Replication of endometriosis-associated single-nucleotide polymorphisms from genome-wide association studies in a Caucasian population

Rapid effects of valproic acid on the fetal brain transcriptome: implications for brain development and autism

There is an increased incidence of autism among the children of women who take the anti-epileptic, mood-stabilizing drug, valproic acid (VPA) during pregnancy; moreover, exposure to VPA in utero causes autistic-like symptoms in rodents and non-human primates. Analysis of RNA-seq data obtained from E12.5 fetal mouse brains 3 hours after VPA administration to the pregnant dam revealed that VPA rapidly and significantly increased or decreased the expression of approximately 7,300 genes. No significant sex differences in VPA-induced gene expression were observed. Expression of 399 autism risk genes was significantly altered by VPA as was expression of 258 genes that have been reported to modulate fetal brain development but are not otherwise linked to autism. Expression of genes associated with intracellular signaling pathways, neurogenesis, and excitation-inhibition balance as well as synaptogenesis, neuronal fate determination, axon and dendritic development, neuroinflammation, circadian rhythms, and epigenetic modulation of gene expression was dysregulated by VPA. Notably, at least 40 genes that are known to regulate embryonic neurogenesis were dysregulated by VPA. The goal of this study was to identify mouse genes that are: (a) significantly up- or downregulated by VPA in the fetal brain and (b) associated with autism and/or known to play a role in embryonic neurodevelopmental processes, perturbation of which has the potential to alter brain connectivity and, consequently behavior, in the adult. The genes meeting these criteria provide potential targets for future hypothesis-driven studies to elucidate the proximal causes of errors in brain connectivity underlying neurodevelopmental disorders such as autism.

Role of HOXA10 in pathologies of the endometrium

HOXA10 belongs to the homeobox gene family and is essential for uterine biogenesis, endometrial receptivity, embryo implantation, and stromal cell decidualization. Available evidence suggests that the expression of HOXA10 is dysregulated in different endometrial disorders like endometrial hyperplasia, endometrial cancer, adenomyosis, endometriosis, recurrent implantation failure, and unexplained infertility. The downregulation of HOXA10 occurs by genetic changes in the HOXA10 gene, methylation of the HOXA10 locus, or selected miRNAs. Endocrine disruptors and organic pollutants also cause the reduced expression of HOXA10 in these conditions. In vivo experiments in mouse models and in vitro studies in human cell lines demonstrate that downregulation of HOXA10 leads to endometrial epithelial cell proliferation, failure of stromal cell decidualization, altered expression of genes involved in cell cycle regulation, immunomodulation, and various signaling pathways. These disruptions are speculated to cause infertility associated with the disorders of the endometrium.

WNT4 (rs7521902 and rs16826658) polymorphism and its association with endometriosis - A systematic review and meta-analysis

IMPORTANCE

This systematic review supports the involvement of the WNT4 gene in the pathophysiology of endometriosis.

OBJECTIVE

To conduct a systematic review and meta-analysis on WNT4 rs7521902 and rs16826658 polymorphism associated with endometriosis based on multi-ethnic case-control studies.

DATA SOURCES

Comprehensive searching was performed using Medline, Embase, and Google Scholar.

STUDY SELECTION AND SYNTHESIS

Keywords used for searching using Boolean operators are endometriosis, WNT4, and polymorphism. This review followed PRISMA guidelines, and meta-analysis was conducted in STATA18.

MAIN OUTCOMES

WNT4 polymorphisms identified in this review were rs7521902, rs16826658, rs2235529, rs3820282, and rs12037376.

RESULTS

A total of 250 studies were identified through databases; 10 were eligible for this review, and eight were included in the meta-analysis. Two WNT4 polymorphisms (rs7521902 and rs16826658) were analysed in the meta-analysis. A lower risk of odds in having endometriosis was apparent in the CC genotype of rs7521092 polymorphism with a pooled OR of 0.86 (0.76, 0.99). Most articles were high-quality case-control studies and were at low risk of bias.

CONCLUSION

This study highlighted the association of WNT4 polymorphisms (rs7521092) and endometriosis across Latin America, Europe, and Asian populations.

RELEVANCE

Following the completion of the Human Genome Project, many genetic aspects of endometriosis were revealed, including the discovery of single nucleotide polymorphisms (SNPs). However, due to a lack of replications and conflicting results between studies, the conclusion of the endometriosis genetic pathway needed to be completed. This finding of WNT4 showed that its association with endometriosis was valid even in varied ethnicities, indicating a general genetic aspect of disease across populations. Nevertheless, further studies are needed to confirm this finding, including functional biological and longitudinal studies.

Genomics of Endometriosis: From Genome Wide Association Studies to Exome Sequencing

This review aims at better understanding the genetics of endometriosis. Endometriosis is a frequent feminine disease, affecting up to 10% of women, and characterized by pain and infertility. In the most accepted hypothesis, endometriosis is caused by the implantation of uterine tissue at ectopic abdominal places, originating from retrograde menses. Despite the obvious genetic complexity of the disease, analysis of sibs has allowed heritability estimation of endometriosis at ~50%. From 2010, large Genome Wide Association Studies (GWAS), aimed at identifying the genes and loci underlying this genetic determinism. Some of these loci were confirmed in other populations and replication studies, some new loci were also found through meta-analyses using pooled samples. For two loci on chromosomes 1 (near CCD42) and chromosome 9 (near CDKN2A), functional explanations of the SNP (Single Nucleotide Polymorphism) effects have been more thoroughly studied. While a handful of chromosome regions and genes have clearly been identified and statistically demonstrated as at-risk for the disease, only a small part of the heritability is explained (missing heritability). Some attempts of exome sequencing started to identify additional genes from families or populations, but are still scarce. The solution may reside inside a combined effort: increasing the size of the GWAS designs, better categorize the clinical forms of the disease before analyzing genome-wide polymorphisms, and generalizing exome sequencing ventures. We try here to provide a vision of what we have and what we should obtain to completely elucidate the genetics of this complex disease.

Systematic review of genome-wide association studies on susceptibility to endometriosis

Endometriosis is a complex and heterogeneous disease in which extrinsic and intrinsic factors, such as genetics, provide to the disease development. Genome-wide association (GWA) studies may be essential to recognize genetic variants associated with the endometriosis risk. However, in the current literature there are some conflicting results between these studies. The aim of the present study was to undertake a systematic review about endometriosis GWA studies, to describe the disease-associated genes and single nucleotide polymorphisms (SNPs) to try to understand the endometriosis etiopathogenesis, besides to discuss possible bias of conflicting results among these studies. This study is a systematic review of GWA studies in endometriosis published until December 31^th, 2019 by PubMed database, considering the following descriptors: endometriosis and ("polymorphism" or "SNP" or "genetic polymorphism" or "variants" or "locus") and ("GWA" or "Genome-wide" or "Genome wide" or "Genetic association study"). The included studies were analyzed with methodological rigor (STROBE and PRISMA) to enable better quality of case-control and meta-analysis studies, respectively. Of the 88 articles found, only 15 were eligible. All articles had appropriate quality evaluated by STROBE and PRISMA checklists (77% and 81%, respectively). Overall, 35,022 endometriosis cases and 181,760 controls were analyzed. The number of participants in each study was quite different (171 to 17,045 for the cases and 308 to 150,021 for the controls), with a predominance of European ethnicity. Most endometriosis cases (86%) were diagnosed by surgery, while selection of the control group was different among studies. About 47% performed only one stage (discovery stage) and 53% performed both the discovery and replication analyses. Eleven genes/SNPs were associated with endometriosis risk in more than one article (chromosome 1, 2, 6, 7, 9 and 12; WNT4, GREB1, FN1, IL1A, ETAA1, RND3, ID4, NFE2L3, CDKN2B-AS1 and VEZT). SNPs were localized in intergenic and intronic regions, their risk allele frequencies varied among the studies and their results were conflicting. In summary, WNT4 rs7521902, GREB1 rs13394619, FN1 rs1250248, IL1A rs6542095 and VEZT rs10859871 variants are highlighted due to high frequency and pathways and function that each gene influences in the development of endometriosis. However, the replication and validation of these variants in different populations are necessary for a better understanding of the endometriosis etiopathogenesis, in order to optimize the diagnosis and improve the efficiency of clinical treatment of the disease.

Genetic Characterization of Endometriosis Patients: Review of the Literature and a Prospective Cohort Study on a Mediterranean Population

The pathogenesis of endometriosis is unknown, but some evidence supports a genetic predisposition. The purpose of this study was to evaluate the recent literature on the genetic characterization of women affected by endometriosis and to evaluate the influence of polymorphisms of the wingless-type mammalian mouse tumour virus integration site family member 4 (WNT4), vezatin (VEZT), and follicle stimulating hormone beta polypeptide (FSHB) genes, already known to be involved in molecular mechanisms associated with the proliferation and development of endometriotic lesions in the Sardinian population. Materials and Methods: In order to provide a comprehensive and systematic tool for those approaching the genetics of endometriosis, the most cited review, observational, cohort and case-control studies that have evaluated the genetics of endometriosis in the last 20 years were collected. Moreover, 72 women were recruited for a molecular biology analysis of whole-blood samples—41 patients affected by symptomatic endometriosis and 31 controls. The molecular typing of three single nucleotide polymorphisms (SNPs) was evaluated in patients and controls: rs7521902, rs10859871 and rs11031006, mapped respectively in the WNT4, VEZT and FSHB genes. In this work, the frequency of alleles, genotypes and haplotypes of these SNPs in Sardinian women is described. Results: From the initial search, a total of 73 articles were chosen. An analysis of the literature showed that in endometriosis pathogenesis, the contribution of genetics has been well supported by many studies. The frequency of genotypes observed in the groups of the study population of 72 women was globally coherent with the law of the Hardy–Weinberg equilibrium. For the SNP rs11031006 (FSHB), the endometriosis group did not show an increase in genotypic or allelic frequency due to this polymorphism compared to the control group (p = 0.9999, odds ratio (OR) = 0.000, 95% confidence interval (CI), 0.000–15.000 and p = 0.731, OR = 1639, 95% CI, 0.39–683, respectively, for the heterozygous genotype and the polymorphic minor allele). For the SNP rs10859871 (VEZT), we found a significant difference in the frequency of the homozygous genotype in the control group compared to the affected women (p = 0.0111, OR = 0.0602, 95% CI, 0.005–0.501). For the SNP rs7521902 (WNT4), no increase in genotypic or allelic frequency between the two groups was shown (p = 0.3088, OR = 0.4133, 95% CI, 0.10–1.8 and p = 0.3297, OR = 2257, 95% CI, 0.55–914, respectively, for the heterozygous genotype and the polymorphic minor allele). Conclusion: An analysis of recent publications on the genetics of endometriosis showed a discrepancy in the results obtained in different populations. In the Sardinian population, the results obtained do not show a significant association between the investigated variants of the genes and a greater risk of developing endometriosis, although several other studies in the literature have shown the opposite. Anyway, the data underline the importance of evaluating genetic variants in different populations. In fact, in different ethnic groups, it is possible that specific risk alleles could act differently in the pathogenesis of the disease.

Association between Single Nucleotide Polymorphisms and Endometriosis in a Brazilian Population

OBJECTIVE

 To investigate the association between genetic polymorphisms in candidate genes or candidate regions and the development of endometriosis in Brazilian women.

METHODS

 A total of 30 women between 25 and 64 years old with a diagnosis of endometriosis participated in the present study, as well as 30 matched control women from the same age group, asymptomatic and without family history of the disease. The patients genotypic and allelic frequencies of polymorphisms in the GREB1 gene (rs13394619) and in the intergenic region at position 7p15.2 (rs12700667) were analyzed and compared.

RESULTS

 There was no significant difference in the frequency of genotypes for the A > G polymorphism (rs13394619) in the GREB1 gene between the two groups. However, the distribution frequencies of the genotypes for the A > G polymorphism (rs12700667) in an intergenic region on chromosome 7 were different for control patients and for patients with endometriosis, with higher frequency of the AG genotype compared to the GG between patients with the disease (odds ratio [OR] = 3.49; confidence interval [CI] = 1.47-8.26).

CONCLUSION

 The present study suggests that the polymorphism in the intergenic region of chromosome 7 is associated with the risk of developing endometriosis in a population of Brazilian women from Juiz de Fora.

The role of gene polymorphisms in endometriosis

Endometriosis is a benign gynecologic disorder, affecting up to 10% of women, characterized by the presence of functional endometrial tissue at ectopic positions generally within the peritoneum. It is a heritable condition influenced by multiple genetic and environmental factors, with an overall heritability estimated at approximately 50%. In this study, we investigated whether single nucleotide polymorphisms (SNPs) rs7521902, rs10859871 and rs11031006, mapping to WNT4, VEZT and FSHB genetic loci, respectively, are associated with risk for endometriosis in a Greek population. This study included 166 women with histologically confirmed endometriosis diagnosed through surgery and 150 normal controls. Genotyping of the rs7521902, rs10859871 and rs11031006 SNPs was performed with Taqman primer/probe sets. A significant association was detected with the AC genotype of rs7521902 (WNT4) in patients with stage III and IV disease only. Evidence for association with endometriosis was also found for the AC genotype of the rs10859871 of VEZT. Notably, a significant difference in the distribution of the AG genotype and the minor allele A of FSHB rs11031006 SNP was found between the endometriosis patients and controls. We found a genetic association between rs11031006 (FSHB) SNP and endometriosis. WNT4 and VEZT genes constitute the most consistently associated genes with endometriosis. In the present study, an association of rs7521902 (WNT4) and rs10859871 (VEZT) was confirmed in women with endometriosis at the genotypic but not the allelic level.

Research Priorities for Endometriosis

The 3rd International Consensus Workshop on Research Priorities in Endometriosis was held in São Paulo on May 4, 2014, following the 12th World Congress on Endometriosis. The workshop was attended by 60 participants from 19 countries and was divided into 5 main sessions covering pathogenesis/pathophysiology, symptoms, diagnosis/classification/prognosis, disease/symptom management, and research policy. This research priorities consensus statement builds on earlier efforts to develop research directions for endometriosis. Of the 56 research recommendations from the 2011 meeting in Montpellier, a total of 41 remained unchanged, 13 were updated, and 2 were deemed to be completed. Fifty-three new research recommendations were made at the 2014 meeting in Sao Paulo, which in addition to the 13 updated recommendations resulted in a total of 66 new recommendations for research. The research recommendations published herein, as well as those from the 2 previous papers from international consensus workshops, are an attempt to promote high-quality research in endometriosis by identifying and agreeing on key issues that require investigation. New areas included in the 2014 recommendations include infertility, patient stratification, and research in emerging nations, in addition to an increased focus on translational research. A revised and updated set of research priorities that builds on this document will be developed at the 13th World Congress on Endometriosis to be held on May 17-20, 2017, in Vancouver, British Columbia, Canada.

Association of Endometriosis-Associated Genetic Polymorphisms From Genome-Wide Association Studies With Ovarian Endometriosis in a Chinese Population

Endometriosis is a common multifactorial disease caused by an interaction between multiple gene loci and environment. Four genome-wide association studies (GWASs) of endometriosis have identified several single-nucleotide polymorphisms (SNPs) associated with endometriosis. However, results from independent replication studies with different populations are inconsistent. The present study aims to evaluate whether the GWAS-derived susceptibility loci are correlated with the risk of the development of ovarian endometriosis in North Chinese women. This case-control study comprised 580 patients with ovarian endometriosis and 606 matched control women. Three SNPs were selected for this association study including rs10965235 in CDKN2BAS, rs2235529 located in LINC00339- WNT4, and rs12700667 in an intergenic region on 7p15.2. The results show that the G/A genotype of rs12700667 can significantly increase the risk of developing ovarian endometriosis when compared with the G/G genotype (odds ratio [OR] = 1.57, 95% confidence interval [CI] = 1.23-2.00). Similarly, the carriers with A allele showed a higher risk of ovarian endometriosis than those with G allele (OR = 1.23, 95% CI = 1.12-1.68). The study suggests that the endometriosis-associated genetic polymorphisms (rs12700667) from GWAS be associated with the risk of developing ovarian endometriosis in North Chinese women.

High temperature requirement A1, transforming growth factor beta1, phosphoSmad2 and Ki67 in eutopic and ectopic endometrium of women with endometriosis

Increasing evidence supports the hypothesis that TGFb1 signalling may be mediated by high temperature requirement A1 (HtrA1) serine protease, acting on important regulatory mechanisms such as cell proliferation and mobility. Evidence is now accumulating to suggest that HtrA1 is involved in the development and progression of several pathologies. The aim of this study was to evaluate: i) if HtrA1 and TGFb1 expressions differ in eutopic and ectopic endometrium in women with endometriosis; ii) if HtrA1 correlates to TGFb1, pSmad and Ki67. This study was carried out including 10 women with ovarian endometriosis (cases) and 10 women with non endometriotic diseases (controls). Endometrial tissue underwent immunohistochemical H-score analysis for HtrA1, TGFb1, pSmad and Ki67 molecules. Data evaluation was performed by a nonparametric Kruskal-Wallis test and Spearman correlation was applied to evaluate the relationship among the molecules investigated in the epithelial and in the stromal compartment. The HtrA1 was significant decreased in ectopic and eutopic endometrium of women with endometriosis when compared with control endometrium in epithelial compartment. TGFb1was significantly increased in eutopic endometrium and decreased in ectopic endometrium in epithelial and stromal compartment. In addition, Ki67 was significant increased and an increase, but not significant, was detected for pSMAd2 in eutopic and ectopic endometrium compared to control one.  In summary, the significant direct correlation between TGFb1 and pSmad2 as well as between HtrA1 and TGFb1 and the very significant increase of Ki67 in stromal compartment of eutopic endometrium suggest a possible involvement of HtrA1 in the pathogenesis of endometriosis.

Independent Replication and Meta-Analysis for Endometriosis Risk Loci

Endometriosis is a complex disease that affects 6-10% of women in their reproductive years and 20-50% of women with infertility. Genome-wide and candidate-gene association studies for endometriosis have identified 10 independent risk loci, and of these, nine (rs7521902, rs13394619, rs4141819, rs6542095, rs1519761, rs7739264, rs12700667, rs1537377, and rs10859871) are polymorphic in European populations. Here we investigate the replication of nine SNP loci in 998 laparoscopically and histologically confirmed endometriosis cases and 783 disease-free controls from Belgium. SNPs rs7521902, rs13394619, and rs6542095 show nominally significant (p < .05) associations with endometriosis, while the directions of effect for seven SNPs are consistent with the original reports. Association of rs6542095 at the IL1A locus with 'All' (p = .066) and 'Grade_B' (p = .01) endometriosis is noteworthy because this is the first successful replication in an independent population. Meta-analysis with the published results yields genome-wide significant evidence for rs7521902, rs13394619, rs6542095, rs12700667, rs7739264, and rs1537377. Notably, three coding variants in GREB1 (near rs13394619) and CDKN2B-AS1 (near rs1537377) also showed nominally significant associations with endometriosis. Overall, this study provides important replication in a uniquely characterized independent population, and indicates that the majority of the original genome-wide association findings are not due to chance alone.

Association of WNT4 polymorphisms with endometriosis in infertile patients

PURPOSE

Recently, several genome-wide association studies have demonstrated an association between endometriosis and markers located in or near to WNT4 gene. In order to assess the validity of the findings, we conducted a replication case-control study in a Brazilian population.

METHODS

Genetic association study comprising 400 infertile women with endometriosis and 400 fertile women as controls. TaqMan allelic discrimination technique was used to investigate the relationship between endometriosis and four single-nucleotide polymorphisms (rs16826658, rs3820282, rs2235529, and rs7521902) in WNT4 gene. Genotype distribution, allele frequency, and haplotype analysis of the WNT4 polymorphisms were performed. A p value <0.05 was considered significant.

RESULTS

The results revealed a significant association of rs16826658 (p = 7e-04) and rs3820282 (p = 0.048) single-nucleotide polymorphisms (SNPs) on WNT4 gene with endometriosis-related infertility, while rs2235529 and rs7521902 SNPs showed no difference between cases and controls.

CONCLUSIONS

Our results suggested that rs16826658 and rs3820282 polymorphisms on WNT4 gene might be involved in the pathogenesis of endometriosis in the infertile women studied. Analysis of WNT4 genetic variants might help to identify patients at high risk for disease development.

DNA repair gene XRCC1 and XRCC4 variations and risk of endometriosis: an association study

BACKGROUND

Endometriosis is a polygenic and multifactorial disease. DNA damage plays a major role in mutagenesis, carcinogenesis and aging and is usually repaired by the action of several DNA repair enzymes. We investigated the association of the common variations of the DNA repair genes XRCC1 and XRCC4 with susceptibility to endometriosis in an Iranian population.

METHODS

In total, 160 patients with endometriosis (stages I-IV) and 174 healthy women were included in this case-control study. Genotyping of XRCC1 codon 399 as well as of XRCC4 -1394T/G, codon 247 and intron 3 insertion/deletion variations was performed using restriction fragment length polymorphism analysis of PCR-amplified fragments.

RESULTS

The XRCC4 -1394TG genotype frequency was significantly lower (p = 0.005) in the patients (9.4%) than in the controls (21.1%). The frequency of the -1394G allele was significantly lower (p < 0.0001) in the patients (6.6%) than in the controls (19.0%). There were no statistically significant differences in the genotype and allele frequencies of the XRCC1 codon 399, XRCC4 codon 247 and XRCC4 intron 3 insertion/deletion polymorphisms between the cases and controls.

CONCLUSIONS

The XRCC4 -1394T/G polymorphism was associated with susceptibility to endometriosis in an Iranian population.

Replication and meta-analysis of previous genome-wide association studies confirm vezatin as the locus with the strongest evidence for association with endometriosis

STUDY QUESTION

Is it possible to replicate the genetic association of single nucleotide polymorphisms (SNPs) rs13394619, rs4141819, rs7739264, rs17694933 and rs10859871 in five genetic loci previously identified as associated with endometriosis in an Italian Caucasian population?

SUMMARY ANSWER

SNP rs10859871 near the vezatin (VEZT) gene was found to be significantly associated with endometriosis in general while SNPs rs17694933 and rs4141819 were associated with Stage III/IV and ovarian disease, respectively.

WHAT IS KNOWN ALREADY

Endometriosis represents a complex disease in which the phenotypic manifestations are influenced by both genetic and environmental factors. Recent genome-wide association studies (GWASs) have allowed to identify some SNPs associated with the predisposition to the disease. A meta-analysis published in 2014 combined results from GWAS and replication studies showing that of the nine loci found to be associated with the disease in at least one of the studies, six (rs7521902, rs1270667, rs13394619, rs7739264, rs1537377 and rs10859871) remained genome-wide significant while two others (rs1250248 and rs4141819) showed borderline genome-wide significant association with more severe disease.

STUDY DESIGN, SIZE, DURATION

Allele frequencies of selected SNPs (rs13394619, rs4141819, rs7739264, rs17694933 and rs10859871) were investigated in 305 women with laparoscopically proven endometriosis, 285 laparoscopic controls and 2425 healthy, blood donor controls from the general population. A meta-analysis with previous data was also conducted.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 590 women who underwent endoscopic surgery were enrolled in the study and a blood sample was collected. After DNA extraction, genotype was obtained using Taq-Man pre-designed assay. Genotype data from healthy blood donor women were obtained from an existing genotype bank.

MAIN RESULTS AND THE ROLE OF CHANCE

A statistically significant association with endometriosis was found for SNP rs10859871, close to the VEZT gene, compared with both general population [odds ratio (OR) = 1.43, 95% confidence interval (CI): 1.20-1.71, P = 6.9 × 10(-5)] and laparoscopic controls (OR = 1.58, 95% CI: 1.24-2.02, P = 2.1 × 10(-4)). Meta-analysis with previous data confirmed the rs10859871 SNP as that with the strongest evidence for association with endometriosis (OR = 1.19, 95% CI: 1.15-1.24, P = 7.9 × 10(-20)). A further meta-analysis conducted using data from Stage III-IV endometriosis resulted in stronger genome-wide significant effect sizes for four out of the five SNPs tested.

LIMITATIONS, REASONS FOR CAUTION

The inability to confirm all previous demonstrated associations considering all stages of endometriosis may be due to a lack of statistical power and differences in the definition of cases included.

WIDER IMPLICATIONS OF THE FINDINGS

The associations with the SNPs identified so far have been obtained with a relatively small sample size supporting a limited heterogeneity across the various datasets. This represents an important advance in the identification of genetic markers of this disease.

STUDY FINDING/COMPETING INTERESTS

No funding to declare. The authors have no competing financial interests in relation to the content of this research paper.

Analysis of WNT4 polymorphism in Chinese Han women with endometriosis

Endometriosis is a complex disease that is influenced by genetic and environmental factors. In endometriosis, WNT4 plays a likely role owing to its biological functions. In this study, the TaqMan allelic discrimination technique was used to investigate the relationship between endometriosis and four single nucleotide polymorphisms in WNT4 (rs7521902 [A/C], rs16826658 [G/T], rs7515106 [C/T] and rs2235529 [A/G]) in Chinese Han women. A total of 646 patients with endometriosis and 766 normal controls were recurited. Regression analyses revealed that rs2235529 was a risk locus for endometriosis (P = 1.80E-03, OR, 95% CI = 1.311, 1.129 to 1.522), particularly in patients with stage III and IV disease. No significant association was found between endometriosis and rs7521902 (A/C), rs16826658 (G/T), or rs7515106 (C/T). For each of the four single nucleotide polymorphisms, no association was found between patients with endometriosis-related infertility or primary infertility and the controls. The results demonstrated that WNT4 rs2235529 is associated with endometriosis in Chinese Han women, which may result in aberrant expression of WNT4, leading to the pathogenesis of endometriosis.

Association between Let-7 microRNA-Binding-Site Polymorphism in the KRAS 3'UTR and Endometriosis: A Replication Study and Meta-Analysis

Background

Endometriosis is inherited as a complex genetic trait, and the single nucleotide polymorphism (SNP) rs61764370 within the KRAS gene on chromosome subband 12p12.1 has been proposed as a potential candidate gene. By disrupting a binding site for microinterference RNA (miRNA) let-7, the rs61764370 SNP variation site may increase activation of KRAS and favor disease development. Conflicting evidence, however, has emerged on the association between the rs61764370 SNP and endometriosis. Due to the potential implications of this issue for the diagnosis and treatment of endometriosis, we sought to replicate the sequencing of the KRAS rs61764370 SNP in a population of cases and controls and to perform a meta-analysis encompassing all currently available studies as well as our novel replication.

Methods

We sought to replicate for the first time the sequencing of KRAS rs61764370 SNP in a highly selected population of 86 cases of women with laparoscopically proven endometriosis and 72 healthy controls, and to perform a meta-analysis encompassing currently available studies and including affected subjects (n = 2,225) and controls (n = 1,923).

Results

The rs61764370 minor allele was observed in 12 of 86 women with endometriosis (14.0%) and in 15 of 72 controls (20.8%) (odds ratio [OR] = 0.76, 95% confidence interval [95% CI], 0.36-1.60, p = 0.48). The meta-analysis failed to identify any significant association (OR = 1.03, 95% CI, 0.89-1.20, p = 0.67, phet = 0.46).

Conclusions

KRAS variation site rs61764370 is unlikely related to disease development, and other loci with potential implications for diagnosis or treatment for endometriosis should be identified.

Genetic variants underlying risk of endometriosis: insights from meta-analysis of eight genome-wide association and replication datasets

BACKGROUND

Endometriosis is a heritable common gynaecological condition influenced by multiple genetic and environmental factors. Genome-wide association studies (GWASs) have proved successful in identifying common genetic variants of moderate effects for various complex diseases. To date, eight GWAS and replication studies from multiple populations have been published on endometriosis. In this review, we investigate the consistency and heterogeneity of the results across all the studies and their implications for an improved understanding of the aetiology of the condition.

METHODS

Meta-analyses were conducted on four GWASs and four replication studies including a total of 11 506 cases and 32 678 controls, and on the subset of studies that investigated associations for revised American Fertility Society (rAFS) Stage III/IV including 2859 cases. The datasets included 9039 cases and 27 343 controls of European (Australia, Belgium, Italy, UK, USA) and 2467 cases and 5335 controls of Japanese ancestry. Fixed and Han and Elkin random-effects models, and heterogeneity statistics (Cochran's Q test), were used to investigate the evidence of the nine reported genome-wide significant loci across datasets and populations.

RESULTS

Meta-analysis showed that seven out of nine loci had consistent directions of effect across studies and populations, and six out of nine remained genome-wide significant (P < 5 × 10⁻⁸), including rs12700667 on 7p15.2 (P = 1.6 × 10⁻⁹), rs7521902 near WNT4 (P = 1.8 × 10⁻¹⁵), rs10859871 near VEZT (P = 4.7 × 10⁻¹⁵), rs1537377 near CDKN2B-AS1 (P = 1.5 × 10⁻⁸), rs7739264 near ID4 (P = 6.2 × 10⁻¹⁰) and rs13394619 in GREB1 (P = 4.5 × 10⁻⁸). In addition to the six loci, two showed borderline genome-wide significant associations with Stage III/IV endometriosis, including rs1250248 in FN1 (P = 8 × 10⁻⁸) and rs4141819 on 2p14 (P = 9.2 × 10⁻⁸). Two independent inter-genic loci, rs4141819 and rs6734792 on chromosome 2, showed significant evidence of heterogeneity across datasets (P < 0.005). Eight of the nine loci had stronger effect sizes among Stage III/IV cases, implying that they are likely to be implicated in the development of moderate to severe, or ovarian, disease. While three out of nine loci were inter-genic, the remaining were in or near genes with known functions of biological relevance to endometriosis, varying from roles in developmental pathways to cellular growth/carcinogenesis.

CONCLUSIONS

Our meta-analysis shows remarkable consistency in endometriosis GWAS results across studies, with little evidence of population-based heterogeneity. They also show that the phenotypic classifications used in GWAS to date have been limited. Stronger associations with Stage III/IV disease observed for most loci emphasize the importance for future studies to include detailed sub-phenotype information. Functional studies in relevant tissues are needed to understand the effect of the variants on downstream biological pathways.

The future for genetic studies in reproduction

Genetic factors contribute to risk of many common diseases affecting reproduction and fertility. In recent years, methods for genome-wide association studies (GWAS) have revolutionized gene discovery for common traits and diseases. Results of GWAS are documented in the Catalog of Published Genome-Wide Association Studies at the National Human Genome Research Institute and report over 70 publications for 32 traits and diseases associated with reproduction. These include endometriosis, uterine fibroids, age at menarche and age at menopause. Results that pass appropriate stringent levels of significance are generally well replicated in independent studies. Examples of genetic variation affecting twinning rate, infertility, endometriosis and age at menarche demonstrate that the spectrum of disease-related variants for reproductive traits is similar to most other common diseases. GWAS 'hits' provide novel insights into biological pathways and the translational value of these studies lies in discovery of novel gene targets for biomarkers, drug development and greater understanding of environmental factors contributing to disease risk. Results also show that genetic data can help define sub-types of disease and co-morbidity with other traits and diseases. To date, many studies on reproductive traits have used relatively small samples. Future genetic marker studies in large samples with detailed phenotypic and clinical information will yield new insights into disease risk, disease classification and co-morbidity for many diseases associated with reproduction and infertility.

Guidelines for the design, analysis and interpretation of 'omics' data: focus on human endometrium

BACKGROUND

'Omics' high-throughput analyses, including genomics, epigenomics, transcriptomics, proteomics and metabolomics, are widely applied in human endometrial studies. Analysis of endometrial transcriptome patterns in physiological and pathophysiological conditions has been to date the most commonly applied 'omics' technique in human endometrium. As the technologies improve, proteomics holds the next big promise for this field. The 'omics' technologies have undoubtedly advanced our knowledge of human endometrium in relation to fertility and different diseases. Nevertheless, the challenges arising from the vast amount of data generated and the broad variation of 'omics' profiling according to different environments and stimuli make it difficult to assess the validity, reproducibility and interpretation of such 'omics' data. With the expansion of 'omics' analyses in the study of the endometrium, there is a growing need to develop guidelines for the design of studies, and the analysis and interpretation of 'omics' data.

METHODS

Systematic review of the literature in PubMed, and references from relevant articles were investigated up to March 2013.

RESULTS

The current review aims to provide guidelines for future 'omics' studies on human endometrium, together with a summary of the status and trends, promise and shortcomings in the high-throughput technologies. In addition, the approaches presented here can be adapted to other areas of high-throughput 'omics' studies.

CONCLUSION

A highly rigorous approach to future studies, based on the guidelines provided here, is a prerequisite for obtaining data on biological systems which can be shared among researchers worldwide and will ultimately be of clinical benefit.

Endometriosis: a disease that remains enigmatic

Endometriosis, a gynecologic pathology, is defined by the presence of a tissue similar to uterine endometrium, which is located in places other than physiologically appropriate. These endometrial heterotopic islets contain glands and stroma and are functionally capable of responding to exogenous, endogenous, or local hormonal stimuli. Endometriosis affects 8%-10% of women of reproductive age; in 30% of the women, the condition is associated with primary or secondary infertility. In several instances, endometriosis persists as a minimal or mild disease, or it can resolve on its own. Other cases of endometriosis show severe symptomatology that ends when menopause occurs. Endometriosis can, however, reactivate in several postmenopausal women when iatrogenic or endogenous hormones are present. Endometriosis is occasionally accompanied by malignant ovarian tumors, especially endometrioid and clear cell carcinomas. Its pathogenesis is widely debated, and its variable morphology appears to represent a continuum of individual presentations and progressions. Endometriosis has no pathognomonic signs or symptoms; it is therefore difficult to diagnose. Because of its enigmatic etiopathogenesis, there is currently no satisfactory therapy for all patients with endometriosis. Treatments include medications, surgery, or combined therapies; currently, the only procedures that seem to cure endometriosis are hysterectomy and bilateral salpingo-oophorectomy. In this paper, we review the most controversial and enigmatic aspects of this disease.

Genetic association studies in female reproduction: from candidate-gene approaches to genome-wide mapping

Many genetic association studies have been performed to investigate disorders of female reproduction, such as polycystic ovary syndrome, premature ovarian failure and endometriosis. These disorders typically manifest heterogeneously, and their pathogeneses are influenced by polygenic and environmental factors. Researchers evaluating these genetic associations have chosen candidate genes related to hormone action, steroid biosynthesis, inflammatory cytokines and autoimmune factors. Several of these genes have yielded statistically significant associations with female reproductive disorders; however, few associations have been robust and reproducible. Whole-genome association studies generate more reliable and unbiased results and represent a breakthrough in genetic studies of female reproduction. Nevertheless, to date only a very small fraction of the overall heritability has been identified and so further studies are needed.