Retinoic acid signaling determines the fate of the uterus from the mouse Müllerian duct

A novel de novo synonymous variant in GREB1L impacts the mRNA splicing associated with aplasia of the urogenital system

GREB1-like retinoic acid receptor coactivator (GREB1L) gene is associated with autosomal dominant renal hypodysplasia/aplasia 3 (RHDA3) and deafness, autosomal dominant 80 (DFNA80). Among the GREB1L variants reported, most of them are missense or frameshift, while no pathogenic synonymous variants have been recorded. Classical theory paid little attention to synonymous variants and classified it as nonpathogenic; however, recent studies suggest that the variants might be equally important. Here, we report a 7-year-old girl with new symptoms of clitoromegaly, uterovaginal, and ovarian agenesis as well as right kidney missing. A novel de novo GREB1L synonymous variant (NM_001142966: c.4731C>T, p.G1577=) was identified via whole exome sequencing. The variant was predicted to be disease-causing through in silico analysis and was classified as likely pathogenic. Minigene splicing assays confirmed a 6 bp deletion in mutant cDNA comparing with the wild type, leading to two amino acids lost in GREB1L protein. Secondary and tertiary structure modeling showed alterations in protein structure. Our finding reveals a novel GREB1L variant with a new phenotype of urogenital system and is the first to report a pathogenic synonymous variant in GREB1L which affects mRNA splicing, suggesting synonymous variants cannot be ignored in prenatal diagnosis and genetic counseling.

Heterozygous ZNHIT3 variants within the 17q12 recurrent deletion region are associated with Mayer-Rokitansky-Kuster Hauser (MRKH) syndrome

The molecular basis of mullerian aplasia, also known as Mayer-Rokitansky-Kuster Hauser (MRKH) or congenital absence of the uterus and vagina, is largely unknown. We applied a multifaceted genetic approach to studying the pathogenesis of MRKH including exome sequencing of trios and duos, genome sequencing of families, qPCR, RT-PCR, and Sanger sequencing to detect intragenic deletions, insertions, splice variants, single nucleotide variants, and rearrangements in 132 persons with MRKH. We identified two heterozygous variants in ZNHIT3 localized to a commonly involved CNV region at chromosome 17q12 in two different families with MRKH. One is a frameshift, truncating variant that is predicted to interfere with steroid hormone binding of the LxxLL sequence of the C-terminal region. The second variant is a double missense/stopgain variant. Both variants impair protein expression in vitro. In addition, four more probands with MRKH harbored the stopgain variant without the nearby missense variant. In total, 6/132 (4.5%) of patients studied, including five with associated anomalies (type 2 MRKH), had ZNHIT3 variants that impair function in vitro. Our findings implicate ZNHIT3 as an important gene associated with MRKH within the 17q12 CNV region.

Renal Hypodysplasia/Aplasia 3 Caused by a Rare Variant of GREB1L With Incomplete Penetrance in a Chinese Family

Renal agenesis represents the most severe form of congenital anomalies of the kidney and urinary tract. Bilateral renal agenesis is almost invariably fatal at birth and has high genetic heterogeneity. Here we report on a Chinese family with two pregnancies affected by a prenatal form of bilateral renal agenesis. Trio-WES was conducted to explore the underlying genetic cause and identified a novel nonsense variant (c .2621G>A: p. Trp874Ter) in the GREB1L gene. Based on previous research, pathogenic mutations in GREB1L can cause renal hypodysplasia/aplasia-3 (RHDA3) with autosomal dominant inheritance. Sanger sequencing performed on the family members revealed that the variant was vertically transmitted from the maternal grandfather through the unaffected mother to the two affected fetuses, fully demonstrating the incomplete dominance of the disease. Our study extends the mutational spectrum associated with RHDA3 and contributes to a more general understanding for the complex genetic inheritance of GREB1L.

Association between serum carotenoids and bacterial vaginosis infection among American women

BACKGROUND

Bacterial vaginosis (BV) is a widely occurring vaginal inflammation in women of childbearing age caused by dysbiosis of the vaginal flora. Few studies have investigated the effect of serum carotenoids on the development and pathogenesis of BV. This study thus aimed to explore the correlation between serum carotenoids and BV in American women.

METHOD

The analysis included 1252 participants with BV from the National Health and Nutrition Examination Survey (NHANES) between 2001 and 2004. Multiple logistic regression was conducted to explore the correlation between BV and serum carotenoids, while smooth curve fitting was utilized to examine potential nonlinear correlations. Furthermore, stratified subgroup analyses and sensitivity analyses were conducted. ORs reflected the correlation between BV and serum carotenoids.

RESULT

Results of multiple logistic regression indicated that total serum carotenoids and BV had an inverse correlation. In the fully adjusted model II, the quartile with the highest levels of α-carotene and β-cryptoxanthin had a substantially lower incidence of BV. Smooth curve fitting revealed a significant negative linear correlation between serum carotenoids and the incidence of BV. The negative correlation between serum carotenoids and BV was relatively stable in stratified analyses. Moreover, in sensitivity analyses, the association between serum carotenoids and BV persisted, and β-carotene became significantly negatively correlated with BV.

CONCLUSION

This study found an inverse correlation between serum carotenoids and the prevalence of BV.

Whole exome sequencing reveals novel candidate variants for endometriosis utilizing multiple affected members in a single family

BACKGROUND

Endometriosis is an estrogen-dependent, chronic inflammatory disease that affects 10% of women during the reproductive ages. Despite the estimated 50% heritability for the condition, only 26% was associated with common genetic variants. Thus, necessity of identifying rare variants for the missing heritability is implicated in the literature. Therefore, our study aimed to identify novel rare genetic variants involved in the pathogenesis of endometriosis utilizing a family of multiple affected members.

METHODS

A family composed of four affected women along with their two unaffected mothers were recruited at a single gynecology and infertility clinic specialized in endometriosis. All patients presented with endometriomas, which was visualized by transvaginal ultrasonography. Two affected individuals had received laparoscopic endometrioma excision and therefore were diagnosed with recurrent disease. One mother had a history of endometrial serous adenocarcinoma (ESC) for which she underwent hysterectomy with bilateral oophorectomy. Three endometriosis cases were whole exome sequenced on Illumina NextSeq 550 platform with an average of 90% coverage. Candidate genes were confirmed by Sanger sequencing and followed-up with family segregation.

RESULTS

Novel rare variants were identified in TNFRSF1B (NM_001066.3: c.1072G>A, p.(Ala358Thr)) and GEN1 (NM_001130009.3: c.1574C>T, p.(Ser525Leu)) as possible genetic causes of endometriosis. A third novel rare variant was identified in CRABP1 (NM_004378.3:c.54G>C, p.(Glu18Asp)) only on the mother with ESC history and her daughters.

CONCLUSION

Novel candidate genetic variants that might contribute to endometriosis were suggested that need replication through independent cohorts or validation by functional studies. The family has also received genetic counseling and that the affected daughters are on clinical follow-up, accordingly.

RA-RAR signaling promotes mouse vaginal opening through increasing β-catenin expression and vaginal epithelial cell apoptosis

BACKGROUND

Retinoic acid (RA) plays important role in the maintenance and differentiation of the Müllerian ducts during the embryonic stage via RA receptors (RARs). However, the function and mechanism of RA-RAR signaling in the vaginal opening are unknown.

METHOD

We used the Rarα knockout mouse model and the wild-type ovariectomized mouse models with subcutaneous injection of RA (2.5 mg/kg) or E2 (0.1 µg/kg) to study the role and mechanism of RA-RAR signaling on the vaginal opening. The effects of Rarα deletion on Ctnnb1 mRNA levels and cell apoptosis in the vaginas were analyzed by real-time PCR and immunofluorescence, respectively. The effects of RA on the expression of β-catenin and apoptosis in the vaginas were analyzed by real-time PCR and western blotting. The effects of E2 on RA signaling molecules were analyzed by real-time PCR and western blotting.

RESULTS

RA signaling molecules were expressed in vaginal epithelial cells, and the mRNA and/or protein levels of RALDH2, RALDH3, RARα and RARγ reached a peak at the time of vaginal opening. The deletion of Rarα resulted in 25.0% of females infertility due to vaginal closure, in which the mRNA (Ctnnb1, Bak and Bax) and protein (Cleaved Caspase-3) levels were significantly decreased, and Bcl2 mRNA levels were significantly increased in the vaginas. The percentage of vaginal epithelium with TUNEL- and Cleaved Caspase-3-positive signals were also significantly decreased in Rarα^-/- females with vaginal closure. Furthermore, RA supplementation of ovariectomized wild-type (WT) females significantly increased the expression of β-catenin, active β-catenin, BAK and BAX, and significantly decreased BCL2 expression in the vaginas. Thus, the deletion of Rarα prevents vaginal opening by reducing the vaginal β-catenin expression and epithelial cell apoptosis. The deletion of Rarα also resulted in significant decreases in serum estradiol (E2) and vagina Raldh2/3 mRNA levels. E2 supplementation of ovariectomized WT females significantly increased the expression of RA signaling molecules in the vaginas, suggesting that the up-regulation of RA signaling molecules in the vaginas is dependent on E2 stimulation.

CONCLUSION

Taken together, we propose that RA-RAR signaling in the vaginas promotes vaginal opening through increasing β-catenin expression and vaginal epithelial cell apoptosis.

Role of EZH2 in Uterine Gland Development

Enhancer of zeste homolog 2 (EZH2) is a core component of polycomb repressive complex 2 that plays a vital role in transcriptional repression of gene expression. Conditional ablation of EZH2 using progesterone receptor (Pgr)-Cre in the mouse uterus has uncovered its roles in regulating uterine epithelial cell growth and stratification, suppressing decidual myofibroblast activation, and maintaining normal female fertility. However, it is unclear whether EZH2 plays a role in the development of uterine glands, which are required for pregnancy success. Herein, we created mice with conditional deletion of Ezh2 using anti-Mullerian hormone receptor type 2 (Amhr2)-Cre recombinase that is expressed in mesenchyme-derived cells of the female reproductive tract. Strikingly, these mice showed marked defects in uterine adenogenesis. Unlike Ezh2 Pgr-Cre conditional knockout mice, deletion of Ezh2 using Amhr2-Cre did not lead to the differentiation of basal-like cells in the uterus. The deficient uterine adenogenesis was accompanied by impaired uterine function and pregnancy loss. Transcriptomic profiling using next generation sequencing revealed dysregulation of genes associated with signaling pathways that play fundamental roles in development and disease. In summary, this study has identified an unrecognized role of EZH2 in uterine gland development, a postnatal event critical for pregnancy success and female fertility.

A New Horizon in Reproductive Research with Pluripotent Stem Cells: Successful In Vitro Gametogenesis in Rodents, Its Application to Large Animals, and Future In Vitro Reconstitution of Reproductive Organs Such as “Uteroid” and “Oviductoid”

Simple Summary

Functional gametes, such as oocytes and spermatozoa, have been derived from rodent pluripotent stem cells, which can be applied to large animals and ultimately, to humans. In addition to summarizing these topics, we also review additional approaches for in vitro reconstitution of reproductive organs. This review illustrates intensive past efforts and future challenges on stem cell research for in vitro biogenesis in various mammalian models.

Abstract

Recent success in derivation of functional gametes (oocytes and spermatozoa) from pluripotent stem cells (PSCs) of rodents has made it feasible for future application to large animals including endangered species and to ultimately humans. Here, we summarize backgrounds and recent studies on in vitro gametogenesis from rodent PSCs, and similar approaches using PSCs from large animals, including livestock, nonhuman primates (NHPs), and humans. We also describe additional developing approaches for in vitro reconstitution of reproductive organs, such as the ovary (ovarioid), testis (testisoid), and future challenges in the uterus (uteroid) and oviduct (oviductoid), all of which may be derived from PSCs. Once established, these in vitro systems may serve as a robust platform for elucidating the pathology of infertility-related disorders and ectopic pregnancy, principle of reproduction, and artificial biogenesis. Therefore, these possibilities, especially when using human cells, require consideration of ethical issues, and international agreements and guidelines need to be raised before opening “Pandora’s Box”.

Retinoic acid exerts sexually dimorphic effects on muscle energy metabolism and function

The retinol dehydrogenase Rdh10 catalyzes the rate-limiting reaction that converts retinol into retinoic acid (RA), an autacoid that regulates energy balance and reduces adiposity. Skeletal muscle contributes to preventing adiposity, by consuming nearly half the energy of a typical human. We report sexually dimorphic differences in energy metabolism and muscle function in Rdh10+/- mice. Relative to wild-type (WT) controls, Rdh10+/- males fed a high-fat diet decrease reliance on fatty-acid oxidation and experience glucose intolerance and insulin resistance. Running endurance decreases 40%. Rdh10+/- females fed this diet increase fatty acid oxidation and experience neither glucose intolerance nor insulin resistance. Running endurance increases 220%. We therefore assessed RA function in the mixed-fiber type gastrocnemius muscles (GM), which contribute to running, rather than standing, and are similar to human GM. RA levels in Rdh10+/- male GM decrease 38% relative to WT. Rdh10+/- male GM increase expression of Myog and reduce Eif6 mRNAs, which reduce and enhance running endurance, respectively. Cox5A, complex IV activity, and ATP decrease. Increased centralized nuclei reveal existence of muscle malady and/or repair in GM fibers. Comparatively, RA in Rdh10+/- female GM decreases by less than half the male decrease, from a more modest decrease in Rdh10 and an increase in the estrogen-induced retinol dehydrogenase Dhrs9. Myog mRNA decreases. Cox5A, complex IV activity, and ATP increase. Centralized GM nuclei do not increase. We conclude that Rdh10/RA affects whole body energy use and insulin resistance partially through sexual dimorphic effects on skeletal muscle gene expression, structure, and mitochondria activity.

The impact of isotretinoin on the pituitary-ovarian axis: An interpretative review of the literature

Isotretinoin (13-cis-retinoic acid), a derivative of vitamin A, is used in the treatment of severe acne resulting in sebum suppression induced by sebocyte apoptosis. Isotretinoin treatment is associated with several adverse effects including teratogenicity, hepatotoxicity, and dyslipidemia. Isotretinoin's effects on endocrine systems and its potential role as an endocrine disruptor are not yet adequately investigated. This review presents clinical, endocrine, and molecular evidence showing that isotretinoin treatment adversely affects the pituitary-ovarian axis and enhances the risk of granulosa cell apoptosis reducing follicular reserve. Isotretinoin is associated with pro-apoptotic signaling in sebaceous glands through upregulated expression of p53, forkhead box O transcription factors (FOXO1, FOXO3), and tumor necrosis factor-related apoptosis inducing ligand (TRAIL). Two literature searches including clinical and experimental studies respectively support the hypothesis that isotretinoin's toxicological mode of action on the pituitary-ovarian axis might be caused by over-expressed p53/FOXO1 signaling resulting in gonadotropin suppression and granulosa cell apoptosis. The reduction of follicular reserve by isotretinoin treatment should be especially considered when this drug will be administered for the treatment of acne in post-adolescent women, in whom fertility may be adversely affected. In contrast, isotretinoin treatment may exert beneficial effects in states of hyperandrogenism, especially in patients with polycystic ovary syndrome.

Altered Expression of Candidate Genes in Mayer-Rokitansky-Küster-Hauser Syndrome May Influence Vaginal Keratinocytes Biology: A Focus on Protein Kinase X

Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome is a rare and complex disease defined by congenital aplasia of the vagina and uterus in 46,XX women, often associated with kidney and urinary tract anomalies. The aetiopathogenesis of MRKH syndrome is still largely unknown. Herein, we investigated the role of selected candidate genes in the aetiopathogenesis of MRKH syndrome, with a focus on PRKX, which encodes for protein kinase X. Through RT-qPCR analyses performed on vaginal dimple samples from patients, and principal component analysis (PCA), we highlighted a phenotype-related expression pattern of PRKX, MUC1, HOXC8 and GREB1L in MRKH patients. By using an in vitro approach, we proved that PRKX ectopic overexpression in a cell model of vaginal keratinocytes promotes cell motility through epithelial-to-mesenchymal transition (EMT) activation, a fundamental process in urogenital tract morphogenesis. Moreover, our findings showed that PRKX upregulation in vaginal keratinocytes is able to affect transcriptional levels of HOX genes, implicated in urinary and genital tract development. Our study identified the dysregulation of PRKX expression as a possible molecular cause for MRKH syndrome. Moreover, we propose the specific role of PRKX in vaginal keratinocyte biology as one of the possible mechanisms underlying this complex disease.

Regulatory Role of Retinoic Acid in Male Pregnancy of the Seahorse

Seahorses epitomize the exuberance of evolution. They have the unique characteristic of male pregnancy, which includes the carrying of many embryos in a brood pouch that incubates and nourishes the embryos, similar to the mammalian placenta. However, the regulatory networks underlying brood pouch formation and pregnancy remain largely unknown. In this study, comparative transcriptomic and metabolomic profiling on the lined seahorse Hippocampus erectus, with unformed, newly formed, and pregnant brood pouches identified a total of 141 and 2,533 differentially expressed genes together with 73 and 121 significantly differential metabolites related to brood pouch formation and pregnancy, respectively. Specifically, integrative omics analysis revealed that retinoic acid (RA) synthesis and signaling pathway played essential roles in the formation of the brood pouch and pregnancy. RA might function upstream of testosterone and progesterone, thereby directly influencing brood pouch formation by regulating the expression of fshr and cyp7a1. Our results also revealed that RA regulates antioxidant defenses, particularly during male pregnancy. Alternatively, pregnancy caused a consistent decrease in RA, canthaxanthin, astaxanthin, and glutathione synthetase, and an increase in susceptibility to oxidative stress, which may balance brood pouch development and reproduction in seahorses and pave the way to successful gestation.

New frontiers of developmental endocrinology opened by researchers connecting irreversible effects of sex hormones on developing organs

In the early 1960's, at Professor Bern's laboratory, University of California, Berkeley) in the US, Takasugi discovered ovary-independent, persistent vaginal changes in mice exposed neonatally to estrogen, which resulted in vaginal cancer later in life. Reproductive abnormalities in rodents were reported as a result of perinatal exposure to various estrogenic chemicals. Ten years later, vaginal cancers were reported in young women exposed in utero to the synthetic estrogen diethylstilbestrol (DES) and this has been called the "DES syndrome". The developing organism is particularly sensitive to developmental exposure to estrogens inducing long-term changes in various organs including the reproductive organs. The molecular mechanism underlying the persistent vaginal changes induced by perinatal estrogen exposure was partly demonstrated. Persistent phosphorylation and sustained expression of EGF-like growth factors, lead to estrogen receptor α (ESR1) activation, and then persistent vaginal epithelial cell proliferation. Agents which are weakly estrogenic by postnatal criteria may have major developmental effects, especially during a critical perinatal period. The present review outlines various studies conducted by four generations of investigators all under the influence of Prof. Bern. The studies include reports of persistent changes induced by neonatal androgen exposure, analyses of estrogen responsive genes, factors determining epithelial differentiation in the Müllerian duct, ESR and growth factor signaling, and polyovular follicles in mammals. This review is then expanded to the studies on the effects of environmental estrogens on wildlife and endocrine disruption in Daphnids.

Whole-exome sequencing identifies a GREB1L variant in a three-generation family with Müllerian and renal agenesis: a novel candidate gene in Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome. A case report

The aetiology of Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome, characterized by uterovaginal agenesis in 46,XX women, remains poorly understood. Since familial occurrences are rare, genetic findings reported so far only apply to a minority of mainly sporadic cases and most studies have not included other family members enabling segregation analysis. Herein, we report on the investigation of a unique three-generation family of two female cousins with MRKH syndrome and unilateral renal agenesis (RA) and two deceased male relatives with RA. We performed whole-exome sequencing (WES) in eight family members leading to the identification of a novel pathogenic (CADD = 33) c.705G>T missense variant in GREB1L, a gene recently identified as a novel cause of RA. Previous reports include several cases of female fetuses with bilateral RA and uterus agenesis, which support GREB1L as an important gene in both kidney and female genital tract development. The pedigree is compatible with autosomal dominant inheritance with incomplete penetrance following a parent-origin-specific manner, which could be due to imprinting. To our knowledge, this is the first investigation of a larger MRKH syndrome pedigree using WES, and we suggest GREB1L as a novel and promising candidate gene in the aetiology of MRKH syndrome.

Estrogen receptor α (ERα)-binding super-enhancers drive key mediators that control uterine estrogen responses in mice

Estrogen receptor α (ERα) modulates gene expression by interacting with chromatin regions that are frequently distal from the promoters of estrogen-regulated genes. Active chromatin-enriched "super-enhancer" (SE) regions, mainly observed in in vitro culture systems, often control production of key cell type-determining transcription factors. Here, we defined super-enhancers that bind to ERα in vivo within hormone-responsive uterine tissue in mice. We found that SEs are already formed prior to estrogen exposure at the onset of puberty. The genes at SEs encoded critical developmental factors, including retinoic acid receptor α (RARA) and homeobox D (HOXD). Using high-throughput chromosome conformation capture (Hi-C) along with DNA sequence analysis, we demonstrate that most SEs are located at a chromatin loop end and that most uterine genes in loop ends associated with these SEs are regulated by estrogen. Although the SEs were formed before puberty, SE-associated genes acquired optimal ERα-dependent expression after reproductive maturity, indicating that pubertal processes that occur after SE assembly and ERα binding are needed for gene responses. Genes associated with these SEs affected key estrogen-mediated uterine functions, including transforming growth factor β (TGFβ) and LIF interleukin-6 family cytokine (LIF) signaling pathways. To the best of our knowledge, this is the first identification of SE interactions that underlie hormonal regulation of genes in uterine tissue and optimal development of estrogen responses in this tissue.