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Cellular and Molecular Life Sciences :... May 2009The major differentiated function of melanocytes is the synthesis of melanin, a pigmented heteropolymer that is synthesized in specialized cellular organelles termed... (Review)
Review
The major differentiated function of melanocytes is the synthesis of melanin, a pigmented heteropolymer that is synthesized in specialized cellular organelles termed melanosomes. Mature melanosomes are transferred to neighboring keratinocytes and are arranged in a supranuclear cap, protecting the DNA against incident ultraviolet light (UV) irradiation. The synthesis and distribution of melanin in the epidermis involves several steps: transcription of melanogenic proteins, melanosome biogenesis, sorting of melanogenic proteins into the melanosomes, transport of melanosomes to the tips of melanocyte dendrites and finally transfer into keratinocytes. These events are tightly regulated by a variety of paracrine and autocrine factors in response to endogenous and exogenous stimuli, principally UV irradiation.
Topics: DNA Damage; Humans; Keratinocytes; Melanins; Melanocytes; Melanosomes; Models, Biological; Paracrine Communication; Signal Transduction; Tumor Suppressor Protein p53; Ultraviolet Rays
PubMed: 19153661
DOI: 10.1007/s00018-009-8703-8 -
Developmental Dynamics : An Official... Oct 2021Amphibians possess three kinds of dermal chromatophore: melanophores, iridophores, and xanthophores. Knockout Xenopus tropicalis that lack the pigmentation of...
BACKGROUND
Amphibians possess three kinds of dermal chromatophore: melanophores, iridophores, and xanthophores. Knockout Xenopus tropicalis that lack the pigmentation of melanophores and iridophores have been reported. The identification of the causal genes for xanthophore pigmentation or differentiation could lead to the creation of a see-through frog without three chromatophores. The genes causing xanthophore differentiation mutants are slc2a11b and slc2a15b in Japanese medaka (Oryzias latipes).
RESULTS
To obtain a heritable line of X tropicalis mutants without yellow pigment, we generated slc2a7 and slc2a15a knockout animals because they have the greatest similarity to the O latipes slc2a11b and slc2a15b genes. The slc2a7 knockout frog had a bluish skin and there were no visible yellow pigments in stereo microscope and skin section observations. Furthermore, no pterinosomes, which are characteristic of xanthophores, were observed via transmission electron microscopy in the skin of knockout animals.
CONCLUSIONS
We report the successful generation of a heritable no-yellow-pigment X tropicalis mutant after knock out of the slc2a7 gene. This finding will enable the creation of a see-through frog with no chromatophores.
Topics: Animals; Animals, Genetically Modified; Chromatophores; Gene Expression Regulation, Developmental; Gene Knockout Techniques; Glucose Transport Proteins, Facilitative; Melanophores; Pigmentation; Xenopus
PubMed: 33760303
DOI: 10.1002/dvdy.334 -
The International Journal of... Jul 2010Melanosomes are the specialized intracellular organelles of pigment cells devoted to the synthesis, storage and transport of melanin pigments, which are responsible for... (Review)
Review
Melanosomes are the specialized intracellular organelles of pigment cells devoted to the synthesis, storage and transport of melanin pigments, which are responsible for most visible pigmentation in mammals and other vertebrates. As a direct consequence, any genetic mutation resulting in alteration of melanosomal function, either because affecting pigment cell survival, migration and differentiation, or because interfering with melanosome biogenesis, transport and transfer to keratinocytes, is immediately translated into color variations of skin, fur, hair or eyes. Thus, over 100 genes and proteins have been identified as pigmentary determinants in mammals, providing us with a deep understanding of this biological system, which functions by using mechanisms and processes that have parallels in other tissues and organs. In particular, many genes implicated in melanosome biogenesis have been characterized, so that melanosomes represent an incredible source of information and a model for organelles belonging to the secretory pathway. Furthermore, the function of melanosomes can be associated with common physiological phenotypes, such as variation of pigmentation among individuals, and with rare pathological conditions, such as albinism, characterized by severe visual defects. Among the most relevant mechanisms operating in melanosome biogenesis are the signal transduction pathways mediated by two peculiar G protein-coupled receptors: the melanocortin-1 receptor (MC1R), involved in the fair skin/red hair phenotype and skin cancer; and OA1 (GPR143), whose loss-of-function results in X-linked ocular albinism. This review will focus on the most recent novelties regarding the functioning of these two receptors, by highlighting emerging signaling mechanisms and general implications for cell biology and pathology.
Topics: Albinism, Ocular; Animals; Eye Proteins; Humans; Melanosomes; Membrane Glycoproteins; Receptor, Melanocortin, Type 1; Signal Transduction; Skin Neoplasms
PubMed: 20381640
DOI: 10.1016/j.biocel.2010.03.023 -
Chemphyschem : a European Journal of... Apr 2010Bacterial photosynthetic membranes, also known as chromatophores, are tightly packed with integral membrane proteins that work together to carry out photosynthesis.... (Review)
Review
Bacterial photosynthetic membranes, also known as chromatophores, are tightly packed with integral membrane proteins that work together to carry out photosynthesis. Chromatophores display a wide range of cellular morphologies; spherical, tubular, and lamellar chromatophores have all been observed in different bacterial species, or with different protein constituents. Through recent computational modeling and simulation, it has been demonstrated that the light-harvesting complexes abundant in chromatophores induce local membrane curvature via multiple mechanisms. These protein complexes assemble to generate a global curvature and sculpt the chromatophores into various cellular-scale architectures.
Topics: Bacterial Proteins; Chromatophores; Light-Harvesting Protein Complexes; Membrane Proteins; Molecular Dynamics Simulation; Photosynthesis; Protein Structure, Tertiary
PubMed: 20183845
DOI: 10.1002/cphc.200900911 -
Neuro-Signals 2004Cephalopods have arguably the largest and most complex nervous systems amongst the invertebrates; but despite the squid giant axon being one of the best studied nerve... (Review)
Review
Cephalopods have arguably the largest and most complex nervous systems amongst the invertebrates; but despite the squid giant axon being one of the best studied nerve cells in neuroscience, and the availability of superb information on the morphology of some cephalopod brains, there is surprisingly little known about the operation of the neural networks that underlie the sophisticated range of behaviour these animals display. This review focuses on a few of the best studied neural networks: the giant fiber system, the chromatophore system, the statocyst system, the visual system and the learning and memory system, with a view to summarizing our current knowledge and stimulating new studies, particularly on the activities of identified central neurons, to provide a more complete understanding of networks within the cephalopod nervous system.
Topics: Animals; Behavior, Animal; Brain; Chromatophores; Learning; Mollusca; Nerve Net; Neural Networks, Computer; Neurons; Ocular Physiological Phenomena; Synapses
PubMed: 15004427
DOI: 10.1159/000076160 -
PeerJ 2023The threespine stickleback () is an important model for studying the evolution of nuptial coloration, but histological analyses of color are largely lacking. Previous...
The threespine stickleback () is an important model for studying the evolution of nuptial coloration, but histological analyses of color are largely lacking. Previous analyses of one nuptial coloration trait, orange-red coloration along the body, have indicated carotenoids are the main pigment producing this color. In addition, recent gene expression studies found variation in the correlates of throat coloration between the sexes and between populations, raising the possibility of variation in the mechanisms underlying superficially similar coloration. We used transmission electron microscopy (TEM) to investigate the histological correlates of color in the throat dermal tissue of threespine stickleback from Western North America, within and between sexes, populations, and ecotypes. Ultrastructural analysis revealed carotenoid-containing erythrophores to be the main chromatophore component associated with orange-red coloration in both males and females across populations. In individuals where some darkening of the throat tissue was present, with no obvious orange-red coloration, erythrophores were not detected. Melanophore presence was more population-specific in expression, including being the only chromatophore component detected in a population of darker fish. We found no dermal chromatophore units within colorless throat tissue. This work confirms the importance of carotenoids and the erythrophore in producing orange-red coloration across sexes, as well as melanin within the melanophore in producing darkened coloration, but does not reveal broad histological differences among populations with similar coloration.
Topics: Female; Male; Animals; Pharynx; Smegmamorpha; Chromatophores; Fishes; Carotenoids
PubMed: 38077425
DOI: 10.7717/peerj.16248 -
Pigment Cell & Melanoma Research Jul 2022The skin acts as a barrier to environmental insults and provides many vital functions. One of these is to shield DNA from harmful ultraviolet radiation, which is...
The skin acts as a barrier to environmental insults and provides many vital functions. One of these is to shield DNA from harmful ultraviolet radiation, which is achieved by skin pigmentation arising as melanin is produced and dispersed within the epidermal layer. This is a crucial defence against DNA damage, photo-ageing and skin cancer. The mechanisms and regulation of melanogenesis and melanin transfer involve extensive crosstalk between melanocytes and keratinocytes in the epidermis, as well as fibroblasts in the dermal layer. Although the predominant mechanism of melanin transfer continues to be debated and several plausible models have been proposed, we and others previously provided evidence for a coupled exo/phagocytosis model. Herein, we performed histology and immunohistochemistry analyses and demonstrated that a newly developed full-thickness three-dimensional reconstructed human pigmented skin model and an epidermis-only model exhibit dispersed pigment throughout keratinocytes in the epidermis. Transmission electron microscopy revealed melanocores between melanocytes and keratinocytes, suggesting that melanin is transferred through coupled exocytosis/phagocytosis of the melanosome core, or melanocore, similar to our previous observations in human skin biopsies. We, therefore, present evidence that our in vitro models of pigmented human skin show epidermal pigmentation comparable to human skin. These findings have a high value for studies of skin pigmentation mechanisms and pigmentary disorders, whilst reducing the reliance on animal models and human skin biopsies.
Topics: Animals; Epidermis; Humans; Keratinocytes; Melanins; Melanocytes; Melanosomes; Pigmentation; Skin; Skin Pigmentation; Ultraviolet Rays
PubMed: 35325505
DOI: 10.1111/pcmr.13039 -
Current Biology : CB Dec 2009Mitochondria can move along and interact with actin, yet the identity of the protein(s) mediating the interactions in metazoans is unknown. A new study reveals that a...
Mitochondria can move along and interact with actin, yet the identity of the protein(s) mediating the interactions in metazoans is unknown. A new study reveals that a novel unconventional myosin, Myo19, is a mitochondria-associated motor that may play a role in either the transport or tethering of this organelle.
Topics: Actins; Animals; Biological Transport; Cytoplasm; Gene Expression Regulation; Melanophores; Mitochondria; Molecular Motor Proteins; Myosins; Signal Transduction; Xenopus
PubMed: 20064407
DOI: 10.1016/j.cub.2009.10.053 -
Molecular Biology and Evolution Jan 2021Eukaryotic photosynthetic organelles, plastids, are the powerhouses of many aquatic and terrestrial ecosystems. The canonical plastid in algae and plants originated >1...
Eukaryotic photosynthetic organelles, plastids, are the powerhouses of many aquatic and terrestrial ecosystems. The canonical plastid in algae and plants originated >1 Ga and therefore offers limited insights into the initial stages of organelle evolution. To address this issue, we focus here on the photosynthetic amoeba Paulinella micropora strain KR01 (hereafter, KR01) that underwent a more recent (∼124 Ma) primary endosymbiosis, resulting in a photosynthetic organelle termed the chromatophore. Analysis of genomic and transcriptomic data resulted in a high-quality draft assembly of size 707 Mb and 32,361 predicted gene models. A total of 291 chromatophore-targeted proteins were predicted in silico, 208 of which comprise the ancestral organelle proteome in photosynthetic Paulinella species with functions, among others, in nucleotide metabolism and oxidative stress response. Gene coexpression analysis identified networks containing known high light stress response genes as well as a variety of genes of unknown function ("dark" genes). We characterized diurnally rhythmic genes in this species and found that over 49% are dark. It was recently hypothesized that large double-stranded DNA viruses may have driven gene transfer to the nucleus in Paulinella and facilitated endosymbiosis. Our analyses do not support this idea, but rather suggest that these viruses in the KR01 and closely related P. micropora MYN1 genomes resulted from a more recent invasion.
Topics: Amoeba; Chromatophores; Genome, Plastid; Genome, Protozoan; Symbiosis; Transcriptome
PubMed: 32790833
DOI: 10.1093/molbev/msaa206 -
Developmental Dynamics : An Official... Sep 2006Mouse coat color mutations have a long history in biomedical research. The viable and visible phenotype of most coat color mutations has made the pigment cell, the... (Review)
Review
Mouse coat color mutations have a long history in biomedical research. The viable and visible phenotype of most coat color mutations has made the pigment cell, the melanocyte, an ideal system for genetic, molecular, and cellular analysis. Molecular cloning and analysis of many of the different coat color mutations have revealed the roles of a diverse range of genes, and today we know more about the pathways and proteins that regulate the development and function of pigment cells than we know about most other cell types in mammalian organisms. Coat color mutations have also provided novel insights into stem cell biology and human diseases, including melanoma. In the future, it will be important to build on this history and knowledge by taking advantage of the extensive repertoire of recently developed genome-wide methodologies, available genomic information, and the powerful methods that have been developed for modifying the mouse genome to systematically dissect the development and function of this important cell type. The usefulness of coat color mutations has just begun to emerge.
Topics: Animals; Cell Differentiation; Genomics; Hair Color; Melanocytes; Melanosomes; Mice; Mutation; Pigments, Biological; Skin Pigmentation; Stem Cells
PubMed: 16691561
DOI: 10.1002/dvdy.20840