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David M Parichy - One of the best experts on this subject based on the ideXlab platform.
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origins of adult Pigmentation diversity in Pigment stem Cell lineages and implications for pattern evolution
Pigment Cell & Melanoma Research, 2015Co-Authors: David M Parichy, Jessica E. SpiewakAbstract:Summary Teleosts comprise about half of all vertebrate species and exhibit an extraordinary diversity of adult Pigment patterns that function in shoaling, camouflage, and mate choice and have played important roles in speciation. Here, we review studies that have identified several distinct neural crest lineages, with distinct genetic requirements, that give rise to adult Pigment Cells in fishes. These lineages include post-embryonic, peripheral nerve-associated stem Cells that generate black melanophores and iridescent iridophores, Cells derived directly from embryonic neural crest Cells that generate yellow-orange xanthophores, and bipotent stem Cells that generate both melanophores and xanthophores. This complexity in adult chromatophore lineages has implications for our understanding of adult traits, melanoma, and the evolutionary diversification of Pigment Cell lineages and patterns.
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Pigment Cell interactions and differential xanthophore recruitment underlying zebrafish stripe reiteration and danio pattern evolution
Nature Communications, 2014Co-Authors: Larissa B Patterson, Emily J Bain, David M ParichyAbstract:Fishes have diverse colour patterns, yet the mechanisms of pattern diversification are poorly understood. Here, the authors show that the uniform Pigment pattern in Danio albolineatus is established by an early differentiation of xanthophores controlled by cis regulatory changes at the csf1a locus.
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thyroid hormone dependent adult Pigment Cell lineage and pattern in zebrafish
Science, 2014Co-Authors: Sarah K Mcmenamin, Larissa B Patterson, Judith S Eisen, Emily J Bain, Anna E Mccann, Zachary P Waller, James C Hamill, Julie A Kuhlman, David M ParichyAbstract:Pigment patterns are useful for elucidating fundamental mechanisms of pattern formation and how these mechanisms evolve. In zebrafish, several Pigment Cell classes interact to generate stripes, yet the developmental requirements and origins of these Cells remain poorly understood. Using zebrafish and a related species, we identified roles for thyroid hormone (TH) in Pigment Cell development and patterning, and in post-embryonic development more generally. We show that adult Pigment Cells arise from distinct lineages having distinct requirements for TH, and that differential TH-dependence can evolve within lineages. Our findings demonstrate critical functions for TH in determining Pigment pattern phenotype and highlight the potential for evolutionary diversification at the intersection of developmental and endocrine mechanisms.
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tetraspanin 3c requirement for Pigment Cell interactions and boundary formation in zebrafish adult Pigment stripes
Pigment Cell & Melanoma Research, 2014Co-Authors: Shinya Inoue, David M Parichy, Shigeru Kondo, Masakatsu WatanabeAbstract:Skin Pigment pattern formation in zebrafish requires Pigment-Cell autonomous interactions between melanophores and xanthophores, yet the molecular bases for these interactions remain largely unknown. Here, we examined the dali mutant that exhibits stripes in which melanophores are intermingled abnormally with xanthophores. By in vitro Cell culture, we found that melanophores of dali mutants have a defect in motility and that interactions between melanophores and xanthophores are defective as well. Positional cloning and rescue identified dali as tetraspanin 3c (tspan3c), encoding a transmembrane scaffolding protein expressed by melanophores and xanthophores. We further showed that dali mutant Tspan3c expressed in HeLa Cell exhibits a defect in N-glycosylation and is retained inappropriately in the endoplasmic reticulum. Our results are the first to identify roles for a tetraspanin superfamily protein in skin Pigment pattern formation and suggest new mechanisms for the establishment and maintenance of zebrafish stripe boundaries.
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post embryonic nerve associated precursors to adult Pigment Cells genetic requirements and dynamics of morphogenesis and differentiation
PLOS Genetics, 2011Co-Authors: Erine H Budi, Larissa B Patterson, David M ParichyAbstract:The Pigment Cells of vertebrates serve a variety of functions and generate a stunning variety of patterns. These Cells are also implicated in human pathologies including melanoma. Whereas the events of Pigment Cell development have been studied extensively in the embryo, much less is known about morphogenesis and differentiation of these Cells during post-embryonic stages. Previous studies of zebrafish revealed genetically distinct populations of embryonic and adult melanophores, the ectotherm homologue of amniote melanocytes. Here, we use molecular markers, vital labeling, time-lapse imaging, mutational analyses, and transgenesis to identify peripheral nerves as a niche for precursors to adult melanophores that subsequently migrate to the skin to form the adult Pigment pattern. We further identify genetic requirements for establishing, maintaining, and recruiting precursors to the adult melanophore lineage and demonstrate novel compensatory behaviors during pattern regulation in mutant backgrounds. Finally, we show that distinct populations of latent precursors having differential regenerative capabilities persist into the adult. These findings provide a foundation for future studies of post-embryonic Pigment Cell precursors in development, evolution, and neoplasia.
Robert N Kelsh - One of the best experts on this subject based on the ideXlab platform.
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dicer1 is required for Pigment Cell and craniofacial development in zebrafish
Biochimica et Biophysica Acta, 2019Co-Authors: Andrea M J Weiner, Robert N Kelsh, Nadia L Scampoli, Tomas J Steeman, Christopher M Dooley, Elisabeth M Buschnentwich, Nora B CalcaterraAbstract:Abstract The multidomain RNase III endoribonuclease DICER is required for the generation of most functional microRNAs (miRNAs). Loss of Dicer affects developmental processes at different levels. Here, we characterized the zebrafish Dicer1 mutant, dicer1sa9205, which has a single point mutation induced by N-ethyl-N-nitrosourea mutagenesis. Heterozygous dicer1sa9205 developed normally, being phenotypically indistinguishable from wild-type siblings. Homozygous dicer1sa9205 mutants display smaller eyes, abnormal craniofacial development and aberrant Pigmentation. Reduced numbers of both iridophores and melanocytes were observed in the head and ventral trunk of dicer1sa9205 homozygotes; the effect on melanocytes was stronger and detectable earlier in development. The expression of microphthalmia-associated transcription factor a (mitfa), the master gene for melanocytes differentiation, was enhanced in dicer1-depleted fish. Similarly, the expression of SRY-box containing gene 10 (sox10), required for mitfa activation, was higher in mutants than in wild types. In silico and in vivo analyses of either sox10 or mitfa 3’UTRs revealed conserved potential miRNA binding sites likely involved in the post-transcriptional regulation of both genes. Based on these findings, we propose that dicer1 participates in the gene regulatory network governing zebrafish melanocyte differentiation by controlling the expression of mitfa and sox10.
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zebrafish adult Pigment stem Cells are multipotent and form Pigment Cells by a progressive fate restriction process clonal analysis identifies shared origin of all Pigment Cell types
BioEssays, 2017Co-Authors: Robert N Kelsh, Karen Camargo Sosa, Jennifer P Owen, Christian A YatesAbstract:Skin Pigment pattern formation is a paradigmatic example of pattern formation. In zebrafish, the adult body stripes are generated by coordinated rearrangement of three distinct Pigment Cell-types, black melanocytes, shiny iridophores and yellow xanthophores. A stem Cell origin of melanocytes and iridophores has been proposed although the potency of those stem Cells has remained unclear. Xanthophores, however, seemed to originate predominantly from proliferation of embryonic xanthophores. Now, data from Singh et al. shows that all three Cell-types derive from shared stem Cells, and that these Cells generate peripheral neural Cell-types too. Furthermore, clonal compositions are best explained by a progressive fate restriction model generating the individual Cell-types. The numbers of adult Pigment stem Cells associated with the dorsal root ganglia remain low, but progenitor numbers increase significantly during larval development up to metamorphosis, likely via production of partially restricted progenitors on the spinal nerves.
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what is a vertebrate Pigment Cell
Pigment Cell & Melanoma Research, 2016Co-Authors: Manfred Schartl, Hisashi Hashimoto, Lionel Larue, Makoto Goda, Marcus Bosenberg, Robert N KelshAbstract: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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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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mutational analysis of endothelin receptor b1 rose during neural crest and Pigment pattern development in the zebrafish danio rerio
Developmental Biology, 2000Co-Authors: David M Parichy, Robert N Kelsh, Susana S Lopes, Eve M Mellgren, John F Rawls, Stephen L. JohnsonAbstract:Abstract Pigment patterns of fishes are a tractable system for studying the genetic and Cellular bases for postembryonic phenotypes. In the zebrafish Danio rerio, neural crest-derived Pigment Cells generate different Pigment patterns during different phases of the life cycle. Whereas early larvae exhibit simple stripes of melanocytes and silver iridophores in a background of yellow xanthophores, this Pigment pattern is transformed at metamorphosis into that of the adult, comprising a series of dark melanocyte and iridophore stripes, alternating with light stripes of iridophores and xanthophores. Although several genes have been identified in D. rerio that contribute to the development of both early larval and adult Pigment patterns, comparatively little is known about genes that are essential for pattern formation during just one or the other life cycle phase. In this study, we identify the gene responsible for the rose mutant phenotype in D. rerio. rose mutants have wild-type early larval Pigment patterns, but fail to develop normal numbers of melanocytes and iridophores during Pigment pattern metamorphosis and exhibit a disrupted pattern of these Cells. We show that rose corresponds to endothelin receptor b1 (ednrb1), an orthologue of amniote Ednrb genes that have long been studied for their roles in neural crest and Pigment Cell development. Furthermore, we demonstrate that D. rerio ednrb1 is expressed both during Pigment pattern metamorphosis and during embryogenesis, and Cells of melanocyte, iridophore, and xanthophore lineages all express this gene. These analyses suggest a phylogenetic conservation of roles for Ednrb signaling in the development of amniote and teleost Pigment Cell precursors. As murine Ednrb is essential for the development of all neural crest derived melanocytes, and D. rerio ednrb1 is required only by a subset of adult melanocytes and iridophores, these analyses also reveal variation among vertebrates in the Cellular requirements for Ednrb signaling, and suggest alternative models for the Cellular and genetic bases of Pigment pattern metamorphosis in D. rerio.
Stephen L. Johnson - One of the best experts on this subject based on the ideXlab platform.
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Gene expression analysis of zebrafish melanocytes, iridophores, and retinal Pigmented epithelium reveals indicators of biological function and developmental origin
2016Co-Authors: Charles W. Higdon, Robi D. Mitra, Stephen L. JohnsonAbstract:In order to facilitate understanding of Pigment Cell biology, we developed a method to concomitantly purify melanocytes, iridophores, and retinal Pigmented epithelium from zebrafish, and analyzed their transcriptomes. Comparing expression data from these Cell types and whole embryos allowed us to reveal gene expression co-enrichment in melanocytes and retinal Pigmented epithelium, as well as in melanocytes and iridophores. We found 214 genes co-enriched in melanocytes and retinal Pigmented epithelium, indicating the shared functions of melanin-producing Cells. We found 62 genes significantly co-enriched in melanocytes and iridophores, illustrative of their shared developmental origins from the neural crest. This is also the first analysis of the iridophore transcriptome. Gene expression analysis for iridophores revealed extensive enrichment of specific enzymes to coordinate production of their guanine-based reflective Pigment. We speculate the coordinated upregulation of specific enzymes from several metabolic pathways recycles the rate-limiting substrate for purine synthesis, phosphoribosyl pyrophosphate, thus constituting a guanine cycle. The purification procedure and expression analysis described here, along with the accompanying transcriptome-wide expression data, provide the first mRNA sequencing data for multiple purified zebrafish Pigment Cell types, and will be a useful resource for further studies of Pigment Cell biology
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mutational analysis of endothelin receptor b1 rose during neural crest and Pigment pattern development in the zebrafish danio rerio
Developmental Biology, 2000Co-Authors: David M Parichy, Robert N Kelsh, Susana S Lopes, Eve M Mellgren, John F Rawls, Stephen L. JohnsonAbstract:Abstract Pigment patterns of fishes are a tractable system for studying the genetic and Cellular bases for postembryonic phenotypes. In the zebrafish Danio rerio, neural crest-derived Pigment Cells generate different Pigment patterns during different phases of the life cycle. Whereas early larvae exhibit simple stripes of melanocytes and silver iridophores in a background of yellow xanthophores, this Pigment pattern is transformed at metamorphosis into that of the adult, comprising a series of dark melanocyte and iridophore stripes, alternating with light stripes of iridophores and xanthophores. Although several genes have been identified in D. rerio that contribute to the development of both early larval and adult Pigment patterns, comparatively little is known about genes that are essential for pattern formation during just one or the other life cycle phase. In this study, we identify the gene responsible for the rose mutant phenotype in D. rerio. rose mutants have wild-type early larval Pigment patterns, but fail to develop normal numbers of melanocytes and iridophores during Pigment pattern metamorphosis and exhibit a disrupted pattern of these Cells. We show that rose corresponds to endothelin receptor b1 (ednrb1), an orthologue of amniote Ednrb genes that have long been studied for their roles in neural crest and Pigment Cell development. Furthermore, we demonstrate that D. rerio ednrb1 is expressed both during Pigment pattern metamorphosis and during embryogenesis, and Cells of melanocyte, iridophore, and xanthophore lineages all express this gene. These analyses suggest a phylogenetic conservation of roles for Ednrb signaling in the development of amniote and teleost Pigment Cell precursors. As murine Ednrb is essential for the development of all neural crest derived melanocytes, and D. rerio ednrb1 is required only by a subset of adult melanocytes and iridophores, these analyses also reveal variation among vertebrates in the Cellular requirements for Ednrb signaling, and suggest alternative models for the Cellular and genetic bases of Pigment pattern metamorphosis in D. rerio.
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an orthologue of the kit related gene fms is required for development of neural crest derived xanthophores and a subpopulation of adult melanocytes in the zebrafish danio rerio
Development, 2000Co-Authors: David M Parichy, David Ransom, Barry H Paw, Leonard I Zon, Stephen L. JohnsonAbstract:Developmental mechanisms underlying traits expressed in larval and adult vertebrates remain largely unknown. Pigment patterns of fishes provide an opportunity to identify genes and Cell behaviors required for postembryonic morphogenesis and differentiation. In the zebrafish, Danio rerio, Pigment patterns reflect the spatial arrangements of three classes of neural crest-derived Pigment Cells: black melanocytes, yellow xanthophores and silver iridophores. We show that the D. rerio Pigment pattern mutant panther ablates xanthophores in embryos and adults and has defects in the development of the adult pattern of melanocyte stripes. We find that panther corresponds to an orthologue of the c-fms gene, which encodes a type III receptor tyrosine kinase and is the closest known homologue of the previously identified Pigment pattern gene, kit. In mouse, fms is essential for the development of macrophage and osteoclast lineages and has not been implicated in neural crest or Pigment Cell development. In contrast, our analyses demonstrate that fms is expressed and required by D. rerio xanthophore precursors and that fms promotes the normal patterning of melanocyte death and migration during adult stripe formation. Finally, we show that fms is required for the appearance of a late developing, kit-independent subpopulation of adult melanocytes. These findings reveal an unexpected role for fms in Pigment pattern development and demonstrate that parallel neural crest-derived Pigment Cell populations depend on the activities of two essentially paralogous genes, kit and fms.
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nacre encodes a zebrafish microphthalmia related protein that regulates neural crest derived Pigment Cell fate
Development, 1999Co-Authors: James A Lister, Stephen L. Johnson, Christie P Robertson, Thierry Lepage, David W. RaibleAbstract:We report the isolation and identification of a new mutation affecting Pigment Cell fate in the zebrafish neural crest. Homozygous nacre (nac(w2)) mutants lack melanophores throughout development but have increased numbers of iridophores. The non-crest-derived retinal Pigment epithelium is normal, suggesting that the mutation does not affect Pigment synthesis per se. Expression of early melanoblast markers is absent in nacre mutants and transplant experiments suggested a Cell-autonomous function in melanophores. We show that nac(w2) is a mutation in a zebrafish gene encoding a basic helix-loop-helix/leucine zipper transcription factor related to microphthalmia (Mitf), a gene known to be required for development of eye and crest Pigment Cells in the mouse. Transient expression of the wild-type nacre gene restored melanophore development in nacre(-/-) embryos. Furthermore, misexpression of nacre induced the formation of ectopic melanized Cells and caused defects in eye development in wild-type and mutant embryos. These results demonstrate that melanophore development in fish and mammals shares a dependence on the nacre/Mitf transcription factor, but that proper development of the retinal Pigment epithelium in the fish is not nacre-dependent, suggesting an evolutionary divergence in the function of this gene.
Hiroki Nishida - One of the best experts on this subject based on the ideXlab platform.
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the bmp chordin antagonism controls sensory Pigment Cell specification and differentiation in the ascidian embryo
Developmental Biology, 2001Co-Authors: Sebastien Darras, Hiroki NishidaAbstract:We have investigated the role of the bone morphogenetic protein (BMP) pathway during neural tissue formation in the ascidian embryo. The orthologue of the BMP antagonist, chordin, was isolated from the ascidian Halocynthia roretzi. While both the expression pattern and the phenotype observed by overexpressing chordin or BMPb (the dpp-subclass BMP) do not suggest a role for these factors in neural induction, BMP/CHORDIN antagonism was found to affect neural patterning. Overexpression of BMPb induced ectopic sensory Pigment Cells in the brain lineages that do not normally form Pigment Cells and suppressed pressure organ formation within the brain. Reciprocally, overexpressing chordin suppressed Pigment Cell formation and induced ectopic pressure organ. We show that Pigment Cell formation occurs in three steps. (1) During cleavage stages ectodermal Cells are neuralized by a vegetal signal that can be substituted by bFGF. (2) At the early gastrula stage, BMPb secreted from the lateral nerve cord blastomeres induces those neuralized blastomeres in close proximity to adopt a Pigment Cell fate. (3) At the tailbud stage, among these Pigment Cell precursors, BMPb induces the differentiation of specifically the anterior type of Pigment Cell, the otolith; while posteriorly, CHORDIN suppresses BMP activity and allows oCellus differentiation.
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notch homologue from halocynthia roretzi is preferentially expressed in the central nervous system during ascidian embryogenesis
Development Genes and Evolution, 1997Co-Authors: Sawako Hori, Takashi Saitoh, Midori Matsumoto, Kazuhiro W Makabe, Hiroki NishidaAbstract:We describe here the primary structure of HrNotch, an ascidian homologue of the Drosophila neurogenic gene Notch. HrNotch transcripts encode a protein of 2352 amino acids and share the principal features of the Notch gene family: extraCellular epidermal growth factor (EGF)-like repeats, three Notch/Lin-12 repeats and six intraCellular ankyrin repeats. Yet ascidian Notch contains only 33 EGF repeats in the putative extramembrane domain and specifically lacks the three EGF-like repeats. In situ hybridization shows that maternal HrNotch mRNA is distributed uniformly in the cytoplasm of the unfertilized egg. During cleavage, maternal HrNotch transcripts are ubiquitous in the ectoderm Cells of the animal hemisphere, which contain less yolk granules. During gastrulation, maternal transcripts persist in most ectoderm lineage Cells. Zygotic expression of HrNotch seems to start at the neural plate stage in both a-line Cells (descendants of anterior-animal blastomeres) of the dorsal neuroectoderm and b-line Cells (descendants of the posterior-animal blastomeres) that comprise the neural fold. Following this stage, transcripts are most evident in the descendants of these Cells, that is, the brain lineage Cells, precursors of a larval adhesive organ, and dorsal part of the nerve cord (roof plate). Brain lineage Cells include the precursors of sensory Pigment Cells that are known to comprise an equivalence group in ascidian embryos. During tail elongation, transcripts disappear. Predominant expression of HrNotch in epidermal and neural Cells is a common feature of chordate Notch genes. Furthermore, the timing of HrNotch expression in sensory Pigment Cell precursors suggests involvement in the determinative events in the sensory Pigment Cell equivalence group.
Christiane Nussleinvolhard - One of the best experts on this subject based on the ideXlab platform.
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Pigment Cell progenitors in zebrafish remain multipotent through metamorphosis
Developmental Cell, 2016Co-Authors: Ajeet Pratap Singh, Uwe Irion, April Dinwiddie, Prateek Mahalwar, U Schach, Claudia Linker, Christiane NussleinvolhardAbstract:The neural crest is a transient, multipotent embryonic Cell population in vertebrates giving rise to diverse Cell types in adults via intermediate progenitors. The in vivo Cell-fate potential and lineage segregation of these postembryonic progenitors is poorly understood, and it is unknown if and when the progenitors become fate restricted. We investigate the fate restriction in the neural crest-derived stem Cells and intermediate progenitors in zebrafish, which give rise to three distinct adult Pigment Cell types: melanophores, iridophores, and xanthophores. By inducing clones in sox10-expressing Cells, we trace and quantitatively compare the Pigment Cell progenitors at four stages, from embryogenesis to metamorphosis. At all stages, a large fraction of the progenitors are multipotent. These multipotent progenitors have a high proliferation ability, which diminishes with fate restriction. We suggest that multipotency of the nerve-associated progenitors lasting into metamorphosis may have facilitated the evolution of adult-specific traits in vertebrates.
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homotypic Cell competition regulates proliferation and tiling of zebrafish Pigment Cells during colour pattern formation
Nature Communications, 2016Co-Authors: Brigitte Walderich, Prateek Mahalwar, Ajeet Pratap Singh, Christiane NussleinvolhardAbstract:Melanophores, iridophores and xanthophores are Pigment-Cell types that interact to form the stripes in zebrafish. Here, the authors study the interaction between Cells of the same kind and show that each Pigment-Cell type covers the skin by contact based competition.
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tight junction protein 1a regulates Pigment Cell organisation during zebrafish colour patterning
eLife, 2015Co-Authors: Andrey Fadeev, Jana Krauss, Uwe Irion, Hans Georg Frohnhofer, Christiane NussleinvolhardAbstract:The striking horizontal striped pattern of the zebrafish makes it a decorative addition to many home aquariums. The stripes are a result of three different Pigment Cells interacting with each other, and first begin to emerge when the animal is two to three weeks old. At that time, iridescent Cells called iridophores begin to multiply and spread in the skin. In the light-coloured stripes, the iridophores are compact and ‘dense’; in the dark stripes the Cells change into a ‘loose’ shape and organisation. Black-Pigmented Cells fill in the dark stripes, and a third Cell type with a yellow hue condenses over the light stripes. How the three types of Cell work together to make the striped pattern is not fully understood. Fadeev et al. examined a zebrafish variant with a genetic mutation that disrupts the function of a protein called Tight Junction Protein 1a (or Tjp1a)—a fish variant of a mammalian protein called ZO-1. This protein helps Cells to interact with each other. The mutant fish appear spotted rather than striped, because light regions containing sheets of the dense iridophores interrupt the dark stripes. Experiments using fluorescent markers showed that Tjp1a is produced in much lower amounts in the loose iridophores in the dark stripes than in the dense iridophores of the light stripes. This led Fadeev et al. to suggest that the transition from the dense to the loose shape is dependent on the presence of Tjp1a in the Cell. Tjp1a is likely to regulate how colour patterns form by controlling how iridophores interact with other types of Pigment Cell. The Tjp1a mutant fish provides the first glimpse into the machinery inside Cells that underlies colour pattern formation, and will help to identify other components and cues responsible for Cell interactions.
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formation of the adult Pigment pattern in zebrafish requires leopard and obelix dependent Cell interactions
Development, 2003Co-Authors: Florian Maderspacher, Christiane NussleinvolhardAbstract:Colour patterns are a prominent feature of many animals and are of high evolutionary relevance. In zebrafish, the adult Pigment pattern comprises alternating stripes of two Pigment Cell types, melanophores and xanthophores. How the stripes are defined and a straight boundary is formed remains elusive. We find that mutants lacking one Pigment Cell type lack a striped pattern. Instead, Cells of one type form characteristic patterns by homotypic interactions. Using mosaic analysis, we show that juxtaposition of melanophores and xanthophores suffices to restore stripe formation locally. Based on this, we have analysed the Pigment pattern of two adult specific mutants: leopard and obelix. We demonstrate that obelix is required in melanophores to promote their aggregation and controls boundary integrity. By contrast, leopard regulates homotypic interaction within both melanophores and xanthophores, and interaction between the two, thus controlling boundary shape. These findings support a view in which Cell-Cell interactions among Pigment Cells are the major driving force for adult Pigment pattern formation.
