inhibition of Rac1 in NRasQ61K induced melanoma suppresses tumor growth, lymph node spread, and tumor cell invasiveness, suggesting a potential value for Rac1 as a therapeutic target for activated NRas-driven tumor growth and invasiveness
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a rac1 independent role for p rex1 in Melanoblasts
Journal of Investigative Dermatology, 2015Co-Authors: Colin R Lindsay, William J Faller, Brad Ozanne, Laura M. Machesky, Heidi C E Welch, Ang Li, Owen J. SansomAbstract:TO THE EDITOR Given the recent discovery of RAC1-activating mutations in melanoma, and our finding that PIP3-dependent Rac-exchanger 1 (PREX1) is overexpressed and drives metastasis in this cancer, an important question is to establish whether the functions of P-Rex1 are mediated specifically by Rac alone (Lindsay et al., 2011; Berger et al., 2012). Here we describe a Rac1-independent in vivo role for P-Rex1 through identification and characterization of a mouse coat color phenotype. P-Rex1 is a guanine-nucleotide exchange factor (GEF) for Rac, whose primary cell function is induction of actin-mediated membrane ruffling and lamellipodia formation at the leading edge of cell migration (Welch et al., 2002; Hill et al., 2005; Barber et al., 2007). To investigate this question we decided to examine the role of Rac1 and P-Rex1 in Melanoblast development. Previously, we reported a “white belly” phenotype of mice with Prex1 deletion (Lindsay et al., 2011). Impaired Melanoblast migration was mostly responsible for this phenotype, with Melanoblasts lacking at the most distal points of migration (belly and paws). Constitutive deletion of Rac1 is embryonically lethal, but a coat color defect of mice with melanocyte-specific RAC1 abrogation (Tyr::Cre Rac1fl/fl) has also been described; these mice have a larger belly spot on their ventral side, suggesting that alternative Rho-GTPases can be activated to enable Melanoblast migration to the perimeter of the Tyr::Cre Racfl/fl white belly (Sugihara et al., 1998; Li et al., 2011). A role for Rac1 in proliferation was also observed, as there was a marked reduction of Melanoblast numbers in this phenotype. In line with these previous studies, and because mice with melanocyte-specific RAC1 abrogation require euthanization shortly after birth because of neurological problems, we used the same embryonic Melanoblast reporter models to assess the downstream effects of P-Rex1 in vivo (Mackenzie et al., 1997; Mort et al., 2010; Li et al., 2011). Melanocyte-specific reporter mouse strains employed were Tyr::Cre Z/EG, which drives green fluorescent protein expression in the Melanoblast lineage, and DCT::β-galactosidase (otherwise referred to as DCT-lacZ). First, we hypothesized that, if the effects of P-Rex1 were mediated exclusively via Rac1, double mutant Tyr::Cre Rac1fl/fl; P-Rex1−/− mice would exhibit the same coat color phenotype as Tyr::Cre Racfl/fl mice alone. However, Tyr::Cre Racfl/fl; P-Rex1−/− mice display a dramatic alteration in coat color phenotype from Tyr::Cre Racfl/fl mice (n=7; Figure 1a). The ventral and dorsal coats of these mice are almost entirely white, with hypo-pigmented limbs and tail. Graying pigmented areas were only observed in the head coat. We concluded from this experiment that P-Rex1 and Rac1 together constitute fundamental signaling components of the mouse coat color phenotype, with minimal rescue of Melanoblast development conferred by other GEFs or Rho-GTPases. It was also clear that P-Rex1 must be able to exert phenotypic effects other than via Rac1. Figure 1 P-Rex1 and Rac1 are fundamental components of a mouse coat color phenotype. (a) Ventral coats of P-Rex1−/−, Tyr::Cre Rac1fl/fl and P-Rex1−/−;Tyr::Cre Rac1fl/flmice. Final photomicrograph shows dorsal and head coat of Tyr::Cre ... To explore the Rac1-independent effects of P-Rex1 further, we crossed Tyr::Cre Racfl/fl; P-Rex1−/− mice with mice carrying the Melanoblast reporter DCT-lacZ transgene (methods detailed in Lindsay et al., 2011). Relative to Tyr::Cre Racfl/flmice or P-Rex1−/− embryos alone, Tyr::Cre Racfl/fl; P-Rex1−/− embryos at E15.5 displayed a substantial reduction in Melanoblast numbers across their entire body (Figure 1b and c). To assess whether the cause of this reduction in Melanoblast numbers could be accounted for by decreased proliferation ± increased cell death, we next treated our previously described primary immortalized Tyr::CrER2 INK4a−/− Racfl/fl melanocyte cell line with short interfering RNA to P-Rex1 (methods detailed in Li et al., 2012). The use of this model system also allowed us to delete Rac1 function when these cells were treated with 4-hydroxytamoxifen (OHT). We first used western blotting to confirm that efficient P-Rex1 knockdown and OHT-induced Rac deletion were achieved (Figure 1d). There was no increase in cleaved caspase-3 evident in the absence of P-Rex1 and/or Rac, suggesting that the reduced cell numbers observed in Tyr::Cre Racfl/fl; P-Rex1−/− embryos were not accounted for by increased cell death (Figure 1d). Growth curves and anti-BrdU immunofluorescence of the same cell lines confirmed that there was a reduced proliferation in P-Rex1-depleted cells, both in the presence and absence of OHT (Figure 1e; Supplementary Figure S1a and b online). Taken together, these results suggest, in addition to our previously reported effects of Rac1 deletion on mouse coat color, that the loss of a Rac1-independent proliferative effect of P-Rex1 also contributes to the coat color phenotype observed in Tyr::Cre Racfl/fl; P-Rex1−/− mice (Li et al., 2011). In line with our previous characterization of the P-Rex1 knockout phenotype alone, we next decided to delineate whether the coat color phenotype of Tyr::Cre Racfl/fl; P-Rex1−/− mice could also be a consequence of reduced Melanoblast migration (Lindsay et al., 2011). To assess this, mice with the Z/EG double reporter transgene were crossed with Tyr::Cre Racfl/fl; P-Rex1−/−mice, driving green fluorescent protein expression in the Melanoblast lineage (methods detailed in Lindsay et al., 2011; Figure 2a). Live imaging of Melanoblasts was performed using E15.5 embryo skin from each genotype (Figure 2b; Supplementary Movies S1–3 online). Consistent with our previous work, significant reductions in migration speed were observed between wild-type, P-Rex1−/− and Tyr::Cre Racfl/fl Melanoblasts (Figure 2c and d). However, there was no significant difference in speed between Tyr::Cre Racfl/fl; P-Rex1−/− and Tyr::Cre Racfl/fl Melanoblasts alone, suggesting that there was no change in migratory characteristics to account for the Tyr::Cre Racfl/fl; P-Rex1−/− phenotype (Figure 2c and d). These results were matched by similar differences between the same genotypes when Euclidean distance was measured (Figure 2e), as well as no observable change in cell morphology evident in Tyr::Cre Racfl/fl; P-Rex1−/− compared with Tyr::Cre Racfl/fl Melanoblasts alone (Supplementary Figure S1c online; methods detailed in Helmy and Azim, 2012). Finally, no cell death was seen in our Melanoblast time-lapse movies of any genotype, again suggesting that P-Rex1 contributes to coat color phenotype by promoting cell proliferation using a Rac1-independent mechanism (Li et al., 2011; Supplementary Movies S1–3 online; methods detailed in Lindsay et al., 2011). Figure 2 P-Rex1 has no additional effect on migration compared with Rac1 alone. All experiments show embryo skin explants at E15.5 (a) Combined Z-stack confocal images of Z/EG Melanoblasts from wild-type (control), P-Rex1−/−, Tyr::Cre Rac1fl/fl ... To conclude, we have elucidated a proliferative role of P-Rex1 when Rac1 is deleted. As E15.5 migratory characteristics are not altered in the Tyr::Cre Racfl/fl; P-Rex1−/− double mutant embryos, this suggests that the role of P-Rex1 in migration is almost exclusively mediated via Rac1. Here we focused on E15.5 embryos, a useful time point to observe the late migratory effects observed with previously described Prex and Rac phenotypes (Li et al., 2011; Lindsay et al., 2011). With a greater number of embryos, we would have performed further embryo time-point analyses at E13.5 to ensure there was no earlier Melanoblast migratory deficit that could contribute to this phenotype, although even this experiment could not completely exclude such a possibility. One potential Rho-GTPase, RhoG, is a likely candidate for P-Rex1 interaction: it is the most structurally similar Rho-GTPase to Rac and has been shown to cooperate with Rac for induction of cell transformation (Roux et al., 1997). Moreover, there are distinct regulatory and functional similarities between P-Rex1 and Vav proteins, which have been characterized as the predominant GEFs required for RhoG activation (Samson et al., 2010; Lawson et al., 2011). Further studies are underway to investigate the phenotypes of these and other potential Rho-GTPases in Melanoblast migration and melanomagenesis. Given that there is now considerable effort to generate Rac1 inhibitors, our data would suggest functions for proteins upstream of Rac1 that may become further therapeutic targets in melanoma. All experiments were conducted and approved in accordance with institutional and UK guidelines, and all animal studies were performed in accordance with local regulatory guidelines.
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fascin 1 is transiently expressed in mouse Melanoblasts during development and promotes migration and proliferation
Development, 2013Co-Authors: William J Faller, Owen J. Sansom, Silvana Libertini, Florencia Fiorito, David A F Gillespie, Shigeko Yamashiro, Laura M. MacheskyAbstract:Fascins, a family of actin-bundling proteins, are expressed in a spatially and temporally restricted manner during development and often in cancer. Fascin 1 has a clear role in cell migration in vitro, but its role in vivo in mammals is not well understood. Here, we investigate the role of fascin 1 in the melanocyte lineage and in melanoma cells. Fascin 1 knockout causes hypopigmentation in adult mice owing to migration and cell cycle progression defects in Melanoblasts, the melanocyte precursor cell. Study of live embryo skin explants reveals that E14.5 fascin 1-null Melanoblasts migrate slower, and generate fewer and thinner pseudopods. By contrast, fascin 1 expression drives faster migration and lamellipodia protrusion in melanocytes in vitro. In addition, fascin 1 depletion retards Melanoblast proliferation in vivo and melanoma cell growth in vitro. These data indicate that fascin 1 not only promotes cell migration in mouse melanocytes but it also has a role in growth and cell cycle progression.
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rac1 drives Melanoblast organization during mouse development by orchestrating pseudopod driven motility and cell cycle progression
Developmental Cell, 2011Co-Authors: Richard L. Mort, Colin R Lindsay, Ian J Jackson, Lionel Larue, David Stevenson, Douglas Strathdee, Robert H Insall, Jonathan Chernoff, Scott B Snapper, Owen J. SansomAbstract:During embryogenesis, Melanoblasts proliferate and migrate ventrally through the developing dermis and epidermis as single cells. Targeted deletion of Rac1 in Melanoblasts during embryogenesis causes defects in migration, cell-cycle progression, and cytokinesis. Rac1 null cells migrate markedly less efficiently, but surprisingly, global steering, crossing the dermal/epidermal junction, and homing to hair follicles occur normally. Melanoblasts navigate in the epidermis using two classes of protrusion: short stubs and long pseudopods. Short stubs are distinct from blebs and are driven by actin assembly but are independent of Rac1, Arp2/3 complex, myosin, or microtubules. Rac1 positively regulates the frequency of initiation of long pseudopods, which promote migration speed and directional plasticity. Scar/WAVE and Arp2/3 complex drive actin assembly for long pseudopod extension, which also depends on microtubule dynamics. Myosin contractility balances the extension of long pseudopods by effecting retraction and allowing force generation for movement through the complex 3D epidermal environment.
Carol A. Erickson - One of the best experts on this subject based on the ideXlab platform.
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FOXD3 regulates the lineage switch between neural crest-derived glial cells and pigment cells by repressing MITF through a non-canonical mechanism
Development (Cambridge England), 2009Co-Authors: Aaron J. Thomas, Carol A. EricksonAbstract:The first neural crest cells to emigrate from the neural tube are specified as neurons and glial cells and are subsequently followed by melanocytes of the skin. We wished to understand how this fate switch is controlled. The transcriptional repressor FOXD3 is expressed exclusively in the neural/glial precursors and MITF is expressed only in Melanoblasts. Moreover, FOXD3 represses melanogenesis. Here we show that avian MITF expression begins very early during Melanoblast migration and that loss of MITF in Melanoblasts causes them to transdifferentiate to a glial phenotype. Ectopic expression of FOXD3 represses MITF in cultured neural crest cells and in B16-F10 melanoma cells. We also show that FOXD3 does not bind directly to the MITF promoter, but instead interacts with the transcriptional activator PAX3 to prevent the binding of PAX3 to the MITF promoter. Overexpression of PAX3 is sufficient to rescue MITF expression from FOXD3-mediated repression. We conclude that FOXD3 controls the lineage choice between neural/glial and pigment cells by repressing MITF during the early phase of neural crest migration.
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stripes and belly spots a review of pigment cell morphogenesis in vertebrates
Seminars in Cell & Developmental Biology, 2009Co-Authors: Robert N Kelsh, Melissa L Harris, Sarah Colanesi, Carol A. EricksonAbstract:Pigment patterns in the integument have long-attracted attention from both scientists and non-scientists alike since their natural attractiveness combines with their excellence as models for the general problem of pattern formation. Pigment cells are formed from the neural crest and must migrate to reach their final locations. In this review, we focus on our current understanding of mechanisms underlying the control of pigment cell migration and patterning in diverse vertebrates. The model systems discussed here - chick, mouse, and zebrafish - each provide unique insights into the major morphogenetic events driving pigment pattern formation. In birds and mammals, Melanoblasts must be specified before they can migrate on the dorsolateral pathway. Transmembrane receptors involved in guiding them onto this route include EphB2 and Ednrb2 in chick, and Kit in mouse. Terminal migration depends, in part, upon extracellular matrix reorganization by ADAMTS20. Invasion of the ectoderm, especially into the feather germ and hair follicles, requires specific signals that are beginning to be characterized. We summarize our current understanding of the mechanisms regulating Melanoblast number and organization in the epidermis. We note the apparent differences in pigment pattern formation in poikilothermic vertebrates when compared with birds and mammals. With more pigment cell types, migration pathways are more complex and largely unexplored; nevertheless, a role for Kit signaling in melanophore migration is clear and indicates that at least some patterning mechanisms may be highly conserved. We summarize the multiple factors thought to contribute to zebrafish embryonic pigment pattern formation, highlighting a recent study identifying Sdf1a as one factor crucial for regulation of melanophore positioning. Finally, we discuss the mechanisms generating a second, metamorphic pigment pattern in adult fish, emphasizing recent studies strengthening the evidence that undifferentiated progenitor cells play a major role in generating adult pigment cells.
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the winged helix transcription factor foxd3 is important for establishing the neural crest lineage and repressing melanogenesis in avian embryos
Development, 2001Co-Authors: Mark V Reedy, Randy L Johnson, Carol A. EricksonAbstract:The winged-helix or forkhead class of transcription factors has been shown to play important roles in cell specification and lineage segregation. We have cloned the chicken homolog of FoxD3, a member of the winged-helix class of transcription factors, and analyzed its expression. Based on its expression in the dorsal neural tube and in all neural crest lineages except the late-emigrating Melanoblasts, we predicted that FoxD3 might be important in the segregation of the neural crest lineage from the neural epithelium, and for repressing melanogenesis in early-migrating neural crest cells. Misexpression of FoxD3 by electroporation in the lateral neural epithelium early in neural crest development produced an expansion of HNK1 immunoreactivity throughout the neural epithelium, although these cells did not undergo an epithelial/mesenchymal transformation. To test whether FoxD3 represses melanogenesis in early migrating neural crest cells, we knocked down expression in cultured neural crest with antisense oligonucleotides and in vivo by treatment with morpholino antisense oligonucleotides. Both experimental approaches resulted in an expansion of the Melanoblast lineage, probably at the expense of neuronal and glial lineages. Conversely, persistent expression of FoxD3 in late-migrating neural crest cells using RCAS viruses resulted in the failure of Melanoblasts to develop. We suggest that FoxD3 plays two important roles in neural crest development. First, it is involved in the segregation of the neural crest lineage from the neuroepithelium. Second, it represses melanogenesis, thereby allowing other neural crest derivatives to differentiate during the early stages of neural crest patterning.
Lionel Larue - One of the best experts on this subject based on the ideXlab platform.
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Activated mutant NRas(Q61K) drives aberrant melanocyte signaling, survival, and invasiveness via a Rac1-dependent mechanism. J Invest Dermatol. 2012; 132:2610–2621. [PubMed: 22718121
2016Co-Authors: Meng Jin, Richard L. Mort, Owen J. Sansom, Lionel Larue, Susan Mason, Karen Blyth, Laura M. MacheskyAbstract:Around a fifth of melanomas exhibit an activating mutation in the oncogene NRas that confers constitutive signaling to proliferation and promotes tumor initiation. NRas signals downstream of the major melanocyte tyrosine kinase receptor c-kit and activated NRas results in increased signaling via the extracellular signal–regulated kinase (ERK)/MAPK/ERK kinase/mitogen-activated protein kinase (MAPK) pathways to enhance proliferation. The Ras oncogene also activates signaling via the related Rho GTPase Rac1, which can mediate growth, survival, and motility signaling. We tested the effects of activated NRasQ61K on the proliferation, motility, and invasiveness of Melanoblasts and melanocytes in the developing mouse and ex vivo explant culture as well as in a melanoma transplant model. We find an important role for Rac1 downstream of NRasQ61K in mediating dermal melanocyte survival in vivo in mouse, but surprisingly NRasQ61K does not appear to affect Melanoblast motility or proliferation during mouse embryogenesis. We also show that genetic deletion or pharmacological inhibition of Rac1 in NRasQ61K induced melanoma suppresses tumor growth, lymph node spread, and tumor cell invasiveness, suggesting a potential value for Rac1 as a therapeutic target for activated NRas-driven tumor growth and invasiveness
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rac1 drives Melanoblast organization during mouse development by orchestrating pseudopod driven motility and cell cycle progression
Developmental Cell, 2011Co-Authors: Richard L. Mort, Colin R Lindsay, Ian J Jackson, Lionel Larue, David Stevenson, Douglas Strathdee, Robert H Insall, Jonathan Chernoff, Scott B Snapper, Owen J. SansomAbstract:During embryogenesis, Melanoblasts proliferate and migrate ventrally through the developing dermis and epidermis as single cells. Targeted deletion of Rac1 in Melanoblasts during embryogenesis causes defects in migration, cell-cycle progression, and cytokinesis. Rac1 null cells migrate markedly less efficiently, but surprisingly, global steering, crossing the dermal/epidermal junction, and homing to hair follicles occur normally. Melanoblasts navigate in the epidermis using two classes of protrusion: short stubs and long pseudopods. Short stubs are distinct from blebs and are driven by actin assembly but are independent of Rac1, Arp2/3 complex, myosin, or microtubules. Rac1 positively regulates the frequency of initiation of long pseudopods, which promote migration speed and directional plasticity. Scar/WAVE and Arp2/3 complex drive actin assembly for long pseudopod extension, which also depends on microtubule dynamics. Myosin contractility balances the extension of long pseudopods by effecting retraction and allowing force generation for movement through the complex 3D epidermal environment.
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Melanoblasts proper location and timed differentiation depend on notch rbp j signaling in postnatal hair follicles
Journal of Investigative Dermatology, 2008Co-Authors: Lionel Larue, Genevieve Aubinhouzelstein, Johanna Djianzaouche, Florence Bernex, Stephanie Gadin, Veronique Delmas, Jeanjacques PanthierAbstract:The Notch/RBP-J pathway is involved in a variety of developmental processes and in tissue homeostasis. In the melanocyte lineage, it has been shown that Notch signaling acts through Hes1 to maintain the melanocyte stem cell population in the hair follicle. This study was designed to determine whether Notch signaling is implicated in other steps of melanocyte-lineage postnatal development. For this purpose, we developed mice in which the RBP-J gene was conditionally ablated in the melanocyte lineage and used the Dct-lacZ reporter transgene to track melanocytes and their precursors in individual hair follicles. We determine that Notch/RBP-J-deficient Melanoblasts are in reduced number within the hair follicle and gather within its lower permanent part. Moreover, our results show that Notch signaling is necessary to prevent differentiation of melanocyte stem cells and of Melanoblasts before they reach the hair bulb. Finally, our data show that Notch signaling is involved in proper location of Melanoblasts in the outer root sheath and of melanocytes in the hair matrix. These findings reveal previously unrecognized roles for Notch signaling in the melanocyte lineage.
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Mitf cooperates with Rb1 and activates p21Cip1 expression to regulate cell cycle progression
Nature, 2005Co-Authors: Suzanne Carreira, Laurence Denat, Jane Goodall, Isil Aksan, S. Anna La Rocca, Marie-dominique Galibert, Lionel Larue, Colin R GodingAbstract:The controls that enable Melanoblasts and melanoma cells to proliferate are likely to be related, but so far no key regulator of cell cycle progression specific to the melanocyte lineage has been identified. The microphthalmia-associated transcription factor Mitf has a crucial but poorly defined role in Melanoblast and melanocyte survival and in differentiation. Here we show that Mitf can act as a novel anti-proliferative transcription factor able to induce a G1 cell-cycle arrest that is dependent on Mitf-mediated activation of the p21(Cip1) (CDKN1A) cyclin-dependent kinase inhibitor gene. Moreover, cooperation between Mitf and the retinoblastoma protein Rb1 potentiates the ability of Mitf to activate transcription. The results indicate that Mitf-mediated activation of p21Cip1 expression and consequent hypophosphorylation of Rb1 will contribute to cell cycle exit and activation of the differentiation programme. The mutation of genes associated with melanoma, such as INK4a or BRAF that would affect either Mitf cooperation with Rb1 or Mitf stability respectively, would impair Mitf-mediated cell cycle control.