Evidence for association of the G1733A polymorphism of the androgen receptor gene with recurrent spontaneous abortions

Investigation of the role of X chromosome inactivation and androgen receptor CAG repeat polymorphisms in patients with recurrent pregnancy loss: a prospective case-control study

BACKGROUND

Previous research has revealed that skewed X chromosome inactivation (SXCI) and androgen receptor (AR) CAG polymorphisms are associated with increased risk of recurrent pregnancy loss (RPL); however, the results are conflicting, and the underlying mechanisms remain unclear. This study investigated the role of SXCI and AR CAG polymorphisms in patients with RPL and explored whether the underlying mechanisms were related to the ovarian reserve and preimplantation embryo aneuploidy.

METHODS

This was a prospective case-control study carried out in a tertiary hospital-based reproductive medicine center. An external validation RPL cohort was recruited during the study period. Data on baseline and cycle characteristics were collected. X-chromosome inactivation (XCI) was measured using a human AR assay. AR polymorphisms were assessed using quantitative fluorescent polymerase chain reactions and direct sequencing. Blastocysts of the patients with RPL were tested by single nucleotide polymorphism microarray based preimplantation genetic testing for aneuploidy.

RESULTS

In total, 131 patients with idiopathic RPL and 126 controls were included for the case-control study. Patients with RPL exhibited a significantly more skewed XCI distribution pattern (67.71 ± 10.50 vs. 64.22 ± 10.62, p = 0.011), as well as significantly shorter bi-allelic mean (18.56 ± 1.97 vs. 19.34 ± 2.38, p = 0.005) and X-weighted bi-allelic mean (18.46 ± 2.02 vs. 19.38 ± 2.53, p = 0.001) of AR CAG repeats. Multivariate logistic regression models indicated that CAG repeat < 20, SXCI, and duration of stimulation were independently associated with the risk of RPL. However, SXCI and AR CAG polymorphisms were not associated with ovarian reserve or preimplantation embryo aneuploidy in the RPL group, and the same results were attained in a separate validation cohort of 363 patients with RPL.

CONCLUSION

SXCI and AR CAG polymorphisms are related to RPL; however, these two factors do not lead to RPL by affecting the ovarian reserve or increasing embryo aneuploidy. The roles of SXCI and AR CAG in RPL may involve other mechanisms that require further investigation.

TRIAL REGISTRATION

NCT02504281, https://www.

CLINICALTRIALS

gov (Date of registration, 21/07/2015; date of enrolment of the first subject, 30/07/2015).

Association between G1733A (rs6152) polymorphism in androgen receptor gene and recurrent spontaneous abortions in Mexican population

INTRODUCTION

Recurrent spontaneous abortion (RSA) is a multifactorial condition that occurs with a frequency of 0.2-5% in women of reproductive age. Among genetic factors, the single nucleotide polymorphism (SNP) G1733A in the androgen receptor (AR) gene has been associated with its presence in Greek and Iranian populations. Therefore, the aim of this study is to determine its possible association with RSA in this population.

PATIENTS AND METHODS

A total of 156 Mexican RSA (with at least 2 consecutive abortions) unrelated patients and 152 unrelated healthy women were included, the presence of karyotype anomalies in the parents as well as uterine anomalies as well as antiphospholipid antibodies was excluded in patients; while all the controls presented at least two healthy pregnancies and no abortion. In all the included women, the presence of the SNP G1733A was determined by restriction fragment length polymorphism (RFLP) technique.

RESULTS

No significant differences were observed in age between groups. The genotype GG, GA, and AA had a frequency of 0.70, 0.27, and 0.03 in patients and of 0.89, 0.10, and 0.01 in controls [corrected] (p < 0.001); while the A allele frequency was of 0.06 and 0.16 in controls and patients, respectively (p < 0.0001). The difference in allele frequency increased 10-15% when patients with primary RSA (with no live births) and with at least three abortions were included.

CONCLUSIONS

The SNP G1733A of the AR gene is significantly associated with RSA in Mexican patients. These results coincide with previous reports in other populations.

Gender Specificity of a Genetic Variant of Androgen Receptor and Risk of Coronary Artery Disease

BACKGROUND

Androgens are known to influence the risk of developing cardiovascular diseases. This study aims at investigating the possible association between G1733A polymorphism in the coding region of androgen receptor (AR) gene and premature coronary artery disease (CAD).

METHODS

A total of 460 Greek subjects were investigated for the G1733A polymorphism. The patient group consisted of 250 CAD individuals, aged less than 58 years, while 210 healthy individuals served as controls. Genotyping was performed using the PCR-RFLP method.

RESULTS

Significant differences in genotype distribution (P = 0.0067) and allele frequencies (P = 0.0060) have been observed between patients and controls in the women's subgroup. Conversely, the genotype/allele frequencies were similar between patients and controls in the subgroup of men.

CONCLUSION

We may conclude that the G1733A polymorphism of AR gene could be a useful genetic marker for the assessment of a woman's risk for CAD in our Caucasian Greek population.

Androgen receptor and histone lysine demethylases in ovine placenta

Sex steroid hormones regulate developmental programming in many tissues, including programming gene expression during prenatal development. While estradiol is known to regulate placentation, little is known about the role of testosterone and androgen signaling in placental development despite the fact that testosterone rises in maternal circulation during pregnancy and in placenta-induced pregnancy disorders. We investigated the role of testosterone in placental gene expression, and focused on androgen receptor (AR). Prenatal androgenization decreased global DNA methylation in gestational day 90 placentomes, and increased placental expression of AR as well as genes involved in epigenetic regulation, angiogenesis, and growth. As AR complexes with histone lysine demethylases (KDMs) to regulate AR target genes in human cancers, we also investigated if the same mechanism is present in the ovine placenta. AR co-immunoprecipitated with KDM1A and KDM4D in sheep placentomes, and AR-KDM1A complexes were recruited to a half-site for androgen response element (ARE) in the promoter region of VEGFA. Androgenized ewes also had increased cotyledonary VEGFA. Finally, in human first trimester placental samples KDM1A and KDM4D immunolocalized to the syncytiotrophoblast, with nuclear KDM1A and KDM4D immunostaining also present in the villous stroma. In conclusion, placental androgen signaling, possibly through AR-KDM complex recruitment to AREs, regulates placental VEGFA expression. AR and KDMs are also present in first trimester human placenta. Androgens appear to be an important regulator of trophoblast differentiation and placental development, and aberrant androgen signaling may contribute to the development of placental disorders.

Evidence for association of the rs605059 polymorphism of HSD17B1 gene with recurrent spontaneous abortions

OBJECTIVE

To investigate whether the missense rs605059 polymorphism of HSD17B1 gene, which is expressed mainly in the placenta, is associated with recurrent spontaneous abortions (RSA).

METHODS

This study group consisted of 138 women with three or more unexplained spontaneous abortions, before the 20th week of gestation, with the same partner, while 140 healthy women served as controls. To genotype the individuals, we used the polymerase chain reaction-restriction fragment length polymorphism method.

RESULTS

The genotyping of the rs605059 polymorphism revealed the frequencies 0.22, 0.45 and 0.33, for AA, GA and GG genotypes, respectively, for the patient group and 0.37, 0.41 and 0.22, respectively, for the control group. The A allele frequencies were 0.44 and 0.57 for the patient and control group, respectively, and the G allele frequencies were 0.56 and 0.43 for the patient and control group, respectively. Statistical analysis of the results indicated the existence of significant differences in genotype and allele frequencies between the two groups.

CONCLUSION

The rs605059 polymorphism of the HSD17B1 gene is associated with increased risk of RSA in our Caucasian Greek population. Thus it could be used as a prognostic genetic marker for RSA.

StuI polymorphism on the androgen receptor gene is associated with recurrent spontaneous abortion

PURPOSE

This is a case- control study to determine whether G1733A polymorphism of androgen receptor gene is associated with an increased risk for recurrent spontaneous abortion (RSA).

METHOD

A total of 85 women with at least two recurrent spontaneous abortion before 20th week of gestation composed the study group. Subjects were genotyped by the polymerase chain reaction restriction fragment length polymorphism method.

RESULTS

The observed frequencies of GG, GA and AA genotypes of the G1733A polymorphism were 5.89 %, 82.35 % and 11.76 %, respectively, for the patient group and 71.76 %, 23.51 % and 4.71 %, respectively, for the control group. Allele frequencies of the G1733A polymorphism among patients and controls were 0.47 and 0.84, respectively, for the dominant allele (G) (wild type) and 0.53 and 0.16, respectively, for the A allele (mutant type).

CONCLUSIONS

These results indicated that the androgen receptor G1733A polymorphism is strongly associated with increased risk for RSA.

A potential novel spontaneous preterm birth gene, AR, identified by linkage and association analysis of X chromosomal markers

Preterm birth is the major cause of neonatal mortality and morbidity. In many cases, it has severe life-long consequences for the health and neurological development of the newborn child. More than 50% of all preterm births are spontaneous, and currently there is no effective prevention. Several studies suggest that genetic factors play a role in spontaneous preterm birth (SPTB). However, its genetic background is insufficiently characterized. The aim of the present study was to perform a linkage analysis of X chromosomal markers in SPTB in large northern Finnish families with recurrent SPTBs. We found a significant linkage signal (HLOD  = 3.72) on chromosome locus Xq13.1 when the studied phenotype was being born preterm. There were no significant linkage signals when the studied phenotype was giving preterm deliveries. Two functional candidate genes, those encoding the androgen receptor (AR) and the interleukin-2 receptor gamma subunit (IL2RG), located near this locus were analyzed as candidates for SPTB in subsequent case-control association analyses. Nine single-nucleotide polymorphisms (SNPs) within these genes and an AR exon-1 CAG repeat, which was previously demonstrated to be functionally significant, were analyzed in mothers with preterm delivery (n = 272) and their offspring (n = 269), and in mothers with exclusively term deliveries (n = 201) and their offspring (n = 199), all originating from northern Finland. A replication study population consisting of individuals born preterm (n = 111) and term (n = 197) from southern Finland was also analyzed. Long AR CAG repeats (≥26) were overrepresented and short repeats (≤19) underrepresented in individuals born preterm compared to those born at term. Thus, our linkage and association results emphasize the role of the fetal genome in genetic predisposition to SPTB and implicate AR as a potential novel fetal susceptibility gene for SPTB.

Genetics of recurrent miscarriage: challenges, current knowledge, future directions

Recurrent miscarriage (RM) occurs in 1-3% of couples aiming at childbirth. Due to multifactorial etiology the clinical diagnosis of RM varies. The design of genetic/"omics" studies to identify genes and biological mechanisms involved in pathogenesis of RM has challenges as there are several options in defining the study subjects (female patient and/or couple with miscarriages, fetus/placenta) and controls. An ideal study would attempt a trio-design focusing on both partners as well as pregnancies of the couple. Application of genetic association studies focusing on pre-selected candidate genes with potential pathological effect in RM show limitations. Polymorphisms in ∼100 genes have been investigated and association with RM is often inconclusive or negative. Also, implication of prognostic molecular diagnostic tests in clinical practice exhibits uncertainties. Future directions in investigating biomolecular risk factors for RM rely on integrating alternative approaches (SNPs, copy number variations, gene/protein expression, epigenetic regulation) in studies of single genes as well as whole-genome analysis. This would be enhanced by collaborative network between research centers and RM clinics.

Genetic variation in the HSD3B1 gene and recurrent spontaneous abortions

OBJECTIVE

HSD3B1 gene encodes the 3β-hydroxysteroid deydrogenases/isomerase (3β-HSD) enzyme, which plays a crucial role in the biosynthesis of all hormonal steroids. The aim of this study was to examine the potential impact of a T → C substitution at codon Leu(338) of HSD3B1 gene on pregnancy outcome.

METHODS

In this prospective case-control study, 162 patients and 139 healthy controls were investigated for the possible association between the HSD3B1 T/C polymorphism and the risk of recurrent spontaneous abortions (RSA). The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was used in order to genotype the subjects.

RESULTS

The frequencies of TT, TC, and CC genotypes were 0.20, 0.51, and 0.29, respectively, in the patient group and 0.20, 0.45, and 0.35, respectively, in the control group. The allele frequencies were 0.456 and 0.428 for T allele for the patient group and control group, respectively and 0.543 and 0.572 for C allele for the patient and control group, respectively. The data between the two groups were analyzed by chi-square test or Fisher's exact test. Our results showed that there are no significant differences in genotype (P = 0.56) or in allele frequencies (P = 0.51) between the patient and the control group.

CONCLUSION

The HSD3B1 T/C polymorphism cannot be used as genetic marker for the risk for RSA in our Caucasian population.

Genetic variation in the CYP17 gene and recurrent spontaneous abortions

PURPOSE

The CYP17 gene encodes the enzyme cytochrome P450c17α, which functions at key steps in the synthesis process of human sex steroid hormones. A T/C polymorphism in the 5' promoter region of the CYP17 gene has been described previously. Serum levels of androgens and estrogens have been shown to be elevated in individuals who carry the C substitution (Α2 allele). We hypothesized that variability in genes that control the sex hormone (estrogens, testosterone) biosynthesis might affect the pregnancy outcome. In the present study, we investigated the possible association between the T/C polymorphism of the promoter of CYP17 gene and the risk of recurrent spontaneous abortions in the Greek population.

METHODS

In the prospective case-control study, 148 patients and 134 healthy controls were studied. Women who had at least three unexplained spontaneous abortions before 20 weeks of gestation were included in the patient group. The PCR-RFLP method was used to genotype the subjects.

RESULTS

The frequencies of A1A1, A1A2, A2A2 genotypes were 0.34, 0.52, 0.14, respectively, in the patient group and 0.32, 0.47, 0.21, respectively, in the control group. The allele frequencies were 0.595 and 0.405 for A1 and A2, in the patient group and 0.555 and 0.445 for A1 and A2, respectively, in the control group. The data between the two groups were analyzed by χ(2) test. Our results showed that there are no significant differences in genotype (P = 0.3883) or in allele frequencies (P = 0.3800) between the patient and the control group.

CONCLUSION

The T/C promoter polymorphism of the CYP17 gene is not associated with the risk for recurrent spontaneous abortions in our Caucasian population.