Linkage and association scan for tanning ability in an isolated Mongolian population

Abstract

Tanning ability is important, because it represents the ability of the skin to protect itself against ultraviolet (UV) radiation. Here, we sought to determine genetic regions associated with tanning ability. Skin pigmentation was measured at the outer forearm and buttock areas to represent facultative and constitutive skin color, respectively. In our study population consisting of isolated Mongolian subjects, with common histories of environmental UV exposure during their nomadic life, facultative skin color adjusted by constitutive skin color was used to indicate tanning ability. Through linkage analysis and family-based association tests of 345 Mongolian subjects, we identified 2 potential linkage regions regulating tanning ability on 5q35.3 and 12q13.2, having 6 and 7 significant single nucleotide polymorphisms (SNPs), respectively. Those significant SNPs were located in or adjacent to potential candidate genes related to tanning ability: GRM6, ATF1, WNT1, and SILV/Pmel17.

Recent evolution of the human skin barrier

“…For example, Nan et al identified SNPs in TYR, MC1R, OCA2, IRF4, and MATP as correlating with tanning ability in European-ancestry populations; these genes are also known to play a role in constitutive pigmentation and/or hair color [37] . In contrast, Paik et al identified loci near GRM6 and ATF1 in a nomadic Mongolian population; these genes are involved in melanocyte signaling [38,39] . It has even been proposed that some populations primarily rely on the ability to tan, rather than dark constitutive pigment, to protect against harmful UV radiation [40] .…”

Inference of kinship coefficients from Korean SNP genotyping data

“…Here, we defined ‘kinship coefficient’ as the level of the relationship between two persons related by blood, such as parent to child, one sibling to another, grandparent to grandchild or uncle to nephew, first cousins, etc. Previous studies have been mainly focused on the analysis of inter-generational relationships and pedigree comparisons (8,10-12). However, few attempts have been made to determine the genetic distances of very closely related individuals based on SNP genotyping data.…”

The Evolution of Tanning Needs Its Day in the Sun

“…Like constitutive pigmentation, this tanning response is variable and there is no reason to assume it, like other types of phenotypic plasticity, is not also partially genetically regulated. Indeed, evidence of inter-population variation in tanning abilities as well as genes association with variation in tanning phenotypes in European (Nan et al 2009), Mongolian (Paik et al 2011), and Korean (Kwak et al 2015) populations have been identified. (It should again be noted that the majority of previous studies in this area have simply compared exposed to unexposed regions of the body as a proxy for tanning capacity.…”

“…Canonical pigmentation genes where variants are associated with differences in tanning capacity include WNT1 and SILV/Pmel17 (Paik et al 2011) in a Mongolian population and SLC45A2/MATP, IRF4, TYR, OCA2, HERC2, PPARGC1B, MITF and MC1R in broadly-collected European and European-American populations (Nan et al 2009;Shoag et al 2012;Zhang et al 2013). Additionally, these association studies identified variants in unexpected loci including GRM6 and ATF1 (Paik et al 2011) and LOC401937 (Nan et al 2009). Not previously considered a pigmentation candidate gene, variation in WWOX within Korean women is related to tanning capacity and regulates the activity of tyrosinase in human melanocytes (Kwak et al 2015).…”

“…The only study to consider facultative pigmentation in a large Central Asian sample determined tanning response by comparing exposed to unexposed regions of the body within an isolated Mongolian nomadic group (Paik et al 2011). This does not take into consideration amount of exposure or persistence of facultative pigmentation.…”