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An evolving hypothesis postulates that melanomas may arise through ‘nevus-associated’ and ‘chronic sun exposure’ pathways. We explored this hypothesis by examining associations between nevus-associated loci and melanoma risk across strata of body site and histological subtype. We genotyped 1028 invasive case patients and 1469 controls for variants in methylthioadenosine phosphorylase (MTAP), phospholipase A2, group VI (PLA2G6), and Interferon regulatory factor 4 (IRF4), and compared allelic frequencies globally and by anatomical site and histological subtype of melanoma. Odds-ratios (ORs) and 95% confidence intervals (CIs) were calculated using classical and multinomial logistic regression models. Among controls, MTAP rs10757257, PLA2G6 rs132985 and IRF4 rs12203592 were the variants most significantly associated with number of nevi. In adjusted models, a significant association was found between MTAP rs10757257 and overall melanoma risk (OR = 1.32, 95% CI = 1.14–1.53), with no evidence of heterogeneity across sites (Phomogeneity =.52). In contrast, MTAP rs10757257 was associated with superficial spreading/nodular melanoma (OR = 1.34, 95% CI = 1.15– 1.57), but not with lentigo maligna melanoma (OR = 0.79, 95% CI = 0.46–1.35) (Phomogeneity =.06), the subtype associated with chronic sun exposure. Melanoma was significantly inversely associated with rs12203592 in children (OR = 0.35, 95% CI = 0.16–0.77) and adolescents (OR = 0.61, 95% CI = 0.42–0.91), but not in adults (Phomogeneity =.0008). Our results suggest that the relationship between MTAP and melanoma is subtype-specific, and that the association between IRF4 and melanoma is more evident for cases with a younger age at onset. These findings lend some support to the ‘divergent pathways’ hypothesis and may provide at least one candidate gene underlying this model. Further studies are warranted to confirm these findings and improve our understanding of these relationships.

We have previously described the role of red hair (melanocortin-1 receptor, MC1R) and blue eye (oculocutaneous albinism type II, OCA2) gene polymorphisms in modulating the risk of cutaneous malignant melanoma (CMM) in a highly sun-exposed population of European descent. A number of recent studies, including genome-wide association studies, have identified numerous polymorphisms controlling human hair, eye, and skin color. In this paper, we test a selected set of polymorphisms in pigmentation loci (ASIP (Agouti signalling protein, nonagouti homolog (mouse) gene), TYR (tyrosinase), TYRP1 (tyrosinase-related protein 1), MC1R, OCA2, IRF4 (interferon regulatory factor 4), SLC24A4 (solute carrier family 24, member 4), and SLC45A2 (solute carrier family 45, member 2)) for association with CMM risk in a large Australian population-based case–control study. Variants in IRF4 and SLC24A4, despite being strongly associated with pigmentation in our sample, did not modify CMM risk, but the other six did. Three single nucleotide polymorphisms (rs28777, rs35391, and rs16891982) in the MATP gene (SLC45A2) exhibited the strongest crude association with risk, but this was attenuated to approximately the same effect size as that of a MC1R red hair color allele by controlling for ancestry of cases and controls. We also detected significant epistatic interactions between SLC45A2 and OCA2 alleles, and MC1R and ASIP alleles. Overall, these measured variants account for 12% of the familial risk of CMM in our population.

Krina Zondervan and colleagues report a genome-wide association study for endometriosis. The authors identify a susceptibility locus on chromosome 7p15. Endometriosis is a common gynecological disease associated with pelvic pain and subfertility. We conducted a genome-wide association study (GWAS) in 3,194 individuals with surgically confirmed endometriosis (cases) and 7,060 controls from Australia and the UK. Polygenic predictive modeling showed significantly increased genetic loading among 1,364 cases with moderate to severe endometriosis. The strongest association signal was on 7p15.2 (rs12700667) for 'all' endometriosis ( P = 2.6 × 10 −7 , odds ratio (OR) = 1.22, 95% CI 1.13–1.32) and for moderate to severe disease ( P = 1.5 × 10 −9 , OR = 1.38, 95% CI 1.24–1.53). We replicated rs12700667 in an independent cohort from the United States of 2,392 self-reported, surgically confirmed endometriosis cases and 2,271 controls ( P = 1.2 × 10 −3 , OR = 1.17, 95% CI 1.06–1.28), resulting in a genome-wide significant P value of 1.4 × 10 −9 (OR = 1.20, 95% CI 1.13–1.27) for 'all' endometriosis in our combined datasets of 5,586 cases and 9,331 controls. rs12700667 is located in an intergenic region upstream of the plausible candidate genes NFE2L3 and HOXA10.

Timothy Spector, Mario Falchi and colleagues report a genome-wide association study for development of cutaneous nevi, the strongest known risk factor for cutaneous melanoma. They report two loci associated with nevus count, and show these loci are also associated with susceptibility to melanoma. A high melanocytic nevi count is the strongest known risk factor for cutaneous melanoma. We conducted a genome-wide association study for nevus count using 297,108 SNPs in 1,524 twins, with validation in an independent cohort of 4,107 individuals. We identified strongly associated variants in MTAP , a gene adjacent to the familial melanoma susceptibility locus CDKN2A on 9p21 (rs4636294, combined P = 3.4 × 10 −15 ), as well as in PLA2G6 on 22q13.1 (rs2284063, combined P = 3.4 × 10 −8 ). In addition, variants in these two loci showed association with melanoma risk in 3,131 melanoma cases from two independent studies, including rs10757257 at 9p21, combined P = 3.4 × 10 −8 , OR = 1.23 (95% CI = 1.15–1.30) and rs132985 at 22q13.1, combined P = 2.6 × 10 −7 , OR = 1.23 (95% CI = 1.15–1.30). This provides the first report of common variants associated to nevus number and demonstrates association of these variants with melanoma susceptibility.

Genetic studies of pigmentation have benefited from spectrophotometric measures of light–dark hair color. Here we use one of those measures, absorbance at 650nm, to look for chromosomal regions that harbor genes affecting hair pigmentation. At 7p15.1, marker D7S1808 was suggestive of linkage to light–dark hair color (LOD≈2.99). Marker D1S235 at 1q42.3 was suggestive of linkage to hair color (light–dark or blonde-black continuum) (LOD≈2.14). However, the most consistent linkage peak was over the gene oculocutaneous albinism type II (OCA2) on chromosome 15. Linkage analysis of both spectrophotometrically quantified and ordered ratings of hair color had LOD scores about 1.2, significant because of the almost perfect concordance. A quantitative transmission disequilibrium test between light–dark hair color and 58 single nucleotide polymorphisms in OCA2 showed that the SNPs rs4778138 (also called rs11855019) and rs1375164 were associated with significantly darker hair color (P≈3 × 10−4 and P≈0.03 after correction for multiple testing, respectively). These two SNPs explain 1.54 and 0.85% of variation in the A650t index, respectively.

Background Severe malaria (SM) syndromes caused by Plasmodium falciparum infection result in major morbidity and mortality each year. However, only a fraction of P. falciparum infections develop into SM, implicating host genetic factors as important determinants of disease outcome. Previous studies indicate that tumour necrosis factor (TNF) and lymphotoxin alpha (LTα) may be important for the development of cerebral malaria (CM) and other SM syndromes. Methods An extensive analysis was conducted of single nucleotide polymorphisms (SNPs) in the TNF, LTA and LTB genes in highland Papuan children and adults, a population historically unexposed to malaria that has migrated to a malaria endemic region. Generated P -values for SNPs spanning the LTA/TNF/LTB locus were corrected for multiple testing of all the SNPs and haplotype blocks within the region tested through 10,000 permutations. A global P-value of < 0.05 was considered statistically significant. Results No associations between SNPs in the TNF/LTA/LTB locus and susceptibility to SM in highland Papuan children and adults were found. Conclusions These results support the notion that unique selective pressure on the TNF/LTA/LTB locus in different populations has influenced the contribution of the gene products from this region to SM susceptibility.

GWAS have identified >200 risk loci for Inflammatory Bowel Disease (IBD). The majority of disease associations are known to be driven by regulatory variants. To identify the putative causative genes that are perturbed by these variants, we generate a large transcriptome data set (nine disease-relevant cell types) and identify 23,650 cis -eQTL. We show that these are determined by ∼9720 regulatory modules, of which ∼3000 operate in multiple tissues and ∼970 on multiple genes. We identify regulatory modules that drive the disease association for 63 of the 200 risk loci, and show that these are enriched in multigenic modules. Based on these analyses, we resequence 45 of the corresponding 100 candidate genes in 6600 Crohn disease (CD) cases and 5500 controls, and show with burden tests that they include likely causative genes. Our analyses indicate that ≥10-fold larger sample sizes will be required to demonstrate the causality of individual genes using this approach. Most of the more than 200 known genetic risk loci for inflammatory bowel disease (IBD) reside in regulatory regions. Here, the authors provide eQTL datasets for six circulating immune cell types and ileal, colonic and rectal biopsies to map regulatory modules and identify potential causative genes for IBD.

John Rioux and colleagues report results of a large genome-wide association meta-analysis and follow-up study of ulcerative colitis. They identify 29 new risk loci for this inflammatory disease and show that many risk loci are shared between ulcerative colitis and Crohn's disease. Genome-wide association studies and candidate gene studies in ulcerative colitis have identified 18 susceptibility loci. We conducted a meta-analysis of six ulcerative colitis genome-wide association study datasets, comprising 6,687 cases and 19,718 controls, and followed up the top association signals in 9,628 cases and 12,917 controls. We identified 29 additional risk loci ( P < 5 × 10 −8 ), increasing the number of ulcerative colitis–associated loci to 47. After annotating associated regions using GRAIL, expression quantitative trait loci data and correlations with non-synonymous SNPs, we identified many candidate genes that provide potentially important insights into disease pathogenesis, including IL1R2 , IL8RA-IL8RB , IL7R , IL12B , DAP , PRDM1 , JAK2 , IRF5 , GNA12 and LSP1 . The total number of confirmed inflammatory bowel disease risk loci is now 99, including a minimum of 28 shared association signals between Crohn's disease and ulcerative colitis.

Endometriosis is a common gynecological disease associated with pelvic pain and subfertility. We conducted a genome-wide association study (GWAS) in 3,194 individuals with surgically confirmed endometriosis (cases) and 7,060 controls from Australia and the UK. Polygenic predictive modeling showed significantly increased genetic loading among 1,364 cases with moderate to severe endometriosis. The strongest association signal was on 7p15.2 (rs12700667) for 'all' endometriosis (P = 2.6 x [10.sup.-7] , odds ratio (OR) = 1.22, 95% CI 1.13-1.32) and for moderate to severe disease (P = 1.5 x [10.sup.-9], OR = 1.38, 95% CI 1.24-1.53). We replicated rs12700667 in an independent cohort from the United States of 2,392 self-reported, surgically confirmed endometriosis cases and 2,271 controls (P = 1.2 x [10.sup.-3], OR = 1.17, 95% CI 1.06-1.28), resulting in a genome-wide significant P value of 1.4 x [10.sup.-9] (OR = 1.20, 95% CI 1.13-1.27) for 'all' endometriosis in our combined datasets of 5,586 cases and 9,331 controls. rs12700667 is located in an intergenic region upstream of the plausible candidate genes NFE2L3 and HOXA10.

An evolving hypothesis postulates that melanomas may arise through “naevus-associated” and “chronic sun exposure” pathways. We explored this hypothesis by examining associations between naevus-associated loci and melanoma risk across strata of body site and histological subtype. We genotyped 1028 invasive case patients and 1469 controls for variants in MTAP, PLA2G6, and IRF4, and compared allelic frequencies globally and by anatomical site and histological subtype of melanoma. Odds-ratios (ORs) and 95% confidence intervals (CIs) were calculated using classical and multinomial logistic regression models. Among controls, MTAP rs10757257, PLA2G6 rs132985 and IRF4 rs12203592 were the variants most significantly associated with number of naevi. In adjusted models, a significant association was found between MTAP rs10757257 and overall melanoma risk (OR=1.32, 95% CI=1.14–1.53), with no evidence of heterogeneity across sites (Phomogeneity=0.52). In contrast, MTAP rs10757257 was associated with superficial spreading/nodular melanoma (OR=1.34, 95% CI=1.15–1.57), but not with lentigo maligna melanoma (OR=0.79, 95% CI=0.46–1.35) (Phomogeneity=0.06), the subtype associated with chronic sun exposure. Melanoma was significantly inversely associated with rs12203592 in children (OR=0.35, 95% CI=0.16–0.77) and adolescents (OR=0.61, 95% CI=0.42–0.91), but not in adults (Phomogeneity=0.0008). Our results suggest that the relationship between MTAP and melanoma is subtype-specific, and that the association between IRF4 and melanoma is more evident for cases with a younger age at onset. These findings lend some support to the “divergent pathways” hypothesis and may provide at least one candidate gene underlying this model. Further studies are warranted to confirm these findings and improve our understanding of these relationships.