Generation of Esr1-knockout rats using zinc finger nuclease-mediated genome editing

Estrogen receptor knockdown suggests its role in gonadal development regulation in Manila clam Ruditapes philippinarum

The estrogen receptor (ER), a ligand-dependent transcription factor, is critical for vertebrate reproduction. However, its role in bivalves is not well understood, with ongoing debates regarding its function in regulating reproduction similarly to vertebrates. To investigate ER's function, we conducted a 21-day RNA interference experiment focusing on its role in gonadal development in bivalves. Histological analyses revealed that ER inhibition significantly suppressed ovarian development in females and, conversely, promoted gonadal development in males. Additionally, levels of 17β-estrogen (E2) were markedly reduced in the gonads of both sexes following ER suppression. Transcriptomic analysis from RNA-seq of testes and ovaries after ER interference showed changes in the expression of key genes such as Vtg, CYP17, 3β-HSD, and 17β-HSD. These genes are involved in the estrogen signaling pathway and steroid hormone biosynthesis. Furthermore, ER suppression significantly affected the expression of genes linked to gametogenesis and the reproductive cycle. Our findings highlight ER's crucial, yet complex and sex-specific roles in gonadal development in bivalves, emphasizing the need for further detailed studies.

Molecular approaches to mammalian uterine receptivity for conceptus implantation

Mammalian reproduction is more inefficient than expected and embryo/conceptus implantation into the maternal endometrium is considered to be a rate-limiting process. Although extensive physiological and structural diversity exists among mammalian species, the basic molecular mechanisms underlying successful implantation are conserved. The extensive use of genetically engineered mouse models has provided considerable information on uterine receptivity for embryo implantation. The molecular mechanisms and cellular processes identified thus far require further validation in other mammalian species. In this review, representative ovarian steroid hormone-induced signaling pathways controlling uterine adaptation are presented based on the results of rodent studies. Selected examples of functional conservation in mammals, such as humans and cattle, are briefly described. To date, molecular therapeutic trials for fertility improvement have not been conducted. Considerable efforts are required to provide further understanding of these molecular mechanisms. Such understanding will contribute to the development of reliable clinical diagnostics and therapeutics for implantation failure, leading to reproductive success in a wide variety of mammals in the future.

Reproductive function and behaviors: an update on the role of neural estrogen receptors alpha and beta

Infertility is becoming a major public health problem, with increasing frequency due to medical, environmental and societal causes. The increasingly late age of childbearing, growing exposure to endocrine disruptors and other reprotoxic products, and increasing number of medical reproductive dysfunctions (endometriosis, polycystic ovary syndrome, etc.) are among the most common causes. Fertility relies on fine-tuned control of both neuroendocrine function and reproductive behaviors, those are critically regulated by sex steroid hormones. Testosterone and estradiol exert organizational and activational effects throughout life to establish and activate the neural circuits underlying reproductive function. This regulation is mediated through estrogen receptors (ERs) and androgen receptor (AR). Estradiol acts mainly via nuclear estrogen receptors ERα and ERβ. The aim of this review is to summarize the genetic studies that have been undertaken to comprehend the specific contribution of ERα and ERβ in the neural circuits underlying the regulation of the hypothalamic-pituitary-gonadal axis and the expression of reproductive behaviors, including sexual and parental behavior. Particular emphasis will be placed on the neural role of these receptors and the underlying sex differences.

Fecundity is optimized by levels of nutrient signal-dependent expression of Dve and EcR in Drosophila male accessory gland

Steroid hormones play various physiological roles including metabolism and reproduction. Steroid hormones in insects are ecdysteroids, and the major form in Drosophila melanogaster is ecdysone. In Drosophila males, the accessory gland is responsive to nutrient-dependent regulation of fertility/fecundity. The accessory gland is composed of two types of binucleated epithelial cells: a main cell and a secondary cell (SC). The transcription factors Defective proventriculus (Dve), Abdominal-B, and Ecdysone receptors (EcRs) are strongly expressed in adult SCs. We show that this EcR expression is regulated by parallel pathways of nutrient signaling and the Dve activity. Induction of Dve expression is also dependent on nutrient signaling, and it becomes nutrient signal-independent during a restricted period of development. Forced dve expression during the restricted period significantly increased the number of SCs. Here, we provide evidence that the level of nutrient signal-dependent Dve expression during the restricted period determines the number of SCs, and that ecdysone signaling is also crucial to optimize male fecundity through nutrient signal-dependent survival and maturation of SCs.

The role of the aryl hydrocarbon receptor in mediating the effects of mono(2-ethylhexyl) phthalate in mouse ovarian antral follicles†

Di(2-ethylhexyl) phthalate (DEHP) is a pervasive environmental toxicant used in the manufacturing of numerous consumer products, medical supplies, and building materials. DEHP is metabolized to mono(2-ethylhexyl) phthalate (MEHP). MEHP is an endocrine disruptor that adversely affects folliculogenesis and steroidogenesis in the ovary, but its mechanism of action is not fully understood. Thus, we tested the hypothesis that the aryl hydrocarbon receptor (AHR) plays a functional role in MEHP-mediated disruption of folliculogenesis and steroidogenesis. CD-1 mouse antral follicles were isolated and cultured with MEHP (0-400 μM) in the presence or absence of the AHR antagonist CH223191 (1 μM). MEHP treatment reduced follicle growth over a 96-h period, and this effect was partially rescued by co-culture with CH223191. MEHP exposure alone increased expression of known AHR targets, cytochrome P450 (CYP) enzymes Cyp1a1 and Cyp1b1, and this induction was blocked by CH223191. MEHP reduced media concentrations of estrone and estradiol compared to control. This effect was mitigated by co-culture with CH223191. Moreover, MEHP reduced the expression of the estrogen-sensitive genes progesterone receptor (Pgr) and luteinizing hormone/choriogonadotropin receptor (Lhcgr) and co-treatment with CH223191 blocked this effect. Collectively, these data indicate that MEHP activates the AHR to impair follicle growth and reduce estrogen production and signaling in ovarian antral follicles.

Streamlined identification of clinically and functionally relevant genetic regulators of lower-tract urogenital development

Congenital anomalies of the lower genitourinary (LGU) tract are frequently comorbid due to genetically linked developmental pathways, and are among the most common yet most socially stigmatized congenital phenotypes. Genes involved in sexual differentiation are prime candidates for developmental anomalies of multiple LGU organs, but insufficient prospective screening tools have prevented the rapid identification of causative genes. Androgen signaling is among the most influential modulators of LGU development. The present study uses SpDamID technology in vivo to generate a comprehensive map of the pathways actively regulated by the androgen receptor (AR) in the genitalia in the presence of the p300 coactivator, identifying wingless/integrated (WNT) signaling as a highly enriched AR-regulated pathway in the genitalia. Transcription factor (TF) hits were then assayed for sexually dimorphic expression at two critical time points and also cross-referenced to a database of clinically relevant copy number variations to identify 252 TFs exhibiting copy variation in patients with LGU phenotypes. A subset of 54 TFs was identified for which LGU phenotypes are statistically overrepresented as a proportion of total observed phenotypes. The 252 TF hitlist was then subjected to a functional screen to identify hits whose silencing affects genital mesenchymal growth rates. Overlap of these datasets results in a refined list of 133 TFs of both functional and clinical relevance to LGU development, 31 of which are top priority candidates, including the well-documented renal progenitor regulator, Sall1. Loss of Sall1 was examined in vivo and confirmed to be a powerful regulator of LGU development.

Sex Steroid Receptors in Polycystic Ovary Syndrome and Endometriosis: Insights from Laboratory Studies to Clinical Trials

Polycystic ovary syndrome (PCOS) and endometriosis are reproductive disorders that may cause infertility. The pathology of both diseases has been suggested to be associated with sex steroid hormone receptors, including oestrogen receptors (ER), progesterone receptors (PRs) and androgen receptors (ARs). Therefore, with this review, we aim to provide an update on the available knowledge of these receptors and how their interactions contribute to the pathogenesis of PCOS and endometriosis. One of the main PCOS-related medical conditions is abnormal folliculogenesis, which is associated with the downregulation of ER and AR expression in the ovaries. In addition, metabolic disorders in PCOS are caused by dysregulation of sex steroid hormone receptor expression. Furthermore, endometriosis is related to the upregulation of ER and the downregulation of PR expression. These receptors may serve as therapeutic targets for the treatment of PCOS-related disorders and endometriosis, considering their pathophysiological roles. Receptor agonists may be applied to increase the expression of a specific receptor and treat endometriosis or metabolic disorders. In contrast, receptor antagonist functions to reduce receptor expression and can be used to treat endometriosis and induce ovulation. Understanding PCOS and the pathological roles of endometriosis sex steroid receptors is crucial for developing potential therapeutic strategies to treat infertility in both conditions. Therefore, research should be continued to fill the knowledge gap regarding the subject.

Identification of the TSSK4 Alternative Spliceosomes and Analysis of the Function of the TSSK4 Protein in Yak (Bos grunniens)

In mammals, the testis-specific serine/threonine kinase (TSSK) is essential for spermatogenesis and male fertility. TSSK4 belongs to the family of the testis-specific serine/threonine-protein kinase (TSSK), with a crucial role in spermatogenesis. This study aimed to analyze the variable spliceosome of the TSSK4 gene in the yak for understanding the regulatory function of the TSSK4 spliceosome in yak testis development using PCR amplification and cloning techniques. The GST pull-down was used for pulling down the protein interacting with TSSK4, and then the protein interacting with TSSK4 was identified using LC–MS/MS. The results of the PCR amplification demonstrated multiple bands of the TSSK4 gene in the yak. The cloning and sequencing yielded a total of six alternative spliceosomes, which included only two alternative spliceosomes before sexual maturity and four alternative spliceosomes after sexual maturity. The sub-cells of the alternative spliceosomes were found to localize in the nucleus before sexual maturity and in the cytoplasm after sexual maturity. The LC–MS/MS analysis of the alternative spliceosome with the highest expression after sexual maturity yielded a total of 223 interacting proteins. The enrichment analysis of the 223 interacting proteins revealed these proteins participate in biological processes, cell composition, and molecular functions. The KEGG analysis indicated that the TSSK4-interacting protein participates in the estrogen signaling pathways, tight junctions, endoplasmic reticulum protein processing, and other signaling pathways. This study cloned the six alternative spliceosomes of the TSSK4 gene laying the foundation for studying the function of each spliceosome in the future.

Sexual Dimorphism in Kisspeptin Signaling

Kisspeptin (KP) and kisspeptin receptor (KPR) are essential for the onset of puberty, development of gonads, and maintenance of gonadal function in both males and females. Hypothalamic KPs and KPR display a high degree of sexual dimorphism in expression and function. KPs act on KPR in gonadotropin releasing hormone (GnRH) neurons and induce distinct patterns of GnRH secretion in males and females. GnRH acts on the anterior pituitary to secrete gonadotropins, which are required for steroidogenesis and gametogenesis in testes and ovaries. Gonadal steroid hormones in turn regulate the KP neurons. Gonadal hormones inhibit the KP neurons within the arcuate nucleus and generate pulsatile GnRH mediated gonadotropin (GPN) secretion in both sexes. However, the numbers of KP neurons in the anteroventral periventricular nucleus and preoptic area are greater in females, which release a large amount of KPs in response to a high estrogen level and induce the preovulatory GPN surge. In addition to the hypothalamus, KPs and KPR are also expressed in various extrahypothalamic tissues including the liver, pancreas, fat, and gonads. There is a remarkable difference in circulating KP levels between males and females. An increased level of KPs in females can be linked to increased numbers of KP neurons in female hypothalamus and more KP production in the ovaries and adipose tissues. Although the sexually dimorphic features are well characterized for hypothalamic KPs, very little is known about the extrahypothalamic KPs. This review article summarizes current knowledge regarding the sexual dimorphism in hypothalamic as well as extrahypothalamic KP and KPR system in primates and rodents.

DOT1L Mediated Gene Repression in Extensively Self-Renewing Erythroblasts

DOT1L is essential for embryonic hematopoiesis but the precise mechanisms of its action remain unclear. The only recognized function of DOT1L is histone H3 lysine 79 (H3K79) methylation, which has been implicated in both transcriptional activation and repression. We observed that deletion of the mouse Dot1L gene (Dot1L-KO) or selective mutation of its methyltransferase domain (Dot1L-MM) can differentially affect early embryonic erythropoiesis. However, both mutations result in embryonic lethality by mid-gestation and growth of hematopoietic progenitor cells (HPCs) is similarly affected in extensively self-renewing erythroblast (ESRE) cultures established from yolk sac cells. To understand DOT1L-mediated gene regulation and to clarify the role of H3K79 methylation, we analyzed whole transcriptomes of wildtype and Dot1L-mutant ESRE cells. We observed that more than 80% of the differentially expressed genes (DEGs) were upregulated in the mutant ESRE cells either lacking the DOT1L protein or the DOT1L methyltransferase activity. However, approximately 45% of the DEGs were unique to either mutant group, indicating that DOT1L possesses both methyltransferase-dependent and -independent gene regulatory functions. Analyses of Gene Ontology and signaling pathways for the DEGs were consistent, with DEGs that were found to be common or unique to either mutant group. Genes related to proliferation of HPCs were primarily impacted in Dot1L-KO cells, while genes related to HPC development were affected in the Dot1L-MM cells. A subset of genes related to differentiation of HPCs were affected in both mutant groups of ESREs. Our findings suggest that DOT1L primarily acts to repress gene expression in HPCs, and this function can be independent of its methyltransferase activity.

Recent Advances in the Production of Genome-Edited Rats

The rat is an important animal model for understanding gene function and developing human disease models. Knocking out a gene function in rats was difficult until recently, when a series of genome editing (GE) technologies, including zinc-finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and the type II bacterial clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated Cas9 (CRISPR/Cas9) systems were successfully applied for gene modification (as exemplified by gene-specific knockout and knock-in) in the endogenous target genes of various organisms including rats. Owing to its simple application for gene modification and its ease of use, the CRISPR/Cas9 system is now commonly used worldwide. The most important aspect of this process is the selection of the method used to deliver GE components to rat embryos. In earlier stages, the microinjection (MI) of GE components into the cytoplasm and/or nuclei of a zygote was frequently employed. However, this method is associated with the use of an expensive manipulator system, the skills required to operate it, and the egg transfer (ET) of MI-treated embryos to recipient females for further development. In vitro electroporation (EP) of zygotes is next recognized as a simple and rapid method to introduce GE components to produce GE animals. Furthermore, in vitro transduction of rat embryos with adeno-associated viruses is potentially effective for obtaining GE rats. However, these two approaches also require ET. The use of gene-engineered embryonic stem cells or spermatogonial stem cells appears to be of interest to obtain GE rats; however, the procedure itself is difficult and laborious. Genome-editing via oviductal nucleic acids delivery (GONAD) (or improved GONAD (i-GONAD)) is a novel method allowing for the in situ production of GE zygotes existing within the oviductal lumen. This can be performed by the simple intraoviductal injection of GE components and subsequent in vivo EP toward the injected oviducts and does not require ET. In this review, we describe the development of various approaches for producing GE rats together with an assessment of their technical advantages and limitations, and present new GE-related technologies and current achievements using those rats in relation to human diseases.

Endocrine disorders and fertility and pregnancy: An update

It is estimated that more and more couples suffer from fertility and pregnancy maintenance disorders. It is associated with impaired androgen secretion, which is influenced by many factors, ranging from genetic to environmental. It is also important to remember that fertility disorders can also result from abnormal anatomy of the reproductive male and female organ (congenital uterine anomalies - septate, unicornuate, bicornuate uterus; acquired defects of the uterus structure - fibroids, polyps, hypertrophy), disturbed hormonal cycle and obstruction of the fallopian tubes resulting from the presence of adhesions due to inflammation, endometriosis, and surgery, abnormal rhythm of menstrual bleeding, the abnormal concentration of hormones. There are many relationships between the endocrine organs, leading to a chain reaction when one of them fails to function properly. Conditions in which the immune system is involved, including infections and autoimmune diseases, also affect fertility. The form of treatment depends on infertility duration and the patient's age. It includes ovulation stimulation with clomiphene citrate or gonadotropins, metformin use, and weight loss interventions. Since so many different factors affect fertility, it is important to correctly diagnose what is causing the problem and to modify the treatment regimen if necessary. This review describes disturbances in the hormone secretion of individual endocrine organs in the context of fertility and the maintenance of pregnancy.

ERβ Regulation of Gonadotropin Responses during Folliculogenesis

Gonadotropins are essential for regulating ovarian development, steroidogenesis, and gametogenesis. While follicle stimulating hormone (FSH) promotes the development of ovarian follicles, luteinizing hormone (LH) regulates preovulatory maturation of oocytes, ovulation, and formation of corpus luteum. Cognate receptors of FSH and LH are G-protein coupled receptors that predominantly signal through cAMP-dependent and cAMP-independent mechanisms that activate protein kinases. Subsequent vital steps in response to gonadotropins are mediated through activation or inhibition of transcription factors required for follicular gene expression. Estrogen receptors, classical ligand-activated transcriptional regulators, play crucial roles in regulating gonadotropin secretion from the hypothalamic-pituitary axis as well as gonadotropin function in the target organs. In this review, we discuss the role of estrogen receptor β (ERβ) regulating gonadotropin response during folliculogenesis. Ovarian follicles in Erβ knockout (Erβ^KO) mutant female mice and rats cannot develop beyond the antral state, lack oocyte maturation, and fail to ovulate. Theca cells (TCs) in ovarian follicles express LH receptor, whereas granulosa cells (GCs) express both FSH receptor (FSHR) and LH receptor (LHCGR). As oocytes do not express the gonadotropin receptors, the somatic cells play a crucial role during gonadotropin induced oocyte maturation. Somatic cells also express high levels of estrogen receptors; while TCs express ERα and are involved in steroidogenesis, GCs express ERβ and are involved in both steroidogenesis and folliculogenesis. GCs are the primary site of ERβ-regulated gene expression. We observed that a subset of gonadotropin-induced genes in GCs, which are essential for ovarian follicle development, oocyte maturation and ovulation, are dependent on ERβ. Thus, ERβ plays a vital role in regulating the gonadotropin responses in ovary.

Kisspeptin Neurons and Estrogen-Estrogen Receptor α Signaling: Unraveling the Mystery of Steroid Feedback System Regulating Mammalian Reproduction

Estrogen produced by ovarian follicles plays a key role in the central mechanisms controlling reproduction via regulation of gonadotropin-releasing hormone (GnRH) release by its negative and positive feedback actions in female mammals. It has been well accepted that estrogen receptor α (ERα) mediates both estrogen feedback actions, but precise targets had remained as a mystery for decades. Ever since the discovery of kisspeptin neurons as afferent ERα-expressing neurons to govern GnRH neurons, the mechanisms mediating estrogen feedback are gradually being unraveled. The present article overviews the role of kisspeptin neurons in the arcuate nucleus (ARC), which are considered to drive pulsatile GnRH/gonadotropin release and folliculogenesis, in mediating the estrogen negative feedback action, and the role of kisspeptin neurons located in the anteroventral periventricular nucleus-periventricular nucleus (AVPV-PeN), which are thought to drive GnRH/luteinizing hormone (LH) surge and consequent ovulation, in mediating the estrogen positive feedback action. This implication has been confirmed by the studies showing that estrogen-bound ERα down- and up-regulates kisspeptin gene (Kiss1) expression in the ARC and AVPV-PeN kisspeptin neurons, respectively. The article also provides the molecular and epigenetic mechanisms regulating Kiss1 expression in kisspeptin neurons by estrogen. Further, afferent ERα-expressing neurons that may regulate kisspeptin release are discussed.

ERβ regulated ovarian kisspeptin plays an important role in oocyte maturation

Kisspeptin (KISS1) signaling in the hypothalamic-pituitary (H-P) axis plays an essential role in regulating gonadotropin secretion. KISS1 and KISS1 receptor (KISS1R) are also expressed in the ovary; however, the role of intraovarian KISS1 signaling remains unclear. Granulosa cell (GC)-specific expression of KISS1, and oocyte-specific expression of KISS1R indicate that GC-derived KISS1 may act on oocytes. Expression of KISS1 in GCs is induced by gonadotropins but it is absent in estrogen receptor β knockout (Erβ^null) rat ovaries. We also observed that gonadotropin stimulation failed to induce maturation of Erβ^null oocytes. Interestingly, KISS1 treatment of cumulus oocyte complexes (COCs) isolated from antral follicles promotes in vitro maturation of oocytes. Treatment of oocytes with KISS1 induced intracellular Ca²⁺ release, and increased activation of MAP kinase ERK1/2. KISS1 treatment also induced the expression of oocyte genes that are crucial for differentiation of GCs, and maturation of oocytes. Our findings suggest that ovarian KISS1-signaling plays an important role in gonadotropin induced follicle development and oocyte maturation.

Advances in Genome Editing and Application to the Generation of Genetically Modified Rat Models

The rat has been extensively used as a small animal model. Many genetically engineered rat models have emerged in the last two decades, and the advent of gene-specific nucleases has accelerated their generation in recent years. This review covers the techniques and advances used to generate genetically engineered rat lines and their application to the development of rat models more broadly, such as conditional knockouts and reporter gene strains. In addition, genome-editing techniques that remain to be explored in the rat are discussed. The review also focuses more particularly on two areas in which extensive work has been done: human genetic diseases and immune system analysis. Models are thoroughly described in these two areas and highlight the competitive advantages of rat models over available corresponding mouse versions. The objective of this review is to provide a comprehensive description of the advantages and potential of rat models for addressing specific scientific questions and to characterize the best genome-engineering tools for developing new projects.

Estrogens and development of the rete testis, efferent ductules, epididymis and vas deferens

Estrogen has always been considered the female hormone and testosterone the male hormone. However, estrogen's presence in the testis and deleterious effects of estrogen treatment during development have been known for nearly 90 years, long before estrogen receptors (ESRs) were discovered. Eventually it was learned that testes actually synthesize high levels of estradiol (E2) and sequester high concentrations in the reproductive tract lumen, which seems contradictory to the overwhelming number of studies showing reproductive pathology following exogenous estrogen exposures. For too long, the developmental pathology of estrogen has dominated our thinking, even resulting in the "estrogen hypothesis" as related to the testicular dysgenesis syndrome. However, these early studies and the development of an Esr1 knockout mouse led to a deluge of research into estrogen's potential role in and disruption of development and function of the male reproductive system. What is new is that estrogen action in the male cannot be divorced from that of androgen. This paper presents what is known about components of the estrogen pathway, including its synthesis and target receptors, and the need to achieve a balance between androgen- and estrogen-action in male reproductive tract differentiation and adult functions. The review focuses on what is known regarding development of the male reproductive tract, from the rete testis to the vas deferens, and examines the expression of estrogen receptors and presence of aromatase in the male reproductive system, traces the evidence provided by estrogen-associated knockout and transgenic animal models and discusses the effects of fetal and postnatal exposures to estrogens. Hopefully, there will be enough here to stimulate discussions and new investigations of the androgen:estrogen balance that seems to be essential for development of the male reproductive tract.

Estrogen Receptors in Polycystic Ovary Syndrome

Female infertility is mainly caused by ovulation disorders, which affect female reproduction and pregnancy worldwide, with polycystic ovary syndrome (PCOS) being the most prevalent of these. PCOS is a frequent endocrine disease that is associated with abnormal function of the female sex hormone estrogen and estrogen receptors (ERs). Estrogens mediate genomic effects through ERα and ERβ in target tissues. The G-protein-coupled estrogen receptor (GPER) has recently been described as mediating the non-genomic signaling of estrogen. Changes in estrogen receptor signaling pathways affect cellular activities, such as ovulation; cell cycle phase; and cell proliferation, migration, and invasion. Over the years, some selective estrogen receptor modulators (SERMs) have made substantial strides in clinical applications for subfertility with PCOS, such as tamoxifen and clomiphene, however the role of ER in PCOS still needs to be understood. This article focuses on the recent progress in PCOS caused by the abnormal expression of estrogen and ERs in the ovaries and uterus, and the clinical application of related targeted small-molecule drugs.

Mini-Review Regarding the Applicability of Genome Editing Techniques Developed for Studying Infertility

Infertility is a highly debated topic today. It has been long hypothesized that infertility has an idiopathic cause, but recent studies demonstrated the existence of a genetic substrate. Fortunately, the methods of editing the human genome proven to be revolutionary. Following research conducted, we identified a total of 21 relevant studies; 14 were performed on mice, 5 on zebrafish and 2 on rats. We concluded that over forty-four genes in total are dispensable for fertility in both sexes without affecting host homeostasis. However, there are genes whose loss-of-function induces moderate to severe phenotypic changes in both sexes. There were situations in which the authors reported infertility, exhibited by the experimental model, or other pathologies such as cryptorchidism, cataracts, or reduced motor activity. Overall, zinc-finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 are techniques that offer a wide range of possibilities for studying infertility, even to create mutant variants. It can be concluded that ZFNs, TALENs, and CRISPR/Cas9 are crucial tools in biomedical research.

Disease gene discovery in male infertility: past, present and future

Identifying the genes causing male infertility is important to increase our biological understanding as well as the diagnostic yield and clinical relevance of genetic testing in this disorder. While significant progress has been made in some areas, mainly in our knowledge of the genes underlying rare qualitative sperm defects, the same cannot be said for the genetics of quantitative sperm defects. Technological advances and approaches in genomics are critical for the process of disease gene identification. In this review we highlight the impact of various technological developments on male infertility gene discovery as well as functional validation, going from the past to the present and the future. In particular, we draw attention to the use of unbiased genomics approaches, the development of increasingly relevant functional assays and the importance of large-scale international collaboration to advance disease gene identification in male infertility.

Estrogen receptor-α prevents right ventricular diastolic dysfunction and fibrosis in female rats

Although women are more susceptible to pulmonary arterial hypertension (PAH) than men, their right ventricular (RV) function is better preserved. Estrogen receptor-α (ERα) has been identified as a likely mediator for estrogen protection in the RV. However, the role of ERα in preserving RV function and remodeling during pressure overload remains poorly understood. We hypothesized that loss of functional ERα removes female protection from adverse remodeling and is permissive for the development of a maladapted RV phenotype. Male and female rats with a loss-of-function mutation in ERα (ERαMut) and wild-type (WT) littermates underwent RV pressure overload by pulmonary artery banding (PAB). At 10 wk post-PAB, WT and ERαMut demonstrated RV hypertrophy. Analysis of RV pressure waveforms demonstrated RV-pulmonary vascular uncoupling and diastolic dysfunction in female, but not male, ERαMut PAB rats. Similarly, female, but not male, ERαMut exhibited increased RV fibrosis, comprised primarily of thick collagen fibers. There was an increased protein expression ratio of TIMP metallopeptidase inhibitor 1 (Timp1) to matrix metalloproteinase 9 (Mmp9) in female ERαMut compared with WT PAB rats, suggesting less collagen degradation. RNA-sequencing in female WT and ERαMut RV revealed kallikrein-related peptidase 10 (Klk10) and Jun Proto-Oncogene (Jun) as possible mediators of female RV protection during PAB. In summary, ERα in females is protective against RV-pulmonary vascular uncoupling, diastolic dysfunction, and fibrosis in response to pressure overload. ERα appears to be dispensable for RV adaptation in males. ERα may be a mediator of superior RV adaptation in female patients with PAH.NEW & NOTEWORTHY Using a novel loss-of-function mutation in estrogen receptor-α (ERα), we demonstrate that female, but not male, ERα mutant rats display right ventricular (RV)-vascular uncoupling, diastolic dysfunction, and fibrosis following pressure overload, indicating a sex-dependent role of ERα in protecting against adverse RV remodeling. TIMP metallopeptidase inhibitor 1 (Timp1), matrix metalloproteinase 9 (Mmp9), kallikrein-related peptidase 10 (Klk10), and Jun Proto-Oncogene (Jun) were identified as potential mediators in ERα-regulated pathways in RV pressure overload.

The role of estrogen receptors in rat Sertoli cells at different stages of development

The aim of the study was to investigate the effects of estrogen receptors (ESR1 and ESR2) on the expression of the proteins involved with proliferation (CCND1) and differentiation (CDKN1B and CTNNB) of Sertoli cells from rat in different stages of development. ESR1-selective agonist PPT, but not ESR2-selective agonist DPN, increased CCND1 expression in Sertoli cells from 5- and 15-day old rats. PPT did not have any effect on CCND1 expression in Sertoli cells from 20- and 30-day-old rats. DPN, but not PPT, increased CDKN1B expression in Sertoli cells from 15-, 20-, 30-day-old rats. DPN did not have any effect on Sertoli cells from 5-day-old rats. 17β-estradiol (E2) and PPT enhanced the [Methyl-³H] thymidine incorporation in Sertoli cells from 15-day-old rats, whereas the treatment did not have any effect in 20-day-old rats. E2 and DPN, but not PPT, increased non-phosphorylated CTNNB expression in Sertoli cells from 20-day-old rats. This upregulation was blocked by ESR2-selective antagonist PHTPP. The activation of ESR1 and ESR2, respectively, plays a role in the proliferation and differentiation of Sertoli cells in a critical period of testicular development. Furthermore, in Sertoli cells from 20-day-old rats, upregulation of non-phosphorylated CTNNB by E2/ESR2, via c-SRC/ERK1/2 and PI3K/AKT, may play a role in the interaction between Sertoli cells and/or in cell-germ cell adhesion and/or in the stabilization and accumulation of CTNNB in the cytosol. CTNNB could be translocated to the nucleus and modulate the transcriptional activity of specific target genes. The present study reinforces the important role of estrogen in normal testis development.

Rat models of human diseases and related phenotypes: a systematic inventory of the causative genes

The laboratory rat has been used for a long time as the model of choice in several biomedical disciplines. Numerous inbred strains have been isolated, displaying a wide range of phenotypes and providing many models of human traits and diseases. Rat genome mapping and genomics was considerably developed in the last decades. The availability of these resources has stimulated numerous studies aimed at discovering causal disease genes by positional identification. Numerous rat genes have now been identified that underlie monogenic or complex diseases and remarkably, these results have been translated to the human in a significant proportion of cases, leading to the identification of novel human disease susceptibility genes, helping in studying the mechanisms underlying the pathological abnormalities and also suggesting new therapeutic approaches. In addition, reverse genetic tools have been developed. Several genome-editing methods were introduced to generate targeted mutations in genes the function of which could be clarified in this manner [generally these are knockout mutations]. Furthermore, even when the human gene causing a disease had been identified without resorting to a rat model, mutated rat strains (in particular KO strains) were created to analyze the gene function and the disease pathogenesis. Today, over 350 rat genes have been identified as underlying diseases or playing a key role in critical biological processes that are altered in diseases, thereby providing a rich resource of disease models. This article is an update of the progress made in this research and provides the reader with an inventory of these disease genes, a significant number of which have similar effects in rat and humans.

A Gatekeeping Role of ESR2 to Maintain the Primordial Follicle Reserve

Over the entire reproductive lifespan in mammals, a fixed number of primordial follicles serve as the source of mature oocytes. Uncontrolled and excessive activation of primordial follicles can lead to depletion of the ovarian reserve. We observed that disruption of estrogen receptor β (ESR2) signaling results in increased activation of primordial follicles in Esr2-null (Esr2-/-) rats. However, follicle assembly was unaffected, and the total number of follicles remained comparable between neonatal wild-type and Esr2-/- ovaries. While the activated follicle counts were increased in Esr2-/- ovary, the number of primordial follicles were markedly decreased. Excessive recruitment of primordial follicles led to premature ovarian senescence in Esr2-/- rats and was associated with reduced levels of serum AMH and estradiol. Disruption of ESR2 signaling through administration of a selective antagonist (PHTPP) increased the number of activated follicles in wildtype rats, whereas a selective agonist (DPN) decreased follicle activation. In contrast, primordial follicle activation was not increased in the absence of ESR1, indicating that the regulation of primordial follicle activation is ESR2 specific. Follicle activation was also increased in Esr2 mutants lacking the DNA binding domain, suggesting a role for the canonical transcriptional activation function. Both primordial and activated follicles express ESR2, suggesting a direct regulatory role for ESR2 within these follicles. We also detected that loss of ESR2 augmented the activation of AKT, ERK, and mTOR pathways. Our results indicate that the lack of ESR2 upregulated both granulosa and oocyte factors, which can facilitate AKT and mTOR activation in Esr2-/- ovaries leading to increased activation of primordial follicles.

Comparative pharmacokinetic study of two kinds of altrenogest oral solutions for sows

This study was to compare the pharmacokinetic characteristics of domestic altrenogest oral solution (DAOS) or imported altrenogest oral solution (IAOS) in healthy sows. A single administration (1 mg/kg body weight) of DAOS or IAOS was performed in sixteen healthy sows according to a two-period crossover design. Plasma concentrations of altrenogest (AT) were measured by high performance liquid chromatography coupled to a tandem mass spectrometer (HPLC-MS/MS) and the concentration-time data of AT was analyzed by WINNONLIN 5.2. It was suggested that the main pharmacokinetic parameters of DAOS and IAOS were as follows: C_max was 227.59 ± 83.35 ng/mL and 152.83 ± 80.34 ng/mL, T_max was 1.16 ± 0.52 h and 1.58 ± 0.85 h, t_1/2 was 3.63 ± 0.72 h and 3.45 ± 0.63 h, MRT was 5.02 ± 0.79 h and 5.21 ± 0.87 h, AUC_0-t was 1050.23 ± 409.80 h·ng/mL and 778.22 ± 397.84 h·ng/mL, and AUC_0-∞ was 1060 h·ng/mL and 786 h·ng/mL, respectively. The relative bioavailability of DAOS was 134.9%. Above results indicated that oral DAOS was better absorbed than IAOS, C_max of DAOS was higher than that of IAOS (p < 0.05). However, there was no significant difference in the main pharmacokinetic parameters between oral DAOS and IAOS (p > 0.05). Our data confirmed that the absorption, fast elimination and bioavailability of DAOS in sows were better than those of IAOS.

The role of the estrogen receptor-α gene, Esr1, in maternal-like behavior in juvenile female and male rats

The estrogen receptor-alpha (ER-α) is an important ligand activated transcription factor that works to control gene transcription in many species. Previous studies have shown estrogen to be an important hormone in the regulation of maternal behavior. Like adult female rats, both male and female juvenile rats exhibit increased level of maternal-like behavior when exposed to pups. The aim of this study was to determine whether ER-α is critical for the expression of maternal-like behavior in juvenile male and female rats. ER-α knock-out and wildtype (WT) juvenile male and female rats were generated and tested for maternal behaviors. Latencies to display maternal-like behaviors that included retrieval, grouping and crouching responses, revealed no genotype differences between KO and WT subjects. Male juvenile rats exhibited slightly shorter latencies than WT juvenile female rats indicating a sex difference in the latency to display these responses. Additionally, ER-α KO females exhibited a delay in onset of vaginal opening compared to WT females, indicating a role for ER-α in sexual maturation. The behavioral findings indicate that ER-α is not obligatory for the expression of full maternal-like behavior in male and female juvenile rats. Understanding this neurobiological system will help to elucidate the developmental involvement of the endocrine and brain networks in the regulation of maternal behaviors in mammals.

Uterine glycolytic enzyme expression is affected by knockout of different estrogen receptor subtypes

The estrogen signaling pathway via nuclear estrogen receptors (ER) α and β is considered to be the master regulator of the cellular glucose metabolism in the uterus. While in vivo animal studies have demonstrated that 17β-estradiol (E2) treatment increases the expression levels and activities of several glycolytic enzymes in the uterus, the specific ER subtype-dependent regulation of key glycolytic enzymes in the uterus has not been experimentally verified. In this study, the localization of ERα and ERβ in human and mouse endometria were evaluated using immunohistology. Given that ERα and ERβ are not functionally equivalent, ERα, ERβ and ERαβ knockout (ERα^-/-, ERβ^-/- and ERαβ^-/-) mice were utilized to determine the expression pattern of glycolytic enzymes in the uterus. It was found that the level of ERα was higher than that of ERβ in the human and mouse endometrial epithelial and stromal cells, and both receptors were downregulated by E2 treatment in the mouse uterus. The expression of the hexokinase 1 and GAPDH was increased in ERα^-/- and ERβ^-/- mice compared with wild-type controls. Increased phosphofructokinase expression was observed in ERα^-/- and ERαβ^-/- mice, whereas increased pyruvate kinase isozyme M2 and pyruvate dehydrogenase expression was observed in ERβ^-/- and ERαβ^-/- mice. The findings indicated for the first time that while estrogen regulates ERα and ERβ expression in the uterus, ERα and ERβ selectively regulate uterine glycolytic enzyme expression during glycolysis. Additionally, the link between endometrial ER subtypes and glycolysis in women with polycystic ovary syndrome (PCOS) is discussed. The findings suggested that the E2-dependent ER-mediated regulation of glycolysis may be involved in the disturbance of the glucose metabolism in patients with PCOS with endometrial dysfunction.

Estrogen in the male: a historical perspective

Estrogens have traditionally been considered female hormones. Nevertheless, the presence of estrogen in males has been known for over 90 years. Initial studies suggested that estrogen was deleterious to male reproduction because exogenous treatments induced developmental abnormalities. However, demonstrations of estrogen synthesis in the testis and high concentrations of 17β-estradiol in rete testis fluid suggested that the female hormone might have a function in normal male reproduction. Identification of estrogen receptors and development of biological radioisotope methods to assess estradiol binding revealed that the male reproductive tract expresses estrogen receptor extensively from the neonatal period to adulthood. This indicated a role for estrogens in normal development, especially in efferent ductules, whose epithelium is the first in the male reproductive tract to express estrogen receptor during development and a site of exceedingly high expression. In the 1990s, a paradigm shift occurred in our understanding of estrogen function in the male, ushered in by knockout mouse models where estrogen production or expression of its receptors was not present. These knockout animals revealed that estrogen's main receptor (estrogen receptor 1 [ESR1]) is essential for male fertility and development of efferent ductules, epididymis, and prostate, and that loss of only the membrane fraction of ESR1 was sufficient to induce extensive male reproductive abnormalities and infertility. This review provides perspectives on the major discoveries and developments that led to our current knowledge of estrogen's importance in the male reproductive tract and shaped our evolving concept of estrogen's physiological role in the male.

Disruption of ESR1 alters the expression of genes regulating hepatic lipid and carbohydrate metabolism in male rats

The liver helps maintain energy homeostasis by synthesizing and storing glucose and lipids. Gonadal steroids, particularly estrogens, play an important role in regulating metabolism. As estrogens are considered female hormones, metabolic disorders related to the disruption of estrogen signaling have mostly been studied in females. Estrogen receptor alpha (ESR1) is the predominant receptor in both the male and female liver, and it mediates the hepatic response to estrogens. Loss of ESR1 increases weight gain and obesity in female rats, while reducing the normal growth in males. Although Esr1-/- male rats have a reduced body weight, they exhibit increased adipose deposition and impaired glucose tolerance. We further investigated whether these metabolic disorders in Esr1-/- male rats were linked with the loss of transcriptional regulation by ESR1 in the liver. To identify the ESR-regulated genes, RNA-sequencing was performed on liver mRNAs from wildtype and Esr1-/- male rats. Based on an absolute fold change of ≥2 with a p-value ≤ 0.05, a total of 706 differentially expressed genes were identified in the Esr1-/- male liver: 478 downregulated, and 228 upregulated. Pathway analyses demonstrate that the differentially expressed genes include transcriptional regulators (Cry1, Nr1d1, Nr0b2), transporters (Slc1a2), and regulators of biosynthesis (Cyp7b1, Cyp8b1), and hormone metabolism (Hsd17b2, Sult1e1). Many of these genes are also integral parts of the lipid and carbohydrate metabolism pathways in the liver. Interestingly, certain critical regulators of the metabolic pathways displayed a sexual dimorphism in expression, which may explain the divergent weight gain in Esr1-/- male and female rats despite common metabolic dysfunctions.

Estrogen receptor-alpha knockouts and maternal memory in nulliparous rats

The current study investigated the role of estrogen receptor alpha (Esr1) in maternal memory in rats, comparing the induction and retention responses of Esr1 knockout (KO) and wild type (WT) nulliparous rats towards foster pups. Thirty days after completion of induction testing, subjects were tested for the retention of maternal care in their home cage and then for maternal behaviors in a novel cage. Both WT and Esr1 KO females displayed similar latencies to respond to foster young during the initial induction testing. Likewise, reinduction latencies to display full maternal responsiveness were similar in the Esr1 KO and WT groups during maternal memory testing in the home cage. However, in the novel cage testing WT subjects displayed modest modifications in maternal care. WT females had shorter latencies to first retrieve and mouth a test pup. These findings suggest that while Esr1 does not appear to affect the establishment of maternal care or the display of maternal memory, it may modulate aspects of pup-directed behaviors associated with the reinduction of maternal care in female rats.

Liver transcriptome data of Esr1 knockout male rats reveals altered expression of genes involved in carbohydrate and lipid metabolism

Estrogens are traditionally considered to be female sex steroid hormones and most of the studies examining estrogen regulation of metabolic function in the liver have been conducted in females. However, the liver expresses high levels of estrogen receptor alpha (ESR1) in both males and females, which mediates the hepatic response to estrogens. In this data article, we investigated whether metabolic disorders in Esr1 knockout (Esr1-/-) male rats were linked with loss of transcriptional regulation by ESR1 in liver. To identify the ESR1 regulated genes in the mutant liver, RNA-sequencing was performed on liver RNAs purified from young male rats. The raw data were analyzed using the CLC Genomics Workbench and high-quality RNA-sequencing reads were aligned to the Rattus norvegicus genome. Transcriptome data obtained from Esr1-/- liver RNAs were compared to that of wild type rats. Based on an absolute fold change of 2 with a p-value ≤ 0.05, a total of 618 differentially expressed genes were identified in the Esr1-/- male liver. Pathway analyses demonstrated that the majority of differentially expressed genes are regulators of carbohydrate and lipid metabolism in the liver. These differentially expressed genes and their potential roles were further examined in a companion manuscript, "Disruption of ESR1 alters the expression of genes regulating hepatic lipid and carbohydrate metabolism in male rats" (Khristi et al., 2018).

Estrogen Receptors: New Directions in the New Millennium

Nineteen years have passed since our previous review in this journal in 1999 regarding estrogen receptors. At that time, we described the current assessments of the physiological activities of estrogen and estrogen receptors. Since that time there has been an explosion of progress in our understanding of details of estrogen receptor-mediated processes from the molecular and cellular level to the whole organism. In this review we discuss the basic understanding of estrogen signaling and then elaborate on the progress and current understanding of estrogen receptor actions that have developed using new models and continuing clinical studies.

Histone demethylase KDM4A and KDM4B expression in granulosa cells from women undergoing in vitro fertilization

PURPOSE

To assess expression of the histone demethylases KDM4A and KDM4B in granulosa collected from women undergoing oocyte retrieval and to determine if expression was related to pregnancy outcome.

METHODS

Cumulus and mural granulosa cells were obtained from women undergoing oocyte retrieval. KDM4A and KDM4B mRNA expression was determined by qRT-PCR. KDM4A and KDM4B proteins were immunohistochemically localized in ovarian tissue sections obtained from archival specimens.

RESULTS

KDM4A and KDM4B protein was localized to oocytes, granulosa cells, and theca and luteal cells in ovaries from reproductive-aged women. KDM4A and KDM4B mRNA expression was overall higher in cumulus compared to mural granulosa. When comparing granulosa demethylase gene expression, KDM4A and KDM4B mRNA expression was higher in both cumulus and mural granulosa from not pregnant patients compared to patients in the pregnant-live birth group.

CONCLUSIONS

Histone demethylases KDM4A and KDM4B mRNA are differentially expressed in cumulus and mural granulosa. Expression of both KDM4A and KDM4B mRNA was lower in cumulus granulosa and mural granulosa from pregnant compared to not pregnant patients. These findings suggest that altered expression of histone demethylases may impact epigenetic changes in granulosa cells associated with pregnancy.

Effect of folate deficiency on promoter methylation and gene expression of Esr1, Cav1, and Elavl1, and its influence on spermatogenesis

This study aims to investigate the effect of folate deficiency on the male reproductive function and the underlying mechanism. A total of 269 screened participants from 421 recruitments were enrolled in this study. An animal model of folate deficiency was constructed. Folate concentration was measured in the ejaculate, and its association with semen parameters was then determined. The expression and promoter methylation status of ESR1, CAV1, and ELAVL1 were also evaluated. Results showed that seminal plasma folate level was significantly lower among subjects with azoospermia than those with normozoospermia. Low folate level was significantly correlated with low sperm concentration in men with normozoospermia. Folate deficiency significantly reduced the expression of ESR1, CAV1, and ELAVL1, which are critical to spermatogenesis. However, low folate levels did not increase the methylation levels of the promoter regions of ESR1, CAV1, and ELAVL1 in human sperm DNA. Thus, folate deficiency impairs spermatogenesis may partly due to inhibiting the expression of these genes. Thus future research should determine the significance of sufficient folate status in male fertilization and subsequent pregnancy outcomes.

Rat models of 17β-estradiol-induced mammary cancer reveal novel insights into breast cancer etiology and prevention

Numerous laboratory and epidemiologic studies strongly implicate endogenous and exogenous estrogens in the etiology of breast cancer. Data summarized herein suggest that the ACI rat model of 17β-estradiol (E2)-induced mammary cancer is unique among rodent models in the extent to which it faithfully reflects the etiology and biology of luminal types of breast cancer, which together constitute ~70% of all breast cancers. E2 drives cancer development in this model through mechanisms that are largely dependent upon estrogen receptors and require progesterone and its receptors. Moreover, mammary cancer development appears to be associated with generation of oxidative stress and can be modified by multiple dietary factors, several of which may attenuate the actions of reactive oxygen species. Studies of susceptible ACI rats and resistant COP or BN rats provide novel insights into the genetic bases of susceptibility and the biological processes regulated by genetic determinants of susceptibility. This review summarizes research progress resulting from use of these physiologically relevant rat models to advance understanding of breast cancer etiology and prevention.

Defining the Role of Estrogen Receptor β in the Regulation of Female Fertility

Estrogens are essential hormones for the regulation of fertility. Cellular responses to estrogens are mediated by estrogen receptor α (ESR1) and estrogen receptor β (ESR2). In mouse and rat models, disruption of Esr1 causes infertility in both males and females. However, the role of ESR2 in reproductive function remains undecided because of a wide variation in phenotypic observations among Esr2-mutant mouse strains. Regulatory pathways independent of ESR2 binding to its cognate DNA response element have also been implicated in ESR2 signaling. To clarify the regulatory roles of ESR2, we generated two mutant rat models: one with a null mutation (exon 3 deletion, Esr2ΔE3) and the other with an inframe deletion selectively disrupting the DNA binding domain (exon 4 deletion, Esr2ΔE4). In both models, we observed that ESR2-mutant males were fertile. ESR2-mutant females exhibited regular estrous cycles and could be inseminated by wild-type (WT) males but did not become pregnant or pseudopregnant. Esr2-mutant ovaries were small and differed from WT ovaries by their absence of corpora lutea, despite the presence of follicles at various stages of development. Esr2ΔE3- and Esr2ΔE4-mutant females exhibited attenuated preovulatory gonadotropin surges and did not ovulate in response to a gonadotropin regimen effective in WT rats. Similarities of reproductive deficits in Esr2ΔE3 and Esr2ΔE4 mutants suggest that DNA binding-dependent transcriptional function of ESR2 is critical for preovulatory follicle maturation and ovulation. Overall, the findings indicate that neuroendocrine and ovarian deficits are linked to infertility observed in Esr2-mutant rats.

Estrogens in Male Physiology

Estrogens have historically been associated with female reproduction, but work over the last two decades established that estrogens and their main nuclear receptors (ESR1 and ESR2) and G protein-coupled estrogen receptor (GPER) also regulate male reproductive and nonreproductive organs. 17β-Estradiol (E2) is measureable in blood of men and males of other species, but in rete testis fluids, E2 reaches concentrations normally found only in females and in some species nanomolar concentrations of estrone sulfate are found in semen. Aromatase, which converts androgens to estrogens, is expressed in Leydig cells, seminiferous epithelium, and other male organs. Early studies showed E2 binding in numerous male tissues, and ESR1 and ESR2 each show unique distributions and actions in males. Exogenous estrogen treatment produced male reproductive pathologies in laboratory animals and men, especially during development, and studies with transgenic mice with compromised estrogen signaling demonstrated an E2 role in normal male physiology. Efferent ductules and epididymal functions are dependent on estrogen signaling through ESR1, whose loss impaired ion transport and water reabsorption, resulting in abnormal sperm. Loss of ESR1 or aromatase also produces effects on nonreproductive targets such as brain, adipose, skeletal muscle, bone, cardiovascular, and immune tissues. Expression of GPER is extensive in male tracts, suggesting a possible role for E2 signaling through this receptor in male reproduction. Recent evidence also indicates that membrane ESR1 has critical roles in male reproduction. Thus estrogens are important physiological regulators in males, and future studies may reveal additional roles for estrogen signaling in various target tissues.

Long-Term Assessment of AAV-Mediated Zinc Finger Nuclease Expression in the Mouse Brain

Gene editing tools like TALENs, ZFNs and Crispr/Cas now offer unprecedented opportunities for targeted genetic manipulations in virtually all species. Most of the recent research in this area has concentrated on manipulation of the genome in isolated cells, which then give rise to transgenic animals or modified stem cell lines. Much less is known about applicability of genetic scissors in terminally differentiated, non-dividing cells like neurons of the adult brain. We addressed this question by expression of a pair of ZFNs targeting the murine cathepsin D gene in CNS neurons by means of an optimized AAV viral vector. We show that ZFN expression resulted in substantial depletion of cathepsin D from neuronal lysosomes, demonstrating a robust gene deletion. Importantly, long-term ZFN expression in CNS neurons did not impair essential neuronal functionality and did not cause inflammation or neurodegeneration, suggesting that potent genetic scissors can be expressed safely in the mouse brain. This finding opens up new venues to create novel research models for neurodegenerative disorders.

Disruption of Estrogen Receptor Alpha in Rats Results in Faster Initiation of Compensatory Regeneration Despite Higher Liver Injury After Carbon Tetrachloride Treatment

Estrogen receptor alpha (ESR1) is 1 of the 2 intracellular receptors for estrogen and is expressed by hepatocytes in the liver. The role of ESR1 in the regulation of toxicant-induced liver injury and compensatory regeneration is not completely clear. We investigated the role of ESR1 in liver regeneration after carbon tetrachloride (CCl₄)-induced liver injury using wild type (WT) and ESR1 knockout (ESR1-KO) rats. Adult female WT and ESR1-KO rats were treated with 1 mL/kg CCl₄ and euthanized over a time course of 0 to 48 hours. Liver injury measured by serum alanine amino transaminase, and histopathological analysis showed significantly higher liver injury in ESR1-KO as compared to WT rats. Hematoxylin and eosin staining revealed 2-fold higher necrosis and significant inflammatory cell infiltration in ESR1-KO rats. Chloracetate esterase staining revealed higher neutrophil infiltration in ESR1-KO rat livers. Interestingly, proliferating cell nuclear antigen immunohistochemistry showed that in spite of 2-fold higher liver injury, the ESR1-KO rats had equal liver regeneration as compared to WT rats. Western blot analysis of cyclin D1 and phosphorylated Rb, proteins involved in the initiation of the cell cycle, was significantly higher at all time points in ESR1-KO rats. Further analysis revealed faster activation of canonical Wnt/β-catenin and NF-κB signaling in ESR1-KO rats characterized by higher activated β-catenin and phosphorylated p65 at 12 hours after CCl₄ treatment. Taken together, these data indicate that ESR1-mediated signaling inhibits liver regeneration by downregulation of Wnt signaling resulting in lower cyclin D1 activation after chemical-induced liver injury.

Modeling estrogen receptor-positive breast cancers in mice: is it the best we can do?

The continuous supplementation of mice with supraphysiological doses of estrogen 
for the growth of estrogen receptor-positive breast cancers has been linked to toxicity in the host and perturbation of cancer cells' function that can misguide preclinical studies. Thus, alternative experimental models with circulating levels of estrogens higher than those of mice may represent more suitable hosts to model estrogen receptor-positive breast cancers.

Placental origins of adverse pregnancy outcomes: potential molecular targets: an Executive Workshop Summary of the Eunice Kennedy Shriver National Institute of Child Health and Human Development

Although much progress is being made in understanding the molecular pathways in the placenta that are involved in the pathophysiology of pregnancy-related disorders, a significant gap exists in the utilization of this information for the development of new drug therapies to improve pregnancy outcome. On March 5-6, 2015, the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health sponsored a 2-day workshop titled Placental Origins of Adverse Pregnancy Outcomes: Potential Molecular Targets to begin to address this gap. Particular emphasis was given to the identification of important molecular pathways that could serve as drug targets and the advantages and disadvantages of targeting these particular pathways. This article is a summary of the proceedings of that workshop. A broad number of topics were covered that ranged from basic placental biology to clinical trials. This included research in the basic biology of placentation, such as trophoblast migration and spiral artery remodeling, and trophoblast sensing and response to infectious and noninfectious agents. Research findings in these areas will be critical for the formulation of the development of future treatments and the development of therapies for the prevention of a number of pregnancy disorders of placental origin that include preeclampsia, fetal growth restriction, and uterine inflammation. Research was also presented that summarized ongoing clinical efforts in the United States and in Europe that has tested novel interventions for preeclampsia and fetal growth restriction, including agents such as oral arginine supplementation, sildenafil, pravastatin, gene therapy with virally delivered vascular endothelial growth factor, and oxygen supplementation therapy. Strategies were also proposed to improve fetal growth by the enhancement of nutrient transport to the fetus by modulation of their placental transporters and the targeting of placental mitochondrial dysfunction and oxidative stress to improve placental health. The roles of microRNAs and placental-derived exosomes, as well as messenger RNAs, were also discussed in the context of their use for diagnostics and as drug targets. The workshop discussed the aspect of safety and pharmacokinetic profiles of potential existing and new therapeutics that will need to be determined, especially in the context of the unique pharmacokinetic properties of pregnancy and the hurdles and pitfalls of the translation of research findings into practice. The workshop also discussed novel methods of drug delivery and targeting during pregnancy with the use of macromolecular carriers, such as nanoparticles and biopolymers, to minimize placental drug transfer and hence fetal drug exposure. In closing, a major theme that developed from the workshop was that the scientific community must change their thinking of the pregnant woman and her fetus as a vulnerable patient population for which drug development should be avoided, but rather be thought of as a deprived population in need of more effective therapeutic interventions.

Rethinking progesterone regulation of female reproductive cyclicity

The progesterone receptor (PGR) is a ligand-activated transcription factor with key roles in the regulation of female fertility. Much has been learned of the actions of PGR signaling through the use of pharmacologic inhibitors and genetic manipulation, using mouse mutagenesis. Characterization of rats with a null mutation at the Pgr locus has forced a reexamination of the role of progesterone in the regulation of the female reproductive cycle. We generated two Pgr mutant rat models, using genome editing. In both cases, deletions yielded a null mutation resulting from a nonsense frame-shift and the emergence of a stop codon. Similar to Pgr null mice, Pgr null rats were infertile because of deficits in sexual behavior, ovulation, and uterine endometrial differentiation. However, in contrast to the reported phenotype of female mice with disruptions in Pgr signaling, Pgr null female rats exhibit robust estrous cycles. Cyclic changes in vaginal cytology, uterine histology, serum hormone levels, and wheel running activity were evident in Pgr null female rats, similar to wild-type controls. Furthermore, exogenous progesterone treatment inhibited estrous cycles in wild-type female rats but not in Pgr-null female rats. As previously reported, pharmacologic antagonism supports a role for PGR signaling in the regulation of the ovulatory gonadotropin surge, a result at variance with experimentation using genetic ablation of PGR signaling. To conclude, our findings in the Pgr null rat challenge current assumptions and prompt a reevaluation of the hormonal control of reproductive cyclicity.

What's new in estrogen receptor action in the female reproductive tract

Estrogen receptor alpha (ERα) is a critical player in development and function of the female reproductive system. Perturbations in ERα response can affect wide-ranging aspects of health in humans as well as in livestock and wildlife. Because of its long-known and broad impact, ERα mechanisms of action continue to be the focus on cutting-edge research efforts. Consequently, novel insights have greatly advanced understanding of every aspect of estrogen signaling. In this review, we attempt to briefly outline the current understanding of ERα mediated mechanisms in the context of the female reproductive system.

Neonatal Progesterone Programs Adult Uterine Responses to Progesterone and Susceptibility to Uterine Dysfunction

In this report, we investigated the consequences of neonatal progesterone exposure on adult rat uterine function. Female pups were subcutaneously injected with vehicle or progesterone from postnatal days 3 to 9. Early progesterone exposure affected endometrial gland biogenesis, puberty, decidualization, and fertility. Because decidualization and pregnancy success are directly linked to progesterone action on the uterus, we investigated the responsiveness of the adult uterus to progesterone. We first identified progesterone-dependent uterine gene expression using RNA sequencing and quantitative RT-PCR in Holtzman Sprague-Dawley rats and progesterone-resistant Brown Norway rats. The impact of neonatal progesterone treatment on adult uterine progesterone responsiveness was next investigated using quantitative RT-PCR. Progesterone resistance affected the spectrum and total number of progesterone-responsive genes and the magnitude of uterine responses for a subset of progesterone targets. Several progesterone-responsive genes in adult uterus exhibited significantly dampened responses in neonatally progesterone-treated females compared with those of vehicle-treated controls, whereas other progesterone-responsive transcripts did not differ between female rats exposed to vehicle or progesterone as neonates. The organizational actions of progesterone on the uterus were dependent on signaling through the progesterone receptor but not estrogen receptor 1. To summarize, neonatal progesterone exposure leads to disturbances in endometrial gland biogenesis, progesterone resistance, and uterine dysfunction. Neonatal progesterone effectively programs adult uterine responsiveness to progesterone.

Adaptive mechanisms controlling uterine spiral artery remodeling during the establishment of pregnancy

Implantation of the embryo into the uterus triggers the initiation of hemochorial placentation. The hemochorial placenta facilitates the acquisition of maternal resources required for embryo/fetal growth. Uterine spiral arteries form the nutrient supply line for the placenta and fetus. This vascular conduit undergoes gestation stage-specific remodeling directed by maternal natural killer cells and embryo-derived invasive trophoblast lineages. The placentation site, including remodeling of the uterine spiral arteries, is shaped by environmental challenges. In this review, we discuss the cellular participants controlling pregnancy-dependent uterine spiral artery remodeling and mechanisms responsible for their development and function.

Neuroendocrine regulation of maternal behavior

The expression of maternal behavior in mammals is regulated by the developmental and experiential events over a female's lifetime. In this review the relationships between the endocrine and neural systems that play key roles in these developmental and experiential processes that affect both the establishment and maintenance of maternal care are presented. The involvement of the hormones estrogen, progesterone, and lactogens are discussed in the context of ligand, receptor, and gene activity in rodents and to a lesser extent in higher mammals. The roles of neuroendocrine factors, including oxytocin, vasopressin, classical neurotransmitters, and other neural gene products that regulate aspects of maternal care are set forth, and the interactions of hormones with central nervous system mediators of maternal behavior are discussed. The impact of prior developmental factors, including epigenetic events, and maternal experience on subsequent maternal care are assessed over the course of the female's lifespan. It is proposed that common neuroendocrine mechanisms underlie the regulation of maternal care in mammals.

Disruption of estrogen receptor signaling and similar pathways in the efferent ductules and initial segment of the epididymis

Seminiferous tubular atrophy may involve indirectly the disruption of estrogen receptor-α (ESR1) function in efferent ductules of the testis. ESR1 helps to maintain fluid resorption by the ductal epithelium and the inhibition or stimulation of this activity in rodent species will lead to fluid accumulation in the lumen. If not resolved, the abnormal buildup of fluid in the head of the epididymis and efferent ductules becomes a serious problem for the testis, as it leads to an increase in testis weight, tubular dilation and seminiferous epithelial degeneration, as well as testicular atrophy. The same sequence of pathogenesis occurs if the efferent ductule lumen becomes occluded. This review provides an introduction to the role of estrogen in the male reproductive tract but focuses on the various overlapping mechanisms that could induce efferent ductule dysfunction and fluid backpressure histopathology. Although efferent ductules are difficult to find, their inclusion in routine histological evaluations is recommended, as morphological images of these delicate tubules may be essential for understanding the mechanism of testicular injury, especially if dilations are observed in the rete testis and/or seminiferous tubules.

Signature Lesion:

The rete testis and efferent ductules can appear dilated, as if the lumens were greatly expanded with excess fluid or the accumulation of sperm. Because the efferent ductules resorb most of the fluid arriving from the rete testis lumen, one of two mechanisms is likely to be involved: a) reduced fluid uptake, which has been caused by the disruption in estrogen receptor signaling or associated pathways; or b) an increased rate of fluid resorption, which results in luminal occlusion. Both mechanisms can lead to a temporary increase in testicular weight, tubular dilation and atrophy of the seminiferous tubules.