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18 results for “pheomelanin”
Eumelanin and pheomelanin pigmentation in mollusc shells may be less common than expected: insights from mass spectrometry
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Differential influence of Slc7a11 expression and body condition on pheomelanin‐based pigmentation in two Eurasian nuthatch Sitta europaea populations with different predation risk
<p><span><span><span><span><span><span><span><span><span><span><span>The expression of the gene <i>Slc7a11</i>promotes the antioxidant capacity of cells by providing them with cysteine that can be used for the synthesis of glutathione (GSH), the most important intracellular antioxidant. In melanocytes, intracellular cysteine can also enter melanosomes and get incorporated in the pigment pheomelanin synthesis pathway, thus decreasing cysteine availability for GSH synthesis and potentially creating chronic oxidative stress. We thus hypothesized that a mechanism limiting the use of intramelanocytic cysteine for pheomelanin synthesis in environmental conditions generating oxidative stress may be physiologically advantageous and favored by natural selection. Here we searched for evidence of such a mechanism by comparing the influence of melanocytic <i>Slc7a11</i>expression on pheomelanin-based pigmentation in developing Eurasian nuthatch <i>Sitta europaea</i>nestlings from two populations differing in predation risk, a natural source of oxidative stress. Pheomelanin synthesis and pigmentation tended to increase with <i>Slc7a11</i>expression in the low-risk population as expected from the activity of this gene, but decreased with <i>Slc7a11</i>expression in the high-risk population. The same was not observed in the expression of five other genes influencing pheomelanin synthesis without affecting cysteine availability in melanocytes. The influence of body condition on the intensity of pheomelanin-based pigmentation also differed between populations, being positive in the low-risk population and negative in the high-risk population. The resulting pigmentation of birds was more intense in the high-risk population. These findings suggest that birds perceiving high predation risk may limit the use of cysteine for pheomelanin synthesis, which becomes independent of <i>Slc7a11</i>expression. Some birds may have thus evolved the ability to adjust their pigmentation phenotype to environmental stress.</span></span></span></span></span></span></span></span></span></span></span></p>
Figure 3 in The shell-eyes of the chiton Acanthopleura granulata (Mollusca, Polyplacophora) use pheomelanin as a screening pigment
Figure 3. High-performance liquid chromatography (HPLC) elution profile of the degradation products of the pigment that we extracted from the valves of the chiton Acanthopleura granulata (where absorption was set at 280 nm). The solid line represents the digestion product of the extracted pigment. For reference, the dashed line represents the same digestion reaction minus the pigment. The inset shows an elution profile for the degradation products of synthetic pheomelanin (DOPA-cysteine melanin) from Panzella et al. (2007), a paper whose methods we replicated. We hypothesize that the distinct peak that we see at 30 min in our elution profile represents BTCA, a diagnostic degradation product of pheomelanin.
Figure 2 in The shell-eyes of the chiton Acanthopleura granulata (Mollusca, Polyplacophora) use pheomelanin as a screening pigment
Figure 2. Absorption spectra of the pigment that we extracted from the valves of the chiton Acanthopleura granulata. The black line represents freshly extracted pigment. The grey line represents the same sample of pigment after it had been digested in alkaline hydrogen peroxide for 14 h. Note that digestion by hydrogen peroxide causes: (1) the absorption peak in the visible wavelengths to drop and shift towards shorter wavelengths; and (2) the appearance of degradation products that absorb strongly in the UV wavelengths. Both of these observations are consistent with the degradation of pheomelanin by hydrogen peroxide.
Figure 1 in The shell-eyes of the chiton Acanthopleura granulata (Mollusca, Polyplacophora) use pheomelanin as a screening pigment
Figure 1. The results of using sodium hydroxide to extract pigment from the decalcified shell plates of the eyed chiton Acanthopleura granulata. (A) An image taken before bleaching, where the dark spots are the rings of screening pigment associated with the shell-eyes (the arrow points to a single eye). The same red-brown pigment is expressed around the shell-eyes and, more broadly, in the proteinaceous extra-cellular matrix that surrounds the eyes and aesthetes. (B) The same valve after 48 h in 1 M sodium hydroxide at room temperature. The scale bar represents 1 mm.
DOPA pheomelanin is increased in nigral neuromelanin of Parkinson's disease
<p>Raw data sets for the manuscript "<strong>DOPA pheomelanin is increased in nigral neuromelanin of Parkinson’s disease"</strong></p>
Five genetic variants explain over 70% of hair coat pheomelanin intensity variation in purebred and mixed breed domestic dogs - Supporting information
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Differential influence of Slc7a11 expression and body condition on pheomelanin‐based pigmentation in two Eurasian nuthatch Sitta europaea populations with different predation risk
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Data from: Brain size and the expression of pheomelanin-based colour in birds
Eumelanin and pheomelanin are the most common vertebrate pigments. They generate different colours and are synthesized under different physiological conditions. While pheomelanogenesis requires high levels of a key intracellular antioxidant (glutathione, GSH), eumelanogenesis is inhibited by GSH. This implies that species that present the molecular basis to produce large amounts of pheomelanin might be more limited to perform other costly processes that generate oxidative stress than species that produce eumelanin. Brain development requires large amounts of energy and antioxidants during ontogeny, so that large-brained species may be constrained in their simultaneous synthesis of large amounts of pheomelanin, but not in their synthesis of eumelanin. Here we tested this hypothesis in a large dataset of 323 bird species. After controlling for the effects of phylogeny, latitude and sexual dichromatism, the proportion of pheomelanic plumage colour was strongly negatively related to the relative brain mass of species, while no relationship was found for the proportion of eumelanic colour. This indicates that the production of pheomelanin is a costly process that cannot evolve together with complex neural structures and thus with large cognitive capacity. This is the first time that the expression of melanic traits is found to correlate with another phenotypic character across species.
Data from: Changes in melanocyte RNA and DNA methylation favor pheomelanin synthesis and may avoid systemic oxidative stress after dietary cysteine supplementation in birds
Cysteine plays essential biological roles, but excessive amounts produce cellular oxidative stress. Cysteine metabolism is mainly mediated by the enzymes cysteine dioxygenase and γ-glutamylcysteine synthetase, respectively coded by the genes CDO1 and GCLC. Here we test a new hypothesis posing that the synthesis of the pigment pheomelanin also contributes to cysteine homeostasis in melanocytes, where cysteine can enter the pheomelanogenesis pathway. We conducted a experiment in the Eurasian nuthatch Sitta europaea, a bird producing large amounts of pheomelanin for feather pigmentation, to investigate if melanocytes show epigenetic lability under exposure to excess cysteine. We increased systemic cysteine levels in nuthatches by supplementing them with dietary cysteine during growth. This caused in feather melanocytes the downregulation of genes involved in intracellular cysteine metabolism (GCLC), cysteine transport to the cytosol from the extracellular medium (Slc7a11) and from melanosomes (CTNS), and regulation of tyrosinase activity (MC1R and ASIP). These changes were mediated by increases in DNA m5C in all genes excepting Slc7a11, which experienced RNA m6A depletion. Birds supplemented with cysteine synthesized more pheomelanin than controls, but did not suffer higher systemic oxidative stress. These results suggest that excess cysteine activates an epigenetic mechanism that favors pheomelanin synthesis and may protect from oxidative stress.
Data from: Exposure to a competitive social environment activates an epigenetic mechanism that limits pheomelanin synthesis in zebra finches
Competitive environments promote high testosterone levels, oxidative stress and, consequently, impair cellular homeostasis. The regulation of genes involved in the synthesis of the pigment pheomelanin in melanocytes seems to help to maintain homeostasis against environmental oxidative stress. Here, we experimentally increased social interactions in some zebra finch Taeniopygia guttata males by keeping them in groups of six birds during feather growth, while others were kept alone, to test if melanocytes show epigenetic lability under a competitive social environment. As these changes may depend on the oxidative status, we administrated buthionine sulfoximine (BSO) to decrease the antioxidant capacity of some birds. The competitive environment downregulated a gene involved in pheomelanin synthesis (Slc7a11) by changing the level of DNA methylation in feather melanocytes. In other genes involved in pheomelanin synthesis (Slc45a2, MC1R and AGRP), DNA methylation was also affected, but no changes in expression were detected. The exposure to the competitive environment did not affect systemic oxidative stress and damage, indicating that a protective epigenetic mechanism that changes the expression of Slc7a11 may have been activated. However, no changes on the pigmentation phenotype of birds were found, likely due to the short duration or low intensity of the competitive environment. BSO treatment did not affect the epigenetic mechanism, suggesting that the antioxidant capacity of birds was high enough to deal with the competitive environment. An epigenetic mechanism limiting pheomelanin synthesis gets therefore activated under exposure to a competitive environment in male zebra finches, which may help avoiding damage caused by competitive interactions.
Data from: Exposure to a competitive social environment activates an epigenetic mechanism that limits pheomelanin synthesis in zebra finches
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Data from: Low-quality birds do not display high-quality signals: the cysteine-pheomelanin mechanism of honesty
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Data from: Brain size and the expression of pheomelanin-based colour in birds
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Data from: Changes in melanocyte RNA and DNA methylation favor pheomelanin synthesis and may avoid systemic oxidative stress after dietary cysteine supplementation in birds
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Data from: Females mate with males with diminished pheomelanin-based coloration in the Eurasian nuthatch Sitta europaea
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Transcriptome analysis of feather follicles reveals candidate genes and pathways associated with pheomelanin pigmentation in chickens
GEO Series GSE146956. Gallus gallus. 12 samples. Type: Expression profiling by high throughput sequencing.
SOX10 regulates multiple genes to direct eumelanin vs. pheomelanin production in domestic rock pigeon
GEO Series GSE175557. Columba livia. 19 samples. Type: Expression profiling by high throughput sequencing.
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