The Experts below are selected from a list of 189 Experts worldwide ranked by ideXlab platform
David M. Parichy - One of the best experts on this subject based on the ideXlab platform.
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interplay between foxd3 and mitf regulates cell fate plasticity in the zebrafish neural crest
Developmental Biology, 2010Co-Authors: Kevin Curran, David M. Parichy, James A Lister, Gary R Kunkel, Andrew Prendergast, David W. RaibleAbstract:Pigment cells of the zebrafish, Danio rerio, offer an exceptionally tractable system for studying the genetic and cellular bases of cell fate decisions. In the zebrafish, neural crest cells generate three types of pigment cells during embryogenesis: yellow xanthophores, iridescent iridophores and black Melanophores. In this study, we present evidence for a model whereby Melanophores and iridophores descend from a common precursor whose fate is regulated by an interplay between the transcription factors Mitf and Foxd3. Loss of mitfa, a key regulator of Melanophore development, resulted in supernumerary ectopic iridophores while loss of foxd3, a mitfa repressor, resulted in fewer iridophores. Double mutants showed a restoration of iridophores, suggesting that one of Foxd3's roles is to suppress mitfa to promote iridophore development. Foxd3 co-localized with pnp4a, a novel marker of early iridophore development, and was necessary for its expression. A considerable overlap was found between iridoblast and melanoblast markers but not xanthoblast markers, which resolved as cells began to differentiate. Cell lineage analyses using the photoconvertible marker, EosFP, revealed that both Melanophores and iridophores develop from a mitfa+ precursor. Taken together, our data reveal a Foxd3/mitfa transcriptional switch that governs whether a bi-potent pigment precursor will attain either an iridophore or a Melanophore fate.
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pigment pattern evolution by differential deployment of neural crest and post embryonic Melanophore lineages in danio fishes
Development, 2004Co-Authors: Ian K Quigley, Jessica M Turner, Richard J Nuckels, Joan L Manuel, Erine H Budi, Erin L Macdonald, David M. ParichyAbstract:Latent precursors or stem cells of neural crest origin are present in a variety of post-embryonic tissues. Although these cells are of biomedical interest for roles in human health and disease, their potential evolutionary significance has been underappreciated. As a first step towards elucidating the contributions of such cells to the evolution of vertebrate form, we investigated the relative roles of neural crest cells and post-embryonic latent precursors during the evolutionary diversification of adult pigment patterns in Danio fishes. These pigment patterns result from the numbers and arrangements of embryonic Melanophores that are derived from embryonic neural crest cells, as well as from post-embryonic metamorphic Melanophores that are derived from latent precursors of presumptive neural crest origin. In the zebrafish D. rerio, a pattern of Melanophore stripes arises during the larval-to-adult transformation by the recruitment of metamorphic Melanophores from latent precursors. Using a comparative approach in the context of new phylogenetic data, we show that adult pigment patterns in five additional species also arise from metamorphic Melanophores, identifying this as an ancestral mode of adult pigment pattern development. By contrast, superficially similar adult stripes of D. nigrofasciatus (a sister species to D. rerio) arise by the reorganization of Melanophores that differentiated at embryonic stages, with a diminished contribution from metamorphic Melanophores. Genetic mosaic and molecular marker analyses reveal evolutionary changes that are extrinsic to D. nigrofasciatus Melanophore lineages, including a dramatic reduction of metamorphic Melanophore precursors. Finally, interspecific complementation tests identify a candidate genetic pathway for contributing to the evolutionary reduction in metamorphic Melanophores and the increased contribution of early larval Melanophores to D. nigrofasciatus adult pigment pattern development. These results demonstrate an important role for latent precursors in the diversification of pigment patterns across danios. More generally, differences in the deployment of post-embryonic neural crest-derived stem cells or their specified progeny may contribute substantially to the evolutionary diversification of adult form in vertebrates, particularly in species that undergo a metamorphosis.
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temporal and cellular requirements for fms signaling during zebrafish adult pigment pattern development
Development, 2003Co-Authors: David M. Parichy, Jessica M TurnerAbstract:Ectothermic vertebrates exhibit a diverse array of adult pigment patterns. A common element of these patterns is alternating dark and light stripes each comprising different classes of neural crest-derived pigment cells. In the zebrafish, Danio rerio, alternating horizontal stripes of black Melanophores and yellow xanthophores are a prominent feature of the adult pigment pattern. In fms mutant zebrafish, however, xanthophores fail to develop and Melanophore stripes are severely disrupted. fms encodes a type III receptor tyrosine kinase expressed by xanthophores and their precursors and is the closest known homologue of kit, which has long been studied for roles in pigment pattern development in amniotes. In this study we assess the cellular and temporal requirements for Fms activity in promoting adult pigment pattern development. By transplanting cells between fms mutants and either wild-type or nacre mutant zebrafish, we show that fms acts autonomously to the xanthophore lineage in promoting the striped arrangement of adult Melanophores. To identify critical periods for fms activity, we isolated temperature sensitive alleles of fms and performed reciprocal temperature shift experiments at a range of stages from embryo to adult. These analyses demonstrate that Fms is essential for maintaining cells of the xanthophore lineage as well as maintaining the organization of Melanophore stripes throughout development. Finally, we show that restoring Fms activity even at late larval stages allows essentially complete recovery of xanthophores and the development of a normal Melanophore stripe pattern. Our findings suggest that fms is not required for establishing a population of precursor cells during embryogenesis but is required for recruiting pigment cell precursors to xanthophore fates, with concomitant effects on Melanophore organization.
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Pigment Patterns of Larval Salamanders (Ambystomatidae, Salamandridae): The Role of the Lateral Line Sensory System and the Evolution of Pattern-Forming Mechanisms
Developmental biology, 1996Co-Authors: David M. ParichyAbstract:In many species of salamanders, pigment cells derived from the neural crest give rise to a horizontal stripe pattern in hatchling larvae. A defining element of these horizontal stripe patterns is a region over the middle of the myotomes that is relatively free of Melanophores. This study shows that formation of a "Melanophore-free region" and horizontal stripe pattern in Ambystoma tigrinum tigrinum (family Ambystomatidae) correlates with the development of the trunk lateral line sensory system. Moreover, prevention of lateral line development results in greater densities of Melanophores in the middle of the flank, essentially eliminating the Melanophore-free region in this taxon. A phylogenetic survey also revealed that ablation of the lateral lines has qualitatively similar effects on Melanophores in seven of eight additional taxa (Ambystomatidae: A. barbouri, A. maculatum, A. talpoideum; Salamandridae: Notophthalmus viridescens, Pleurodeles waltl, Taricha granulosa, T. rivularis). In Taricha torosa, however, a superficially similar Melanophore-free region forms prior to lateral line development, and ablation of the lateral lines does not perturb the horizontal stripe pattern. Finally, heterospecific grafting experiments demonstrated that T. torosa lateral lines are competent to generate a Melanophore-free region, and T. torosa Melanophores are competent to respond to cues associated with the lateral lines. These results indicate that lateral line-dependent pattern-forming mechanisms are common and probably ancestral within the families Ambystomatidae and Salamandridae and suggest that these ancestral mechanisms have been retained in T. torosa as redundant, lateral line-dependent mechanisms for stripe formation have evolved.
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When Neural Crest and Placodes Collide: Interactions between Melanophores and the Lateral Lines That Generate Stripes in the SalamanderAmbystoma tigrinum tigrinum(Ambystomatidae)
Developmental biology, 1996Co-Authors: David M. ParichyAbstract:Abstract A prominent element of the early larval pigment pattern in the salamanderAmbystoma tigrinum tigrinum(family Ambystomatidae) is a horizontal stripe over the lateral surface of the myotomes where otherwise abundant, neural crest-derived Melanophores are not found. This study examines the formation of this “Melanophore-free region.” When the trunk lateral lines were ablated (by removing cranial lateral line placodes), the Melanophore-free region did not form; instead, Melanophores populated the middle of the flank and the distribution of yellow, neural crest-derived xanthophores was perturbed. Time-lapse videomicrography demonstrated that during normal development, the Melanophore-free region is established because Melanophores retreat from the midbody lateral line primordium as it migrates caudally along the inner side of the epidermis. Melanophores do not repopulate the middle of the flank after primordium migration and heterochronic grafting experiments suggest that extracellular factors contribute to maintaining the Melanophore-free region during these later stages. Finally, photographic series, microsurgical manipulations, electron microscopy, and staining for molecules of the extracellular matrix (peanut agglutinin-binding components, tenascin, chondroitin sulfate proteoglycans, fibronectin, laminin) suggest that several factors contribute to establishing and maintaining the Melanophore-free region, including steric effects of the lateral lines, interactions between Melanophores and xanthophores, lateral line-dependent alterations of the subepidermal basement membrane, and a general elaboration of the extracellular matrix. Lateral line effects on Melanophores are inferred to be a shared, ancestral feature of pigment pattern development for the families Ambystomatidae and Salamandridae (D. M. Parichy,Dev. Biol.174, 265–282. 1996). The results of this study thus provide insights into a phylogenetically primitive mechanism for stripe formation, and a context for interpreting evolutionary innovations in pattern-forming mechanisms.
Robert A. Cornell - One of the best experts on this subject based on the ideXlab platform.
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Cell Death of Melanophores in Zebrafish trpm7 Mutant Embryos Depends on Melanin Synthesis
The Journal of investigative dermatology, 2007Co-Authors: Matthew S. Mcneill, Jennifer Paulsen, Gregory Bonde, Erin R. Burnight, Mei-yu Hsu, Robert A. CornellAbstract:Transient receptor potential melastatin 7 (TRPM7) is a broadly expressed, non-selective cation channel. Studies in cultured cells implicate TRPM7 in regulation of cell growth, spreading, and survival. However, zebrafish trpm7 homozygous mutants display death of Melanophores and temporary paralysis, but no gross morphological defects during embryonic stages. This phenotype implies that Melanophores are unusually sensitive to decreases in Trpm7 levels, a hypothesis we investigate here. We find that pharmacological inhibition of caspases does not rescue Melanophore viability in trpm7 mutants, implying that Melanophores die by a mechanism other than apoptosis. Consistent with this possibility, ultrastructural analysis of dying Melanophores in trpm7 mutants reveals abnormal melanosomes and evidence of a ruptured plasma membrane, indicating that cell death occurs by necrosis. Interestingly, inhibition of melanin synthesis largely prevents Melanophore cell death in trpm7 mutants. These results suggest that Melanophores require Trpm7 in order to detoxify intermediates of melanin synthesis. We find that unlike TRPM1, TRPM7 is expressed in human melanoma cell lines, indicating that these cells may also be sensitized to reduction of TRPM7 levels.
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Cell death of Melanophores in zebrafish trpm7 mutant embryos depends on melanin synthesis.Commentery
Journal of Investigative Dermatology, 2007Co-Authors: Aurel O. Iuga, Matthew S. Mcneill, Jennifer Paulsen, Gregory Bonde, Erin R. Burnight, Mei-yu Hsu, Ethan A. Lerner, Robert A. CornellAbstract:Transient receptor potential melastatin 7 (TRPM7) is a broadly expressed, non-selective cation channel. Studies in cultured cells implicate TRPM7 in regulation of cell growth, spreading, and survival. However, zebrafish trpm7 homozygous mutants display death of Melanophores and temporary paralysis, but no gross morphological defects during embryonic stages. This phenotype implies that Melanophores are unusually sensitive to decreases in Trpm7 levels, a hypothesis we investigate here. We find that pharmacological inhibition of caspases does not rescue Melanophore viability in trpm7 mutants, implying that Melanophores die by a mechanism other than apoptosis. Consistent with this possibility, ultrastructural analysis of dying Melanophores in trpm7 mutants reveals abnormal melanosomes and evidence of a ruptured plasma membrane, indicating that cell death occurs by necrosis. Interestingly, inhibition of melanin synthesis largely prevents Melanophore cell death in trpm7 mutants. These results suggest that Melanophores require Trpm7 in order to detoxify intermediates of melanin synthesis. We find that unlike TRPM1, TRPM7 is expressed in human melanoma cell lines, indicating that these cells may also be sensitized to reduction of TRPM7 levels.
D. Burton - One of the best experts on this subject based on the ideXlab platform.
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in vitro pattern related effects of forskolin on Melanophore adrenoceptor mediated responses of winter flounder
Journal of Fish Biology, 2005Co-Authors: D. BurtonAbstract:In vitro experiments were performed on Melanophores on scales carrying small slips of skin (scale slips) sampled from the white spot, dark band and general background components of patterning in winter flounder Pseudopleuronectes americanus. In vitro, forskolin (10 -4 to to 10 -7 M) was employed to increase Melanophore intracellular cytosolic adenosine-3'-5'-monophosphate (cAMP) levels by stimulating adenylate cyclase. Such increase shifted noradrenaline concentration-response curves to the right, general background Melanophores being least sensitive to the forskolin, indicating a relatively higher proportion of α 2 -adrenoceptors, and those from white spots the most sensitive. Melanosome dispersion, in balanced salt solution, was also enhanced by such raised levels of cAMP. Without forskolin, Melanophores from white spots displayed the shortest pigment dispersion time in balanced salt solution, the slower Melanophores from the other pattern components being those most affected by the addition of forskolin. The results demonstrate that differences in Melanophore physiological responsiveness associated with flatfish patterns involve differential intracellular levels of cAMP, as well as differences in Melanophore size and rates of melanosome movement.
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The relative in vitro responsiveness of Melanophores of winter flounder to α‐MSH and MCH
Journal of Fish Biology, 2000Co-Authors: D. Burton, J. E. VokeyAbstract:Melanin-concentrating hormone (MCH) was more potent than the antagonistic Melanophore stimulating hormone (α-MSH) for the winter flounder Pleuronectes americanus when mixtures of the two were tested on Melanophore preparations. Melanophores from individual pattern components displayed different relative sensitivities to the two hormones. These differences indicate that there are pattern-related variations in MCH and α-MSH receptor density and affinity suggesting that these hormones may have modulatory roles on the pattern-related differential neural regulation of the Melanophores.
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the effects of background colouration and α msh treatment on Melanophore frequency in winter flounder pleuronectes americanus
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 1993Co-Authors: D. BurtonAbstract:Winter flounder, Pleuronectes americanus, adapting to black or white backgrounds display significant increase and decline respectively in the number of visible epidermal Melanophores over periods up to 8 weeks or longer. This contrasts with a stability in the number of visible dermal Melanophores during the same periods of exposure to each background. Flounders treated with α-Melanophore stimulating hormone exhibited an enhanced rate of increase in number of visible epidermal Melanophores when the background was changed from white to black, whereas white-adapted flounder treated with α-Melanophore stimulating hormone without background change did not manifest any such increase in number of epidermal Melanophores. Flounder treated with α-Melanophore stimulating hormone after transfer from black to white displayed a similar initial decline in visible epidermal Melanophore number as in control fish, but the final decline was significantly attenuated. Thus α-Melanophore stimulating hormone, which has no apparent influence on melanosome dispersion in this species, may have a limited morphological Melanophore regulatory role which is discussed in relation to possible antagonistic and synergistic factors that could influence melanogenesis and visible Melanophore numbers.
Aurel O. Iuga - One of the best experts on this subject based on the ideXlab platform.
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rapid responses of a Melanophore cell line to chemical contaminants in water
Journal of Applied Toxicology, 2009Co-Authors: Aurel O. Iuga, Ethan A. Lerner, Tommy R Shedd, William H Van Der SchalieAbstract:We have evaluated a Xenopus cell line as a potential sensor for detecting toxins in water. X. laevis Melanophores responded rapidly by dispersing melanosomes following exposure to six (ammonia, arsenic, copper, mercury, pentachlorophenol and phenol) of 12 tested chemicals in the desired sensitivity range. For two additional chemicals (nicotine and paraquat) the Melanophore response improved upon the response capabilities of several available toxicity sensors. These results suggest that a Melanophore-based sensor could be useful for the rapid assessment of chemical toxicity in drinking water.
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Cell death of Melanophores in zebrafish trpm7 mutant embryos depends on melanin synthesis.Commentery
Journal of Investigative Dermatology, 2007Co-Authors: Aurel O. Iuga, Matthew S. Mcneill, Jennifer Paulsen, Gregory Bonde, Erin R. Burnight, Mei-yu Hsu, Ethan A. Lerner, Robert A. CornellAbstract:Transient receptor potential melastatin 7 (TRPM7) is a broadly expressed, non-selective cation channel. Studies in cultured cells implicate TRPM7 in regulation of cell growth, spreading, and survival. However, zebrafish trpm7 homozygous mutants display death of Melanophores and temporary paralysis, but no gross morphological defects during embryonic stages. This phenotype implies that Melanophores are unusually sensitive to decreases in Trpm7 levels, a hypothesis we investigate here. We find that pharmacological inhibition of caspases does not rescue Melanophore viability in trpm7 mutants, implying that Melanophores die by a mechanism other than apoptosis. Consistent with this possibility, ultrastructural analysis of dying Melanophores in trpm7 mutants reveals abnormal melanosomes and evidence of a ruptured plasma membrane, indicating that cell death occurs by necrosis. Interestingly, inhibition of melanin synthesis largely prevents Melanophore cell death in trpm7 mutants. These results suggest that Melanophores require Trpm7 in order to detoxify intermediates of melanin synthesis. We find that unlike TRPM1, TRPM7 is expressed in human melanoma cell lines, indicating that these cells may also be sensitized to reduction of TRPM7 levels.
R. U. Ahmad - One of the best experts on this subject based on the ideXlab platform.
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Transitory colour changes in the new Melanophores formed by quantitative colour change in the minnow Phoxinus phoxinus
Journal of Zoology, 2009Co-Authors: R. U. AhmadAbstract:Minnows (TeJeosiei: Phoxinus phoxinus (L.)) were exposed on a black background for varying periods to allow Melanophore formation. The ages and times of appearance of Melanophores were photographically determined. The background responses of the newly-formed Melanophores were assessed microscopically in fixed preparations of animals killed in liquid nitrogen at different time-intervals. The results were interpreted according to the generally accepted belief that rapid and slow colour changes indicate nervous and hormonal mediation respectively. The age of the newly-formed Melanophores appeared to influence their background responses, the older Melanophores being more responsive. It is suggested that the sensitivity to hormonal control develops first in the life of a pigment cell, to be followed later by sensitivity to nervous control. Nervous control, however, does not appear simultaneously for W/B and B/W adaptations but develops first for the latter. This differential development is considered to provide evidence for double innervation of Melanophores.