An X chromosome-wide association analysis identifies variants in GPR174 as a risk factor for Graves' disease.

BACKGROUND: Graves' disease is a female preponderant autoimmune illness and the contribution of the X chromosome to its risk has long been appreciated. However, no X-linked susceptibility loci have been indentified from recent genome-wide association studies (GWAS). METHODS: We re-examined the X chromosome data from our recent GWAS for Graves' disease by including males that were previously excluded from the X chromosome analyses. The data were analysed using logistic regression analysis including sex as a covariate, and an additive method assuming X chromosome inactivation, implemented in snpMatrix. RESULTS: A cluster of single nucleotide polymorphism (SNPs) at Xq21.1 was found showing association with genome-wide significance, among which rs3827440 was a non-synonymous SNP of GPR174 (P(logistic regression)= 9.52×10(-8); P(snpMatrix)=4.60×10(-9); OR=1.76, 95% CI 1.45 to 2.13). The association was reproduced in an independent sample collection set including 4564 Graves' disease cases and 3968 sex matched controls (combined P(logistic regression)=5.53×10(-21); combined P(snpMatrix)=4.26×10(-22); OR=1.69, 95% CI 1.53 to 1.86). Notably, GPR174 was widely expressed in immune related tissues and rs3827440 genotypes were associated with distinct mRNA levels (p=0.002). GPR174 did not show sex biased gene expression in our expression analysis. Resequencing study suggested the contribution of some rare variants in the GPR174 gene region to disease risk with a collapsing p value of 1.16×10(-3). CONCLUSIONS: The finding of an X-linked risk locus for Graves' disease expands our understanding of the role of the X chromosome in disease susceptibility.

Y-chromosome distributions among populations in Northwest China identify significant contribution from Central Asian pastoralists and lesser influence of western Eurasians.

Northwest China is closely adjacent to Central Asia, an intermediate region of the Eurasian continent. Moreover, the Silk Road through the northwest of China once had a vital role in the east-west intercommunications. Nevertheless, little has been known about the genetic makeup of populations in this region. We collected 503 male samples from 14 ethnic groups in the northwest of China, and surveyed 29 Y-chromosomal biallelic markers and 8 short tandem repeats (STRs) loci to reconstruct the paternal architecture. Our results illustrated obvious genetic difference among these ethnic groups, and in general their genetic background is more similar with Central Asians than with East Asians. The ancestors of present northwestern populations were the admixture of early East Asians peopling northwestward and later Central Asians immigrating eastward. This population mixture was dated to occur within the past 10 000 years. The J2-M172 lineages likely entered China during the eastward migration of Central Asians. The influence from West Eurasia through gene flows on the extant ethnic groups in Northwest China was relatively weak.

Winter temperature and UV are tightly linked to genetic changes in the p53 tumor suppressor pathway in Eastern Asia.

The tumor suppressor p53 is a master sensor of stress. Two human-specific polymorphisms, p53 codon 72 and MDM2 SNP309, influence the activities of p53. There is a tight association between cold winter temperature and p53 Arg72 and between low UV intensity and MDM2 SNP309 G/G in a cohort of 4029 individuals across Eastern Asia that suggests causative selection. Moreover, the two polymorphisms are not coselected. Haplotype-based selection analysis further suggests that this is a striking example of two functional polymorphisms being strongly selected for in human populations in response to environmental stresses.