MC1R Mutations Research Articles

Agouti-Signaling Protein and Melanocortin-1-Receptor Mutations Associated with Coat Color Phenotypes in Fallow Deer (Dama dama).

Four dominant coat color phenotypes are found in fallow deer (Dama dama). Brown is the most common. Black, menil, and white occur with varying frequencies. In order to gain insights into the molecular genetic background of these phenotypes, 998 fallow animals (772 brown, 62 black, 126 menil, and 38 white) were examined for mutations in the ASIP, MC1R, TYR, and SLC45A2 genes. In ASIP, two mutations (ASIP-M-E2, located at the boundary from exon 2 to intron 2; and ASIP-M-E3, an InDel of five nucleotides) were found, leading to black fallow deer being either homozygous or heterozygous in combination. There were also two mutations found in MC1R. Whereby the mutation MC1R-M1 (leucine to proline, L48P) homozygous leads to a white coat, while the mutation MC1R-M2 (glycine to aspartic acid, G236D) homozygous is associated with the menil phenotype. When both mutations occur together in a heterozygous character state, it results in a menil coat. Since the mutations in the two genes are only present alternatively, 36 genotypes can be identified that form color clusters to which all animals can be assigned. No mutations were found in the TYR and SLC45A2 genes. Our investigations demonstrate that the four dominant coat colors in fallow deer can be explained by ASIP and MC1R mutations only.

Molecular Basis of MC1R Activation: Mutation-Induced Alterations in Structural Dynamics.

The MC1R protein is a receptor found in melanocytes that plays a role in melanin synthesis. Mutations in this protein can impact hair color, skin tone, tanning ability, and increase the risk of skin cancer. The MC1R protein is activated by the alpha-melanocyte-stimulating hormone (α-MSH). Previous studies have shown that mutations affect the interaction between MC1R and α-MSH; however, the mechanism behind this process is poorly understood. Our study aims to shed light on this mechanism using molecular dynamics (MD) simulations to analyze the Asp84Glu and Asp294His variants. We simulated both the wild-type (WT) protein and the mutants with and without ligand. Our results reveal that mutations induce unique conformations during state transitions, hindering the switch between active and inactive states and decreasing cellular levels of cAMP. Interestingly, Asp294His showed increased ligand affinity but decreased protein activity, highlighting that tighter binding does not always lead to increased activation. Our study provides insights into the molecular mechanisms underlying the impact of MC1R mutations on protein activity.

Phenotypic and Genetic Features that Differ Between Hereditary and Sporadic Melanoma: Results of a Preliminary Study from a Single Center from Turkey.

Most melanoma patients under our supervision lack characteristic phenotypic features for melanoma. In contrast, history of cancers other than melanoma and early age at onset were common. This observation was in favor of hereditary melanoma. To search for the phenotypic and genetic features that differ between sporadic and hereditary melanomas. In order to reveal phenotypic features, detailed physical exam was conducted to all melanoma patients (N = 43) and for genetic features. CDKN2A and MC1R mutations were detected with Sanger sequencing method. Assignment to hereditary and sporadic groups was done according to the "melanoma cancer syndrome assessment tool". Patients who were diagnosed before the age of 50 were also assigned to the hereditary melanoma group. Thirty-one patients were assigned to the hereditary group and 12 to the sporadic group. Fair eye color was statistically significantly higher in the sporadic group (P = 0.000). CDKN2A was detected in only 1 patient in the hereditary group. MC1R mutations were found in 12 out of 13 (92.3%) in the hereditary group with a score =3 points, 13 out of 18 (72.2%) in the early age at onset group and 5 out of 12 (41.7%) in the sporadic group (P = 0.024). Incidence of CDKN2A mutations in our hereditary group is in accordance with the reported incidences from Mediterranean countries. The difference between the hereditary and sporadic groups in terms of MC1R mutations supports the idea that MC1R genetic testing might help to determine patients with higher risk for hereditary melanoma.

Indications for Digital Monitoring of Patients With Multiple Nevi: Recommendations from the International Dermoscopy Society.

In patients with multiple nevi, sequential imaging using total body skin photography (TBSP) coupled with digital dermoscopy (DD) documentation reduces unnecessary excisions and improves the early detection of melanoma. Correct patient selection is essential for optimizing the efficacy of this diagnostic approach. The purpose of the study was to identify, via expert consensus, the best indications for TBSP and DD follow-up. This study was performed on behalf of the International Dermoscopy Society (IDS). We attained consensus by using an e-Delphi methodology. The panel of participants included international experts in dermoscopy. In each Delphi round, experts were asked to select from a list of indications for TBSP and DD. Expert consensus was attained after 3 rounds of Delphi. Participants considered a total nevus count of 60 or more nevi or the presence of a CDKN2A mutation sufficient to refer the patient for digital monitoring. Patients with more than 40 nevi were only considered an indication in case of personal history of melanoma or red hair and/or a MC1R mutation or history of organ transplantation. Our recommendations support clinicians in choosing appropriate follow-up regimens for patients with multiple nevi and in applying the time-consuming procedure of sequential imaging more efficiently. Further studies and real-life data are needed to confirm the usefulness of this list of indications in clinical practice.

The feather pattern autosomal barring in chicken is strongly associated with segregation at the MC1R locus.

Color patterns within individual feathers are common in birds but little is known about the genetic mechanisms causing such patterns. Here, we investigate the genetic basis for autosomal barring in chicken, a horizontal striping pattern on individual feathers. Using an informative backcross, we demonstrate that the MC1R locus is strongly associated with this phenotype. A deletion at SOX10, underlying the dark brown phenotype on its own, affects the manifestation of the barring pattern. The coding variant L133Q in MC1R is the most likely causal mutation for autosomal barring in this pedigree. Furthermore, a genetic screen across six different breeds showing different patterning phenotypes revealed that the most striking shared characteristics among these breeds were that they all carried the MC1R alleles Birchen or brown. Our data suggest that the presence of activating MC1R mutations enhancing pigment synthesis is an important mechanism underlying pigmentation patterns on individual feathers in chicken. We propose that MC1R and its antagonist ASIP play a critical role for determining within-feather pigmentation patterns in birds by acting as activator and inhibitor possibly in a Turing reaction-diffusion model.

Genome-wide association analyses for coat colour patterns in the autochthonous Nero Siciliano pig breed

Nero Siciliano (or Sicilian Black) is an Italian autochthonous pig breed reared in the Sicily island, mainly under extensive management systems. Nero Siciliano pigs are black (with black skin and black hair), but animals with white face or partially white face ("suino facciolo") can be registered to the breed herd book. Sometimes, other white patterns on extreme portions of legs could appear in this population. This study took advantage from the rare occurrence of pigs with white patterns in the Nero Siciliano population to carry out a genome-wide association study and comparative genome-wide Fixation index (FST) analysis to identify genomic regions that could affect coat colour variability (solid black vs white patterns over black) in this autochthonous pig breed. Analyses have been conducted on 66 Nero Siciliano pigs: 30 completely black and 36 black with white patterns. All samples have been genotyped for the KIT gene duplication and MC1R mutations, two genes well known to affect coat colours in pigs. Only pigs that did not carry any duplication of the KIT gene and were homozygous for the ED2 black dominant MC1R gene allele (n = 26 completely black and n. 22 with white patterns) were genotyped with the Illumina PorcineSNP60 BeadChip. The genome-wide analyzes identified on chromosome 2 a significant marker (rs81329493) associated with the coat colour white patterns in this breed. The homologous chromosome region in felids contains the gene responsible for the blotched tabby and striped coat colour patterns. Further studies, including a larger number of pigs, are needed to confirm this result and identify the causative mutation(s) affecting this coat colour diversity, which might be used to design a conservation programme in this breed aiming to maintain phenotypic homogeneity (i.e. solid black) that is typically associated with Nero Siciliano pigs. This study demonstrated how genetic diversity segregating in an autochthonous genetic resource can be explored to understand the genetic mechanisms affecting phenotypic traits in a livestock species.

Skin transcriptome profiles associated with black- and white-coated regions in Boer and Macheng black crossbred goats

To increase the current understanding of the gene-expression profiles in different skin regions associated with different coat colors and identify key genes for the regulation of color patterns in goats, we used the Illumina RNA-Seq method to compare the skin transcriptomes of the black- and white-coated regions containing hair follicles from the Boer and Macheng Black crossbred goat, which has a black head and a white body. Six cDNA libraries derived from skin samples of the white-coated region (n = 3) and black-coated region (n = 3) were constructed from three full-sib goats. On average, we obtained approximately 76.5 and 73.5 million reads for skin samples from black- and white-coated regions, respectively, of which 75.39% and 76.05% were covered in the genome database. A total of 165 differentially expressed genes (DEGs) were detected between these two color regions, among which 110 were upregulated and 55 were downregulated in the skin samples of white- vs. black-coated regions. The results of Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses revealed that some of these DEGs may play an important role in controlling the pigmentation of skin or hair follicles. We identified three key DEGs, i.e., Agouti, DCT, and TYRP1, in the pathway related to melanogenesis in the different skin regions of the crossbred goat. DCT and TYRP1 were downregulated and Agouti was upregulated in the skin of the white-coated region, suggesting a lack of mature melanocytes in this region and that Agouti might play a key developmental role in color-pattern formation. All data sets (Gene Expression Omnibus) are available via public repositories. In addition, MC1R was genotyped in 200 crossbred goats with a black head and neck. Loss-of-function mutations in MC1R as well as homozygosity for the mutant alleles were widely found in this population. The MC1R gene did not seem to play a major role in determining the black head and neck in our crossbred goats. Our study provides insights into the transcriptional regulation of two distinct coat colors, which might serve as a key resource for understanding coat color pigmentation in goats. The region-specific expression of Agouti may be associated with the distribution of pigments across the body in Boer and Macheng Black crossbred goats.

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.

Differential expression of MC1R gene in Liaoning Cashmere goats with different coat colors

Melanocyte stimulating hormone receptor (MC1R) has been known as a regulator of eumelanin and phaeomelanin production in the melanocytes, and MC1R mutations causing coat color changes are known in many vertebrates; however, there are no research reports about the differentially expression of MC1R gene and its coding protein in Cashmere goats with different coat color. We examined the presence of MC1R distribution and MC1R protein and gene expression in the white Cashmere goats and black Cashmere goats, respectively; q-PCR, Western blot and immunhistochemical analysis showed that the expression of the MC1R gene in the black Cashmere goats was 3.39 fold more than the white ones (p < 0.01), and Cashmere goats with black genotype had significantly higher (2.03, p < 0.01) MC1R protein expression than white genotype in the all investigated samples. Moreover, all Cashmere goats with different coat color available for immunhistochemical analysis showed either lower (white Cashmere goats) or higher (black Cashmere goats) expression of the MC1R protein; these findings suggested that it had a relationship between the MC1R and the coat color of Cashmere goats. That could lay the foundation for the further research of the MC1R and coat color controllability regulation of the Cashmere goats.

211 Co-Inheritance of mutations in CDKN2A and MC1R increases melanoma predisposition independently of deregulation of cell cycle and UV response in melanocytes

211 Co-Inheritance of mutations in CDKN2A and MC1R increases melanoma predisposition independently of deregulation of cell cycle and UV response in melanocytes

Genomic evidence for convergent evolution of a key trait underlying divergence in island birds.

Reproductive isolation can be initiated by changes in one or a few key traits that prevent random mating among individuals in a population. During the early stages of speciation, when isolation is often incomplete, there will be a heterogeneous pattern of differentiation across regions of the genome between diverging populations, with loci controlling these key traits appearing the most distinct as a result of strong diversifying selection. In this study, we used Illumina-sequenced ddRAD tags to identify genomewide patterns of differentiation in three recently diverged island populations of the Monarcha castaneiventris flycatcher of the Solomon Islands. Populations of this species have diverged in plumage colour, and these differences in plumage colour, in turn, are used in conspecific recognition and likely important in reproductive isolation. Previous candidate gene sequencing identified point mutations in MC1R and ASIP, both known pigmentation genes, to be associated with the difference in plumage colour between islands. Here, we show that background levels of genomic differentiation based on over 70,000 SNPs are extremely low between populations of distinct plumage colour, with no loci reaching the level of differentiation found in either candidate gene. Further, we found that a phylogenetic analysis based on these SNPs produced a taxonomy wherein the two melanic populations appear to have evolved convergently, rather than from a single common ancestor, in contrast to their original classification as a single subspecies. Finally, we found evidence that the pattern of low genomic differentiation is the result of both incomplete lineage sorting and gene flow between populations.

Unexpected but welcome. Artificially selected traits may increase fitness in wild boar.

Artificial selection affects phenotypes differently by natural selection. Domestic traits, which pass into the wild, are usually negatively selected. Yet, exceptionally, this axiom may fail to apply if genes, from the domestic animals, increase fertility in the wild. We studied a rare case of a wild boar population under the framework of Wright's interdemic selection model, which could explain gene flow between wild boar and pig, both considered as demes. We analysed the MC1R gene and microsatellite neutral loci in 62 pregnant wild boars as markers of hybridization, and we correlated nucleotide mutations on MC1R (which are common in domestic breeds) to litter size, as an evaluation of fitness in wild sow. Regardless of body size and phyletic effects, wild boar sows bearing nonsynonymous MC1R mutations produced larger litters. This directly suggests that artificially selected traits reaching wild populations, through interdemic gene flow, could bypass natural selection if and only if they increase the fitness in the wild.

The Relationship between MC1R Mutation and Plumage Color Variation in Pigeons.

The polymorphisms of MC1R gene play a crucial role in coat color variation in mammals; however, the relationship is still unclear in pigeons. In this study, we sequenced 741 bp fragment of the MC1R for 39 individuals with five plumage color patterns (gray plumage, n = 12; black plumage, n = 9; white plumage, n = 3; spotted plumage, n = 12; red plumage, n = 3). A total of three single nucleotide polymorphisms (SNPs) were detected, including G199A, G225A, and A466G, which subsequently determined four haplotypes (H1–H4). Among them, H1 is the predominant haplotype. Association analysis revealed that H1 and H3 were significantly associated with the black plumage trait (P < 0.05), while the H4 was significantly associated with gray plumage trait (P < 0.05). Furthermore, only diplotype H1H1 was significantly associated with black and gray traits of pigeons. Collectively, our study suggested an association between genetic variation of MC1R and plumage color in pigeon.

A 6-bp deletion in exon 8 and two mutations in introns of TYRP1 are associated with blond coat color in Liangshan pigs

Melanocortin receptor 1 (MC1R), Agouti signaling protein (ASIP), and Tyrosinase-related protein 1 (TYRP1) are reported critical genes that regulate pheomelanin and eumelanin synthesis in mammals. Liangshan pig is a special Chinese indigenous pig breed with two completely different coat colors, solid black and blond. In this study, we detected polymorphisms of the above three genes and assessed the relationships between the variations and coat color phenotypes in Liangshan pigs. The findings revealed that the blond phenotype of Liangshan pig was related to dominant mutations in TYRP1, but not related to mutations in MC1R or ASIP. We found three closely linked mutations in TYRP1, g.8406G>A in intron 4, g.11100A>G in intron 5, and g.17599_17604del in exon 8, that were completely associated with blond coat color in Liangshan pigs. Further analysis revealed that a 6-bp deletion mutation resulted in deletion of Met and Gly residues at positions 495 and 496 in TYRP1 protein, and altered the structure of transmembrane domain of TYRP1. Together, our findings indicated that these three mutations in TYRP1 cause the blond phenotype in Liangshan pigs.

The associations between Parkinson's disease and cancer: the plot thickens.

Epidemiological studies support a general inverse association between the risk of cancer development and Parkinson’s disease (PD). In recent years however, increasing amount of eclectic evidence points to a positive association between PD and cancers through different temporal analyses and ethnic groups. This positive association has been supported by several common genetic mutations in SNCA, PARK2, PARK8, ATM, p53, PTEN, and MC1R resulting in cellular changes such as mitochondrial dysfunction, aberrant protein aggregation, and cell cycle dysregulation. Here, we review the epidemiological and biological advances of the past decade in the association between PD and cancers to offer insight on the recent and sometimes contradictory findings.

Alterations in Mc1r gene expression are associated with regressive pigmentation in Astyanax cavefish.

Diverse changes in coloration across distant taxa are mediated through alterations in certain highly conserved pigmentation genes. Among these genes, Mc1r is a frequent target for mutation, and many documented alterations involve coding sequence changes. We investigated whether regulatory mutations in Mc1r may also contribute to pigmentation loss in the blind Mexican cavefish, Astyanax mexicanus. This species comprises multiple independent cave populations that have evolved reduced (or absent) melanic pigmentation as a consequence of living in darkness for millions of generations. Among the most salient cave-associated traits, complete absence (albinism) or reduced levels of pigmentation (brown) have long been the focus of degenerative pigmentation research in Astyanax. These two Mendelian traits have been linked to specific coding mutations in Oca2 (albinism) and Mc1r (brown). However, four of the seven caves harboring the brown phenotype exhibit unaffected coding sequences compared to surface fish. Thus, diverse genetic changes involving the same genes likely impact reduced pigmentation among cavefish populations. Using both sequence and expression analyses, we show that certain cave-dwelling populations harboring the brown mutation have substantial alterations to the putative Mc1r cis-regulatory region. Several of these sequence mutations in the Mc1r 5' region were present across multiple, independent cave populations. This study suggests that pigmentation reduction in Astyanax cavefish evolves through a combination of both coding and cis-regulatory mutations. Moreover, this study represents one of the first attempts to identify regulatory alterations linked to regressive changes in cave-dwelling populations of A. mexicanus.

Increased risk of developing cutaneous malignant melanoma is associated with variation in pigmentation genes and VDR, and may involve epistatic effects.

Cutaneous malignant melanoma (CMM) is a malicious human skin cancer that primarily affects individuals with light pigmentation and heavy sun exposure, but also has a known familial association. Multiple genes and polymorphisms have been reported as low-penetrance susceptibility loci for CMM. Here, we examined 33 candidate polymorphisms located in 11 pigmentation genes and the vitamin D receptor gene (VDR) in a population of 130 cutaneous melanoma patients and 707 healthy controls. The genotypes obtained were evaluated for main association effects and potential gene-gene interactions. MC1R, TYR, VDR and SLC45A2 genes were found to be associated with CMM in our population. The results obtained for major function MC1R mutations were the most significant [with odds ratio (OR)=1.787, confidence interval (CI)=1.320-2.419 and P=1.715(-4)], followed by TYR (rs1393350) (with OR=1.569, CI=1.162-2.118, P=0.003), VDR (GCCC haplotype in rs2238136-rs4516035-rs7139166-rs11568820 block) (with OR=5.653, CI=1.794-17.811, P=0.003) and SLC45A2 (rs16891982) (with OR=0.238, CI=0.057-0.987, P=0.048). The study also detected significant intermolecular epistatic effects between MC1R and TYR, SLC45A2 and VDR, HERC2 and VDR, OCA2 and TPCN2, as well as intramolecular interactions between variants within the genes MC1R and VDR. In the final multivariate logistic regression model for CMM development, only the gene-gene interactions discovered remained significant, showing that epistasis may be an important factor in the risk of melanoma.

Molecular population genetics of the melanic plumage polymorphism in Arctic skuas (Stercorarius parasiticus): evidence for divergent selection on plumage colour

The Arctic skua (Stercorarius parasiticus) is a classic example of an avian plumage polymorphism, with variation in melanin-based ventral plumage coloration defining pale, intermediate and dark morphs in adults of both sexes. However, despite several decades of field research, there is an incomplete understanding of how the polymorphism in ventral plumage colour is maintained and the selective forces involved. Here, we investigate selection on a locus (MC1R) that is strongly associated with plumage colour variation in Arctic skuas using patterns of nucleotide variation and comparison to neutral loci (nuclear introns and mtDNA). We find that three linked nonsynonymous mutations in MC1R, including the single mutation described previously, are associated with plumage colour in the Arctic skua. The position of nonsynonymous mutations on a MC1R haplotype network implies that divergent selection drove the initial evolution of the colour morphs. Comparisons of F(ST)s of MC1R vs. nuclear introns among five skua populations differing in proportion of dark morphs along an approximate north-south cline reveal a signature of divergent selection on MC1R. In contrast, we find limited evidence for balancing selection on MC1R within populations, although the power is low. Our results provide strong evidence for both past and ongoing selection on MC1R, and, by implication, plumage colour in Arctic skuas. The results suggest that a fruitful avenue for future ecological studies will be analysis of selection on morphs in colonies at the extremes along the morph ratio cline.

Coat Color Genotypes and Risk and Severity of Melanoma in Gray Quarter Horses

Both graying and melanoma formation in horses have recently been linked to a duplication in the STX17 gene. This duplication, as well as a mutation in the ASIP gene that increases MC1R pathway signaling, affects melanoma risk and severity in gray horses. To determine if melanoma susceptibility in gray Quarter Horses (QH) is lower than gray horses from other breeds because of decreased MC1R signaling resulting from a high incidence of the MC1R chestnut coat color allele in the QH population. A total of 335 gray QH with and without dermal melanomas. Blood or hair root samples were collected from all horses for DNA extraction and genotyping for STX17, ASIP, and MC1R genotypes. Age, sex, and external melanoma presence and grade were recorded. The effect of age and genotype on melanoma presence and severity was evaluated by candidate gene association. Melanoma prevalence (16%) and grade (0.35) in this QH cohort was lower than that reported in other breeds. Age was significantly associated with melanoma prevalence (P = 5.28 × 10(-11)) and severity (P = 2.2 × 10(-13)). No significant effect of MC1R genotype on melanoma prevalence or severity was identified. An effect of ASIP genotype on melanoma risk was not detected. Low STX17 homozygosity precluded evaluation of the gray allele effect. Melanoma prevalence and severity is lower in this population of gray QH than what is reported in other breeds. This could be because of the infrequent STX17 homozygosity, a mitigating effect of the MC1R mutation on ASIP potentiation of melanoma, other genes in the MC1R signaling pathway, or differences in breed genetic background.

BRAF and MC1R in Melanoma: Different in Head and Neck Tumors?

In this issue, Hacker et al. (2012) report the largest study to date on the association between MC1R variants and BRAF mutant melanoma. Although they did not observe a significant overall correlation, there was a significant negative association between BRAF and MC1R mutations for head/neck melanomas. This suggests a fundamental difference in pathogenesis between head/neck and truncal melanomas, which could contribute to their divergent prognoses.