Independent Replication and Meta-Analysis for Endometriosis Risk Loci

Pathogenesis of Endometriosis and Endometriosis-Associated Cancers

Endometriosis is a hormone-dependent, chronic inflammatory condition that affects 5-10% of reproductive-aged women. It is a complex disorder characterized by the growth of endometrial-like tissue outside the uterus, which can cause chronic pelvic pain and infertility. Despite its prevalence, the underlying molecular mechanisms of this disease remain poorly understood. Current treatment options are limited and focus mainly on suppressing lesion activity rather than eliminating it entirely. Although endometriosis is generally considered a benign condition, substantial evidence suggests that it increases the risk of developing specific subtypes of ovarian cancer. The discovery of cancer driver mutations in endometriotic lesions indicates that endometriosis may share molecular pathways with cancer. Moreover, the application of single-cell and spatial genomics, along with the development of organoid models, has started to illuminate the molecular mechanisms underlying disease etiology. This review aims to summarize the key genetic mutations and alterations that drive the development and progression of endometriosis to malignancy. We also review the significant recent advances in the understanding of the molecular basis of the disorder, as well as novel approaches and in vitro models that offer new avenues for improving our understanding of disease pathology and for developing new targeted therapies.

A GREB1-steroid receptor feedforward mechanism governs differential GREB1 action in endometrial function and endometriosis

Cellular responses to the steroid hormones, estrogen (E2), and progesterone (P4) are governed by their cognate receptor's transcriptional output. However, the feed-forward mechanisms that shape cell-type-specific transcriptional fulcrums for steroid receptors are unidentified. Herein, we found that a common feed-forward mechanism between GREB1 and steroid receptors regulates the differential effect of GREB1 on steroid hormones in a physiological or pathological context. In physiological (receptive) endometrium, GREB1 controls P4-responses in uterine stroma, affecting endometrial receptivity and decidualization, while not affecting E2-mediated epithelial proliferation. Of mechanism, progesterone-induced GREB1 physically interacts with the progesterone receptor, acting as a cofactor in a positive feedback mechanism to regulate P4-responsive genes. Conversely, in endometrial pathology (endometriosis), E2-induced GREB1 modulates E2-dependent gene expression to promote the growth of endometriotic lesions in mice. This differential action of GREB1 exerted by a common feed-forward mechanism with steroid receptors advances our understanding of mechanisms that underlie cell- and tissue-specific steroid hormone actions.

Is endometriosis due to evolutionary maladaptation?

Similar to diabetes and unlike many pathogen-induced diseases, endometriosis is likely a result of maladaptation to the evolutionary heritage of humans. The objective of this article is to review the literature and improve understanding of the evolutionary factors behind endometriosis, leading to more effective prevention and treatment approaches. In primates, spontaneous decidualization of the endometrium evolved to ensure optimal implantation of a limited number of early embryos, unlike many non-primates which depend on early embryos to induce decidualization and subsequent pregnancy. Spontaneous decidualization results in menstrual bleeding when embryo implantation does not occur, and endometriosis is commonly believed to be caused by retrograde menstruation. Although direct evidence is lacking, it is likely that hunter-gatherer women experienced fewer menstrual periods due to pregnancy shortly after menarche, followed by repeated pregnancies and lactation. However, the mismatch between the evolved uterine physiology and rapid societal changes has led to modern women delaying pregnancy and experiencing numerous menstrual periods, potentially increasing the incidence of endometriosis. The symptoms of endometriosis are often managed by suppressing menstruation through systemic hormonal treatments, but these may have side effects. For patients with a family history of endometriosis or in the early stages of the disease, intrauterine devices releasing progesterone locally could prevent uterine bleeding and the development of endometriosis while preserving fertility and minimizing side effects.

Association of endometriosis with Sjögren's syndrome: Genetic insights (Review)

Patients with a history of endometriosis have an increased risk of developing various autoimmune diseases such as rheumatoid arthritis, ankylosing spondylitis, systemic lupus erythematosus, multiple sclerosis and celiac disease. There is a potential association between endometriosis and an increased susceptibility for Sjögren's syndrome (SS). SS is a common chronic, inflammatory, systemic, autoimmune, multifactorial disease of complex pathology, with genetic, epigenetic and environmental factors contributing to the development of this condition. It occurs in 0.5‑1% of the population, is characterized by the presence of ocular dryness, lymphocytic infiltrations and contributes to neurological, gastrointestinal, vascular and dermatological manifestations. Endometriosis is an inflammatory, estrogen‑dependent, multifactorial, heterogeneous gynecological disease, affecting ≤10% of reproductive‑age women. It is characterized by the occurrence of endometrial tissue outside the uterine cavity, mainly in the pelvic cavity, and is associated with pelvic pain, dysmenorrhea, deep dyspareunia and either subfertility or infertility. It is still unclear whether SS appears as a secondary response to endometriosis, or it is developed due to any potential shared mechanisms of these conditions. The aim of the present review was to explore further the biological basis only of the co‑occurrence of these disorders but not their association at clinical basis, focusing on the analysis of the partially shared genetic background between endometriosis and SS, and the clarification of the possible similarities in the underlying pathogenetic mechanisms and the relevant molecular pathways.

Investigation of biomarkers in Endometriosis-associated infertility: Systematic Review

The relationship between endometriosis and infertility is still unknown, but it is possible that genetic polymorphisms influence these two variables. This study aims to identify, in the literature, which polymorphisms are related to infertility in women with endometriosis. A search was performed in databases using the descriptors: polymorphisms genetics and infertility and endometriosis. 386 articles were identified, and after applying the inclusion and exclusion criteria, 33 case-control studies were included. Genes and their respective polymorphisms, which exhibited statistically significant values, were classified into three categories: related to metabolic/cellular processes, steroidogenesis and sex hormone receptors, inflammation and immune response. In summary, the results of these studies suggest that the polymorphisms rs882605 of MUC4 gene, rs16826658 of WNT4 gene, rs10953316 of MUC17 gene, rs10928050 of KAZN gene, rs1799889 of PAI-1 gene, (TA)n repeats of ESR1 gene, (CA)n repeats of ESR2 gene, rs605059 of HSD17B1 gene, rs743572 of CYP17A1 gene, insLQ of LHR gene, p.Ile49Ser of AMH gene, rs12700667 of NPVF/NFE2L3 gene, G1502A of LHβ gene, G + 1730A of ERβ gene, rs7528684 of FCRL3 gene, rs3761549 of FOXP3 gene and rs28362491 of NFKβ1 gene are implicated in the etiology of infertility in women with endometriosis.

Endometriosis: Epidemiology, Classification, Pathogenesis, Treatment and Genetics (Review of Literature)

Endometriosis is a “mysterious” disease and its exact cause has not yet been established. Among the etiological factors, congenital, environmental, epigenetic, autoimmune and allergic factors are listed. It is believed that the primary mechanism of the formation of endometriosis foci is retrograde menstruation, i.e., the passage of menstrual blood through the fallopian tubes into the peritoneal cavity and implantation of exfoliated endometrial cells. However, since this mechanism is also observed in healthy women, other factors must also be involved in the formation of endometriosis foci. Endometriosis is in many women the cause of infertility, chronic pain and the deterioration of the quality of life. It also represents a significant financial burden on health systems. The article presents a review of the literature on endometriosis—a disease affecting women throughout the world.

Molecular Basis of Endometriosis and Endometrial Cancer: Current Knowledge and Future Perspectives

The human endometrium is a unique tissue undergoing important changes through the menstrual cycle. Under the exposure of different risk factors in a woman's lifetime, normal endometrial tissue can give rise to multiple pathologic conditions, including endometriosis and endometrial cancer. Etiology and pathophysiologic changes behind such conditions remain largely unclear. This review summarizes the current knowledge of the pathophysiology of endometriosis and its potential role in the development of endometrial cancer from a molecular perspective. A better understanding of the molecular basis of endometriosis and its role in the development of endometrial pathology will improve the approach to clinical management.

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.

Pathogenesis of Endometriosis: The Origin of Pain and Subfertility

Endometriosis (EM) and adenomyosis (AM) are common conditions with pain and infertility as the principal symptoms. The pathophysiology of pain in EM and AM comprises sensory and somatoform pain mechanisms. Over time, these may aggravate and lead to individual complex disease patterns if not diagnosed and treated. Despite the known facts, several years often pass between the onset of symptoms and diagnosis. Chronic pain disorders with changes on a neuronal level frequently arise and are linked to depressive disorders, with the process becoming a vicious cycle. Additionally, women with EM and AM suffer from sub- and infertility. Low fecundity rates are caused by anatomical changes in combination with behavioral changes in the sexual activity of women with chronic pain as well as local proinflammatory factors that not only decrease implantation rates but also promote early abortions.

The Genetic Background of Endometriosis: Can ESR2 and CYP19A1 Genes Be a Potential Risk Factor for Its Development?

Endometriosis is defined as the presence of endometrial foci, localized beyond their primary site, i.e., the uterine cavity. The etiology of this disease is rather complex. Its development is supported by hormonal, immunological, and environmental factors. During recent years, particular attention has been focused on the genetic mechanisms that may be of particular significance for the increased incidence rates of endometriosis. According to most recent studies, ESR2 and CYP19A1 genes may account for the potential risk factors of infertility associated with endometriosis. The paper presents a thorough review of the latest reports and data concerning the genetic background of the risk for endometriosis development.

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.

Nursing Genetic Research: New Insights Linking Breast Cancer Genetics and Bone Density

Nursing research is expected to provide options for the primary prevention of disease and health promotion, regardless of pathology or disease. Nurses have the skills to develop and lead research that addresses the relationship between genetic factors and health. Increasing genetic knowledge and research capacity through interdisciplinary cooperation as well as the development of research resources, will accelerate the rate at which nurses contribute to the knowledge about genetics and health. There are currently different fields in which knowledge can be expanded by research developed from the nursing field. Here, we present an emerging field of research in which it is hypothesized that genetics may affect bone metabolism. Better insight of genetic factors that are contributing to metabolic bone diseases would allow for focused nursing care and preventive interventions.

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.

Role of FN1 and GREB1 gene polymorphisms in endometriosis

Endometriosis is a complex gynecological disorder, affecting up to 10% of women of childbearing age, characterized by the presence of functional endometrial tissue at ectopic positions generally within the peritoneum. It is a heritable condition influenced by multiple genetic, epigenetic and environmental factors, with an overall heritability estimated at approximately 50%. The aim of the present study was to evaluate the association of rs1250248 and rs11674184 single nucleotide polymorphisms (SNPs), mapping to fibronectin 1 (FN1) and growth regulation by estrogen in breast cancer 1 (GREB1) genetic loci, respectively, with the risk of endometriosis. A total of 166 women with endometriosis (stages I–IV) who were hospitalized for the condition, diagnosed by laparoscopic intervention and histologically confirmed, and 168 normal controls were recruited and genotyped. Genotyping of the rs1250248 and rs11674184 SNPs was performed with TaqMan primer/probe sets. A significant association was detected with the A allele, as well as the AA and AG genotypes of rs1250248 (FN1) in patients with endometriosis, as well as in patients with stage I and II of the disease only. The rs11674184 SNP of the GREB1 gene was not found to be associated with an increased susceptibility to endometriosis either for all patients (stages I–IV) or for subgroups of stage I and II or III and IV of the disease only. Our results demonstrated a genetic association between the rs1250248 (FN1) SNP and endometriosis at both the genotypic and allelic level. However, although rs11674184 of GREB1 constitutes one of the most consistently associated SNPs with endometriosis in European ancestry populations, it was not found to be associated with endometriosis in this study.

Defining the genetic profile of endometriosis

Endometriosis is a pathological condition which has been extensively studied, since its pathophysiology stems from a broad spectrum of environmental influences and genetic factors. Familial studies aim at defining inheritance trends, while linkage analysis studies focus on the identification of genetic sites related to endometriosis susceptibility. Genetic association studies take into account candidate genes and single nucleotide polymorphisms, and hence target at unraveling the association between disease severity and genetic variation. The common goal of various types of studies is, through genetic mapping methods, the timely identification of therapeutic strategies for disease symptoms, including pelvic pain and infertility, as well as efficient counselling. While genome-wide association studies (GWAS) play a primary role in depicting genetic contributions to disease development, they entail a certain bias as regards the case-control nature of their design and the reproducibility of the results. Nevertheless, genetic-oriented studies and the implementation of the results through clinical tests, hold a considerable advantage in proper disease management. In this review article, we present information about gene-gene and gene-environment interactions involved in endometriosis and discuss the effectiveness of GWAS in identitying novel potential therapeutic targets in an attempt to develop novel therapeutic strategies for a better management and treatment of patients with endometriosis.

Non-coding RNAs in endometriosis: a narrative review

BACKGROUND

Endometriosis is a benign gynaecological disorder, which affects 10% of reproductive-aged women and is characterized by endometrial cells from the lining of the uterus being found outside the uterine cavity. However, the pathophysiological mechanisms causing the development of this heterogeneous disease remain enigmatic, and a lack of effective biomarkers necessitates surgical intervention for diagnosis. There is international recognition that accurate non-invasive diagnostic tests and more effective therapies are urgently needed. Non-coding RNA (ncRNA) molecules, which are important regulators of cellular function, have been implicated in many chronic conditions. In endometriosis, transcriptome profiling of tissue samples and functional in vivo and in vitro studies demonstrate that ncRNAs are key contributors to the disease process.

OBJECTIVE AND RATIONALE

In this review, we outline the biogenesis of various ncRNAs relevant to endometriosis and then summarize the evidence indicating their roles in regulatory pathways that govern disease establishment and progression.

SEARCH METHODS

Articles from 2000 to 2016 were selected for relevance, validity and quality, from results obtained in PubMed, MEDLINE and Google Scholar using the following search terms: ncRNA and reproduction; ncRNA and endometriosis; miRNA and endometriosis; lncRNA and endometriosis; siRNA and endometriosis; endometriosis; endometrial; cervical; ovary; uterus; reproductive tract. All articles were independently screened for eligibility by the authors.

OUTCOMES

This review integrates extensive information from all relevant published studies focusing on microRNAs, long ncRNAs and short inhibitory RNAs in endometriosis. We outline the biological function and synthesis of microRNAs, long ncRNAs and short inhibitory RNAs and provide detailed findings from human research as well as functional studies carried out both in vitro and in vivo, including animal models. Although variability in findings between individual studies exists, collectively, the extant literature justifies the conclusion that dysregulated ncRNAs are a significant element of the endometriosis condition.

WIDER IMPLICATIONS

There is a compelling case that microRNAs, long non-coding RNAs and short inhibitory RNAs have the potential to influence endometriosis development and persistence through modulating inflammation, proliferation, angiogenesis and tissue remodelling. Rapid advances in ncRNA biomarker discovery and therapeutics relevant to endometriosis are emerging. Unravelling the significance of ncRNAs in endometriosis will pave the way for new diagnostic tests and identify new therapeutic targets and treatment approaches that have the potential to improve clinical options for women with this disabling condition.

Role for Growth Regulation by Estrogen in Breast Cancer 1 (GREB1) in Hormone-Dependent Cancers

Sex hormones play important roles in the onset and progression of several cancers, such as breast, ovarian, and prostate cancer. Although drugs targeting sex hormone function are useful in treating cancer, tumors often develop resistance. Thus, we need to define the downstream effectors of sex hormones in order to develop new treatment strategies for these cancers. Recent studies unearthed one potential mediator of steroid hormone action in tumors: growth regulation by estrogen in breast cancer 1 (GREB1). GREB1 is an early estrogen-responsive gene, and its expression is correlated with estrogen levels in breast cancer patients. Additionally, GREB1 responds to androgen in prostate cancer cells, and can stimulate the proliferation of breast, ovarian, and prostate cancer cells. Recent studies have shown that GREB1 also responds to progesterone in human endometrial cells, suggesting that GREB1 is a pan steroid-responsive gene. This mini-review examines evidence that GREB1 participates in several hormone-dependent cancers and could be targeted to treat these cancers.

Japanese GWAS identifies variants for bust-size, dysmenorrhea, and menstrual fever that are eQTLs for relevant protein-coding or long non-coding RNAs

Traits related to primary and secondary sexual characteristics greatly impact females during puberty and day-to-day adult life. Therefore, we performed a GWAS analysis of 11,348 Japanese female volunteers and 22 gynecology-related phenotypic variables, and identified significant associations for bust-size, menstrual pain (dysmenorrhea) severity, and menstrual fever. Bust-size analysis identified significant association signals in CCDC170-ESR1 (rs6557160; P = 1.7 × 10-16) and KCNU1-ZNF703 (rs146992477; P = 6.2 × 10-9) and found that one-third of known European-ancestry associations were also present in Japanese. eQTL data points to CCDC170 and ZNF703 as those signals' functional targets. For menstrual fever, we identified a novel association in OPRM1 (rs17181171; P = 2.0 × 10-8), for which top variants were eQTLs in multiple tissues. A known dysmenorrhea signal near NGF replicated in our data (rs12030576; P = 1.1 × 10-19) and was associated with RP4-663N10.1 expression, a putative lncRNA enhancer of NGF, while a novel dysmenorrhea signal in the IL1 locus (rs80111889; P = 1.9 × 10-16) contained SNPs previously associated with endometriosis, and GWAS SNPs were most significantly associated with IL1A expression. By combining regional imputation with colocalization analysis of GWAS/eQTL signals along with integrated annotation with epigenomic data, this study further refines the sets of candidate causal variants and target genes for these known and novel gynecology-related trait loci.

Genetic Variation at Chromosome 2q13 and Its Potential Influence on Endometriosis Susceptibility Through Effects on the IL-1 Family

Endometriosis is characterized by the growth of epithelial and stromal cells outside the uterine cavity. It has a complex etiology and affects ∼10% of reproductive age women. It is accompanied by a chronic inflammatory response with substantial evidence to indicate genetic susceptibility. The causal genes and their pathways leading to endometriosis, however, are still unknown. Recently, genomewide association studies on endometriosis identified 14 genomic risk loci in women of European and Japanese ancestry. It is becoming increasingly clear that these risk regions are intergenic and thus contribute to disease susceptibility through regulatory mechanisms, most likely mediated through regulation of genes within a restricted distance from the risk variants. One endometriosis risk locus has been detected at chromosome 2q13 within an inflammatory-rich region of gene transcripts and thus may play a role in the inflammation component of the disease. We carried out detailed analysis of the genomic region 250 kb on either side of sentinel SNP rs10167914 and identified 21 transcripts which contained 6 interleukin (IL)-1 family genes, 3 previously reported coding genes that have a relationship to inflammation, 4 novel coding, or pseudogenes, and 8 noncoding RNA transcripts. Through an extensive literature search, we examined the roles these genes and their resultant proteins play in endometriosis pathogenesis. The results suggest alteration in the expression the IL-1 family transcripts either alone or as a complex milieu could have a significant influence on endometriosis and should be prioritized for future study on the implications of inflammation on endometriotic lesions.

How Artificial Intelligence Can Improve Our Understanding of the Genes Associated with Endometriosis: Natural Language Processing of the PubMed Database

Endometriosis is a disease characterized by the development of endometrial tissue outside the uterus, but its cause remains largely unknown. Numerous genes have been studied and proposed to help explain its pathogenesis. However, the large number of these candidate genes has made functional validation through experimental methodologies nearly impossible. Computational methods could provide a useful alternative for prioritizing those most likely to be susceptibility genes. Using artificial intelligence applied to text mining, this study analyzed the genes involved in the pathogenesis, development, and progression of endometriosis. The data extraction by text mining of the endometriosis-related genes in the PubMed database was based on natural language processing, and the data were filtered to remove false positives. Using data from the text mining and gene network information as input for the web-based tool, 15,207 endometriosis-related genes were ranked according to their score in the database. Characterization of the filtered gene set through gene ontology, pathway, and network analysis provided information about the numerous mechanisms hypothesized to be responsible for the establishment of ectopic endometrial tissue, as well as the migration, implantation, survival, and proliferation of ectopic endometrial cells. Finally, the human genome was scanned through various databases using filtered genes as a seed to determine novel genes that might also be involved in the pathogenesis of endometriosis but which have not yet been characterized. These genes could be promising candidates to serve as useful diagnostic biomarkers and therapeutic targets in the management of endometriosis.

Meta-analysis identifies five novel loci associated with endometriosis highlighting key genes involved in hormone metabolism

Endometriosis is a heritable hormone-dependent gynecological disorder, associated with severe pelvic pain and reduced fertility; however, its molecular mechanisms remain largely unknown. Here we perform a meta-analysis of 11 genome-wide association case-control data sets, totalling 17,045 endometriosis cases and 191,596 controls. In addition to replicating previously reported loci, we identify five novel loci significantly associated with endometriosis risk (P<5 × 10⁻⁸), implicating genes involved in sex steroid hormone pathways (FN1, CCDC170, ESR1, SYNE1 and FSHB). Conditional analysis identified five secondary association signals, including two at the ESR1 locus, resulting in 19 independent single nucleotide polymorphisms (SNPs) robustly associated with endometriosis, which together explain up to 5.19% of variance in endometriosis. These results highlight novel variants in or near specific genes with important roles in sex steroid hormone signalling and function, and offer unique opportunities for more targeted functional research efforts.

Endometriosis is a major cause of infertility. Molecular mechanisms underlying the disease involve genetic and environmental risk factors. In a meta-analysis of eleven GWA studies, Sapkota and colleagues identify five novel risk loci, implicating steroid sex hormone pathways in the pathogenesis.

Common variants in ZMIZ1 and near NGF confer risk for primary dysmenorrhoea

Primary dysmenorrhoea, defined as painful menstrual cramps in the absence of pelvic pathology, is a common problem in women of reproductive age. Its aetiology and pathophysiology remain largely unknown. Here we performed a two-stage genome-wide association study and subsequent replication study to identify genetic factors associated with primary dysmenorrhoea in a total of 6,770 Chinese individuals. Our analysis provided evidence of a significant (P<5 × 10⁻⁸) association at rs76518691 in the gene ZMIZ1 and at rs7523831 near NGF. ZMIZ1 has previously been associated with several autoimmune diseases, and NGF plays a key role in the generation of pain and hyperalgesia and has been associated with migraine. These findings provide future directions for research on susceptibility mechanisms for primary dysmenorrhoea. Furthermore, our genetic architecture analysis provides molecular support for the heritability and polygenic nature of this condition.

Primary dysmenorrhoea, the most common gynaecologic complaint, remains genetically and pathophysiologically elusive. Here, Li and colleagues identify common variants in ZMIZ1 and near NGF conferring risk for primary dysmenorrhoea using genome-wide association study in a Chinese population.

Endometrial vezatin and its association with endometriosis risk

STUDY QUESTION

Do endometriosis risk-associated single nucleotide polymorphisms (SNPs) found at the 12q22 locus have effects on vezatin ( ITALIC! VEZT) expression?

SUMMARY ANSWER

The original genome-wide association study (GWAS) SNP (rs10859871), and other newly identified association signals, demonstrate strong evidence for ITALIC! cis-expression quantitative trait loci (eQTL) effects on ITALIC! VEZT expression.

WHAT IS KNOWN ALREADY

GWAS have identified several disease-risk loci (SNPs) associated with endometriosis. The SNP rs10859871 is located within the ITALIC! VEZT gene. ITALIC! VEZT expression is altered in the endometrium of endometriosis patients and is an excellent candidate for having a causal role in endometriosis. Most of the SNPs identified from GWAS are not located within the coding region of the genome. However, they are likely to have an effect on the regulation of gene expression. Genetic variants that affect levels of gene expression are called expression quantitative trait loci (eQTL).

STUDY DESIGN, SIZE, DURATION

Samples for genotyping and ITALIC! VEZT variant screening were drawn from women recruited for genetic studies in Australia/New Zealand and women undergoing surgery in a tertiary care centre. Coding variants for ITALIC! VEZT were screened in blood from 100 unrelated individuals (endometriosis-dense families) from the QIMR Berghofer Medical Research Institute dataset. SNPs at the 12q22 locus were imputed and reanalysed for their association with endometriosis. Reanalysis of endometriosis risk-association was performed on a final combined Australian dataset of 2594 cases and 4496 controls. Gene expression was performed on 136 endometrial samples. eQTL analysis in whole blood was performed on 862 individuals from the Brisbane Systems Genetics Study. Endometrial tissue-specific eQTL analysis was performed on 122 samples (eutopic endometrium) collected following laparoscopic surgery. VEZT protein expression studies employed ITALIC! n = 56 (western blotting) and ITALIC! n = 42 (immunohistochemistry) endometrial samples.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The women recruited for this study provided blood and/or endometrial tissue samples in a hospital setting. Genomic DNA was screened for common and coding variants. SNPs of interest in the 12q22 region were genotyped using Agena MassARRAY technology or Taqman SNP genotyping assay. Gene expression profiles from RNA extracted from blood and endometrial tissue samples were generated using Illumina whole-genome expression chips (Human HT-12 v4.0). Whole protein extracted from endometrium was used for VEZT western blots, and paraffin sections of endometrium were employed for VEZT immunohistochemistry semi-quantitative analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 11 coding variants of ITALIC! VEZT (including one novel variant) were identified from an endometriosis-dense cohort. Polymorphic coding and imputed SNPs were combined with previous GWAS data to reanalyse the endometriosis risk association of the 12q22 region. The disease association signal at 12q22 was due to coding variants in ITALIC! VEZT or ITALIC! FGD6 (FYVE, RhoGEF and PH domain-containing 6) and SNPs with the strongest signals were either intronic or intergenic. We found strong evidence for ITALIC! VEZT cis-eQTLs with the sentinel SNP (rs10859871) in blood and endometrium, where the endometriosis risk allele (C) was associated with an increase in ITALIC! VEZT expression. We could not demonstrate this genotype-specific effect on VEZT protein expression in endometrium. However, we did observe a menstrual cycle stage specific increase in VEZT protein expression in endometrial glands, specific to the secretory phase ( ITALIC! P = 2.0 × 10(-4)).

LIMITATIONS, REASONS FOR CAUTION

In comparison to the blood sample datasets, the study numbers of endometrial tissues were substantially reduced. Protein studies failed to complement RNA results, also likely a reflection of the low study numbers in these experiments. ITALIC! In silico prediction tools used in this investigation are typically based on cell lines different to our tissues of interest, thus any functional annotations drawn from these approaches should be considered carefully. Therefore, functional studies on VEZT and related pathway components are still warranted to unequivocally implicate a causal role for VEZT in endometriosis pathophysiology.

WIDER IMPLICATIONS OF THE FINDINGS

GWAS have proven to be very valuable tools for deciphering complex diseases. Endometriosis is a text-book example of a complex disease, involving genetic, lifestyle and environmental influences. Our focused investigation of the 12q22 region validates an association with increased endometriosis risk. Endometriosis risk SNPs (including rs10859871) located within this locus demonstrated evidence for ITALIC! cis-eQTLs on ITALIC! VEZT expression. By examining women who possess an enhanced genetic risk of developing endometriosis, we have identified an effect on ITALIC! VEZT expression and therefore a potential gene/gene pathway in endometriosis disease establishment and development.

STUDY FUNDING/COMPETING INTERESTS

Funding for this work was provided by NHMRC Project Grants GNT1012245, GNT1026033, GNT1049472 and GNT1046880. G.W.M. is supported by the NHMRC Fellowship scheme (GNT1078399). S.J.H.-C. is supported by the J.N. Peters Bequest Fellowship. The authors declare no competing interests.

TRIAL REGISTRATION NUMBER

N/A.