Search for genetic loci involved in the constitution and skin type of a Japanese women using a genome-wide association study

Comparisons between wrinkles and photo-ageing detected and self-reported by the participant or identified by trained assessors reveal insights from Chinese individuals in the Singapore/Malaysia Cross-sectional Genetics Epidemiology Study (SMCGES) cohort

BACKGROUND

Changes develop on the facial skin as a person ages. Other than chronological time, it has been discovered that gender, ethnicity, air pollution, smoking, nutrition, and sun exposure are notable risk factors that influence the development of skin ageing phenotypes such as wrinkles and photo-ageing. These risk factors can be quantified through epidemiological collection methods. We previously studied wrinkles and photo-ageing in detail using photo-numeric scales. The analysis was performed on the ethnic Chinese skin by three trained assessors. Recent studies have shown that it is possible to use self-reported data to identify skin-related changes including skin colour and skin cancer. In order to investigate the association between risk factors and skin ageing phenotypic outcomes in large-scale epidemiological studies, it would be useful to evaluate whether it is also possible for participants to self-report signs of ageing on their skin.

AIM

We have previously identified several validated photo-numeric scales for wrinkling and photo-ageing to use on ethnic Chinese skin. Using these scales, our trained assessors grade wrinkling and photo-ageing with moderately high inter-assessor concordance and agreement. The main objective of this study involves letting participants grade self-reported wrinkling and photo-ageing using these same scales. We aim to compare the concordance and agreement between signs of skin ageing by the participant and signs of ageing identified by our assessors.

METHOD

Three trained assessors studied facial photo-ageing on 1081 ethnic Chinese young adults from the Singapore/Malaysia Cross-sectional Genetics Epidemiology Study (SMCGES) cohort. Self-reported facial photo-ageing data by the same 1081 participants were also collated and the two sets of data are compared.

RESULTS

Here, we found that self-reported signs of photo-ageing are concordant with photo-ageing detected by our assessors. This finding is consistent whether photo-ageing is evaluated through studying wrinkle variations (Spearman's rank correlation (ρ) value: 0.246-0.329) or through studying dyspigmentation patterns (Spearman's rank correlation (ρ) value 0.203-0.278). When studying individual wrinkles, both participants and assessors often detect the presence of the same wrinkle (Spearman's rank correlation (ρ) value 0.249-0.366). A weak-to-fair level of agreement between both participants and assessors (Cohen's kappa (κ) values: 0.041-0.233) persists and is statistically significant after accounting for agreements due to chance. Both the participant and the assessor are largely consistent in evaluating the extent of photo-ageing (area under curve (AUC) values 0.689-0.769) and in discerning between the presence or absence of a given facial wrinkle (area under curve (AUC) values 0.601-0.856).

CONCLUSION

When we analyse the overall appearance of the face, our results show that signs of photo-ageing identified by the participant are concordant with signs of photo-ageing identified by our assessors. When we focused our analysis on specific areas of the face, we found that participants were more likely to identify and self-report the same wrinkles that our assessors have also detected. Here, we found that self-reported signs of skin ageing provide a satisfactory approximation to the signs of skin ageing identified by our assessors. The ability to use self-reported signs of skin ageing should also be evaluated on scales beyond the ones discussed in this study. Currently, there are not as many photo-numeric scales for quantifying dyspigmentation patterns as there are for quantifying wrinkle variations. As Chinese skin is known to become dyspigmented more easily with age, more photo-numeric scales need to be developed and properly validated.

Comparisons between eyebags, droopy eyelids, and eyebrow positioning identified by photo-numeric scales or identified by written descriptive scales: Insights from the Singapore/Malaysia cross-sectional genetics epidemiology study (SMCGES) cohort

BACKGROUND

We evaluate skin sagging phenotypes (eyebags, droopy eyelids, low eyebrow positioning) using written descriptive scales and photo-numeric scales. We also study how anti-ageing interventions and digital screen time influence skin sagging.

AIM

We compare the two phenotype assessment methods with each other.

METHOD

Skin sagging and personal lifestyle data obtained from 2885 ethnic Chinese young adults from the Singapore/Malaysia cross-sectional genetics epidemiology study (SMCGES) cohort were collated and compared.

RESULTS

Significant correlations (p-value < 0.001) between written descriptive scales and photo-numeric scales were observed for eyebags (0.25) and eyebrow positioning (0.08). Significant correlations (p-value < 0.001) were observed after combining both scales for eyebags (0.38), droopy eyelids (0.30), and eyebrow positioning (0.30). Anti-ageing interventions are associated with delayed progression of eyebags from 18-45 years old, droopy eyelids from 31-45 years old, and eyebrow positioning from 35-40 years old. Significantly lower (p-value < 0.02) eyebrow positioning is associated with both <1 and 1-3 h of screen time stratified by age.

CONCLUSION

Written descriptive scales provide comparable results to photo-numeric scales. However, validating and adapting photo-numeric scales for different populations identifies phenotypes better. Anti-ageing interventions are beneficial at different age ranges. Screen time is associated with skin sagging in young (18-30 years old) participants.

Genome-wide association studies in the Japanese population identified genetic loci and target gene associated with epidermal turnover

The epidermis is an essential organ for life by retaining water and as a protective barrier. The epidermis is maintained through metabolism, in which basal cells produced from epidermal stem cells differentiate into spinous cells, granular cells and corneocytes, and are finally shed from the epidermal surface. This is epidermal turnover, and with aging, there is a decline in epidermis function. Other factors that may affect epidermal turnover include ultraviolet damage and genetic factors. These genetic factors are of particular interest as little is known. Although recent skin-focused genome-wide association studies (GWAS) have been conducted, the genetic regions associated with epidermal turnover are almost uninvestigated. Therefore, we conducted a GWAS on epidermal turnover in the Japanese population, using the corneocyte area, which correlates to the rate of epidermal turnover, as an indicator. As a result, rs2278431 (p = 1.29 × 10-7 ) in 19q13.2 was associated with corneocyte size. Furthermore, eQTL analysis suggested that rs2278431 was related to the SPINT2 gene. In addition, SPINT2 knockdown studies using epidermal keratinocytes revealed that SPINT2 is involved in keratinocyte proliferation and in corneocyte size regulation in reconstructed epidermis. These results suggest that rs2278431 is involved in the expression of SPINT2 and affects epidermal turnover.

Analysis of the effect of daily stress on the skin and search for genetic loci involved in the perceived stress of an individual

Background

Stress may have various effects on our bodies. In particular, the skin may be readily influenced by stress. In addition, there are individual differences in the way we feel stress, suggesting the involvement of genetic factors in such individual differences.

Objectives

In this study, we analysed the influence of stress on skin condition and ageing involving Japanese females, and investigated single nucleotide polymorphisms (SNPs) that influence perceived stress of an individual.

Methods

We collected genotype data from 1200 Japanese females. At the same time, a questionnaire was conducted on the degree of stress that each subject feels on a daily basis and the current skin condition. We analysed the effects of stress on skin condition and searched for SNPs related to individual stress susceptibility by genome‐wide association studies.

Results

Our data suggested that stress influences skin condition and ageing, as previously reported. And, we found rs74548608 as a SNP that affects perceived stress of an individual. This SNP is located on the upstream of Patched‐1, which is a gene that functions as a sonic hedgehog receptor.

Conclusions

Our study has identified new genetic factors for perceived stress of an individual in the Japanese female. The SNP found in this study may be a candidate factor important for understanding the perceived stress of an individual of Japanese.

A systematic review of skin ageing genes: gene pleiotropy and genes on the chromosomal band 16q24.3 may drive skin ageing

Skin ageing is the result of intrinsic genetic and extrinsic lifestyle factors. However, there is no consensus on skin ageing phenotypes and ways to quantify them. In this systematic review, we first carefully identified 56 skin ageing phenotypes from multiple literature sources and sought the best photo-numeric grading scales to evaluate them. Next, we conducted a systematic review on all 44 Genome-wide Association Studies (GWAS) on skin ageing published to date and identified genetic risk factors (2349 SNPs and 366 genes) associated with skin ageing. We identified 19 promising SNPs found to be significantly (p-Value < 1E-05) associated with skin ageing phenotypes in two or more independent studies. Here we show, using enrichment analyses strategies and gene expression data, that (1) pleiotropy is a recurring theme among skin ageing genes, (2) SNPs associated with skin ageing phenotypes are mostly located in a small handful of 44 pleiotropic and hub genes (mostly on the chromosome band 16q24.3) and 32 skin colour genes. Since numerous genes on the chromosome band 16q24.3 and skin colour genes show pleiotropy, we propose that (1) genes traditionally identified to contribute to skin colour have more than just skin pigmentation roles, and (2) further progress towards understand the development of skin pigmentation requires understanding the contributions of genes on the chromosomal band 16q24.3. We anticipate our systematic review to serve as a hub to locate primary literature sources pertaining to the genetics of skin ageing and to be a starting point for more sophisticated work examining pleiotropic genes, hub genes, and skin ageing phenotypes.

Genome-wide association studies in Japanese women identified genetic loci associated with wrinkles and sagging

Wrinkles and sagging are caused by various factors, such as ultraviolet rays; however, recent findings demonstrated that some individuals are genetically predisposed to these phenotypes of skin aging. The contribution of single nucleotide polymorphisms (SNPs) to the development of wrinkles and sagging has been demonstrated in genome-wide association studies (GWAS). However, these findings were mainly obtained from European and Chinese populations. Limited information is currently available on the involvement of SNPs in the development of wrinkles and sagging in a Japanese population. Therefore, we herein performed GWAS on wrinkles at the outer corners of the eyes and nasolabial folds in 1041 Japanese women. The results obtained revealed that 5 SNPs (19p13.2: rs2303098 (p = 3.39×10^-8 ), rs56391955 (p = 3.39×10^-8 ), rs67560822 (p = 3.50×10^-8 ), rs889126 (p = 3.78×10^-8 ), rs57490083 (p = 3.99×10^-8 )) located within the COL5A3 gene associated with wrinkles at the outer corners of the eyes. Regarding nasolabial folds, 8q24.11 (rs4876369; p = 1.05×10^-7 , rs6980503; p = 1.25×10^-7 , rs61027543; p = 1.25×10^-7 , rs16889363; p = 1.38×10^-7 ) was suggested to be associated with RAD21 gene expression. These SNPs have not been reported in other populations, and were first found in Japanese women population. These SNPs may be used as markers to examine the genetic predisposition of individuals to wrinkles and sagging.

Genome-wide association study for meat tenderness in beef cattle identifies patterns of the genetic contribution in different post-mortem stages

The beef tenderization process during the post-mortem period is one of the most important sensorial attributes and it is well-established. The aim of this study was to identify the genetic contribution pattern to meat tenderness at 7-(LMD7), 14-(LMD14), and 21-(LMD21) days post-mortem. The heritabilities for LMD7 (0.194), LMD14 (0.142) and LMD21 (0.048) are well established in the population evaluated here. However, its genetic contribution in terms of genomic candidate regions is still poorly understood. Tenderness was measured in the Longissiums thoracis using Warner-Bratzler shear force in the three post-mortem periods. A total of 4323 crossbred beef cattle were phenotyped and genotyped using the Illumina BovineSNP50K. The percentage of the total genetic variance was estimated using the weighted single-step genomic best linear unbiased prediction method. The main candidate windows for LMD7 were associated with proteolysis of myofibrillar structures and the weakening endomysium and perimysium. Candidate windows for LMD14 and LMD21 were mapped in bovine QTLs for body composition, height and growth. Results presented herein highlight, the largest contribution of proteolysis related processes before 14-days post-mortem and body composition characteristics in later stages for meat tenderness.