Estrogen regulates transcription of the ovine oxytocin receptor gene through GC-rich SP1 promoter elements

Role of sexually dimorphic oxytocin receptor-expressing neurons in the anteroventral periventricular nucleus on maternal behavior

Oxytocin is a neuropeptide produced by magnocellular neurosecretory neurons located primarily in the supraoptic nucleus and paraventricular nucleus of the hypothalamus. The long axons of these neurons project to the neurohypophysis where oxytocin is released into the general circulation in response to the physiological demands. Oxytocin plays critical roles in female reproductive physiology, specifically in uterine contraction during labor and milk ejection while nursing. Oxytocin is also called "the love hormone" due to its modulatory roles in prosocial behaviors, including social recognition, maternal behavior, and pair bonding. Oxytocin influences behaviors by binding to oxytocin receptors (OXTR) located in various parts of the brain. Previously, we discovered a group of estrogen-dependent OXTR neurons that is exclusively present in the anteroventral periventricular nucleus (AVPV) of females but not of males. The female-specific expression of OXTR in the AVPV is a rare case of neurochemically-demonstrated, all-or-none sexual dimorphism in the brain. In this review, the cellular characterization and functional significance of the sexually dimorphic OXTR neurons in the AVPV as well as the clinical implications of the research will be discussed.

Estrogen regulates the transcription of guppy isotocin receptors

Estrogen can regulate oxytocin receptor expression, which is mediated through estrogen receptors (ESRs) in mammals, initiating parturition. To further study the reproductive physiological process of ovoviviparous teleosts, guppies (Poecilia reticulata) were employed as the research model in the present study to identify the transcriptional regulation of ESRs on isotocin receptors (itrs). Since guppy embryos develop inside the ovary, in the present study, the levels of itrs in the ovarian stroma of pregnant female guppies treated with estradiol (E2) in vitro were tested. E2 increased only itr2 mRNA levels 3 h post-treatment, with no variation in itr1 mRNA expression levels. In vivo, pregnant guppies were immersed in different concentrations of E2, significantly increasing the relative expression levels of itr1 and itr2 in the ovary. Moreover, based on dual-fluorescence in situ hybridization (ISH), both esrs and itrs mRNAs were localized in the same cells around the embryos in the ovary. To further investigate the regulation of itr transcription by estrogen, a luciferase reporter assay was performed, and the results demonstrated that E2 treatment could induce E2-dependent repression of luciferase activity in cells transfected with ESR1. However, overexpression of ESR2a or ESR2b caused a robust ligand-independent increase in itr2 promoter activity. Deletion analysis of the itr2 promoter indicated that there were novel potential ESR transcription factor-binding sites at -360 bp upstream of the 5' end of the itr2 promoter. Overall, our study provided novel results regarding the ESRs mediating the onset of parturition in ovoviviparous teleosts.

Genetic and epigenetic signatures associated with plasma oxytocin levels in children and adolescents with autism spectrum disorder

Oxytocin (OT), the brain's most abundant neuropeptide, plays an important role in social salience and motivation. Clinical trials of the efficacy of OT in autism spectrum disorder (ASD) have reported mixed results due in part to ASD's complex etiology. We investigated whether genetic and epigenetic variation contribute to variable endogenous OT levels that modulate sensitivity to OT therapy. To carry out this analysis, we integrated genome-wide profiles of DNA-methylation, transcriptional activity, and genetic variation with plasma OT levels in 290 participants with ASD enrolled in a randomized controlled trial of OT. Our analysis identified genetic variants with novel association with plasma OT, several of which reside in known ASD risk genes. We also show subtle but statistically significant association of plasma OT levels with peripheral transcriptional activity and DNA-methylation profiles across several annotated gene sets. These findings broaden our understanding of the effects of the peripheral oxytocin system and provide novel genetic candidates for future studies to decode the complex etiology of ASD and its interaction with OT signaling and OT-based interventions. LAY SUMMARY: Oxytocin (OT) is an abundant chemical produced by neurons that plays an important role in social interaction and motivation. We investigated whether genetic and epigenetic factors contribute to variable OT levels in the blood. To this, we integrated genetic, gene expression, and non-DNA regulated (epigenetic) signatures with blood OT levels in 290 participants with autism enrolled in an OT clinical trial. We identified genetic association with plasma OT, several of which reside in known autism risk genes. We also show statistically significant association of plasma OT levels with gene expression and epigenetic across several gene pathways. These findings broaden our understanding of the factors that influence OT levels in the blood for future studies to decode the complex presentation of autism and its interaction with OT and OT-based treatment.

Embryo developmental toxicity in marine medaka (Oryzias melastigma) due to parental and embryonic 17α-ethinylestradiol exposure

The synthetic estrogen 17α-ethinylestradiol (EE2) is a common component of hormone therapy and oral contraceptives and has been widely used for nearly 60 years. Numerous studies have shown that exposure to EE2 can affect embryonic development in a number of fish species. The effects of parental and embryonic EE2 exposure on embryo developmental toxicity and the underlying molecular mechanisms, however, have rarely been examined. In this study, embryos collected from parental EE2-exposed adult fish were examined to assess EE2-induecd toxicity during embryo development. The rate of embryo development including heart rate, hatching rate, and larval locomotion were measured to assess embryo developmental toxicity. The embryonic transcriptome was used to delineate the related developmental toxicity pathways. Our results suggest that parental and embryonic EE2 exposure resulted in growth retardation including a reduction in embryo heart rate, a delay in the appearance eye pigmentation, decreased hatching rate and impaired larval locomotion. In addition, gene ontology (GO) enrichment analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, and Ingenuity Pathway Analysis (IPA) of transcriptome revealed that these impairments are controlled by estrogen receptor and related to eye structure, neuronal and synaptic structure, and behaviour. The key factors identified, including PRKAA2, APOB, EPHB2, OXTR, NR2E3, and POU4F2, could serve as biomarkers for assessing EE2-induced embryo developmental toxicity. For the first time, our results show that eye pigmentation is a potentially sensitive marker of EE2-induced embryo developmental toxicity.

Unravelling the role of 17β-estradiol on advancing uterine luteolytic cascade in cattle

In cattle, 17β-estradiol (E2) stimulates prostaglandin F2α (PGF2α) synthesis, which causes luteolysis. Except for the well-established upregulation of oxytocin receptor gene (OXTR), molecular mechanisms of E2-induced PGF2α release in vivo remain unknown. We hypothesized that E2-induced PGF2α release requires de novo transcription of components of the PGF2α synthesis machinery. Beef cows (n = 52) were assigned to remain untreated (Control; n = 10), to receive 50% ethanol infusion intravenously (Placebo; n = 21), or 3 mg E2 in 50% ethanol infusion intravenously (Estradiol; n = 21) on day 15 (D15) after estrus. We collected a single endometrial biopsy per animal at the time of the treatment (0h; Control B0h group), 4 hours (4h; Placebo B4h group and Estradiol B4h group), or 7 hours (7h; Placebo B7h group and Estradiol B7h group) post-treatment. Compared to the Placebo group, the Estradiol group presented significantly greater 13,14-dihydro-15-keto-PGF2α concentrations between 4h and 7h and underwent earlier luteolysis. At 4h, the qPCR analysis showed a lower abundance of ESR1, ESR2 and aldo-keto reductase family 1 member B1 (AKR1B1) genes in the Estradiol B4h group, and a greater abundance of OXTR compared to the Placebo B4h group. Similarly, the E2 treatment significantly reduced the abundance of AKR1B1, and AKR1C4 in the Estradiol B7h group, compared to the placebo group. Overall, E2-induced PGF2α release and luteolysis involved an unexpected and transient downregulation of components of the PGF2α-synthesis cascade, except for OXTR, which was upregulated. Collectively, our data suggest that E2 connects newly-synthesized OXTR to pre-existing cellular machinery to synthesize PGF2α and cause luteal regression.

A Role for Fructose Metabolism in Development of Sheep and Pig Conceptuses

The period of conceptus (embryo and extraembryonic membrane) development between fertilization and implantation in mammalian species is critical as it sets the stage for placental and fetal development. The trophectoderm and endoderm of pre-implantation ovine and porcine conceptuses undergo elongation, which requires rapid proliferation, migration, and morphological modification of the trophectoderm cells. These complex events occur in a hypoxic intrauterine environment and are supported through the transport of secretions from maternal endometrial glands to the conceptus required for the biochemical processes of cell proliferation, migration, and differentiation. The conceptus utilizes glucose provided by the mother to initiate metabolic pathways that provide energy and substrates for other metabolic pathways. Fructose, however, is in much greater abundance than glucose in amniotic and allantoic fluids, and fetal blood during pregnancy. Despite this, the role(s) of fructose is largely unknown even though a switch to fructosedriven metabolism in subterranean rodents and some cancers are key to their adaptation to hypoxic environments.

Insights into the Regulation of Implantation and Placentation in Humans, Rodents, Sheep, and Pigs

Precise cell-specific spatio-temporal molecular signaling cascades regulate the establishment and maintenance of pregnancy. Importantly, the mechanisms regulating uterine receptivity, conceptus apposition and adhesion to the uterine luminal epithelia/superficial glandular epithelia and, in some species, invasion into the endometrial stroma and decidualization of stromal cells, are critical prerequisite events for placentation which is essential for the appropriate regulation of feto-placental growth for the remainder of pregnancy. Dysregulation of these signaling cascades during this critical stage of pregnancy can lead to pregnancy loss, impaired growth and development of the conceptus, and alterations in the transplacental exchange of gasses and nutrients. While many of these processes are conserved across species, significant variations in the molecular mechanisms governing maternal recognition of pregnancy, conceptus implantation, and placentation exist. This review addresses the complexity of key mechanisms that are critical for the establishment and maintenance of a successful pregnancy in humans, rodents, sheep, and pigs. Improving understanding of the molecular mechanisms governing these processes is critical to enhancing the fertility and reproductive health of humans and livestock species.

Conserved and breed-specific differences in the cervical transcriptome of sheep with divergent fertility at the follicular phase of a natural oestrus cycle

BACKGROUND

The outcome of cervical artificial insemination (AI) with frozen-thawed semen in sheep is limited by the inability of sperm to traverse the cervix of some ewe breeds. Previous research has demonstrated that cervical sperm transport is dependent on ewe breed, as sperm can traverse the cervix in greater numbers in some higher fertility ewe breeds. However, the molecular mechanisms underlying ewe breed differences in sperm transport through the cervix remain unknown. In this study, we aimed to characterise the cervical transcriptome of four European ewe breeds with known differences in pregnancy rates following cervical AI using frozen-thawed semen at the follicular phase of a natural oestrous cycle. Cervical post mortem tissue samples were collected from two Irish ewe breeds (Belclare and Suffolk; medium and low fertility, respectively) and from two Norwegian ewe breeds (Norwegian White Sheep (NWS) and Fur; high fertility compared to both Irish breeds) at the follicular phase of a natural oestrous cycle (n = 8 to 10 ewes per breed).

RESULTS

High-quality RNA extracted from biopsies of the mid-region of the cervix was analysed by RNA-sequencing and Gene Ontology (GO). After stringent filtering (P <  0.05 and FC > 1.5), a total of 11, 1539 and 748 differentially expressed genes (DEGs) were identified in Belclare, Fur and NWS compared to the low fertility Suffolk breed, respectively. Gene ontology analysis identified significantly enriched biological processes involved in muscle contraction, extracellular matrix (ECM) development and the immune response. Gene co-expression analysis revealed similar patterns in muscle contraction and ECM development modules in both Norwegian ewe breeds, which differed to the Irish ewe breeds.

CONCLUSIONS

These breed-specific biological processes may account for impaired cervical sperm transport through the cervix in sheep during the follicular phase of the reproductive cycle. This novel and comprehensive dataset provides a rich foundation for future targeted initiatives to improve cervical AI in sheep.

Combined approaches identify known and novel genes associated with sheep litter size and non-seasonal breeding

Improvement of ewe reproduction is considerable by appropriately increasing litter size and sustaining non-seasonal breeding. However, their genetic makeups have not been entirely elucidated. Genome-wide analyses of 821 individuals were performed by combining three genomic approaches (genome-wide association study, XP-nSL, and runs of homozygosity). Consequently, 35 candidate genes including three domestication genes (TSHR, GTF2A1, and KITLG) were identified. Other than the FecB mutation at BMPR1B, we described a significant association of a missense mutation rs406686139 at seasonal lambing-associated TSHR gene with litter size. Some promising novel genes may be relevant for sheep reproduction by multitude biological processes, such as FETUB functioning in fertilization, HNRNPA1 in oogenesis, DCUN1D1 in spermatogenesis, and HRG in fertility outcome. The present study suggests that improvement of ewe reproduction is attributed to selective breeding, and casts light on the genetic basis and improvement of sheep reproduction.

Characterization and regulation of extracellular vesicles in the lumen of the ovine uterus†

Secretions of the endometrium are vital for peri-implantation growth and development of the sheep conceptus. Extracellular vesicles (EVs) are present in the uterine lumen, emanate from both the endometrial epithelia of the uterus and trophectoderm of the conceptus, and hypothesized to mediate communication between those cell types during pregnancy establishment in sheep. Size-exclusion chromatography and nanoparticle tracking analysis determined that total EV number in the uterine lumen increased from days 10 to 14 of the cycle but was lower on days 12 and 14 of pregnancy in sheep. Intrauterine infusions of interferon tau (IFNT) did not affect total EV number in the uterine lumen. Quantitative mass spectrometric analyses defined proteins and lipids in EVs isolated from the uterine lumen of day 14 cyclic and pregnant sheep. In vitro analyses found that EVs decreased ovine trophectoderm cell proliferation and increased IFNT production without effects on gene expression as determined by RNA-seq. Collective results support the idea EVs impact conceptus growth during pregnancy establishment via effects on trophectoderm cell growth.

Enhanced drug delivery to the reproductive tract using nanomedicine reveals therapeutic options for prevention of preterm birth

Inflammation contributes to nearly 4 million global premature births annually. Here, we used a mouse model of intrauterine inflammation to test clinically used formulations, as well as engineered nanoformulations, for the prevention of preterm birth (PTB). We observed that neither systemic 17a-hydroxyprogesterone caproate (Makena) nor vaginal progesterone gel (Crinone) was sufficient to prevent inflammation-induced PTB, consistent with recent clinical trial failures. However, we found that vaginal delivery of mucoinert nanosuspensions of histone deacetylase (HDAC) inhibitors, in some cases with the addition of progesterone, prevented PTB and resulted in delivery of live pups exhibiting neurotypical development. In human myometrial cells in vitro, the P4/HDAC inhibitor combination both inhibited cell contractility and promoted the anti-inflammatory action of P4 by increasing progesterone receptor B stability. Here, we demonstrate the use of vaginally delivered drugs to prevent intrauterine inflammation-induced PTB resulting in the birth of live offspring in a preclinical animal model.

Pregnancy-induced changes in the transcriptome of the bovine corpus luteum during and after embryonic interferon-tau secretion†

Understanding luteal maintenance during early pregnancy is of substantial biological and practical importance. Characterizing effects of early pregnancy, however, has historically been confounded by use of controls with potential exposure to early Prostaglandin F2-alpha (PGF) pulses or differences in Corpus Luteum (CL) age. To avoid this, the present study utilized bihourly blood sampling to ensure control CL (n = 6) were of a similar age to CL from pregnant animals (n = 5), yet without exposure to PGF pulses. Additionally, CL from second month of pregnancy (n = 4) were analyzed to track fate of altered genes after cessation of embryonic interferon tau (IFNT) secretion. The major alteration in gene expression in first month of pregnancy occurred in interferon-stimulated genes (ISGs), with immune/interferon signaling pathways enriched in three independent over-representation analyses. Most ISGs decreased during second month of pregnancy, though, surprisingly, some ISGs remained elevated in the second month even after cessation of IFNT secretion. Investigation of luteolytic genes found few altered transcripts, in contrast to previous reports, likely due to removal of controls exposed to PGF pulses. An exception to this trend was decreased expression of transcription factor NR4A1. Beyond luteolytic genes and ISGs, over representation analyses highlighted the prevalence of altered genes within the extracellular matrix and regulation of Insulin-like growth factor (IGF) availability, confirming results of other studies independent of luteolytic genes. These results support the idea that CL maintenance in early pregnancy is related to lack of PGF exposure, although potential roles for CL expression of diverse ISGs and other pathways activated during early pregnancy remain undefined.

Conceptus-induced, interferon tau-dependent gene expression in bovine endometrial epithelial and stromal cells†

Bovine endometrium consists of epithelial and stromal cells that respond to conceptus interferon tau (IFNT), the maternal recognition of pregnancy (MRP) signal, by increasing expression of IFN-stimulated genes (ISGs). Endometrial epithelial and stromal-cell-specific ISGs are largely unknown but hypothesized to have essential functions during pregnancy establishment. Bovine endometrial epithelial cells were cultured in inserts above stromal fibroblast (SF) cells for 6 h in medium alone or with IFNT. The epithelial and SF transcriptomic response was analyzed separately using RNA sequencing and compared to a list of 369 DEGs recently identified in intact bovine endometrium in response to elongating bovine conceptuses and IFNT. Bovine endometrial epithelial and SF shared 223 and 70 DEGs in common with the list of 369 endometrial DEGs. Well-known ISGs identified in the epithelial and SF were ISG15, MX1, MX2, and OAS2. DEGs identified in the epithelial but not SF included a number of IRF molecules (IRF1, IRF2, IRF3, and IRF8), mitochondria SLC transporters (SLC25A19, SLC25A28, and SLC25A30), and a ghrelin receptor. Expression of ZC3HAV1, an anti-retroviral gene, increased specifically within the SF. Gene ontology analysis identified the type I IFN signaling pathway and activation of nuclear factor kappa B transcription factors as biological processes associated with the epithelial cell DEGs. This study has identified biologically relevant IFNT-stimulated genes within specific endometrial cell types. The findings provide critical information regarding the effects of conceptus IFNT on specific endometrial compartments during early developmental processes in cattle.

Gene Expression Profiling of Corpus luteum Reveals Important Insights about Early Pregnancy in Domestic Sheep

The majority of pregnancy loss in ruminants occurs during the preimplantation stage, which is thus the most critical period determining reproductive success. Here, we performed a comparative transcriptome study by sequencing total mRNA from corpus luteum (CL) collected during the preimplantation stage of pregnancy in Finnsheep, Texel and F1 crosses. A total of 21,287 genes were expressed in our data. Highly expressed autosomal genes in the CL were associated with biological processes such as progesterone formation (STAR, CYP11A1, and HSD3B1) and embryo implantation (e.g., TIMP1, TIMP2 and TCTP). Among the list of differentially expressed genes, sialic acid-binding immunoglobulin (Ig)-like lectins (SIGLEC3, SIGLEC14, SIGLEC8), ribosomal proteins (RPL17, RPL34, RPS3A, MRPS33) and chemokines (CCL5, CCL24, CXCL13, CXCL9) were upregulated in Finnsheep, while four multidrug resistance-associated proteins (MRPs) were upregulated in Texel ewes. A total of 17 known genes and two uncharacterized non-coding RNAs (ncRNAs) were differentially expressed in breed-wise comparisons owing to the flushing diet effect. The significantly upregulated TXNL1 gene indicated potential for embryonic diapause in Finnsheep and F1. Moreover, we report, for the first time in any species, several genes that are active in the CL during early pregnancy (including TXNL1, SIGLEC14, SIGLEC8, MRP4, and CA5A).

Impact of Perfluorooctane Sulfonate on Reproductive Ability of Female Mice through Suppression of Estrogen Receptor α-Activated Kisspeptin Neurons

Perfluorooctane sulfonate (PFOS) is used extensively in industrial and household applications. High exposure to PFOS has been associated with increased odds of irregular and long menstrual cycles in women. However, the underlying mechanisms remain to be elucidated. Herein, we show that adult female mice appeared prolongation of diestrus and reduction of corpora luteum within a week of oral administration of PFOS (10 mg/kg), which are associated with decreases in the levels of serum progesterone, LH and hypothalamic GnRH. The number of AVPV-kisspeptin neurons and the AVPV-kisspeptin expression were increased in proestrus mice or OVX-mice treated with high-dose estradiol benzoate (0.05 mg/kg), which were suppressed by the administration of PFOS. The administration of PFOS or GPR54 antagonist P234 prevented the generation of LH-surge in OVX-mice treated with high-dose E2. In hypothalamic slices incubated in 100 nM E2 for 4 h, the AVPV-kisspeptin expression was significantly enhanced, which was inhibited by PFOS in a dose-dependent manner or estrogen receptor α (ERα) antagonist MPP, but not ERβ antagonist PHTPP. The incubation of ERα agonist PPT rather than ERβ agonist DPN could increase the level of AVPV-kisspeptin expression, which was sensitive to the treatment with PFOS. The administration of GPR54 agonist kisspeptin-10 in PFOS-mice could correct the prolongation of diestrus and reduction of corpora luteum, and recover the LH-surge and the levels of LH and GnRH. The results indicate that exposure to PFOS suppressed ERα-induced activation of AVPV-kisspeptin neurons leads to diestrus prolongation and ovulation reduction.

Reproductive hormones modulate differentially brain and ovarian vasotocin receptor gene expression in early and late recrudescent catfish, Heteropneustes fossilis

Investigations on the role of the reproductive hormones on VT receptor gene expression are lacking in teleosts. Previously we reported that gonadotropin and steroid hormones modulate the secretion and gene expression of brain and ovarian vasotocin (VT) in the catfish Heteropneustes fossilis. In continuation, in the present study we investigated the role of estradiol-17β (E₂), the maturation-inducing steroid (MIS) 17α, 20β-dihydroxy-4-pregnen-3-one (17, 20β-DP), and human chorionic gonadotropin (hCG) on the expression of VT receptor genes (v1a1, v1a2 and v2a) in the brain and ovary of the catfish in early (previtellogenic, preparatory) and late (post vitellogenic, prespawning) phases of the ovarian cycle. The steroid treatments (in vivo and in vitro) modulated only the v1a1 and v1a2 expression in both tissues, but not the v2a expression. The E₂-induced modulation of the v1a1 and v1a2 gene expression varied with the reproductive phase. In the preparatory phase, E₂ up regulated the expression of brain and ovarian v1a1 and v1a2 gene expression, the response varied with the dose and duration. In the prespawning phase, E₂ inhibited the expression in a dose- and duration-dependent manner. On the other hand, 17, 20β-DP up regulated the expression of brain and ovarian v1a1 and v1a2 in both phases, and the response was higher in the prespawning phase and varied with dose and duration. In contrast to the steroid effects, the hCG treatment modulated the expression of all the VT receptor genes only in the prespawning phase and the response varied with dose and duration. The results indicate differential modulatory roles of steroid hormones and hCG on the VT receptor gene expression, to mediate VT's reproductive or osmoregulatory functions. While the hCG effect on v1a type receptor expression may be steroid- dependent, that of v2a expression seems to be steroid-independent.

Sexually dimorphic oxytocin receptor-expressing neurons in the preoptic area of the mouse brain

Oxytocin is involved in the regulation of social behaviors including parental behaviors in a variety of species. Oxytocin triggers social behaviors by binding to oxytocin receptors (OXTRs) in various parts of the brain. OXTRs are present in the preoptic area (POA) where hormone-sensitive sexually dimorphic nuclei exist. The present study was conducted to examine whether sex differences exist in the distribution of neurons expressing OXTRs in the POA. Using OXTR-Venus (an enhanced variant of yellow fluorescent protein) mice, the distribution of OXTR-Venus cells in the POA was compared between sexes. The total number of OXTR-Venus cells in the medial POA (MPOA) was significantly greater in females than in males. No detectable OXTR-Venus cells were observed in the anteroventral periventricular nucleus (AVPV) within the MPOA in most of the brain sections from males. We further examined the total number of OXTR-Venus cells in the AVPV and the rest of the MPOA between the sexes. The total number of OXTR-Venus cells in the AVPV in females (615 ± 43) was significantly greater than that in males (14 ± 2), whereas the total number of OXTR-Venus cells in the rest of the MPOA did not differ significantly between the sexes. Thus, the sexually dimorphic expression of OXTR-Venus specifically occurred in the AVPV, but not in the rest of the MPOA. We also examined whether the expression of OXTR in the AVPV is driven by the female gonadal hormone, estrogen. Immunocytochemistry and single-cell RT-PCR revealed the presence of the estrogen receptor α in OXTR-Venus cells in the female AVPV. Moreover, ovariectomy resulted in the absence of OXTR-Venus expression in the AVPV, whereas estrogen replacement therapy restored OXTR-Venus expression. These results demonstrate that the expression of OXTR in the AVPV is primarily female specific and estrogen dependent. The presence of the sexually dimorphic expression of OXTR in the AVPV suggests the involvement of OXTR neurons in the AVPV in the regulation of female-specific behavior and/or physiology.

Genomic and transcriptomic investigations of the evolutionary transition from oviparity to viviparity

Viviparous (live-bearing) vertebrates have evolved repeatedly within otherwise oviparous (egg-laying) clades. Over two-thirds of these changes in vertebrate reproductive parity mode happened in squamate reptiles, where the transition has happened between 98 and 129 times. The transition from oviparity to viviparity requires numerous physiological, morphological, and immunological changes to the female reproductive tract, including eggshell reduction, delayed oviposition, placental development for supply of water and nutrition to the embryo by the mother, enhanced gas exchange, and suppression of maternal immune rejection of the embryo. We performed genomic and transcriptomic analyses of a closely related oviparous-viviparous pair of lizards (Phrynocephalus przewalskii and Phrynocephalus vlangalii) to examine these transitions. Expression patterns of maternal oviduct through reproductive development of the egg and embryo differ markedly between the two species. We found changes in expression patterns of appropriate genes that account for each of the major aspects of the oviparity to viviparity transition. In addition, we compared the gene sequences in transcriptomes of four oviparous-viviparous pairs of lizards in different genera (Phrynocephalus, Eremias, Scincella, and Sphenomorphus) to look for possible gene convergence at the sequence level. We discovered low levels of convergence in both amino acid replacement and evolutionary rate shift. This suggests that most of the changes that produce the oviparity-viviparity transition are changes in gene expression, so occasional reversals to oviparity from viviparity may not be as difficult to achieve as has been previously suggested.

Mechanisms for the establishment and maintenance of pregnancy: synergies from scientific collaborations

Research on the functions of interferon tau (IFNT) led to the theory of pregnancy recognition signaling in ruminant species. But IFNT does much more as it induces expression of interferon regulatory factor 2 (IRF2) in uterine luminal (LE), superficial glandular (sGE), but not glandular (GE) epithelia. First, IRF2 silences transcription of the estrogen receptor alpha gene and, indirectly, transcription of the oxytocin receptor gene to abrogate development of the luteolytic mechanism to prevent regression of the corpus luteum and its production of progesterone for establishing and maintaining pregnancy. Second, IRF2 silences expression of classical interferon-stimulated genes in uterine LE and sGE; however, uterine LE and sGE respond to progesterone (P4) and IFNT to increase expression of genes for transport of nutrients into the uterine lumen such as amino acids and glucose. Other genes expressed by uterine LE and sGE encode for adhesion molecules such as galectin 15, cathepsins, and cystatins for tissue remodeling, and hypoxia-inducible factor relevant to angiogenesis and survival of blastocysts in a hypoxic environment. IFNT is also key to a servomechanism that allows uterine epithelia, particularly GE, to proliferate and to express genes in response to placental lactogen and placental growth hormone in sheep. The roles of secreted phosphoprotein 1 are also discussed regarding its role in implantation in sheep and pigs, as well as its stimulation of expression of mechanistic target of rapamycin mRNA and protein which is central to proliferation, migration, and gene expression in the trophectoderm cells.

Paracrine and endocrine actions of interferon tau (IFNT)

This review focuses on the paracrine and endocrine actions of interferon tau (IFNT) during pregnancy recognition and establishment in ruminants. Pregnancy recognition involves the suppression of the endometrial luteolytic mechanism by the conceptus to maintain progesterone production by the corpus luteum (CL). The paracrine antiluteolytic effects of conceptus-derived IFNT inhibit upregulation of oxytocin receptors in the endometrial epithelia of the uterus, thereby preventing the production of luteolytic prostaglandin F2 alpha (PGF2α) pulses. In the endometrium, IFNT induces or upregulates a large number of classical IFN-stimulated genes (ISGs) and regulates expression of many other genes in a cell-specific manner that are likely important for conceptus elongation, implantation and establishment of pregnancy. Further, IFNT has endocrine effects on extrauterine cells and tissues. In sheep, IFNT induces luteal resistance to PGF2α, thereby ensuring survival of the CL for maintenance of pregnancy. The ISGs induced in circulating peripheral blood mononuclear cells by IFNT may also be useful as an indicator of pregnancy status in cattle. An increased knowledge of IFNT and ISGs is important to improve the reproductive efficiency in ruminants.

Chronicling the discovery of interferon tau

It has been 38 years since a protein, now known as interferon tau (IFNT), was discovered in ovine conceptus-conditioned culture medium. After 1979, purification and testing of native IFNT revealed its unique antiluteolyic activity to prevent the regression of corpora lutea on ovaries of nonpregnant ewes. Antiviral, antiproliferative and immunomodulatory properties of native and recombinant IFNT were demonstrated later. In addition, progesterone and IFNT were found to act cooperatively to silence expression of classical interferon stimulated genes in a cell-specific manner in ovine uterine luminal and superficial glandular epithelia. But, IFNT signaling through a STAT1/STAT2-independent pathway stimulates expression of genes, such as those for transport of glucose and amino acids, which are required for growth and development of the conceptus. Further, undefined mechanisms of action of IFNT are key to a servomechanism that allows ovine placental lactogen and placental growth hormone to affect the development of uterine glands and their expression of genes throughout gestation. IFNT also acts systemically to induce the expression of interferon stimulated genes that influence secretion of progesterone by the corpus luteum. Finally, IFNT has great potential as a therapeutic agent due to its low cytotoxicity, anti-inflammatory properties and effects to mitigate diabetes, obesity-associated syndromes and various autoimmune diseases.

Cryptic sexual dimorphism in spatial memory and hippocampal oxytocin receptors in prairie voles (Microtus ochrogaster)

Sex differences are well documented and are conventionally associated with intense sex-specific selection. For example, spatial memory is frequently better in males, presumably due to males' tendency to navigate large spaces to find mates. Alternatively, monogamy (in which sex-specific selection is relatively relaxed) should diminish or eliminate differences in spatial ability and the mechanisms associated with this behavior. Nevertheless, phenotypic differences between monogamous males and females persist, sometimes cryptically. We hypothesize that sex-specific cognitive demands are present in monogamous species that will influence neural and behavioral phenotypes. The effects of these demands should be observable in spatial learning performance and neural structures associated with spatial learning and memory. We analyzed spatial memory performance, hippocampal volume and cell density, and hippocampal oxytocin receptor (OTR) expression in the socially monogamous prairie vole. Compared to females, males performed better in a spatial memory and spatial learning test. Although we found no sex difference in hippocampal volume or cell density, male OTR density was significantly lower than females, suggesting that performance may be regulated by sub-cellular mechanisms within the hippocampus that are less obvious than classic neuroanatomical features. Our results suggest an expanded role for oxytocin beyond facilitating social interactions, which may function in part to integrate social and spatial information.

Cloprostenol administration in the first week postpartum reduces expression of oxytocin receptors in the endometrium in Holstein-Zebu cows

ABSTRACT The present study investigated the hormonal profile and expression of prostaglandin F2α (PGF2α), oxytocin and estrogen receptors in uterine tissues of postpartum cows treated with cloprostenol. Twenty Holstein-Zebu crossbred cows were treated with saline solution (treatment CONT) or cloprostenol (treatment CLO), both administered two and five days postpartum. Blood samples were collected on days two, seven, 14, 21 and 28 postpartum for progesterone, PGF2α metabolite (PGFM) and estradiol determination, and endometrial biopsy was performed in order to quantify the expression of oxytocin receptor (OXTR), prostaglandin F receptor (PTGFR) and estrogen receptor 1 (ERS1) genes. In the CLO treatment, expression of OXTR was reduced (P<0.05) but no difference (P>0.05) between treatments was found for PTGFR and ERS1 expression. Estrogen concentrations increased progressively until day 14 (P<0.05) and the highest OXTR expression and lowest PTGFR expression were observed on day 14 (P<0.05) in both treatments. Serum PGFM concentrations were high throughout the experiment. In conclusion, cloprostenol administration at days two and five of postpartum seems to reduce OXTR expression in the endometrium in crossbred cows.

A novel polymorphism in the oxytocin receptor encoding gene (OXTR) affects milk fatty acid composition in Italian Mediterranean river buffalo

The oxytocin receptor, also known as OXTR, is a protein which functions as receptor for the hormone and neurotransmitter oxytocin and the complex oxytocin–oxytocin receptor plays an important role in the uterus during calving. A characterisation of the river buffalo OXTR gene, amino acid sequences and phylogenetic analysis is presented. The DNA regions of the OXTR gene spanning exons 1, 2 and 3 of ten Mediterranean river buffalo DNA samples were analysed and 7 single nucleotide polymorphisms were found. We focused on the g.129C > T SNP detected in exon 3 and responsible for the amino acid replacement CGCArg > TGCCys in position 353. The relative frequency of T allele was of 0·257. An association study between this detected polymorphism and milk fatty acids composition in Italian Mediterranean river buffalo was carried out. The fatty acid composition traits, fatty acid classes and fat percentage of 306 individual milk samples were determined. Associations between OXTR g.129C > T genotype and milk fatty acids composition were tested using a mixed linear model. The OXTR CC genotype was found significantly associated with higher contents of odd branched-chain fatty acids (OBCFA) (P < 0·0006), polyunsaturated FA (PUFA n 3 and n 6) (P < 0·0032 and P < 0·0006, respectively), stearic acid (C18) (P < 0·02) and lower level of palmitic acid (C16) (P < 0·02). The results of this study suggest that the OXTR CC animals might be useful in selection toward the improvement of milk fatty acid composition.

Oxytocin receptor DNA methylation in postpartum depression

The oxytocin receptor (OXTR) is a key regulator of stress and anxiety and may be regulated by both psychosocial risk factors and gonadal hormones, making it an attractive candidate for study in postpartum depression (PPD). The objective of this study was to investigate both serum hormone and PPD specific DNA methylation variation in the OXTR. Illumina HM450 microarray data generated in a prospective PPD cohort identified significant associations (P=0.014) with PPD in an intronic region in the OXTR located 4bp proximal to an estrogen receptor (ER) binding region. Pyrosequencing confirmed moderate evidence for an interaction of CpGs in the region with childhood abuse status to mediate PPD. These CpGs located on chr3 at positions 8810078 and 8810069 exhibited significant associations with postpartum depression scores from an independent cohort of 240 women with no prior psychiatric history. Hormone analysis suggested a PPD specific negative correlation of DNA methylation in the region with serum estradiol levels. Estradiol levels and OXTR DNA methylation exhibited a significant interaction to associate with the ratio of allopregnanolone to progesterone. Cumulatively, the data corroborate our previous hypotheses of a PPD specific increased sensitivity of epigenetic reprogramming at estrogen target genes and suggests that OXTR epigenetic variation may be an important mediator of mood relevant neuroactive steroid production.

Novel concepts on the role of prostaglandins on luteal maintenance and maternal recognition and establishment of pregnancy in ruminants

In ruminants, the corpus luteum (CL) of early pregnancy is resistant to luteolysis. Prostaglandin (PG)E2 is considered a luteoprotective mediator. Early studies indicate that during maternal recognition of pregnancy (MRP) in ruminants, a factor(s) from the conceptus or gravid uterus reaches the ovary locally through the utero-ovarian plexus (UOP) and protects the CL from luteolysis. The local nature of the embryonic antiluteolytic or luteoprotective effect precludes any direct effect of a protein transported or acting between the gravid uterus and CL in ruminants. During MRP, interferon tau (IFNT) secreted by the trophoblast of the conceptus inhibits endometrial pulsatile release of PGF2α and increases endometrial PGE2. Our recent studies indicate that (1) luteal PG biosynthesis is selectively directed toward PGF2α at the time of luteolysis and toward PGE2 at the time of establishment of pregnancy (ESP); (2) the ability of the CL of early pregnancy to resist luteolysis is likely due to increased intraluteal biosynthesis and signaling of PGE2; and (3) endometrial PGE2 is transported from the uterus to the CL through the UOP vascular route during ESP in sheep. Intrauterine co-administration of IFNT and prostaglandin E2 synthase 1 (PGES-1) inhibitor reestablishes endometrial PGF2α pulses and regresses the CL. In contrast, intrauterine co-administration of IFNT and PGES-1 inhibitor along with intraovarian administration of PGE2 rescues the CL. Together, the accumulating information provides compelling evidence that PGE2 produced by the CL in response to endometrial PGE2 induced by pregnancy may counteract the luteolytic effect of PGF2α as an additional luteoprotective mechanism during MRP or ESP in ruminants. Targeting PGE2 biosynthesis and signaling selectively in the endometrium or CL may provide luteoprotective therapy to improve reproductive efficiency in ruminants.

An in vitro investigation of the actions of reproductive hormones on the cervix of the ewe in the follicular stage: the effects of 17β-estradiol, oxytocin, FSH, and arachidonic acid on the cervical pathway for the synthesis of prostaglandin E2

During the periovulatory period, the cervix of the ewe relaxes and this mechanism is thought to be mediated by oxytocin and prostaglandin E2 (PGE2) in response to increased concentrations of 17β-estradiol and perhaps FSH. The aim of the study was to determine the in vitro effects of 17β-estradiol, FSH, oxytocin, and arachidonic acid (AA) on the synthesis of PGE2 and on the expression of oxytocin receptor (OTR), cytoplasmic phospholipase A2 (cPLA2), and cyclooxygenase 2 (COX-2) in explants of cervical tissue collected from ewes in the periovulatory phase of the estrous cycle. Cervical minces from ewes in the follicular phase of the estrous cycle were cultured in supplemented Eagle's Minimum Essential Medium for 48 hours with 17β-estradiol, FSH, oxytocin, or AA. After incubation, the tissue was stored at -80 °C and the media at -20 °C. Western immunoblotting was used to determine relative levels of OTR, cPLA2, and COX-2 in cervical tissue, and the media was analyzed by RIA, to determine the concentration of PGE2. The addition of 17β-estradiol increased the concentration of PGE2 in the media (P = 0.001), the levels of COX-2 (P = 0.02) and OTR (P = 0.006) but not those of cPLA2 (P = 0.15). The addition of FSH increased the levels of COX-2 (P = 0.01) but, it had no effect on the concentration of PGE2 (P = 0.08) or on the levels of OTR (P = 0.07) and cPLA2 (P = 0.15). Oxytocin did not increase the levels of COX-2 (P = 0.38) but increased those of OTR (P = 0.001) and cPLA2 (P = 0.01) but not on the concentration of PGE2 in the media. Arachidonic acid increased the levels of cPLA2 (P = 0.01) and those of COX-2 (P = 0.02) but not the concentration of PGE2 in the media. Our findings suggest that the PGE2-mediated mechanisms of cervical relaxation in the ewe during the follicular phase are stimulated by FSH, 17β-estradiol, oxytocin, and AA. They all appear to act by inducing receptors and enzymes along the synthetic pathway for PGE2.

Oxytocin decreases colonic motility of cold water stressed rats via oxytocin receptors

AIM: To investigate whether cold water intake into the stomach affects colonic motility and the involvement of the oxytocin-oxytocin receptor pathway in rats.

METHODS: Female Sprague Dawley rats were used and some of them were ovariectomized. The rats were subjected to gastric instillation with cold (0-4 °C, cold group) or room temperature (20-25 °C, control group) saline for 14 consecutive days. Colon transit was determined with a bead inserted into the colon. Colonic longitudinal muscle strips were prepared to investigate the response to oxytocin in vitro. Plasma concentration of oxytocin was detected by ELISA. Oxytocin receptor expression was investigated by Western blot analysis. Immunohistochemistry was used to locate oxytocin receptors.

RESULTS: Colon transit was slower in the cold group than in the control group (P < 0.05). Colonic smooth muscle contractile response to oxytocin decreased, and the inhibitory effect of oxytocin on muscle contractility was enhanced by cold water intake (0.69 ± 0.08 vs 0.88 ± 0.16, P < 0.05). Atosiban and tetrodotoxin inhibited the effect of oxytocin on colonic motility. Oxytocin receptors were located in the myenteric plexus, and their expression was up-regulated in the cold group (P < 0.05). Cold water intake increased blood concentration of oxytocin, but this effect was attenuated in ovariectomized rats (286.99 ± 83.72 pg/mL vs 100.56 ± 92.71 pg/mL, P < 0.05). However, in ovariectomized rats, estradiol treatment increased blood oxytocin, and the response of colonic muscle strips to oxytocin was attenuated.

CONCLUSION: Cold water intake inhibits colonic motility partially through oxytocin-oxytocin receptor signaling in the myenteric nervous system pathway, which is estrogen dependent.

Molecular characterization of oxytocin receptor gene in water buffalo (Bubalus bubalis)

Buffaloes are known for their productivity as compared to average yielding cows due to higher fat percentage, better feed conversion ability and disease resistance. On the other hand, the reproductive performances of buffaloes are often considered as poor owing to late sexual maturity, weak/silent oestrus, repeat breeder and prolonged intercalving interval. The study of cascade of events during oestrus and oestrous cycle can be useful for the improvement of reproductive efficiency of buffaloes. More precisely, the hormonal changes initiated at the molecular level within the animal determine the reproductive nature of the species. Nucleotide/protein sequence analysis serves as a vital tool in analysing the binding of the hormones for their effect or functions. In this study, we have reported cloning and characterization of the complete coding (cDNA) sequence of oxytocin receptor gene (OXTR) in buffaloes. Buffalo OXTR gene contains an uninterrupted ORF of 1176 nucleotides corresponding to an inferred polypeptide length of 391 amino acids (aa). The molecular weight of the deduced aa sequence was found to be 43 kDa with an isoelectric point of 9.253 and 16.328 charge at pH 7.0. The deduced protein sequence consists of 38 strongly basic (+) (K,R), 22 strongly acidic (-) (D,E), 186 hydrophobic (A, I, L, F, W, V) and 95 Polar (N, C, Q, S, T, Y) aa. Results indicated that aspartate (D) at aa position 85 and D, R and C at aa positions 136, 137 and 138, respectively, are conserved in buffaloes. The buffalo OXTR gene shared a per cent similarity ranging from 84.7 to 98.1 and 88.5 to 97.7 at nucleotide and deduced aa sequence levels, respectively, with that of other species. Phylogram constructed on the basis of either nucleotide or deduced aa sequences of buffalo OXTR gene showed that buffalo, cattle and sheep have diverged from human and swine and formed a separate clad. The buffalo sequence has shown maximum similarity and closeness with cattle followed by sheep both at nucleotide and at aa level.

Membrane-localized estrogen receptor α is required for normal organ development and function

Steroid receptors are found in discrete cellular locations, but it is unknown whether extranuclear pools are necessary for normal organ development. To assess this, we developed a point mutant estrogen receptor α (ERα) knockin mouse (C451A) that precludes palmitoylation and membrane trafficking of the steroid receptor in all organs. Homozygous knockin female mice (nuclear-only ERα [NOER]) show loss of rapid signaling that occurs from membrane ERα in wild-type mice. Multiple developmental abnormalities were found, including infertility, relatively hypoplastic uteri, abnormal ovaries, stunted mammary gland ductal development, and abnormal pituitary hormone regulation in NOER mice. These abnormalities were rescued in heterozygous NOER mice that were comparable to wild-type mice. mRNAs implicated in organ development were often poorly stimulated by estrogen only in homozygous NOER mice. We conclude that many organs require membrane ERα and resulting signal transduction to collaborate with nuclear ERα for normal development and function.

Roles of conceptus secretory proteins in establishment and maintenance of pregnancy in ruminants

Reproduction in ruminant species is a highly complex biological process requiring a dialogue between the developing conceptus (embryo-fetus and associated placental membranes) and maternal uterus which must be established during the peri-implantation period for pregnancy recognition signaling and regulation of gene expression by uterine epithelial and stromal cells. The uterus provide a microenvironment in which molecules secreted by uterine epithelia and transported into the uterine lumen represent histotroph, also known as the secretome, that are required for growth and development of the conceptus and receptivity of the uterus to implantation by the elongating conceptus. Pregnancy recognition signaling as related to sustaining the functional lifespan of the corpora lutea, is required to sustain the functional life-span of corpora lutea for production of progesterone which is essential for uterine functions supportive of implantation and placentation required for successful outcomes of pregnancy. It is within the peri-implantation period that most embryonic deaths occur in ruminants due to deficiencies attributed to uterine functions or failure of the conceptus to develop appropriately, signal pregnancy recognition and/or undergo implantation and placentation. The endocrine status of the pregnant ruminant and her nutritional status are critical for successful establishment and maintenance of pregnancy. The challenge is to understand the complexity of key mechanisms that are characteristic of successful reproduction in humans and animals and to use that knowledge to enhance fertility and reproductive health of ruminant species in livestock enterprises.

Intrauterine coadministration of ERK1/2 inhibitor U0126 inhibits interferon TAU action in the endometrium and restores luteolytic PGF2alpha pulses in sheep

In ruminants, prostaglandin F2 alpha (PGF2alpha) is synthesized and released in a pulsatile pattern from the endometrial luminal epithelial (LE) cells during the process of luteolysis. Interferon tau (IFNT) is a Type 1 IFN secreted by the trophoblast cells of the developing conceptus. IFNT acts locally on endometrial LE cells to inhibit pulsatile releases of PGF2alpha and thus establish an endocrine environment for recognition of pregnancy. Cell signaling pathways through which IFNT stimulates expression of multiple genes or proteins in endometrial LE are largely unknown. Results of the present investigation indicate that intrauterine administration of IFNT inhibits pulsatile release of PGF2alpha, while coadministration IFNT and ERK 1/2 inhibitor U0126 restores luteolytic PGF2alpha pulses in sheep. IFNT increases phosphorylation of ERK1/2 proteins and increases its interaction with PGT proteins in endometrial LE. Blockade of ERK1/2 pathways inhibits IFNT action, decreases pERK1/2 and PGT protein interactions, and re-establishes the spatial expression of the oxytocin receptor protein completely and the estrogen receptor protein partially without modulating the expression of interferon regulatory factor-2 (IRF-2) protein in endometrial LE. IFNT does not decrease expression of COX-2, PGDH, or PGT protein in endometrial LE. Our results provide important new insights into IFNT signaling and the molecular endocrine control of PGF2alpha release at the time of establishment of pregnancy in ruminants. This novel IFNT-ERK1/2 signaling module needs to be explored in future studies to understand molecular and cellular mechanisms of IFNT action in endometrial LE in ruminants.

Non-classical mechanisms of steroid sensing in the ovary: lessons from the bovine oxytocin model

Steroidogenic tissues such as the ovary, testes or adrenal glands are paradoxical in that they often indicate actions of steroid hormones within a dynamic range of ligand concentration in a high nanomolar or even micromolar level, i.e. at the natural concentrations existing within those organs. Yet ligand-activated nuclear steroid receptors act classically by direct interaction with DNA in the picomolar or low nanomolar range. Moreover, global genomic studies suggest that less than 40% of steroid-regulated genes involve classical responsive elements in gene promoter regions. The bovine oxytocin gene is a key element in the maternal recognition of pregnancy in ruminants and is regulated via an SF1 site in its proximal promoter. This gene is also regulated by steroids acting in a non-classical manner, involving nuclear receptors which do not interact directly with DNA. Dose-response relationships for these actions are in the high nanomolar range. Similar 'steroid sensing' mechanisms may prevail for other SF1-regulated genes and predict alternative pathways by which environmental endocrine disruptors might influence the functioning of steroid-producing organs and hence indirectly the steroid-dependent control of physiology and development.

Brain region-specific methylation in the promoter of the murine oxytocin receptor gene is involved in its expression regulation

Oxytocin is a nine amino acid neuropeptide that is known to play a critical role in fetal expulsion and breast-feeding, and has been recently implicated in mammalian social behavior. The actions of both central and peripheral oxytocin are mediated through the oxytocin receptor (Oxtr), which is encoded by a single gene. In contrast to the highly conserved expression of oxytocin in specific hypothalamic nuclei, the expression of its receptor in the brain is highly diverse among different mammalian species or even within individuals of the same species. The diversity in the pattern of brain Oxtr expression among mammals is thought to contribute to the broad range of social systems and organizations. Yet, the mechanisms underlying this diversity are poorly understood. DNA methylation is a major epigenetic mechanism that regulates gene transcription, and has been linked to reduced expression levels of the Oxtr in individuals with autism. Here we hypothesize that DNA methylation is involved in the expression regulation of Oxtr in the mouse brain. By combining bisulfite DNA conversion and Next-Generation Sequencing we found that specific CpG sites are differentially methylated between distinct brain regions expressing different levels of Oxtr mRNA. Some of these CpG sites are located within putative binding sites of transcription factors known to regulate Oxtr expression, including estrogen receptor α (ERα) and SP1. Specifically, methylation of the SP1 site was found to positively correlate with Oxtr expression. Furthermore, we revealed that the methylation levels of these sites in the various brain regions predict the relationship between ERα and Oxtr mRNA levels. Collectively, our results suggest that brain region-specific expression of the mouse Oxtr gene is epigenetically regulated by DNA methylation of its promoter.

Progesterone inhibition of oxytocin signaling in endometrium

Expression of the oxytocin receptor (OXTR) in the endometrium of ruminant species is regulated by the ovarian steroids progesterone (P) and estradiol (E). Near the end of the estrous cycle, long-term exposure of endometrial epithelial cells to P results in loss of genomic P receptors (PGRs), leading to an increase in E receptors (ERs). Genomic regulation of the OXTR is mediated via suppression of ER signaling by P. Upon OT binding at the plasma membrane of endometrial cells, a signaling cascade is generated stimulating release of prostaglandin F2α (PGF2α). Transport of PGF2α to the ovary results in release of OT by luteal cells in a positive feedback loop leading to luteal regression. This signaling cascade can be rapidly blocked by exposing endometrial cells to physiologic levels of P. This mini review will focus on the mechanisms by which P may act to block OXTR signaling and the luteolytic cascade in the ruminant endometrium, with special focus on both non-genomic signaling pathways and non-receptor actions of P at the level of the plasma membrane. While this review focuses on ruminant species, non-classical blockage of OXTR signaling may be important for fertility in women.

The androgen metabolite, 5α-androstane-3β,17β-diol (3β-diol), activates the oxytocin promoter through an estrogen receptor-β pathway

Testosterone has been shown to suppress the acute stress-induced activation of the hypothalamic-pituitary-adrenal axis; however, the mechanisms underlying this response remain unclear. The hypothalamic-pituitary-adrenal axis is regulated by a neuroendocrine subpopulation of medial parvocellular neurons in the paraventricular nucleus of the hypothalamus (PVN). These neurons are devoid of androgen receptors (ARs). Therefore, a possibility is that the PVN target neurons respond to a metabolite in the testosterone catabolic pathway via an AR-independent mechanism. The dihydrotestosterone metabolite, 5α-androstane-3β,17β-diol (3β-diol), binds and activates estrogen receptor-β (ER-β), the predominant ER in the PVN. In the PVN, ER-β is coexpressed with oxytocin (OT). Therefore, we tested the hypothesis that 3β-diol regulates OT expression through ER-β activation. Treatment of ovariectomized rats with estradiol benzoate or 3β-diol for 4 days increased OT mRNA selectively in the midcaudal, but not rostral PVN compared with vehicle-treated controls. 3β-Diol treatment also increased OT mRNA in the hypothalamic N38 cell line in vitro. The functional interactions between 3β-diol and ER-β with the human OT promoter were examined using an OT promoter-luciferase reporter construct (OT-luc). In a dose-dependent manner, 3β-diol treatment increased OT-luc activity when cells were cotransfected with ER-β, but not ER-α. The 3β-diol-induced OT-luc activity was reduced by deletion of the promoter region containing the composite hormone response element (cHRE). Point mutations of the cHRE also prevented OT-luc activation by 3β-diol. These results indicate that 3β-diol induces OT promoter activity via ER-β-cHRE interactions.

DNA methylation of specific CpG sites in the promoter region regulates the transcription of the mouse oxytocin receptor

Oxytocin is a peptide hormone, well known for its role in labor and suckling, and most recently for its involvement in mammalian social behavior. All central and peripheral actions of oxytocin are mediated through the oxytocin receptor, which is the product of a single gene. Transcription of the oxytocin receptor is subject to regulation by gonadal steroid hormones, and is profoundly elevated in the uterus and mammary glands during parturition. DNA methylation is a major epigenetic mechanism that regulates gene transcription, and has been linked to reduced expression of the oxytocin receptor in individuals with autism. Here, we hypothesized that transcription of the mouse oxytocin receptor is regulated by DNA methylation of specific sites in its promoter, in a tissue-specific manner. Hypothalamus-derived GT1-7, and mammary-derived 4T1 murine cell lines displayed negative correlations between oxytocin receptor transcription and methylation of the gene promoter, and demethylation caused a significant enhancement of oxytocin receptor transcription in 4T1 cells. Using a reporter gene assay, we showed that methylation of specific sites in the gene promoter, including an estrogen response element, significantly inhibits transcription. Furthermore, methylation of the oxytocin receptor promoter was found to be differentially correlated with oxytocin receptor expression in mammary glands and the uterus of virgin and post-partum mice, suggesting that it plays a distinct role in oxytocin receptor transcription among tissues and under different physiological conditions. Together, these results support the hypothesis that the expression of the mouse oxytocin receptor gene is epigenetically regulated by DNA methylation of its promoter.

Hosting the preimplantation embryo: potentials and limitations of different approaches for analysing embryo - endometrium interactions in cattle

Ongoing detailed investigations into embryo–maternal communication before implantation reveal that during early embryonic development a plethora of events are taking place. During the sexual cycle, remodelling and differentiation processes in the endometrium are controlled by ovarian hormones, mainly progesterone, to provide a suitable environment for establishment of pregnancy. In addition, embryonic signalling molecules initiate further sequences of events; of these molecules, prostaglandins are discussed herein as specifically important. Inadequate receptivity may impede preimplantation development and implantation, leading to embryonic losses. Because there are multiple factors affecting fertility, receptivity is difficult to comprehend. This review addresses different models and methods that are currently used and discusses their respective potentials and limitations in distinguishing key messages out of molecular twitter. Transcriptome, proteome and metabolome analyses generate comprehensive information and provide starting points for hypotheses, which need to be substantiated using further confirmatory methods. Appropriate in vivo and in vitro models are needed to disentangle the effects of participating factors in the embryo–maternal dialogue and to help distinguish associations from causalities. One interesting model is the study of somatic cell nuclear transfer embryos in normal recipient heifers. A multidisciplinary approach is needed to properly assess the importance of the uterine milieu for embryonic development and to use the large number of new findings to solve long-standing issues regarding fertility.

Contributions of an animal scientist to understanding the biology of the uterus and pregnancy

I developed a passion for reproductive biology when taking a course in Physiology of Reproduction at Louisiana State University while preparing to apply for Veterinary School at Texas A&M University. My career path changed. I entered graduate school, obtained a Ph.D. and have enjoyed an academic career conducting research in uterine biology and pregnancy in animal science departments at the University of Florida and at Texas A&M University. My contributions to science include: (1) identification of molecules secreted by or transported by uterine epithelia into the uterine lumen that are critical to successful establishment and maintenance of pregnancy, (2) discovery of steroids and proteins required for pregnancy-recognition signalling and their mechanisms of action in pigs and ruminants, (3) patterns of fetal–placental development and placental transport of nutrients, (4) identification of links between nutrients and components of histotroph that affect fetal–placental development, (5) characterising aspects of the endocrinology of pregnancy and (6) contributing to efforts to exploit the therapeutic value of interferon tau, particularly for treatment of autoimmune and inflammatory diseases. Current research focuses on select nutrients in the uterine lumen, specifically amino acids, glucose and fructose, that affect conceptus development, the therapeutic potential for interferon tau, stromal–epithelial cell signalling whereby progesterone and oestrogen act via steroid receptors in uterine stromal cells to stimulate secretion of growth factors (e.g. fibroblast growth factors and hepatocyte growth factor) that regulate uterine epithelial cells and conceptus trophectoderm, and roles of toll-like receptors expressed by uterine epithelia and conceptus trophectoderm in pregnancy.

Mitochondria-localized glutamic acid-rich protein (MGARP) gene transcription is regulated by Sp1

Background

Mitochondria-localized glutamic acid-rich protein (MGARP) is a novel mitochondrial transmembrane protein expressed mainly in steroidogenic tissues and in the visual system. Previous studies showed that MGARP functions in hormone biosynthesis and its expression is modulated by the HPG axis.

Methodology/Principal Findings

By bioinformatics, we identified two characteristic GC-rich motifs that are located proximal to the transcription start site (TSS) of MGARP, and each contains two Specificity protein 1 (Sp1) binding elements. We then determined that the −3 kb proximal MGARP promoter is activated in a Sp1-dependent manner using reporter assays and knockdown of Sp1 led to decreased expression of endogenous MGARP messages. We also demonstrated that one of the two GC-rich motifs, GC-Box1, harbors prominent promoter activity mediated by Sp1, and that it requires both GC boxes for full transcriptional activation. These findings suggest a dominant role for these GC boxes and Sp1 in activating the MGARP promoter through a synergistic mechanism. Consistently, the results of an Electrophoretic Mobility Gel Shift Assay (EMSA) and Chromatin Immunoprecipitation (ChIP) confirmed that Sp1 specifically interacts with the GC-rich region. We further found that estrogen receptor α (ERα), a known Sp1 co-activator, could potentiate GC-boxes containing MGARP promoter activity and this effect is mediated by Sp1. Knockdown of Sp1 significantly diminished the MGARP promoter transactivation and the expression of endogenous MGARP mediated by both Sp1 and ERα.

Conclusions/Significance

The present study identified a proximal core sequence in the MGARP promoter that is composed of two enriched Sp1 binding motifs and established Sp1 as one major MGARP transactivator whose functions are synergistic with ERα, providing a novel understanding of the mechanisms of MGARP gene transcriptional regulation.

Phorbol esters enhance 1α,25-dihydroxyvitamin D3-regulated 25-hydroxyvitamin D-24-hydroxylase (CYP24A1) gene expression through ERK-mediated phosphorylation of specific protein 3 (Sp3) in Caco-2 cells

Phorbol 12-myristate 13-acetate (PMA) increased 1,25(OH)(2)D(3)-induced human 25 hydroxyvitamin d-24 hydroxylase (hCYP24A1) gene expression and vitamin D receptor (VDR) binding to the hCYP24A1 promoter. It did not alter transient receptor potential cation channel, subfamily V, member 6 (TRPV6) expression, VDR binding to the TRPV6 promoter, or VDR binding to a crude chromatin preparation. PMA activated Extracellular signal-Regulated Kinases (ERK) 1/2 and p38 mitogen activated protein kinases (MAPK) and inhibiting these kinases reduced 1,25(OH)(2)D(3)-induced and PMA-enhanced hCYP24A1 promoter activity. Mithramycin A inhibits Specific Protein (Sp) family member binding to DNA and reduced 1,25(OH)(2)D(3)-induced and PMA-enhanced hCYP24A1 promoter activity. Sp1 or Sp3 siRNA knockdown reduced 1,25(OH)(2)D(3)-regulated hCYP24A1 promoter activity but only Sp3 siRNA reduced PMA-enhanced hCYP24A1 promoter activity. PMA increased MAPK-dependent Sp3 phosphorylation, Sp3-VDR interactions, and Sp3 binding to the hCYP24A1 promoter. These data suggest that MAPK signaling contributes to 1,25(OH)(2)D(3)-induced and PMA-enhanced CYP24A1 gene transcription by modulating Sp3 function.