Cited by 317melanin and skin pigmentationGenetic Associations and EpidemiologyGenetic Mapping and Diversity in Plants and Animals

The DOI matches its Crossref record; 57 of the 57 references it cites were found in a registry or an index; none of the 37 sources its claims cite is checked for support yet.

A Genomewide Association Study of Skin Pigmentation in a South Asian Population

Open access

Abstract

We have conducted a multistage genomewide association study, using 1,620,742 single-nucleotide polymorphisms to systematically investigate the genetic factors influencing intrinsic skin pigmentation in a population of South Asian descent. Polymorphisms in three genes--SLC24A5, TYR, and SLC45A2--yielded highly significant replicated associations with skin-reflectance measurements, an indirect measure of melanin content in the skin. The associations detected in these three genes, in an additive manner, collectively account for a large fraction of the natural variation of skin pigmentation in a South Asian population. Our study is the first to interrogate polymorphisms across the genome, to find genetic determinants of the natural variation of skin pigmentation within a human population.

Overview

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TL;DR

This multistage genomewide association study measured 1,620,742 SNPs and identified replicated associations between skin reflectance and polymorphisms in SLC24A5, TYR, and SLC45A2 in a South Asian population. The three associated nonsynonymous SNPs act additively and collectively account for a large fraction of natural skin-pigmentation variation.

Key findings

  • In cohort 1, 42 SNPs reached genomewide significance (Bonferroni threshold P = 3.3 × 10⁻⁸); 39 of 42 were in a single 2.4-Mb region of 15q21.1-21.2. The strongest SNP, rs1834640, had P = 1.0 × 10⁻⁵⁰ and a 45% allele-frequency difference between high- and low-reflectance groups, located 21 kb from SLC24A5.
  • In the independent replication cohort 2, 32 (76%) of 42 SNPs had P < .05. rs1834640 replicated with P = 3.28 × 10⁻¹⁵ and a 36% allele-frequency difference. Dense genotyping of 408 SNPs in the chromosome 15 region identified rs1426654 (SLC24A5 p.A111T) as most significant (P = 1.06 × 10⁻¹⁸; 39% allele-frequency difference; R² = 0.93 with rs1834640), and conditional analysis supported a single primary association.
  • Three nonsynonymous SNPs showed genomewide significance: rs1426654 in SLC24A5, rs16891982 in SLC45A2, and rs1042602 in TYR. Their squared correlations with the dichotomous skin-reflectance trait were R² = 0.33, 0.036, and 0.025, respectively. No significant dominance effects (P = .58, .20, .91) or pairwise interactions (P = .77, .38, .12) were found, consistent with an additive model.
  • Candidate-gene results included OCA2 rs1037208 (joint cohort P = 5.6 × 10⁻⁵) and MC1R rs2228479 (P = 6.8 × 10⁻⁴); ASIP rs6058017 showed no allele-frequency difference between reflectance groups (|Dp| = 0.008), and individual genotyping of it was unsuccessful.

Methods

  • South Asian volunteers were recruited at 150 UK sites; inclusion required parents or all four grandparents born in India, Pakistan, Bangladesh, or Sri Lanka. Skin pigmentation was measured by reflectance spectroscopy (Minolta chromameter L* value); low-reflectance (L) was maxL* ≤56 and high-reflectance (H) was maxL* ≥63. Cohort 1 recruited 395 L and 383 H individuals; cohort 2 recruited 119 L and 116 H individuals.
  • Pooled genotyping estimated allele-frequency differences for 1,620,742 SNPs using DNA pools from 286 L and 285 H cohort 1 individuals. The top 30,000 SNPs were individually genotyped in 737 cohort 1 individuals (363 L, 374 H) after quality control; 42 genomewide-significant SNPs were then genotyped in cohort 2, and 408 SNPs were genotyped across the chromosome 15 region.
  • Association tests used logistic regression with sex and the first five principal components from 292 genomic-control SNPs as covariates, with likelihood-ratio tests. The genomewide Bonferroni threshold was 0.05/1,502,205 = 3.3 × 10⁻⁸. Conditional, dominance, and pairwise-interaction models were also tested.

Limitations

  • Stated by the authors: the strict Bonferroni correction across 1,502,205 tests combined with the pooled genotyping design greatly reduces power to detect real SNP associations with small effects, so loci other than TYR, SLC45A2, and SLC24A5 may affect skin-pigmentation variation in South Asians.
  • Stated by the authors: because the study used the tails of the skin-reflectance distribution, it cannot directly determine the overall fraction of trait variance in the population accounted for by the associated SNPs; the authors also note they cannot completely exclude multiple independent associations in the chromosome 15 region.
  • Evident from the text: the sample is a UK South Asian population, and the authors note that the three implicated SNPs are essentially monomorphic in African and East Asian populations, so their contribution to pigmentation variation in other global populations is likely to differ. The ASIP SNP could not be individually genotyped, and the mixed-sex pooled design would not have power to detect a female-specific association.

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Integrity signals

Registry

Crossref · 10.1086/522235

Cites

57 of 57 references verified0 citation errors · 0 not checkable

Statistics

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  • It may state two separate claims as one. 35
  • The quote only partly states this claim. 2
  • Probably not a substantial claim. 16
45 of 45
  • The paper relies on this without support.

    This study is the first to interrogate polymorphisms across the genome to find genetic determinants of natural variation of skin pigmentation within a human population.

    “Our study is the first to interrogate polymorphisms across the genome, to find genetic determinants of the natural variation of skin pigmentation within a human population.”
  • The paper relies on this without support.

    The 98 randomly selected individuals used to estimate the maxL* distribution are representative of the South Asian population in the United Kingdom.

    “Skin chromameter measurements for 98 randomly selected individuals of South Asian ancestry living in the United Kingdom were used to estimate the distribution of maxL* within the South Asian population (fig.1).”
  • The paper relies on this without support.

    The South Asian population is highly genetically diverse and ancestry is highly confounded with skin pigmentation.

    “This population is known to be highly genetically diverse, and, because ancestry is known to be highly confounded with skin pigmentation, the treatment of population structure was crucial to our association analysis.”
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Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • SLC24A5 is called SLC24A4

    Minor

    The discussion identifies the three pigmentation loci as including SLC24A4, whereas its other statement of the three identified loci names SLC24A5.

  • Chromosome 15 assay interval is mislabeled as 2.4 Mb

    Minor

    The stated cohort 2 assay interval spans 2,946,727 bases, or about 2.95 Mb, rather than the 2.4 Mb stated in the table title. The 2.4-Mb description fits the narrower cohort 1 association interval, not the extended cohort 2 interval.

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Metadata

Authors
Stokowski, R. P., Pant, P. V. K., Dadd, T., Fereday, A., Hinds, D. A., Jarman, C., Filsell, W., Ginger, R. S., Green, M. R., van der Ouderaa, F. J., & Cox, D. R.
Affiliations
  • Perlegen (United States) (US)
  • Unilever (United Kingdom) (GB)
Corresponding author
Stokowski, Renee P.
Venue
The American Journal of Human Genetics
Publisher
Elsevier BV
Published
2007-12
Volume
81
Issue
6
Pages
1119-1132
ISSN
0002-9297 (ISSN-L)
OpenAlex
W1982516085
Cited by
315
References
57
Citations by year
2026: 12 · 2025: 13 · 2024: 18 · 2023: 6 · 2022: 12 · 2021: 12 · 2020: 17 · 2019: 12 · 2018: 25 · 2017: 25 · 2016: 20 · 2015: 14 · 2014: 23 · 2013: 20 · 2012: 20
FWCI
7.15
Type
journal article
Language
en
Open access
Locations
  • The American Journal of Human Genetics (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › melanin and skin pigmentation
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Genetic Associations and Epidemiology
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Genetic Mapping and Diversity in Plants and Animals
Keywords
skin pigmentation, melanin content, skin reflectance, SLC24A5, TYR, SLC45A2, single nucleotide polymorphisms, South Asian populations, genetic variation
MeSH terms
Antigens, Neoplasm, Bangladesh, Gene Frequency, Humans, India, Melanins, Pakistan, Phenotype, Skin Physiological Phenomena, Skin Pigmentation, Sri Lanka, Genome, Human, Antiporters, Polymorphism, Single Nucleotide, Membrane Transport Proteins

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