The genetics of human pigmentary disorders

In vitro antioxidant and antityrosinase activities of Manilkara kauki

Manilkara kauki L. Dubard is a tropical plant in the genus Manilkara of family Sapotaceae. This study investigated the total phenolic and flavonoid contents, and antioxidant and antityrosinase activities in different parts of M. kauki (fruits, leaves, seeds, stem barks and woods) and in fractions of stem barks. The total phenolic and flavonoid contents of the methanol and aqueous crude extracts of different parts of M. kauki ranged from 10.87 to 176.56 mg GAE (gallic acid equivalents) per gram of crude extract and 14.33 to 821.67 mg QE (quercetin equivalents) per gram of crude extract, resp. Leaves and stem barks exhibited higher total phenolic and flavonoid contents and antioxidant and anti-tyrosinase activities than fruits, seeds and woods. Stem barks were sequentially extracted with n-hexane, ethyl acetate, methanol and water and then the fractionated extracts were subjected to antioxidant and antityrosinase activities testing. The ethyl acetate and methanol extracts of stem barks exhibited higher total phenolic and flavonoid contents and antioxidant and antityrosinase activities than the n-hexane and aqueous extracts. Moreover, ethyl acetate extract of M. kauki stem exhibited the highest antityrosinase activity. It may be a potential source of tyrosinase inhibitors for pharmaceutical and cosmetic applications.

[Genetics and dermatology]

Many types of genodermatosis exist, with numerous modes of transmission. The development of molecular genetic methods, in particular the most recent sequencing techniques, can be used to identify an increasing number of genes involved in these forms of genodermatosis while providing confirmation or more details regarding clinical diagnosis. Thanks to this approach, it is possible to determine risk of recurrence and to formulate an antenatal strategy. These technologies have led to improved molecular definition and to a better understanding of the physiopathological mechanisms involved in different genodermatoses such as bullous epidermolysis, keratinisation disorders, pigmentation disorders, potentially tumoral conditions, and epidermal and pilar dysplasia. The large amount of information provided by high-throughput sequencing makes it possible to study modifying genes as well as genotype-phenotype correlations. However, this genetic information in its turn poses problems of interpretation and of control of the resulting data. The use of genetics in dermatology for the purposes of diagnosis or research requires a consultation to provide patients with information regarding the genetic tests involved and the potential consequences thereof for them and their families. Furthermore, with pangenomic approaches there is a higher probability of fortuitous discovery of abnormalities such as variants associated with risks predisposing to cancer or neurodegenerative disease. Collaboration between dermatologists and geneticists enables optimisation of patient management in terms of diagnosis and genetic counselling in the event of such rare diseases. Therapeutic applications are beginning to be developed. The scope of therapeutic application includes gene therapy, replacement therapy (enzyme therapy) and targeted therapy.

MC1R, eumelanin and pheomelanin: their role in determining the susceptibility to skin cancer

Skin pigmentation is due to the accumulation of two types of melanin granules in the keratinocytes. Besides being the most potent blocker of ultraviolet radiation, the role of melanin in photoprotection is complex. This is because one type of melanin called eumelanin is UV absorbent, whereas the other, pheomelanin, is photounstable and may even promote carcinogenesis. Skin hyperpigmentation may be caused by stress or exposure to sunlight, which stimulates the release of α-melanocyte stimulating hormone (α-MSH) from damaged keratinocytes. Melanocortin 1 receptor (MC1R) is a key signaling molecule on melanocytes that responds to α-MSH by inducing expression of enzymes responsible for eumelanin synthesis. Persons with red hair have mutations in the MC1R causing its inactivation; this leads to a paucity of eumelanin production and makes red-heads more susceptible to skin cancer. Apart from its effects on melanin production, the α-MSH/MC1R signaling is also a potent anti-inflammatory pathway and has been shown to promote antimelanoma immunity. This review will focus on the role of MC1R in terms of its regulation of melanogenesis and influence on the immune system with respect to skin cancer susceptibility.

Genetic parameters and genome-wide association study of hyperpigmentation of the visceral peritoneum in chickens

BACKGROUND

Hyperpigmentation of the visceral peritoneum (HVP) has recently garnered much attention in the poultry industry because of the possible risk to the health of affected animals and the damage it causes to the appearance of commercial chicken carcasses. However, the heritable characters of HVP remain unclear. The objective of this study was to investigate the genetic parameters of HVP by genome-wide association study (GWAS) in chickens.

RESULTS

HVP was found to be influenced by genetic factors, with a heritability score of 0.33. HVP had positive genetic correlations with growth and carcass traits, such as leg muscle weight (rg = 0.34), but had negative genetic correlations with immune traits, such as the antibody response to Newcastle disease virus (rg = -0.42). The GWAS for HVP using 39,833 single nucleotide polymorphisms indicated the genetic factors associated with HVP displayed an additive effect rather than a dominance effect. In addition, we determined that three genomic regions, involving the 50.5-54.0 Mb region of chicken (Gallus gallus) chromosome 1 (GGA1), the 58.5-60.5 Mb region of GGA1, and the 10.5-12.0 Mb region of GGA20, were strongly associated (P < 6.28 × 10-7) with HVP in chickens. Variants in these regions explained >50% of additive genetic variance for HVP. This study also confirmed that expression of BMP7, which codes for a bone morphogenetic protein and is located in one of the candidate regions, was significantly higher in the visceral peritoneum of Huiyang Beard chickens with HVP than in that of chickens without pigmentation (P < 0.05).

CONCLUSIONS

HVP is a quantitative trait with moderate heritability. Genomic variants resulting in HVP were identified on GGA1 and GGA20, and expression of the BMP7 gene appears to be upregulated in HVP-affected chickens. Findings from this study should be used as a basis for further functional validation of candidate genes involved in HVP.