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At least 1,225 records · Page 68Linked to original sources
PubMed2002

A missense mutation disrupting a dibasic prohormone processing site in pro-opiomelanocortin (POMC) increases susceptibility to early-onset obesity through a novel molecular mechanism.

The functional loss of both alleles of the human pro-opiomelanocortin (POMC) gene leads to a very rare syndrome of hypoadrenalism, red hair and early-onset obesity. In order to examine whether more subtle genetic variants in POMC might contribute to early-onset obesity, the coding region of the gene was sequenced in 262 Caucasian subjects with a history of severe obesity from childhood. Two children were found to be heterozygous for a missense mutation, R236G, which disrupts the dibasic cleavage site between beta melanocyte-stimulating hormone (beta-MSH) and beta-endorphin. Beta-TC3 cells transfected with the mutant POMC cDNA produced a mutant beta-MSH/beta-endorphin fusion protein. This fusion protein bound to the human melanocortin-4 receptor (hMC4R) with an affinity similar to its natural ligands, but had a markedly reduced ability to activate the receptor. This variant co-segregated with early-onset obesity over three generations in one family and was absent in 412 normal weight UK Caucasian controls. Combining the results in UK Caucasians with a new case-control study in French subjects and three previously published reports, mutations disrupting this processing site were present in 0.88% of subjects with early-onset obesity and 0.22% of normal-weight controls. These results suggest that the R236G mutation may confer an inherited susceptibility to obesity through the production of an aberrant fusion protein that has the capacity to interfere with central melanocortin signalling.

Adolescent↗
PubMed1997

Homologous pigmentation mutations in human, mouse and other model organisms.

Mouse coat colour genes have long been studied as a paradigm for genetic interactions in development. A number of these genes have been cloned and most correspond to human genetic disease loci. The proteins encoded by these genes include transcription factors, receptor tyrosine kinases and growth factors, G-protein coupled receptors and their ligands, membrane proteins, structural proteins and enzymes. Many of the mutations have pleiotropic effects, indicating that these proteins play a wider role in developmental or cellular processes. In this review I tabulate the available data on all pigmentation genes cloned from mouse or human, and I focus on three particular systems. One family of genes, including LYST and HPS/ep, shows the relationship between melanosomes and lysosomes. The G-protein coupled receptor, endothelin receptor-B, and its ligand, endothelin-3, are required for the development of both melanocytes and enteric neurons. The melanocortin-1 receptor is expressed only on melanocytes, but mutations that cause overexpression of agouti protein, an antagonist of the receptor, result in obesity, and highlight a role of melanocortins in weight homoeostasis.

Agouti Signaling Protein↗
PubMed1997

Characterization of melanocyte stimulating hormone receptor variant alleles in twins with red hair.

The association between MSHR coding region variation and hair colour in humans has been examined by genotyping 25 red haired and 62 non-red Caucasians, all of whom were 12 years of age and members of a twin pair study. Twelve amino acid substitutions were seen at 11 different sites, nine of these being newly described MSHR variants. The previously reported Val92Met allele shows no association with hair colour, but the three alleles Arg151Cys, Arg160Trp and Asp294His were associated with red hair and one Val60Leu variant was most frequent in fair/blonde and light brown hair colours. Variant MSHR genotypes are associated with lighter skin types and red hair (P < 0.001). However, comparison of the MSHR genotypes in dizygotic twin pairs discordant for red hair colour indicates that the MSHR gene cannot be solely responsible for the red hair phenotype, since five of 13 pairs tested had both haplotypes identical by state (with three of the five having both identical by descent). Rather, it is likely that additional modifier genes exist, making variance in the MSHR gene necessary but not always sufficient, for red hair production.

Alleles↗
PubMed2000

Pleiotropic effects of the melanocortin 1 receptor (MC1R) gene on human pigmentation.

Variants of the melanocortin 1 receptor (MC1R) gene are common in individuals with red hair and fair skin, but the relative contribution to these pigmentary traits in heterozygotes, homozygotes and compound heterozygotes for variants at this locus from the multiple alleles present in Caucasian populations is unclear. We have investigated 174 individuals from 11 large kindreds with a preponderance of red hair and an additional 99 unrelated redheads, for MC1R variants and have confirmed that red hair is usually inherited as a recessive characteristic with the R151C, R160W, D294H, R142H, 86insA and 537insC alleles at this locus. The V60L variant, which is common in the population may act as a partially penetrant recessive allele. These individuals plus 167 randomly ascertained Caucasians demonstrate that heterozygotes for two alleles, R151C and 537insC, have a significantly elevated risk of red hair. The shade of red hair frequently differs in heterozygotes from that in homozygotes/compound heterozygotes and there is also evidence for a heterozygote effect on beard hair colour, skin type and freckling. The data provide evidence for a dosage effect of MC1R variants on hair as well as skin colour.

Alleles↗
PubMed2005

Altered cell surface expression of human MC1R variant receptor alleles associated with red hair and skin cancer risk.

The human melanocortin-1 receptor gene (MC1R) encodes a G-protein coupled receptor that is primarily expressed on melanocytes, where it plays a key role in pigmentation regulation. Variant alleles are associated with red hair colour and fair skin, known as the RHC phenotype, as well as skin cancer risk. The R151C, R160W and D294H alleles, designated 'R', are strongly associated with the RHC phenotype and have been proposed to result in loss of function receptors due to impaired G-protein coupling. We recently provided evidence that the R151C and R160W variants can efficiently couple to G-proteins in response to alpha-melanocyte stimulating hormone. The possibility that altered cellular localization of the R151C and R160W variant receptors could underlie their association with RHC was therefore considered. Using immunofluorescence and ligand binding studies, we found that melanocytic cells exogenously or endogenously expressing MC1R show strong surface localization of the wild-type and D294H alleles but markedly reduced cell surface expression of the R151C and R160W receptors. In additional exogenous expression studies, the R variant D84E and the rare I155T variant, also demonstrated a significant reduction in plasma membrane receptor numbers. The V60L, V92M and R163Q weakly associated RHC alleles, designated 'r', were expressed with normal or intermediate cell surface receptor levels. These results indicate that reduced receptor coupling activity may not be the only contributing factor to the genetic association between the MC1R variants and the RHC phenotype, with MC1R polymorphisms now linked to a change in receptor localization.

Alleles↗
PubMedDate not supplied

Laser hair reduction in the hirsute patient: a critical assessment.

Hirsutism affects 5-10% of unselected women, depending on ethnicity and definition. The past two decades have seen the development of lasers for the removal of unwanted hair, using selective destruction of the hair follicle without damage to adjacent tissues. Selective photothermolysis relies on the absorption of a brief radiation pulse by specific pigmented targets, which generates and confines the heat to that selected target. In general, laser hair removal is most successful in patients with lighter skin colours and dark coloured hairs. Some studies have documented the results of laser hair removal in a controlled setting, although few have extended their observations beyond 1 year. In general, treatment with the ruby, alexandrite or diode lasers, or the use of intense pulsed light results in similar success rates, although these are somewhat lower for the neodymium:Yttrium-Aluminum-Garnet (nd:YAG) laser. Overall, laser hair removal should not be considered 'permanent', at least when considering the current data available. Repeated therapies are necessary, although complete alopoecia is rarely achieved and it is unclear at what point the maximum benefit is achieved from multiple therapies. While larger prospective, controlled, blinded and uniform studies are still needed, laser hair removal appears to be a useful adjuvant in the treatment of the hirsute patient.

Diagnosis, Differential↗
PubMed1990

Malignant melanoma in England: risks associated with naevi, freckles, social class, hair colour, and sunburn.

In a case-control study in the Midlands of England, 195 subjects with superficial spreading or nodular melanoma were compared to age- and sex-matched controls chosen from all inpatients or outpatients in hospitals serving the defined source population. Significant increases in melanoma risk, after adjustment for other factors, were seen in association with total naevi on the arms (odds ratio (OR), for 15+ naevi compared to none = 3.8), intense freckling as an adult (OR = 6.2), and as a child (OR = 6.0), and higher social class (OR = 2.4). Positive single factor associations were also seen with light or red hair colour, tendency to sunburn easily, and a history of sunburn at ages 8-12, although these were not significant when adjusted for the other factors. No significant effect was seen with naevi greater than 6 mm, or with raised naevi, when adjusted for total number of naevi. Total arm naevi and density of freckling had independent effects, consistent with a multiplicative effect, the OR in those with 10+ naevi and heavy freckling being 20.8. The risk associated with red hair was independent of naevi, but associated with freckling. The strongest association with sunburn history was seen with a history of sunburn in childhood, with sunburn at later times, having smaller effects, or none. These results shows that freckling and social class as well as naevi are strong and independent risk indicators for melanoma. These associations were generally consistent by type of melanoma, sex, age, and extent of regular exposure of the body site affected, although the social class gradient was observed neither for nodular melanoma nor for melanomas occurring on the most exposed body sites.

Adult↗
PubMed1990

Simultaneous assessment of risk factors for malignant melanoma and non-melanoma skin lesions, with emphasis on sun exposure and related variables.

The purpose of this case-control study was to identify differences in risk factors between melanoma and non-melanoma skin lesions. The study group, interviewed from 1979 to 1982, consisted of 289 subjects with melanoma, 75 subjects with non-melanoma sun-related skin lesions and 527 controls. Simultaneous comparison of the three subgroups was accomplished by polychotomous logistic regression. The highest exposure category of lifetime sun exposure was associated with a nearly threefold risk of both melanoma and non-melanoma. Poor tanning was associated with an approximately twofold risk of both disease types. Similarly, northern European ethnicity was associated with an approximately twofold risk of disease. Number of moles on the body exhibited a relationship with melanoma only: having more than 25 moles, compared to their absence, was associated with a thirteenfold risk of melanoma. History of freckling was associated with a twofold risk of melanoma, but no increase in the risk of non-melanoma. Alternatively, mixed indoor-outdoor recreational exposure was associated with a 50% increased risk of non-melanoma, but a 25% decreased risk of melanoma. History of severe sunburn was associated with a twofold risk of non-melanoma only. For history of prior sun-related lesions the nearly sevenfold risk of melanoma was exceeded by the 14-fold risk of non-melanoma.

Case-Control Studies↗
PubMed2003

Quantitative analysis of desmethylselegiline, methamphetamine, and amphetamine in hair and plasma from Parkinson patients on long-term selegiline medication.

Hair and plasma from patients on long-term selegiline medication were analyzed to evaluate the relationships between plasma and hair melanin concentrations and the incorporation of the selegiline metabolites methamphetamine and amphetamine in hair, and to evaluate hair analyses for determining compliance in medication. Analyses were performed on both the whole hairs, as well as pigmented and non-pigmented hairs from gray-haired patients. Melanin was quantitated by spectrophotometry, and metabolites were quantitated by gas chromatography-mass spectrometry. Concentrations in pigmented and non-pigmented hairs differed significantly for both methamphetamine (p < 0.01) and amphetamine (p < 0.02), with mean concentration ratios being 3.69 +/- 1.88 and 2.95 +/- 1.16 for methamphetamine and amphetamine, respectively. Segmental analysis indicated that some patients had not been compliant with medication. We concluded that the incorporation of methamphetamine and amphetamine into hair of single individuals shows a preference for pigmented hairs over white hairs and that segmental analysis of hair may be useful when measuring compliance with medication.

Aged↗
PubMedDate not supplied

Opiate concentrations in hair from subjects in a controlled heroin-maintenance program and from opiate-associated fatalities.

One month before (T-1) and 12 months after (T12) controlled intravenous administration of pharmaceutical heroin-HCl (10-1000 mg/d) in the context of a heroin-maintenance program, concentrations of opiates in head hair were determined (n = 46), using a validated gas chromatography-mass spectrometry method with limits of detection (LOD) between 0.02 and 0.04 ng/mg. In addition, a collective of opiate-associated fatalities was examined (n = 24). The obtained concentrations in the proximal segment (1 cm) of the patients were between 0.04 and 1.16 ng/mg (mean 0.13 ng/mg) for heroin (HER), between 0.02 and 32.41 ng/mg (mean 1.48 ng/mg) for 6-monoacetylmorphine (MAM) and between 0.03 and 11.79 ng/mg (mean 1.19 ng/mg) for morphine (MOR). With the exception of the analyte HER, there was no other statistically significant difference in the concentrations in comparison to the opiate fatalities [HER 1.55-5.20 ng/mg mean 3.38 ng/mg), MAM 0.04-30.01 ng/mg (mean 2.14 ng/mg), and MOR 0.03-11.87 ng/mg (mean 1.15 ng/mg) in the proximal segments]. After controlled HER administration, a correlation between the dose and the total opiate concentration in the hair was found (r = 0.66). These results disagree with the observations of authors who found only limited dose-concentration relationships after heroin abuse in hair. When considering a single analyte, the coefficient of correlation increased in correspondence to the respective plasma half-life (r = 0.42, r = 0.58, and r = 0.69 for HER, MAM, and MOR). The latter findings are in agreement with the report that states that this correlation is influenced by the plasma half-lifes of analytes. Codeine and acetylcodeine (AC) were detected in 50% and 43.5% (T-1) and 13% and 10.9% (T12) of the samples of the HER-maintenance program, as well as in 33.3% and 16.7% in opiate-associated fatalities, respectively. The lack of differences between obtained opiate concentrations in the hair of participants in a controlled heroin maintenance program and of opiate-associated fatalities does not support the hypothesis that an absence of tolerance can be regarded as a potential cause of death. In addition, the lack of AC, which was also observed in the majority of the deaths, questions its applicability as a characteristic marker of the consumption of illicit heroin.

Codeine↗
PubMed2002

Cats require more dietary phenylalanine or tyrosine for melanin deposition in hair than for maximal growth.

In 1986, the NRC recommended a dietary concentration of 4.0 g/kg of phenylalanine and 8.5 g/kg of total aromatic amino acids for growing kittens on the basis of maximal growth rate and nitrogen balance. Black hair-coated cats were given purified diets containing the following phenylalanine + tyrosine (Phe + Tyr) concentrations (g/kg diet): 4 + 2, 4 + 4, 4 + 6, 4 + 8, 10 + 0, 10 + 2, 10 + 4, 10 + 6, 10 + 8, 10 + 10, 24 + 0 for at least 6 mo. All other amino acids were present at about twice the requirements. Total melanin and the oxidation product of eumelanin, pyrrole-2,3,5-tricarboxylic acid (PTCA) were measured in hair. There was a significant linear relationship between the concentrations of tyrosine in plasma and PTCA in hair. The relationship between PTCA concentration in hair and Phe + Tyr in the diet had a point of inflection at approximately 16 g/kg Phe + Tyr. Cats fed diets with <16 g Phe + Tyr developed "red hair." We confirmed the anecdotal reports that the black hair of cats can change from black to reddish brown. An aromatic amino acid concentration > or =18 g/kg is recommended for the prevention of visually discernible red hair in black-coated cats. Dietary concentrations >18 g total aromatic amino acids/kg diet promote a greater ratio of PTCA:total melanin in hair. We are unaware of a secondary nutrient requirement being so much greater than the requirement for growth.

Animals↗
PubMed1995

Evaluation of tyrosinase minigene co-injection as a marker for genetic manipulations in transgenic mice.

The utility of tyrosinase minigene co-injection was evaluated as a visual marker for the generation and breeding of transgenic mice. In an evaluation of 39 transgenic founder animals and 44 transgenic lines five phenotypic patterns of pigmentation were consistently observed, including albino, dark, light, mottled and himalayan. In these studies co-injection of the tyrosinase minigene along with the transgene of interest (TOI) resulted in genomic integration of the two transgenes in 95% of the F0 generation. Co-segregation of transgenes occurred in 94% of doubly transgenic mice in the F1 generation, without dissociation in subsequent generations. All pigmented phenotypes proved useful for distinguishing homozygous from heterozygous F2 animals via backcross trials, while the light, mottled and himalayan phenotypes proved useful in visually discriminating between homozygous and heterozygous F2 animals. In addition, the light, mottled and himalayan phenotypes proved useful in determining segregation patterns of transgenes in the progeny of crosses between separate transgenic lines. Moreover, there appears to be a correlation between intensity of pigmentation and degree of expression of the co-injected TOI. These studies confirm that tyrosinase co-injection is a useful adjunct in transgenic mouse studies and can serve to reduce routine genetic validation of transgenic lines.

Animals↗
PubMedDate not supplied

The Goodale white-spotted mice: a historical report.

After tracing the history of Dr. Goodale's selection study of white-spotted mice, it appears that the white spotting selected for was controlled by a complex of genetic factors. Spot occurrence was controlled by a single gene pair, causing small white areas on the forehead. The size of head spot was determined by a few modifier gene loci, among which some nonadditive gene action may have taken place. The B locus appeared to be associated with head-spot size, either through linkage or pleiotropic effects. There may also have been some maternal effects on head-spot size. Selection for increased head-spot size was successful, the heritability of the trait being between 0.1 and 0.2. The increase in spot size was fairly slow; a total score of about 13 units was reached over 16 years of selection. Accumulation of factors favoring increased head-spot size led eventually to the appearance of body spots, and selection began to concentrate on these. Body-spot size was controlled by a larger number of gene pairs; gene action appeared to be more nearly additive, and there appeared to be no maternal effect or association with B locus alleles. Heritability of body-spot size was 0.3 to 0.5. Total score increased from 13 to 56 units over the 11 years of selection.

Animals↗
PubMedDate not supplied

Mutant allele frequencies among domestic cats in some eastern areas of Canada: regional homogeneity of factors in Canadian Atlantic Provinces and the French colony of Saint Pierre.

Surveys to determine mutant allele frequencies in domestic cats of the Canadian Atlantic Provinces (Halifax, Nova Scotia; Fredericton, New Brunswick; Charlottetown, Prince Edward Island; St. John's Newfoundland) and the French colony of Saint Pierre, Saint Pierre et Miquelon, reveal a general regional homogeneity for most factors. Despite diverse historical patterns of settlement, a strong common component of origin is indicated. This is tentatively identified as late 18th and early 19th century British. One mutant, polydactyly, which is of New England origin appears to have been distributed largely by loyalist refugees from New England at the time of the American Rebellion. No elements of a specific Acadian (French) character have yet been identified. Siamese cats have been "introduced" to the region in recent years and are now so abundant that they will undoubtedly cause a significant change in some mutant allele frequencies over the next few decades. Interregional exchanges of cats no doubt are contributing to homogenizing the populations of the area, but the practice of sterilization of pets offsets this to some degree.

Alleles↗
PubMedDate not supplied

Allele frequencies in a cat population in Budapest.

Allelic frequencies were determined for the domestic cat population of Budapest, Hungary. Most of the frequencies are in the range of those of western European populations, but there are two unusual features. The first is the apparent absence of blotched tabby and a relatively high frequency of Abyssinian tabby. The second is in the distribution of frequencies of white spotting phenotypes. There is an approximately normal distribution around the most common pattern, which is 50 percent white fur, contrasted to western populations in which frequency is maximal between approximately 10-30 percent white fur and declines with increasing white fur.

Alleles↗
PubMedDate not supplied

Gene frequencies in the cat deme of Tampa, Florida.

The frequencies of mutant alleles at five loci were calculated for a sample of cats from the deme of Tampa, Florida. Owing to certain diagnostic problems, precise comparisons to other populations are unwarranted. However, there is general concordance with other U.S. cat populations.

Alleles↗