Pigmented spots in the wool-bearing skin on white merino sheep induced by ultraviolet light

Black-grey pigmented skin spots, some of which contained pigmented wool fibres, were observed in a flock of 8.5-year-old white Merino ewes. The spots were concentrated along the backline and increased in number following shearing, suggesting exposure to sunlight to be of importance in the development of these non-congenital pigmented skin spots in genetically white Merino sheep. To test the effect of ultraviolet light, white Merino sheep, ranging in age from 3 to 8 years, had a closely clipped midside area of wool-bearing skin irradiated on each of 28 consecutive days. Pigmented skin spots developed in 6 of the 16 white Merino sheep irradiated. Spots first appeared after 10 days of irradiation, the number subsequently increasing with time, and two skin spots were found to contain sparse numbers of black-grey pigmented wool fibres. Histological examination showed both the naturally occurring and irradiation-induced pigmented skin spots resulted from an increase in both number and activity of melanocytes localized along the epidermal-dermal border of the epidermis. With time, the melanocytes were observed to have entered, to varying depths, the outer-root sheath of follicles still producing white wool fibres. These ultraviolet-light-induced changes to epidermal melanocytes in white Merino sheep presumably occur due to alterations within the local tissue environment in which the melanocytes lie.     

Characterisation of white and black merino wools: a proteomics study

Wool is an important agricultural commodity with merino wool being rated alongside the finest quality fibres, which include the goat fibres Mohair and Cashmere. Although pigmented wool merinos have become extremely rare, the market for this wool is increasing. In Portugal, there are two merino breeds: white and black, descendants of animals originally bred on the Iberian Peninsula. These breeds have the potential to assist in our understanding of how protein expression relates to wool traits of importance to the textile industry. Herein, we study the characteristics and protein expression profiles of wool from ewes of the Portuguese black and white merino (n=15). Both breeds had very similar results for fibre diameter (25 µm) and curvature (105 to 111°/mm). Significant between-breed differences were found in the two types of keratin-associated proteins (KAPs): high-sulphur proteins (HSPs) and high-glycine–tyrosine proteins (HGTPs). The expression of HSPs, KAP2-3 and KAP2-4, decreased expression in the pigmented animals, whereas KAP13-1 was found in higher amounts. Likewise, the expression of the ultra-high-sulphur proteins, KAP4-3 and KAP4-7-like, was reduced in black sheep to half the levels of the white wools, whereas the HGTPs, KAP6, KAP6-1, KAP6-2 and KAP16-2, were more abundant in black sheep. These results suggest structural differences between the black and white merino wool, because of differences among some KAPs. These differences have important implications for the textile industry.     

The color of a Dalmatian's spots: Linkage evidence to support the TYRP1 gene

Background  

The distinctive coat pattern of a Dalmatian is the result of the interaction of several loci. While the encoded function of these genes is not fully understood, it is known the Piebald, Ticking, and Flecking loci interact to produce the Dalmatian's classic pigmented spots on a white background. The color of the pigmented spots in purebred Dalmatians can either be black or liver, but the locus responsible for color determination is unknown. Studies have been conducted to determine the underlying genes involved in coat color determination in the dog, e.g., in the Labrador Retriever, but none to date have addressed black versus liver in the Dalmatian.     

Identification of the e allele at the Extension locus (MC1R) in Brazilian Creole sheep and its role in wool color variation

The melanocortin 1 receptor (MC1R) gene has been described as responsible for the black color in some breeds of sheep, but little is known about its function in many colored breeds, particularly those with a wide range of pigmentation phenotypes. The Brazilian Creole is a local breed of sheep from southern Brazil that has a wide variety of wool colors. We examined the MC1R gene (Extension locus) to search for the e allele and determine its role in controlling wool color variation in this breed. One hundred and twenty-five animals, covering the most common Creole sheep phenotypes (black, brown, dark gray, light gray, and white), were sequenced to detect the mutations p.M73K and p.D121N. Besides these two mutations, three other synonymous sites (429, 600, and 725) were found. The dominant allele (E(D): p.73K, and p.121N) was found only in colored animals, whereas the recessive allele (E(+): p.73M, and p.121D) was homozygous only in white individuals. We concluded that MC1R is involved in the control of wool color in Brazilian Creole sheep, particularly the dark phenotypes, although a second gene may be involved in the expression of the white phenotype in this breed.     

Skin Transcriptome Profiles Associated with Skin Color in Chickens

Nutritional and medicinal benefits have been attributed to the consumption of tissues from the black-boned chickens in oriental countries. Lueyang black-boned chicken is one of the native chicken breeds. However, some birds may instead have white or lighter skin, which directly causes economic losses every year. Previous studies of pigmentation have focused on a number of genes that may play important roles in coat color regulation. Illumina2000 sequencing technology was used to catalog the global gene expression profiles in the skin of the Lueyang chicken with white versus black skin. A total of 18,608 unigenes were assembled from the reads obtained from the skin of the white and black chickens. A total of 649 known genes were differentially expressed in the black versus white chickens, with 314 genes that were up regulated and 335 genes that were down-regulated, and a total of 162 novel genes were differentially expressed in the black versus white chickens, consisting of 73 genes that were up-regulated (including 4 highly expressed genes that were expressed exclusively in the skin of the black chickens) and 89 genes that were down-regulated. There were also a total of 8 known coat-color genes expressed in previous studies (ASIP, TYR, KIT, TYRP1, OCA2, KITLG, MITF and MC1R). In this study, 4 of which showed greater expression in the black chickens, and several were up-regulated, such as KIT, ASIP, TYR and OCA2. To our surprise, KITLG, MITF and MC1R showed no significant difference in expression between the black- and white-skinned chickens, and the expression of TYRP1 was not detected in either skin color. The expression of ASIP, TYR, KIT, TYRP1, OCA2, KITLG, MITF and MC1R was validated by real-time quantitative polymerase chain reaction (qPCR), and the results of the qPCR were consistent with the RNA-seq. This study provides several candidate genes that may be associated with the development of black versus white skin. More importantly, the fact that the MC1R gene showed no significant difference in expression between the black and white chickens is of particular interest for future studies that aim to elucidate its functional role in the regulation of skin color.     

Redundancy analysis,genome-wide association studies and the pigmentation of brown trout (Salmo trutta L.)

The association of molecular variants with phenotypic variation is a main issue in biology, often tackled with genome-wide association studies (GWAS). GWAS are challenging, with increasing, but still limited, use in evolutionary biology. We used redundancy analysis (RDA) as a complimentary ordination approach to single- and multitrait GWAS to explore the molecular basis of pigmentation variation in brown trout (Salmo trutta) belonging to wild populations impacted by hatchery fish. Based on 75,684 single nucleotide polymorphic (SNP) markers, RDA, single- and multitrait GWAS allowed the extraction of 337 independent colour patterning loci (CPLs) associated with trout pigmentation traits, such as the number of red and black spots on flanks. Collectively, these CPLs (i) mapped onto 35 out of 40 brown trout linkage groups indicating a polygenic genomic architecture of pigmentation, (ii) were found to be associated with 218 candidate genes, including 197 genes formerly mentioned in the literature associated to skin pigmentation, skin patterning, differentiation or structure notably in a close relative, the rainbow trout (Onchorhynchus mykiss), and (iii) related to functions relevant to pigmentation variation (e.g., calcium- and ion-binding, cell adhesion). Annotated CPLs include genes with well-known pigmentation effects (e.g., PMEL, SLC45A2, SOX10), but also markers associated with genes formerly found expressed in rainbow or brown trout skins. RDA was also shown to be useful to investigate management issues, especially the dynamics of trout pigmentation submitted to several generations of hatchery introgression.     

QTL and association analysis for skin and fibre pigmentation in sheep provides evidence of a major causative mutation and epistatic effects

The pursuits of white features and white fleeces free of pigmented fibre have been important selection objectives for many sheep breeds. The cause and inheritance of non‐white colour patterns in sheep has been studied since the early 19th century. Discovery of genetic causes, especially those which predispose pigmentation in white sheep, may lead to more accurate selection tools for improved apparel wool. This article describes an extended QTL study for 13 skin and fibre pigmentation traits in sheep. A total of 19 highly significant, 10 significant and seven suggestive QTL were identified in a QTL mapping experiment using an Awassi × Merino × Merino backcross sheep population. All QTL on chromosome 2 exceeded a LOD score of greater than 4 (range 4.4–30.1), giving very strong support for a major gene for pigmentation on this chromosome. Evidence of epistatic interactions was found for QTL for four traits on chromosomes 2 and 19. The ovine TYRP1 gene on OAR 2 was sequenced as a strong positional candidate gene. A highly significant association (P < 0.01) of grandparental haplotypes across nine segregating SNP/microsatellite markers including one non‐synonymous SNP with pigmentation traits could be shown. Up to 47% of the observed variation in pigmentation was accounted for by models using TYRP1 haplotypes and 83% for models with interactions between two QTL probabilities, offering scope for marker‐assisted selection for these traits.     

Physiological condition and wing pigmentation expression in a damselfly with seasonal polyphenism

Secondary sexual traits can be indicators of individual condition that may present seasonal polyphenism as a result of the differential costs of expression along the season. Wing spots in male damselflies of the Calopterygidae family are secondary sexual traits associated with intrasexual competition and mate choice. Hetaerina titia Drury is a calopterygid damselfly where males show red and black wing spots, contrasting with other species of the genus whose males only express a red wing spot. In the present study, we evaluate the seasonal variation of the expression of male's red and black wing spots and their allometric patterns. Additionally, we measure male condition in the form of proteins, lipids, soluble carbohydrates and glycogen in early and late seasons. Black wing spots present higher variation than red wing spots and males of the late season are more pigmented. Allometry is positive for wing red spot in the early season and for black spot in the late season. Males of the late season present a higher concentration of proteins, soluble carbohydrates and glycogen, although there is no variation in the lipid content. The results of the present study suggest that, in H. titia males, black pigmentation replaces the function of the red pigmentation to signal condition. Both traits, however, may be heavily affected by environmental situations (e.g. food availability).     

Mutations in ASIP and MC1R: dominant black and recessive black alleles segregate in native Swedish sheep populations

By studying genes associated with coat colour, we can understand the role of these genes in pigmentation but also gain insight into selection history. North European short‐tailed sheep, including Swedish breeds, have variation in their coat colour, making them good models to expand current knowledge of mutations associated with coat colour in sheep. We studied ASIP and MC1R, two genes with known roles in pigmentation, and their association with black coat colour. We did this by sequencing the coding regions of ASIP in 149 animals and MC1R in 129 animals from seven native Swedish sheep breeds in individuals with black, white or grey fleece. Previously known mutations in ASIP [recessive black allele: g.100_105del (D₅) and/or g.5172T>A] were associated with black coat colour in Klövsjö and Roslag sheep breeds and mutations in both ASIP and MC1R (dominant black allele: c.218T>A and/or c.361G>A) were associated with black coat colour in Swedish Finewool. In Gotland, Gute, Värmland and Helsinge sheep breeds, coat colour inheritance was more complex: only 11 of 16 individuals with black fleece had genotypes that could explain their black colour. These breeds have grey individuals in their populations, and grey is believed to be a result of mutations and allelic copy number variation within the ASIP duplication, which could be a possible explanation for the lack of a clear inheritance pattern in these breeds. Finally, we found a novel missense mutation in MC1R (c.452G>A) in Gotland, Gute and Värmland sheep and evidence of a duplication of MC1R in Gotland sheep.     

A golden clue to human skin colour variation

Variations in human skin pigmentation are obvious, but how have skin colour differences evolved? Although clearly a polymorphic trait, the number and identity of key variants has remained unclear. Investigation of pigmentation phenotypes in model organisms provides a route to identify these genes and showed MC1R to be one key locus. Now, cloning of a classic zebrafish mutant, golden, identifies slc24a5 as a gene involved in fish skin pigmentation. 1 Strikingly this study identifies the human orthologue, SLC24A5, as likely to make a major contribution to the pale skin colouration of Western Europeans. BioEssays 28: 578–582, 2006. © 2006 Wiley Periodicals, Inc.     

Color reversion of the albino medaka fish associated with spontaneous somatic excision of the Tol‐1 transposable element from the tyrosinase gene

The medaka fish albino mutant, i¹ is one of the Tomita collection of medaka pigmentation mutants which exhibits a complete albino phenotype, because of inactivation of the tyrosinase gene due to insertion of a transposable element, Tol‐1. Recently, mosaic black‐pigmented i¹ medaka fish have arisen in one of our laboratory breeding populations. Their pigmented cells have been observed in all of the tissues, including the eye and skin, in which melanin is detectable in the wild type. In this study, we analyzed the tyrosinase gene of revertants and showed Tol‐1 to have been precisely excised from the gene, suggesting a causal relationship. Mosaic patterns of pigmentation indicate spontaneous somatic excision of the element from the tyrosinase gene. To our knowledge, this is the first transposable element with somatic excision activity demonstrated phenotypically in vertebrates. The pattern of pigmentation in mosaic revertants indicates frequencies of melanin pigments to be consistent with the numbers of melanophores per unit area of body sites, such as the eyes, head and dorsal trunk.     

Genomic regions influencing coat color saturation and facial markings in Fleckvieh cattle

Genomic regions associated with coat color and pigmented areas of the head were identified for Fleckvieh (dual‐purpose Simmental), a red‐spotted and white‐headed cattle breed. Coat color was measured with a chromameter, implementing the CIELAB color space and resulting in numerical representation of lightness, color intensity, red/green and blue/yellow color components, rather than subjective classification. Single marker regression analyses with fixed effects of the sex and barn were applied, and significant regions were determined with the local false discovery rate methodology. The PMEL and ERBB3 genes on chromosome 5 were in the most significant region for the color measurements. In addition to the blue/yellow color component and color intensity, the AP3B2 gene on chromosome 21 was identified. Its function was confirmed for similar traits in a range of model species. The KIT gene on chromosome 6 was found to be strongly associated with the inhibition of circum‐ocular pigmentation and pigmented spots on the cheek.     

A genomics-informed,SNP association study reveals FBLN1 and FABP4 as contributing to resistance to fleece rot in Australian Merino sheep

Background  

Fleece rot (FR) and body-strike of Merino sheep by the sheep blowfly Lucilia cuprina are major problems for the Australian wool industry, causing significant losses as a result of increased management costs coupled with reduced wool productivity and quality. In addition to direct effects on fleece quality, fleece rot is a major predisposing factor to blowfly strike on the body of sheep. In order to investigate the genetic drivers of resistance to fleece rot, we constructed a combined ovine-bovine cDNA microarray of almost 12,000 probes including 6,125 skin expressed sequence tags and 5,760 anonymous clones obtained from skin subtracted libraries derived from fleece rot resistant and susceptible animals. This microarray platform was used to profile the gene expression changes between skin samples of six resistant and six susceptible animals taken immediately before, during and after FR induction. Mixed-model equations were employed to normalize the data and 155 genes were found to be differentially expressed (DE). Ten DE genes were selected for validation using real-time PCR on independent skin samples. The genomic regions of a further 5 DE genes were surveyed to identify single nucleotide polymorphisms (SNP) that were genotyped across three populations for their associations with fleece rot resistance.     

Granulocyte‐Macrophage Colony‐Stimulating Factor (GM‐CSF) Controls the Proliferation and Differentiation of Mouse Epidermal Melanocytes from Pigmented Spots Induced by Ultraviolet Radiation B

Repeated exposure of ultraviolet radiation B (UVB) on the dorsal skin of hairless mice induces the development of pigmented spots long after its cessation. The proliferation and differentiation of epidermal melanocytes in UVB‐induced pigmented spots are greatly increased, and those effects are regulated by keratinocytes rather than by melanocytes. However, it remains to be resolved what factor(s) derived from keratinocytes are involved in regulating the proliferation and differentiation of epidermal melanocytes. In this study, primary melanoblasts (c. 80%) and melanocytes (c. 20%) derived from epidermal cell suspensions of mouse skin were cultured in a basic fibroblast growth factor‐free medium supplemented with granulocyte‐macrophage colony‐stimulating factor (GM‐CSF). GM‐CSF induced the proliferation and differentiation of melanocytes in those keratinocyte‐depleted cultures. Moreover, an antibody to GM‐CSF inhibited the proliferation of melanoblasts and melanocytes from epidermal cell suspensions derived from the pigmented spots of UV‐irradiated mice, but not from control mice. Further, the GM‐CSF antibody inhibited the proliferation and differentiation of melanocytes co‐cultured with keratinocytes derived from UV‐irradiated mice, but not from control mice. The quantity of GM‐CSF secreted from keratinocytes derived from the pigmented spots of UV‐irradiated mice was much greater than that secreted from keratinocytes derived from control mice. Moreover, immunohistochemistry revealed the expression of GM‐CSF in keratinocytes derived from the pigmented spots of skin in UV‐irradiated mice, but not from normal skin in control mice. These results suggest that GM‐CSF is one of the keratinocyte‐derived factors involved in regulating the proliferation and differentiation of mouse epidermal melanocytes from UVB‐induced pigmented spots.     

GPR143在绵羊皮肤组织中的表达及定位分析

G蛋白偶联受体143(G-protein coupled receptor143, GPR143)在黑素体的生物合成中起重要作用,本文旨在研究GPR143基因在不同毛色绵羊皮肤组织中的差异表达及定位,探索GPR143基因与毛色形成的相关性。通过qRT-PCR方法和免疫印迹方法分别检测不同毛色绵羊皮肤组织中GPR143基因mRNA水平和蛋白水平的表达差异;运用免疫荧光法对不同毛色绵羊皮肤组织中的GPR143基因进行定位并对结果进行光密度值分析。qRT-PCR结果显示,GPR143基因在黑色绵羊皮肤组织中mRNA相对表达量为白色绵羊的7.84倍,二者差异极显著(P<0.01);免疫印迹结果显示,黑色绵羊皮肤组织中GPR143蛋白表达量是白色绵羊的1.3倍,二者差异显著(P<0.05)。免疫荧光结果显示,GPR143蛋白的主要表达部位为绵羊皮肤组织毛囊外根鞘和表皮层,经光密度值分析后发现,GPR143在黑色绵羊皮肤毛囊外根鞘和表皮层的表达量显著高于白色绵羊。本研究结果表明不同毛色绵羊皮肤组织均能表达GPR143基因,但黑色绵羊皮肤组织中该基因的mRNA和蛋白水平都显著高于白色绵羊,说明GPR143的mRNA和蛋白在黑色绵羊皮肤组织中表达上调,在白色绵羊皮肤组织中表达下调。GPR143基因可能通过调控MITF水平和黑素体的数量、大小、运动和成熟进而参与绵羊毛色的形成过程。