Mutations in SLC45A2 lead to loss of melanin in parrot feathers

Bird plumage coloration is a complex and multifactorial process that involves both genetic and environmental factors. Diverse pigment groups contribute to plumage variation in different birds. In parrots, the predominant green color results from the combination of 2 different primary colors: yellow and blue. Psittacofulvin, a pigment uniquely found in parrots, is responsible for the yellow coloration, while blue is suggested to be the result of light scattering by feather nanostructures and melanin granules. So far, genetic control of melanin-mediated blue coloration has been elusive. In this study, we demonstrated that feather from the yellow mutant rose-ringed parakeet displays loss of melanosome granules in spongy layer of feather barb. Using whole genome sequencing, we found that mutation in SLC45A2, an important solute carrier protein in melanin synthetic pathway, is responsible for the sex-linked yellow phenotype in rose-ringed parakeet. Intriguingly, one of the mutations, P53L found in yellow Psittacula krameri is already reported as P58A/S in the human albinism database, known to be associated with human OCA4. We further showed that mutations in SLC45A2 gene affect melanin production also in other members of Psittaculidae family such as alexandrine and plum-headed parakeets. Additionally, we demonstrate that the mutations associated with the sex-linked yellow phenotype, localized within the transmembrane domains of the SLC45A2 protein, affect the protein localization pattern. This is the first evidence of plumage color variation involving SLC45A2 in parrots and confirmation of associated mutations in the transmembrane domains of the protein that affects its localization.

Oculocutaneous albinism type 4: Novel compound heterozygous mutations in the SLC45A2 gene in a Chinese case

BACKGROUND

Oculocutaneous albinism type 4 (OCA4) is a rare autosomal recessive disorder characterized by a reduction of pigmentation in skin, hair, and eyes, and OCA4 is mainly seen in the SLC45A2 gene variants.

OBJECTIVE

To report a Chinese patient suspected of oculocutaneous albinism and identify the causing mutation.

METHODS

Genomic DNA was extracted from the peripheral blood samples of the patient, his parents, and elder brother. Whole exome sequencing was performed in the family, and Sanger sequencing was then used to verify the mutations.

RESULTS

Compound heterozygous variants, c.1304C>A (p.S435Y) and c.301C>G (p.R101G) in SLC45A2 gene, were detected in the proband, which were inherited from his father and mother respectively. Based on the ACMG guidelines, we can interpret the c.1304C>A (p.S435Y) variant as a suspected pathogenic variant and the c.301C>G (p.R101G) variant as a clinically significant unspecified variant. The diagnosis of OCA4 is confirmed.

CONCLUSION

We firstly reported this case of OCA4 with the compound heterozygous variants in the SLC45A2 gene. Our findings further enrich the reservoir of SLC45A2 mutations in OCA4.

Effects of SLC45A2 and GPNMB on Melanin Deposition Based on Transcriptome Sequencing in Chicken Feather Follicles

As an essential genetic and economic trait, chicken feather color has long been an important research topic. To further understand the mechanism of melanin deposition associated with coloration in chicken feathers, we selected feather follicle tissues from the neck and wings of chickens with differently colored feathers (yellow, sub-Columbian, and silver) for transcriptome analysis. We focused on genes that were expressed in both the wings and neck and were expressed with the same trends in breeds with two different plumage colors, specifically, SLC45A2, GPNMB, MLPH, TYR, KIT, WNT11, and FZD1. GO and KEGG enrichment analyses showed the DEGs were enriched in melanin-related pathways, such as tyrosine metabolic pathway and melanogenesis, and PPI analysis highlighted the genes SLC45A2 and GPNMB as associated with melanin deposition. Verification experiments in chicken melanocytes demonstrated that these two genes promote melanocyte melanin deposition. These data enrich our knowledge of the mechanisms that regulate chicken feather color.

Phenotypic and Dermoscopic Patterns of Familial Melanocytic Lesions: A Pilot Study in a Third-Level Center

Cutaneous melanoma is a highly aggressive skin cancer. It is estimated that 5% to 10% of the underlying mutations are hereditary and responsible for familial (or hereditary) melanoma. These patients are prone to the early development and higher risk of multiple melanomas. In recent years, an increasing number of genes have been identified thanks to genetic testing, allowing the subsequent surveillance of individuals at risk, yet it is still difficult to predict the presence of these mutations on a clinical basis. In this scenario, specific phenotypic and dermoscopic features could help clinicians in their identification. The aim of this work has been to correlate mutations to prevalent dermoscopic patterns, paving the way for reference models useful in clinical practice. In our cohort, out of 115 patients referred to genetic counseling for melanoma, 25 tested positive (21.7%) for critical mutations: CDKN2A (n = 12), MITF (n = 3), BAP1 (n = 1), MC1R (n = 3), PTEN (n = 1), TYR (n = 2), OCA2 (n = 1), and SLC45A2 (n = 2). The phenotype profiles obtained through the digital acquisition, analysis, and description of both benign and malignant pigmented lesions showed a predominance of the type II skin phenotype, with an elevated mean total nevus number (182 moles, range 75-390). As for dermoscopic features, specific mutation-related patterns were described in terms of pigmentation, areas of regression, and vascular structures. Although further studies with larger cohorts are needed, our work represents the beginning of a new approach to the study and diagnosis of familial melanoma, underlining the importance of clinical and dermoscopic patterns, which may constitute a reference model for each gene, enabling comparison.

Oculo-Cutaneous Albinism Type 4 (OCA4): Phenotype-Genotype Correlation

Albinism is a genetic disorder, present worldwide, caused by mutations in genes affecting melanin production or transport in the skin, hair and eyes. To date, mutations in at least 20 different genes have been identified. Oculo-cutaneous Albinism type IV (OCA4) is the most frequent form in Asia but has been reported in all populations, including Europeans. Little is known about the genotype-phenotype correlation. We identified two main phenotypes via the analysis of 30 OCA4 patients with a molecularly proven diagnosis. The first, found in 20 patients, is clinically indistinguishable from the classical OCA1 phenotype. The genotype-to-phenotype correlation suggests that this phenotype is associated with homozygous or compound heterozygous nonsense or deletion variants with frameshift leading to translation interruption in the SLC45A2 gene. The second phenotype, found in 10 patients, is characterized by very mild hypopigmentation of the hair (light brown or even dark hair) and skin that is similar to the general population. In this group, visual acuity is variable, but it can be subnormal, foveal hypoplasia can be low grade or even normal, and nystagmus may be lacking. These mild to moderate phenotypes are associated with at least one missense mutation in SLC45A2.

Red and blond Mangalitza pigs display a signature of divergent directional selection in the SLC45A2 gene

The Mangalitza lard-type pig breed is well known for its fat appearance and curly hair, and it is mainly distributed in Eastern Europe. Four main lines were created in the nineteenth century by artificial selection: Blond Mangalitza, Black Mangalitza, Swallow-Belly Mangalitza and Red Mangalitza. The Swallow-Belly line has a black coat combined with yellow-blond throat and underbelly. In the current work, we aimed to investigate if the colourations of Mangalitza pigs are genetically determined by one or a few loci whose frequencies have been modified by artificial selection. The results of selection scans, with HapFLK and BayeScan, and of a GWAS for coat colour highlighted the existence of one region on SSC16 (18-20 Mb) with potential effects on hair pigmentation (Red vs. Blond contrast). The analysis of the gene content of this region allowed us to detect the solute carrier family 45 member 2 (SLC45A2) locus as a candidate gene for this trait. The polymorphism of the SLC45A2 locus has been associated with reduced levels or the absence of melanin in several mammalian species. The genotyping of four missense polymorphisms evidenced that rs341599992:G > A and rs693695020:G > A SNPs are strongly but not fully associated with the red and blond coat colours of Mangalitza pigs, a result that was confirmed by performing a haplotype association test. The near fixation of alternative SLC45A2 genotypes in Red and Blond Mangalitza pigs provides a compelling example of the consequences of a divergent directional selection for coat colour in a domestic species.

Identification and Computational Analysis of Novel TYR and SLC45A2 Gene Mutations in Pakistani Families With Identical Non-syndromic Oculocutaneous Albinism

Non-syndromic oculocutaneous albinism (nsOCA) is an inherited disorder of melanin biosynthesis with autosomal recessive mode of inheritance, presenting either hypopigmented or depigmented skin, hair, and eyes. It is genetically heterogeneous with seven loci (OCA1–OCA7) reported to date. In the present study, we have reported three consanguineous families (A, B, C) presenting identical nsOCA phenotypes. Sanger sequencing revealed a novel [NM_000372.5: c.826 T > C, p.(Cys276Arg)] and a recurrent variant [NM_000372.5: c.832C > T, p.(Arg278^∗)] in tyrosinase (TYR) in families A and B, respectively. Microsatellite marker-based homozygosity mapping linked family C to OCA4. Sequence analysis identified a novel insertion variant (NM_016180.5: c.1331_1332insA) in the SLC45A2. Further, in silico mutagenesis and dynamic simulation approaches revealed that a novel Cys276Arg variant abolished the cysteine bridge and might contribute toward decreased stability of the TYR protein. Our study expands the mutation spectrum of the TYR and SLC45A2 genes and emphasizes that molecular investigations are essential for accurate disease diagnosis.

Mutation Analysis of 63 Northwest Chinese Probands with Oculocutaneous Albinism

PURPOSE

To identify the mutational spectrum of 63 northwest Chinese probands with Oculocutaneous albinism (OCA), and identify correlations between phenotype and genotype.

METHODS

We recruited 63 clinically diagnosed with OCA patients in Gansu Provincial Maternal and Child Health Care Hospital. Mutation screening analysis was performed by direct sequencing and NGS-target sequencing to screen the variants on genes related to OCA. PolyPhen2 and PROVEN tools were used to predict the possible functional role of the novel variants. We assessed the pathogenicity of the novel mutations according to the clinical interpretation of genetic variants by ACMG/AMP 2015 guideline.

RESULTS

By molecular testing, 56 of the OCA probands were diagnosed as OCA 1, three were OCA 2 and one was OCA 4. The most common variants of TYR were c.929insC(33.7%), c.896 G > A(12.5%), c.832 C > T(9.6%).We found five novel variants of TYR that have not previously been reported.

CONCLUSIONS

We make an accurate diagnosis and classification for the OCA probands. Our result enlarged the mutational spectrum of TYR and SLC45A2. These findings could be useful for genetic counseling and gene diagnosis of OCA in Northwest of China.

Non-syndromic Oculocutaneous Albinism: Novel Genetic Variants and Clinical Follow Up of a Brazilian Pediatric Cohort

Oculocutaneous albinism (OCA) is a genetic disorder characterized by skin, hair, and eye hypopigmentation due to a reduction or absence of melanin. Clinical manifestations include vision problems and a high susceptibility to skin cancer. In its non-syndromic form, OCA is associated with six genes and one chromosomal region. Because OCA subtypes are not always clinically distinguishable, molecular analysis has become an important tool for classifying types of OCA, which facilitates genetic counseling and can guide the development of new therapies. We studied eight Brazilian individuals aged 1.5–18 years old with clinical diagnosis of OCA. Assessment of ophthalmologic characteristics showed results consistent with albinism, including reduced visual acuity, nystagmus, and loss of stereoscopic vision. We also observed the appearance of the strabismus and changes in static refraction over a 2-year period. Dermatologic evaluation showed that no participants had preneoplastic skin lesions, despite half of the participants reporting insufficient knowledge about skin care in albinism. Whole-exome and Sanger sequencing revealed eight different mutations: six in the TYR gene and two in the SLC45A2 gene, of which one was novel and two were described in a population study but were not previously associated with the OCA phenotype. We performed two ophthalmological evaluations, 2 years apart; and one dermatological evaluation. To the best of our knowledge, this is the first study to perform clinical follow-up and genetic analysis of a Brazilian cohort with albinism. Here, we report three new OCA causing mutations.

Tigers of the World: Genomics and Conservation

Of all the big cats, or perhaps of all the endangered wildlife, the tiger may be both the most charismatic and most well-recognized flagship species in the world. The rapidly changing field of molecular genetics, particularly advances in genome sequencing technologies, has provided new tools to reconstruct what characterizes a tiger. Here we review how applications of molecular genomic tools have been used to depict the tiger's ancestral roots, phylogenetic hierarchy, demographic history, morphological diversity, and genetic patterns of diversification on both temporal and geographical scales. Tiger conservation, stabilization, and management are important areas that benefit from use of these genome resources for developing survival strategies for this charismatic megafauna both in situ and ex situ.

Genome-wide association studies for iris pigmentation and heterochromia patterns in Large White pigs

Eye colour genetics have been extensively studied in humans since the rediscovery of Mendel's laws. This trait was first interpreted using simplistic genetic models but soon it was realised that it is more complex. In this study, we analysed eye colour variability in a Large White pig population (n = 897) and report the results of GWASs based on several comparisons including pigs having four main eye colour categories (three with both pigmented eyes of different brown grades: pale, 17.9%; medium, 14.8%; and dark, 54.3%; another one with both eyes completely depigmented, 3.8%) and heterochromia patterns (heterochromia iridis - depigmented iris sectors in pigmented irises, 3.2%; heterochromia iridum - one whole eye iris of depigmented phenotype and the other eye with the iris completely pigmented, 5.9%). Pigs were genotyped with the Illumina PorcineSNP60 BeadChip and GEMMA was used for the association analyses. The results indicated that SLC45A2 (on chromosome 16, SSC16), EDNRB (SSC11) and KITLG (SSC5) affect the different grades of brown pigmentation of the eyes, the bilateral eye depigmentation defect and the heterochromia iridis defect recorded in this white pig population respectively. These genes are involved in several mechanisms affecting pigmentation. Significant associations for the eye depigmented patterns were also identified for SNPs on two SSC4 regions (including two candidate genes: NOTCH2 and PREX2) and on SSC6, SSC8 and SSC14 (including COL17A1 as candidate gene). This study provided useful information to understand eye pigmentation mechanisms, further valuing the pig as animal model to study complex phenotypes in humans.

Germline variants in oculocutaneous albinism genes and predisposition to familial cutaneous melanoma

Approximately 1%-2% of cutaneous melanoma (CM) is classified as strongly familial. We sought to investigate unexplained CM predisposition in families negative for the known susceptibility genes using next-generation sequencing of affected individuals. Segregation of germline variants of interest within families was assessed by Sanger sequencing. Several heterozygous variants in oculocutaneous albinism (OCA) genes: TYR, OCA2, TYRP1 and SLC45A2, were present in our CM cohort. OCA is a group of autosomal recessive genetic disorders, resulting in pigmentation defects of the eyes, hair and skin. Missense variants classified as pathogenic for OCA were present in multiple families and some fully segregated with CM. The functionally compromised TYR p.T373K variant was present in three unrelated families. In OCA2, known pathogenic variants: p.V443I and p.N489D, were present in three families and one family, respectively. We identified a likely pathogenic SLC45A2 frameshift variant that fully segregated with CM in a family of four cases. Another four-case family harboured cosegregating variants (p.A24T and p.R153C) of uncertain functional significance in TYRP1. We conclude that rare, heterozygous variants in OCA genes confer moderate risk for CM.

Mutational Analysis of TYR, OCA2, and SLC45A2 Genes in Chinese Families with Oculocutaneous Albinism

BACKGROUND

Oculocutaneous albinism (OCA) is a group of heterogeneous autosomal recessive genetic disorder of melanin synthesis results in hypopigmented hair, skin, and eyes. OCA type 1, OCA type 2, and OCA type 4, which are respectively caused by mutations in TYR, OCA2, and SLC45A2 have high morbidity rates in Asia.

METHODS

TYR, OCA2, and SLC45A2 mutation analysis was carried out on 18 nonconsanguineous OCA patients and four fetuses were included for prenatal diagnose. Three genes of all individuals were amplified by polymerase chain reaction and examined by Sanger sequencing. The pathogenicity of the detected mutations were analyzed by Mutation Taster, PolyPhen 2, and SIFT software, and the conservation of the substituted amino acids were analyzed by MEGA software.

RESULTS

Eleven TYR mutations, three OCA2 mutations, and two SLC45A2 mutations were identified in 14 OCA type 1 patients, two OCA type 2 patients, and two OCA type 4 patients. c.1021A>G, p.R341G in TYR, c.1096_1104del, p.V366*, and c.1079C>T, p.S360F in OCA2 were novel. One of the four fetuses carried compound heterozygous mutation of TYR and became spontaneous abortion, the other three carried no mutations and appeared normal at birth.

CONCLUSION

In this study, specific clinical characteristics of OCA patients were described. Three novel pathogenic mutations were identified which will enrich the mutation spectrum of OCA, and the prenatal genetic screening in fetus at risk of OCA can provide vital information for genetic counseling.

Interaction of mammalian and plant H+/sucrose transporters with 14-3-3 proteins

The solute carrier 45 family (SLC45) was defined in the course of the Human Genome Project and consists of four members, A1-A4, which show only 20-30% identity of amino acid sequences among each other. All these members exhibit an identity of ∼20% to plant H⁺/sucrose cotransporters. Recently, we expressed members of the murine SLC45 family in yeast cells and demonstrated that they are, like their plant counterparts, H⁺/sucrose cotransporters. In contrast with the plant proteins, SLC45 transporters recognise also the monosaccharides glucose and fructose as physiological substrates and seem to be involved in alternative sugar supply as well as in osmoregulation of several mammalian tissues. In the present study, we provide novel insights into the regulation of SLC45 transporters. By screening for interaction partners, we found a 14-3-3 protein as a promising candidate for control of transport activity. Indeed, co-expression of the gamma isoform of murine 14-3-3 protein in yeast and Xenopus oocytes led to a significant decrease in transport rates of the murine SLC45 transporters as well as of the plant H⁺/sucrose transporter Sut1.

Mutation analysis of a Chinese family with oculocutaneous albinism

Oculocutaneous albinism (OCA) is an autosomal recessive disorder characterized by either complete lack of or a reduction in melanin biosynthesis in the skin, hair, and eyes. OCA1, the most common and severe type, is caused by mutations in the tyrosinase (TYR) gene. In this study, we report a Chinese family with two members affected by OCA. Blood samples were collected from all family members. Genomic DNA was isolated from blood leukocytes, and all coding exons and adjacent intronic sequences of the TYR gene were examined for mutation analysis using polymerase chain reaction (PCR)-based sequencing. A pedigree chart was drawn, and clinical examinations and paraclinical tests were performed. Compound heterozygous mutations in TYR (c.832C>T and c.929_930insC, which resulted in p.Arg278* and p.Arg311Lysfs*7, respectively) were identified in the two patients with milky skin, white hair, photophobia, and reduced visual acuity, while other family members only carried one of two heterozygous mutations. In addition, a homozygous missense mutation c.814G>A (p.Glu272Lys) in the solute carrier family 45 member 2 (SLC45A2) gene was found in both patients and unaffected family members, suggesting that this may not be a causative mutation. The findings of this study expand the mutational spectrum of OCA. Compound heterozygous mutations (c.832C>T and c.929_930insC) in the TYR gene may be responsible for partial clinical manifestations of OCA, while the homozygous missense mutation c.814G>A (p.Glu272Lys) in the SLC45A2 gene may not be associated with OCA.

Mutational analysis of a Chinese family with oculocutaneous albinism type 2

Oculocutaneous albinism (OCA) is an autosomal recessive disorder characterized by hypopigmentation of the skin, hair, and eyes accompanied with ophthalmologic abnormalities. Molecular genetic test can confirm the diagnosis of the four subtypes of OCA (OCA1-4). Herein, we report a Chinese family with two patients affected by OCA. Mutations of TYR, OCA2, TYRP1, and SLC45A2 were examined by using PCR-sequencing. Large deletions or duplications of TYR and OCA2 were examined by Multiplex Ligation-dependent Probe Amplification (MLPA) assay. Compound heterozygous mutations of OCA2, (c.808-3C>G and c.2080-2A>G), were identified in both patients characterized with yellow hair and milky skin, heterochromia iridis, and nystagmus. Several computer-assisted approaches predicted that c.808-3C>G and c.2080-2A>G in OCA2 might potentially be pathogenic splicing mutations. No exon rearrangement (deletion/duplication) of TYR and OCA2 was observed in the patients by MLPA analysis. This study suggests that compound heterozygous mutations, (c.808-3C>G and c.2080-2A>G), in OCA2 may be responsible for partial clinical manifestations of OCA.

Distribution and expression of SLC45A2 in the skin of sheep with different coat colors

INTRODUCTION

To investigate whether the membrane-associated transporter protein SLC45A2 is differentially expressed in the skin of sheep with different coat colors and to determine its correlation with coat color establishment in sheep.

MATERIAL AND METHODS

The expression of SLC45A2 in sheep skin samples with different coat colors was qualitatively and quantitatively analyzed by PCR amplification, RT-PCR, immunohistochemical staining and Western blotting.

RESULTS

A 193-bp SLC45A2 CDS sequence was successfully amplified from sheep skin samples with diverse coat colors. RT-PCR analysis revealed that SLC45A2 mRNA was expressed in all sheep skin samples tested, with relative expression levels of 512.74 ± 121.51 in black skin, 143.38 ± 119.31 and 1.36 ± 0.09 in black dots and white dots of piebald skin, respectively, and 1.02 ± 0.23 in white skin (p < 0.01**). Positive SLC45A2 protein bands were also detected in all skin samples by Western blot analysis, with relative expression levels of 0.85 ± ± 0.17** in black skin, 0.60 ± 0.05** and 0.34 ± 0.07 in black dots and white dots of piebald skin, respectively, and 0.20 ± 0.05 in white skin (p < 0.01**). Immunohistochemical assays revealed that SLC45A2 was expressed in the hair follicle matrix, the inner and outer root sheath, and the dermal papilla in the skin tissues with different coat colors. These patterns were quantified by optical density (OD) analysis, which yielded relative expression levels of 0.23 ± 0.11 in black skin, 0.19 ± 0.09 and 0.10 ± 0.03 in black dots and white dots of piebald skin, respectively, and 0.08 ± 0.01 in white skin (p < 0.05*).

CONCLUSION

SLC45A2 is detectably expressed in sheep skin of all coat colors, though at significantly different levels. SLC45A2 may participate in the establishment of coat color by regulating the synthesis and trafficking of melanin.

Distribution of coat-color-associated alleles in the domestic horse population and Przewalski's horse

Considering the hidden mode of inheritance of some coat-color-associated alleles, we investigated the presence/absence of coat-color-associated alleles in 1093 domestic horses of 55 breeds and 20 specimens of Przewalski's horse. For coat-color genotyping, allele specific PCR, pyrosequencing and Li-Cor analyses were conducted on 12 coat-color-associated alleles of five genes. Our data provide deep insight into the distribution of coat-color-associated alleles within breeds. We found that the alleles for the basic colorations (bay, black, and chestnut) are widely distributed and occur in nearly all breeds. Alleles leading to dilutions or patterns are rare in domestic breeds and were not found in Przewalski's horse. Higher frequencies of these alleles are only found in breeds that are selected for their expressed phenotypes (e.g., Kinsky horse, Lewitzer, Tinker). Nevertheless, our study produced strong evidence that molecular testing of the coat color is necessary for well-defined phenotyping to avoid unexpected colorations of offspring that can result in legal action.

SLC45A2 mutation frequency in Oculocutaneous Albinism Italian patients doesn't differ from other European studies

BACKGROUND

Oculocutaneous Albinism (OCA) is a heterogeneous group of inherited diseases involving hair, skin and eyes. To date, six forms are recognized on the effects of different melanogenesis genes. OCA4 is caused by mutations in SLC45A2 showing a heterogeneous phenotype ranging from white hair, blue irides and nystagmus to brown/black hair, brown irides and no nystagmus. The high clinic variety often leads to misdiagnosis. Our aim is to contribute to OCA4 diagnosis defining SLC45A2 genetic variants in Italian patients with OCA without any TYR, OCA2 and TYRP1 gene defects.

MATERIALS AND METHODS

After the clinical diagnosis of OCA, all patients received genetic counseling and genetic test. Automatic sequencing of TYR, OCA2, and TYRP1 genes was performed on DNA of 117 albino patients. Multiplex Ligation-dependent Probe Amplification (MLPA) was carried out on TYR and OCA2 genes to increase the mutation rate. SLC45A2 gene sequencing was then executed in the patients with a single mutation in one of the TYR, OCA2, TYRP1 genes and in the patients, which resulted negative at the screening of these genes.

RESULTS

SLC45A2 gene analysis was performed in 41 patients and gene alterations were found in 5 patients. Four previously reported SLC45A2 mutations were found: p.G100S, p.W202C, p.A511E and c.986delC, and three novel variants were identified: p.M265L, p.H94D, and c.1156+1G>A. All the alterations have been detected in the group of patients without mutations in the other OCA genes.

CONCLUSIONS

Three new variants were identified in OCA4 gene; the analysis allowed the classification of a patient previously misdiagnosed as OA1 because of skin and hair pigmentation presence. The molecular defects in SLC45A2 gene represent the 3.4% in this cohort of Italian patients, similar to other Caucasian populations; our data differ from those previously published by an Italian researcher group, obtained on a smaller cohort of patients.

Pleiotropic effects of coat colour-associated mutations in humans, mice and other mammals

The characterisation of the pleiotropic effects of coat colour-associated mutations in mammals illustrates that sensory organs and nerves are particularly affected by disorders because of the shared origin of melanocytes and neurocytes in the neural crest; e.g. the eye-colour is a valuable indicator of disorders in pigment production and eye dysfunctions. Disorders related to coat colour-associated alleles also occur in the skin (melanoma), reproductive tract and immune system. Additionally, the coat colour phenotype of an individual influences its general behaviour and fitness. Mutations in the same genes often produce similar coat colours and pleiotropic effects in different species (e.g., KIT [reproductive disorders, lethality], EDNRB [megacolon] and LYST [CHS]). Whereas similar disorders and similar-looking coat colour phenotypes sometimes have a different genetic background (e.g., deafness [EDN3/EDNRB, MITF, PAX and SNAI2] and visual diseases [OCA2, RAB38, SLC24A5, SLC45A2, TRPM1 and TYR]). The human predilection for fancy phenotypes that ignore disorders and genetic defects is a major driving force for the increase of pleiotropic effects in domestic species and laboratory subjects since domestication has commenced approximately 18,000 years ago.