Hypothalamic transcriptomic alterations in male and female California mice (Peromyscus californicus) developmentally exposed to bisphenol A or ethinyl estradiol

Evaluating endocrine disrupting chemicals: A perspective on the novel assessments in CLARITY-BPA

BACKGROUND

The Consortium Linking Academic and Regulatory Insights on Bisphenol A Toxicity (CLARITY-BPA) was a collaborative research effort to better link academic research with governmental guideline studies. This review explores the secondary goal of CLARITY-BPA: to identify endpoints or technologies from CLARITY-BPA and prior/concurrent literature from these laboratories that may enhance the capacity of rodent toxicity studies to detect endocrine disrupting chemicals (EDCs).

METHODS

A systematic literature search was conducted with search terms for BPA and the CLARITY-BPA participants. Relevant studies employed a laboratory rodent model and reported results on 1 of the 10 organs/organ systems evaluated in CLARITY-BPA (brain and behavior, cardiac, immune, mammary gland, ovary, penile function, prostate gland and urethra, testis and epididymis, thyroid hormone and metabolism, and uterus). Study design and findings were summarized, and a risk-of-bias assessment was conducted.

RESULTS

Several endpoints and methods were identified as potentially helpful to detect effects of EDCs. For example, molecular and quantitative morphological approaches were sensitive in detecting alterations in early postnatal development of the brain, ovary, and mammary glands. Hormone challenge studies mimicking human aging reported increased susceptibility of the prostate to disease following developmental BPA exposure. Statistical analyses for nonmonotonic dose responses, and computational approaches assessing multiple treatment-related outcomes concurrently in linked hormone-sensitive organ systems, reported effects at low BPA doses.

CONCLUSIONS

This review provided an opportunity to evaluate the unique insights provided by nontraditional assessments in CLARITY-BPA to identify technologies and endpoints to enhance detection of EDCs in future studies.

Transcriptome analysis of changes in M. aeruginosa growth and microcystin production under low concentrations of ethinyl estradiol

Ethinyl estradiol (EE2) is a synthetic environmental estrogen with considerable estrogenic activity. It has been found to consequently pose a significant threat to the aquatic ecosystem. Harmful algal blooms are a major aquatic ecological issue. However, the relationship between EE2 and cyanobacterial bloom is mainly unknown. In this study, the physiological and molecular responses of Microcystis aeruginosa to EE2 exposure were investigated. A low level of EE2 (0.02 μg/L) significantly enhanced the growth of algal cells (P < 0.05), whereas higher concentrations of EE2 (0.2-200 μg/L) inhibited it. EE2 at doses ranging from 0.02 to 200 μg/L promoted the production of microcystins (MCs), with genes mcyABD playing a key role in the regulation of MC synthesis. The alterations of chlorophyll-a, carotenoid, and phycocyanin contents caused by EE2 showed the same trend as cell growth. At the molecular level, 200 μg/L EE2 significantly down-regulated genes in photosynthetic pigment synthesis, light harvesting, electron transfer, NADPH, and ATP generation. High concentrations of EE2 caused oxidative damage to algal cells on the 4th d. After 12d exposure, although there was no significant change in superoxide dismutase (SOD) content and no damage observed in membrane lipids, genes related to SOD and glutathione were changed. In addition, due to the down-regulation of pckA, PK, gltA, nrtA, pstS, etc., carbon fixation, glycolysis, TCA cycle, nitrogen and phosphorus metabolism were hindered by EE2 (200 μg/L). Gene fabG in fatty acid biosynthesis was significantly up-regulated, promoting energy storage in cells. These findings provide important clues to elucidate the effects and mechanisms of cyanobacterial blooms triggered by EE2 and help to effectively prevent and control cyanobacterial blooms.

Oral contraceptives and stroke: Foes or friends

Incidents of strokes are increased in young women relative to young men, suggesting that oral contraceptive (OC) use is one of the causes of stroke among young women. Long-term exposures to the varying combinations of estrogen and progestogen found in OCs affect blood clotting, lipid and lipoprotein metabolism, endothelial function, and de novo synthesis of neurosteroids, especially brain-derived 17β-estradiol. The latter is essential for neuroprotection, memory, sexual differentiation, synaptic transmission, and behavior. Deleterious effects of OCs may be exacerbated due to comorbidities like polycystic ovary syndrome, sickle cell anemia, COVID-19, exposures to endocrine disrupting chemicals, and conventional or electronic cigarette smoking. The goal of the current review is to revisit the available literature regarding the impact of OC use on stroke, to explain possible underlying mechanisms, and to identify gaps in our understanding to promote future research to reduce and cure stroke in OC users.

Behavioral and hypothalamic transcriptome analyses reveal sex-specific responses to phenanthrene exposure in the fathead minnow (Pimephales promelas)

Environmental concentrations of the polycyclic aromatic hydrocarbon phenanthrene can become elevated with petroleum processing, industrial activities, and urban run-off into waterbodies. However, mechanisms related to its neurotoxicity in fish are not fully described. Here, we exposed adult fathead minnows (FHM) to an average measured concentration of 202 μg phenanthrene/L over a 47-d period. Behaviors of male and female FHM were assessed using a novel aquarium test. Phenanthrene exposed females displayed equilibrium loss, while phenanthrene exposed males spent less time in the aquarium bottom, suggesting phenanthrene reduced anxiety-related behavior. To elucidate putative mechanisms underlying behaviors, we determined the hypothalamic transcriptome profile, a critical integration centre for the regulation of behaviors. There were 1075 hypothalamic transcripts differentially expressed between males and females (sex-specific) while 15 transcripts were phenanthrene-specific. Thus, sex of the animal was more pervasive at influencing the transcriptome compared to phenanthrene and this may partially explain the divergent behavioral responses between sexes. Transcripts altered by phenanthrene included palmitoylated 3 membrane protein, plectin 1,ATP synthase membrane subunit c, and mitochondrial ribosomal protein S11. Gene set enrichment analysis revealed less than 5% of the gene networks perturbed by phenanthrene were shared between males and females, thus phenanthrene altered the hypothalamic transcriptome in a sex-specific manner. Gene networks shared between both sexes and associated with phenanthrene-induced neurotoxicity included processes related to mitochondrial respiratory chain dysfunction, epinephrine/norepinephrine release, and glutamate biosynthesis pathways. Such energy deficits and neurotransmitter disruptions are hypothesized to lead to behavioral deficits in fish. This study provides mechanistic insights into phenanthrene-induced neurotoxicity and how it may relate to changes in fish behaviors.

Maternal Oxycodone Treatment Results in Neurobehavioral Disruptions in Mice Offspring

Opioid drugs are increasingly being prescribed to pregnant women. Such compounds can also bind and activate opioid receptors in the fetal brain, which could lead to long-term brain and behavioral disruptions. We hypothesized that maternal treatment with oxycodone (OXY), the primary opioid at the center of the current crisis, leads to later neurobehavioral disorders and gene expression changes in the hypothalamus and hippocampus of resulting offspring. Female mice were treated daily with 5 mg OXY/kg or saline solution (control; CTL) for two weeks before breeding and then throughout gestation. Male and female offspring from both groups were tested with a battery of behavioral and metabolic tests to measure cognition, exploratory-like, anxiety-like, voluntary physical activity, and socio-communication behaviors. qPCR analyses were performed for candidate gene expression patterns in the hypothalamus and hippocampus of OXY and CTL derived offspring. Developmental exposure to OXY caused socio-communication changes that persisted from weaning through adulthood. Such offspring also showed cognitive impairments, reduced voluntary physical activity, and weighed more than CTL counterparts. In the hippocampus, prenatal exposure to OXY caused sex-dependent differences in expression of genes encoding opioid receptors and those involved in serotonin signaling. OXY exposure induced changes in neuropeptide hormone expression and the epigenetic modulator, Dnmt3a, in the hypothalamus, which could result in epigenetic changes in this brain region. The findings suggest cause for concern that consumption of OXY by pregnant mothers may result in permanent neurobehavioral changes in their offspring. Further work is needed to determine the potential underpinning epigenetic mechanisms.

Disruption of global hypothalamic microRNA (miR) profiles and associated behavioral changes in California mice (Peromyscus californicus) developmentally exposed to endocrine disrupting chemicals

Developmental exposure to endocrine disrupting chemicals (EDCs), e.g., bisphenol A (BPA) or genistein (GEN), causes longstanding epigenome effects. MicroRNAs (miRs) regulate which mRNAs will be translated to proteins and thereby serve as the final checkpoint in epigenetic control. Scant amount is known, however, whether EDCs affect neural miRNA (miR) patterns. We aimed to test the hypothesis that developmental exposure of California mice (Peromyscus californicus) to GEN, BPA, or both chemicals influences hypothalamic miR/small RNA profiles and ascertain the extent such biomolecular alterations correlate with behavioral and metabolic changes. California mice were developmentally exposed to GEN (250 mg/kg feed weight, FW), GEN (250 mg/kg FW)+BPA (5 mg/kg FW), low dose (LD) BPA (5 mg/kg FW), or upper dose (UD) BPA (50 mg/kg FW). Adult offspring were tested in a battery of behavioral and metabolic tests; whereupon, mice were euthanized, brains were collected and frozen, small RNAs were isolated from hypothalamic punches, and subsequently sequenced. California mice exposed to one or both EDCs engaged in one or more repetitive behaviors. GEN, LD BPA, and UD BPA altered aspects of ultrasonic and audible vocalizations. Each EDC exposure led to sex-dependent differences in differentially expressed miR/small RNAs with miR7-2, miR146, and miR148a being increased in all female and male EDC exposed groups. Current findings reveal that developmental exposure to GEN and/or BPA affects hypothalamic miR/small RNA expression patterns, and such changes correlate with EDC-induced behavioral and metabolic alterations. miR146 is likely an important mediator and biomarker of EDC exposure in mammals, including humans.

Data integration, analysis, and interpretation of eight academic CLARITY-BPA studies

"Consortium Linking Academic and Regulatory Insights on BPA Toxicity" (CLARITY-BPA) was a comprehensive "industry-standard" Good Laboratory Practice (GLP)-compliant 2-year chronic exposure study of bisphenol A (BPA) toxicity that was supplemented by hypothesis-driven independent investigator-initiated studies. The investigator-initiated studies were focused on integrating disease-associated, molecular, and physiological endpoints previously found by academic scientists into an industry standard guideline-compliant toxicity study. Thus, the goal of this collaboration was to provide a more comprehensive dataset upon which to base safety standards and to determine whether industry-standard tests are as sensitive and predictive as molecular and disease-associated endpoints. The goal of this report is to integrate the findings from the investigator-initiated studies into a comprehensive overview of the observed impacts of BPA across the multiple organs and systems analyzed. For each organ system, we provide the rationale for the study, an overview of methodology, and summarize major findings. We then compare the results of the CLARITY-BPA studies across organ systems with the results of previous peer-reviewed studies from independent labs. Finally, we discuss potential influences that contributed to differences between studies. Developmental exposure to BPA can lead to adverse effects in multiple organs systems, including the brain, prostate gland, urinary tract, ovary, mammary gland, and heart. As published previously, many effects were at the lowest dose tested, 2.5μg/kg /day, and many of the responses were non-monotonic. Because the low dose of BPA affected endpoints in the same animals across organs evaluated in different labs, we conclude that these are biologically - and toxicologically - relevant.

Maternal oxycodone treatment causes pathophysiological changes in the mouse placenta

INTRODUCTION

Pregnant women are increasingly being prescribed and abusing opioid drugs. As the primary communication organ between mother and conceptus, the placenta may be vulnerable to opioid effects but also holds the key to better understanding how these drugs affect long-term offspring health. We hypothesized that maternal treatment with oxycodone (OXY), the primary opioid at the center of the current crisis, deleteriously affects placental structure and gene expression patterns.

METHODS

Female mice were treated daily with 5 mg OXY/kg or saline solution (Control, CTL) for two weeks prior to breeding and until placenta were collected at embryonic age 12.5. A portion of the placenta was fixed for histology, and the remainder was frozen for RNA isolation followed by RNAseq.

RESULTS

Maternal OXY treatment reduced parietal trophoblast giant cell (pTGC) area and decreased the maternal blood vessel area within the labyrinth region. OXY exposure affected placental gene expression profiles in a sex dependent manner with female placenta showing up-regulation of many placental enriched genes, including Ceacam11, Ceacam14, Ceacam12, Ceacam13, Prl7b1, Prl2b1, Ctsq, and Tpbpa. In contrast, placenta of OXY exposed males had alteration of many ribosomal proteins. Weighted correlation network analysis revealed that in OXY female vs. CTL female comparison, select modules correlated with OXY-induced placental histological changes. Such associations were lacking in the male OXY vs. CTL male comparison.

DISCUSSION

Results suggest OXY exposure alters placental histology. In response to OXY exposure, female placenta responds by upregulating placental enriched transcripts that are either unchanged or downregulated in male placenta. Such changes may shield female offspring from developmental origins of health and disease-based diseases.

Impacts of bisphenol A analogues on zebrafish post-embryonic brain

Bisphenol A (BPA) is a widely studied and well-recognised endocrine-disrupting chemical, and one of the current issues is its safe replacement by various analogues. Using larva zebrafish as a model, the present study reveals that moderate and chronic exposure to BPA analogues such as bisphenol S, bisphenol F and bisphenol AF may also affect vertebrate neurodevelopment and locomotor activity. Several parameters of embryo-larval development were investigated, such as mortality, hatching, number of mitotically active cell, as defined by 5-bromo-2'-deoxyuridine incorporation and proliferative cell nuclear antigen labelling, aromatase B protein expression in radial glial cell and locomotor activity. Our results show that exposure to several bisphenol analogues induced an acceleration of embryo hatching rate. At the level of the developing brain, a strong up-regulation of the oestrogen-sensitive Aromatase B was also detected in the hypothalamic region. This up-regulation was not associated with effects on the numbers of mitotically active progenitors nor differentiated neurones in the preoptic area and in the nuclear recessus posterior of the hypothalamus zebrafish larvae. Furthermore, using a high-throughput video tracking system to monitor locomotor activity in zebrafish larvae, we show that some bisphenol analogues, such as bisphenol AF, significantly reduced locomotor activity following 6 days of exposure. Taken together, our study provides evidence that BPA analogues can also affect the neurobehavioural development of zebrafish.

Changes in nucleus accumbens gene expression accompany sex-specific suppression of spontaneous physical activity in aromatase knockout mice

Aromatase catalyzes conversion of testosterone to estradiol and is expressed in a variety of tissues, including the brain. Suppression of aromatase adversely affects metabolism and physical activity behavior, but mechanisms remain uncertain. The hypothesis tested herein was that whole body aromatase deletion would cause gene expression changes in the nucleus accumbens (NAc), a brain regulating motivated behaviors such as physical activity, which is suppressed with loss of estradiol. Metabolic and behavioral assessments were performed in male and female wild-type (WT) and aromatase knockout (ArKO) mice. NAc-specific differentially expressed genes (DEGs) were identified with RNAseq, and associations between the measured phenotypic traits were determined. Female ArKO mice had greater percent body fat, reduced spontaneous physical activity (SPA), consumed less energy, and had lower relative resting energy expenditure (REE) than WT females. Such differences were not observed in ArKO males. However, in both sexes, a top DEG was Pts, a gene encoding an enzyme necessary for catecholamine (e.g., dopamine) biosynthesis. In comparing male and female WT mice, top DEGs were related to sexual development/fertility, immune regulation, obesity, dopamine signaling, and circadian regulation. SPA correlated strongly with Per3, a gene regulating circadian function, thermoregulation, and metabolism (r = -0.64, P = .002), which also correlated with adiposity (r = 0.54, P = .01). In conclusion, aromatase ablation leads to gene expression changes in NAc, which may in turn result in reduced SPA and related metabolic abnormalities. These findings may have significance to post-menopausal women and those treated with an aromatase inhibitor.

Endocrine disruption of gene expression and microRNA profiles in hippocampus and hypothalamus of California mice: Association of gene expression changes with behavioural outcomes

The hypothalamus and hippocampus are sensitive to early exposure to endocrine disrupting chemicals (EDCs). Two EDCs that have raised particular concerns are bisphenol A (BPA), a widely prevalent chemical in many common household items, and genistein (GEN), a phyto-oestrogen present in soy and other plants. We hypothesised that early exposure to BPA or GEN may lead to permanent effects on gene expression profiles for both coding RNAs (mRNAs) and microRNAs (miRs), which can affect the translation of mRNAs. Such EDC-induced biomolecular changes may affect behavioural and metabolic patterns. California mice (Peromyscus californicus) male and female offspring were developmentally exposed via the maternal diet to BPA (5 mg kg^-1 feed weight low dose [LD] and 50 mg kg^-1 feed weight upper dose [UD]), GEN (250 mg kg^-1 feed weight) or a phyto-oestrogen-free diet (AIN) control. Behavioural and metabolic tests were performed at 180 days of age. A quantitative polymerase chain reacttion analysis was performed for candidate mRNAs and miRs in the hypothalamus and hippocampus. LD BPA and GEN exposed California mice offspring showed socio-communication impairments. Hypothalamic Avp, Esr1, Kiss1 and Lepr were increased in LD BPA offspring. miR-153 was elevated but miR-181a was reduced in LD BPA offspring. miR-9 and miR-153 were increased in the hippocampi of LD BPA offspring, whereas GEN decreased hippocampal miR-7a and miR-153 expression. Correlation analyses revealed neural expression of miR-153 and miR-181a was associated with socio-communication deficits in LD BPA individuals. The findings reveal a cause for concern such that developmental exposure of BPA or GEN in California mice (and potentially by translation in humans) can lead to long standing neurobehavioural consequences.

Bisphenol a Exposure in Utero Disrupts Hypothalamic Gene Expression Particularly Genes Suspected in Autism Spectrum Disorders and Neuron and Hormone Signaling

Bisphenol A (BPA) is an endocrine-disrupting compound detected in the urine of more than 92% of humans, easily crosses the placental barrier, and has been shown to influence gene expression during fetal brain development. The purpose of this study was to investigate the effect of in utero BPA exposure on gene expression in the anterior hypothalamus, the basal nucleus of the stria terminalis (BNST), and hippocampus in C57BL/6 mice. Mice were exposed in utero to human-relevant doses of BPA, and then RNA sequencing was performed on male PND 28 tissue from whole hypothalamus (n = 3/group) that included the medial preoptic area (mPOA) and BNST to determine whether any genes were differentially expressed between BPA-exposed and control mice. A subset of genes was selected for further study using RT-qPCR on adult tissue from hippocampus to determine whether any differentially expressed genes (DEGs) persisted into adulthood. Two different RNA-Seq workflows indicated a total of 259 genes that were differentially expressed between BPA-exposed and control mice. Gene ontology analysis indicated that those DEGs were overrepresented in categories relating to mating, cell-cell signaling, behavior, neurodevelopment, neurogenesis, synapse formation, cognition, learning behaviors, hormone activity, and signaling receptor activity, among others. Ingenuity Pathway Analysis was used to interrogate novel gene networks and upstream regulators, indicating the top five upstream regulators as huntingtin, beta-estradiol, alpha-synuclein, Creb1, and estrogen receptor (ER)-alpha. In addition, 15 DE genes were identified that are suspected in autism spectrum disorders.

Mice lacking uterine enhancer of zeste homolog 2 have transcriptomic changes associated with uterine epithelial proliferation

Enhancer of zeste homolog 2 (EZH2) is a histone methyltransferase that suppresses gene expression. Previously, we developed a conditional null model where EZH2 is knocked out in uterus. Deletion of uterine EZH2 increased proliferation of luminal and glandular epithelial cells. Herein, we used RNA-Seq in wild-type (WT) and EZH2 conditional knockout (Ezh2cKO) uteri to obtain mechanistic insights into the gene expression changes that underpin the pathogenesis observed in these mice. Ovariectomized adult Ezh2cKO mice were treated with vehicle (V) or 17β-estradiol (E2; 1 ng/g). Uteri were collected at postnatal day (PND) 75 for RNA-Seq or immunostaining for epithelial proliferation. Weighted gene coexpression network analysis was used to link uterine gene expression patterns and epithelial proliferation. In V-treated mice, 88 transcripts were differentially expressed (DEG) in Ezh2cKO mice, and Bmp5, Crabp2, Lgr5, and Sprr2f were upregulated. E2 treatment resulted in 40 DEG with Krt5, Krt15, Olig3, Crabp1, and Serpinb7 upregulated in Ezh2cKO compared with control mice. Transcript analysis relative to proliferation rates revealed two module eigengenes correlated with epithelial proliferation in WT V vs. Ezh2cKO V and WT E2 vs. Ezh2cKO E2 mice, with a positive relationship in the former and inverse in the latter. Notably, the ESR1, Wnt, and Hippo signaling pathways were among those functionally enriched in Ezh2cKO females. Current results reveal unique gene expression patterns in Ezh2cKO uterus and provide insight into how loss of this critical epigenetic regulator assumingly contributes to uterine abnormalities.

Oxidative Stress and DNA methylation in male rat pups provoked by the transplacental and translactational exposure to bisphenol A

The epigenetic changes induced by environmental contaminants play important roles in the inheritance of male reproductive dysfunction. The present study investigated DNA methylation changes and some oxidative stress biomarkers induced by bisphenol A (BPA) in male offspring. A total number of 48 female albino rats were administered orally with 50 μg/kg of BPA/day during gestation and/or lactation periods. At postnatal day 60, the samples were collected from the male pups to assess the serum testosterone, malondialdehyde (MDA) level, superoxide dismutase (SOD), glutathione S-transferase, and glutathione peroxidase (GSH-Px) activities in testicular tissue. DNA methylation in both DNA (cytosine-5)-methyltransferase 3A and estrogen receptor alpha genes was detected by methylation-specific PCR. BPA exposure resulted in significant decrease in the anogenital distance, testis and epididymis weights, serum testosterone level, SOD, GST, and GSH-Px levels with significant increase in weaning body weight and the MDA level. Additionally, BPA caused marked hypermethylation within Dnmt3A and ER- ∝ genes promoter regions in the testis of rat male pups. Graphical abstract.

The parental brain and behavior: A target for endocrine disruption

During pregnancy, the sequential release of progesterone, 17β-estradiol, prolactin, oxytocin and placental lactogens reorganize the female brain. Brain structures such as the medial preoptic area, the bed nucleus of the stria terminalis and the motivation network including the ventral tegmental area and the nucleus accumbens are reorganized by this specific hormonal schedule such that the future mother will be ready to provide appropriate care for her offspring right at parturition. Any disruption to this hormone pattern, notably by exposures to endocrine disrupting chemicals (EDC), is therefore likely to affect the maternal brain and result in maladaptive maternal behavior. Development effects of EDCs have been the focus of intense study, but relatively little is known about how the maternal brain and behavior are affected by EDCs. We encourage further research to better understand how the physiological hormone sequence prepares the mother's brain and how EDC exposure could disturb this reorganization.

Sex-Specific Gene Expression in the Mouse Nucleus Accumbens Before and After Cocaine Exposure

The nucleus accumbens plays a major role in the response of mammals to cocaine. In animal models and human studies, the addictive effects of cocaine and relapse probability have been shown to be greater in females. Sex-specific differential expression of key transcripts at baseline and after prolonged withdrawal could underlie these differences. To distinguish between these possibilities, gene expression was analyzed in four groups of mice (cycling females, ovariectomized females treated with estradiol or placebo, and males) 28 days after they had received seven daily injections of saline or cocaine. As expected, sensitization to the locomotor effects of cocaine was most pronounced in the ovariectomized mice receiving estradiol, was greater in cycling females than in males, and failed to occur in ovariectomized/placebo mice. After the 28-day withdrawal period, RNA prepared from the nucleus accumbens of the individual cocaine- or saline-injected mice was subjected to RNA sequencing analysis. Baseline expression of 3% of the nucleus accumbens transcripts differed in the cycling female mice compared with the male mice. Expression of a similar number of transcripts was altered by ovariectomy or was responsive to estradiol treatment. Nucleus accumbens transcripts differentially expressed in cycling female mice withdrawn from cocaine exhibited substantial overlap with those differentially expressed in cocaine-withdrawn male mice. A small set of transcripts were similarly affected by cocaine in the placebo- or estradiol-treated ovariectomized mice. Sex and hormonal status have profound effects on RNA expression in the nucleus accumbens of naive mice. Prolonged withdrawal from cocaine alters the expression of a much smaller number of common and sex hormone-specific transcripts.

Prenatal Bisphenol A Exposure in Mice Induces Multitissue Multiomics Disruptions Linking to Cardiometabolic Disorders

The health impacts of endocrine-disrupting chemicals (EDCs) remain debated, and their tissue and molecular targets are poorly understood. In this study, we leveraged systems biology approaches to assess the target tissues, molecular pathways, and gene regulatory networks associated with prenatal exposure to the model EDC bisphenol A (BPA). Prenatal BPA exposure at 5 mg/kg/d, a dose below most reported no-observed-adverse-effect levels, led to tens to thousands of transcriptomic and methylomic alterations in the adipose, hypothalamus, and liver tissues in male offspring in mice, with cross-tissue perturbations in lipid metabolism as well as tissue-specific alterations in histone subunits, glucose metabolism, and extracellular matrix. Network modeling prioritized main molecular targets of BPA, including Pparg, Hnf4a, Esr1, Srebf1, and Fasn as well as numerous less studied targets such as Cyp51 and long noncoding RNAs across tissues, Fa2h in hypothalamus, and Nfya in adipose tissue. Lastly, integrative analyses identified the association of BPA molecular signatures with cardiometabolic phenotypes in mouse and human. Our multitissue, multiomics investigation provides strong evidence that BPA perturbs diverse molecular networks in central and peripheral tissues and offers insights into the molecular targets that link BPA to human cardiometabolic disorders.

Sexual dimorphism in brain transcriptomes of Amami spiny rats (Tokudaia osimensis): a rodent species where males lack the Y chromosome

Background

Brain sexual differentiation is sculpted by precise coordination of steroid hormones during development. Programming of several brain regions in males depends upon aromatase conversion of testosterone to estrogen. However, it is not clear the direct contribution that Y chromosome associated genes, especially sex-determining region Y (Sry), might exert on brain sexual differentiation in therian mammals. Two species of spiny rats: Amami spiny rat (Tokudaia osimensis) and Tokunoshima spiny rat (T. tokunoshimensis) lack a Y chromosome/Sry, and these individuals possess an XO chromosome system in both sexes. Both Tokudaia species are highly endangered. To assess the neural transcriptome profile in male and female Amami spiny rats, RNA was isolated from brain samples of adult male and female spiny rats that had died accidentally and used for RNAseq analyses.

Results

RNAseq analyses confirmed that several genes and individual transcripts were differentially expressed between males and females. In males, seminal vesicle secretory protein 5 (Svs5) and cytochrome P450 1B1 (Cyp1b1) genes were significantly elevated compared to females, whereas serine (or cysteine) peptidase inhibitor, clade A, member 3 N (Serpina3n) was upregulated in females. Many individual transcripts elevated in males included those encoding for zinc finger proteins, e.g. zinc finger protein X-linked (Zfx).

Conclusions

This method successfully identified several genes and transcripts that showed expression differences in the brain of adult male and female Amami spiny rat. The functional significance of these findings, especially differential expression of transcripts encoding zinc finger proteins, in this unusual rodent species remains to be determined.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5426-6) contains supplementary material, which is available to authorized users.

Gene expression and DNA methylation changes in the hypothalamus and hippocampus of adult rats developmentally exposed to bisphenol A or ethinyl estradiol: a CLARITY-BPA consortium study

Bisphenol A (BPA), an endocrine disrupting chemical (EDC), is a ubiquitous pollutant. As part of the Consortium Linking Academic and Regulatory Insights on BPA Toxicity (CLARITY-BPA), we sought to determine whether exposure of Sprague-Dawley rats to 2,500 μg/kg/day BPA (BPA) or 0.5 μg/kg/day ethinyl estradiol (EE) from gestational day 6 through postnatal day 21 induces behavior-relevant gene expression and DNA methylation changes in hippocampus and hypothalamus at adulthood. RNA and DNA were isolated from both regions. Expression of ten genes (Dnmt1, Dnmt3a, Dnmt3b, Esr1, Esr2, Avp, Ar, Oxt, Otr, and Bdnf) presumably altered by early-life BPA/EE exposure was examined. Three genes (Bdnf, Dnmt3b, and Esr1) were studied for DNA methylation changes in their putative 5' promoter regions. Molecular changes in hippocampus were correlated to prior Barnes maze performance, including sniffing correct holes, distance traveled, and velocity. Exposure to BPA and/or EE disrupted patterns of sexually dimorphic gene expression/promoter DNA methylation observed in hippocampus and hypothalamus of controls. In the hippocampus of female offspring, BPA exposure resulted in hypermethylation of the putative 5' promoter region of Bdnf, while EE exposure induced hypomethylation. Bdnf methylation was weakly associated with Bdnf expression in hippocampi of female rats. Hippocampal Bdnf expression in females showed a weak negative association with sniffing correct hole in Barnes maze. Hippocampal expression of Avp, Esr2, Oxt, and Otr was strongly associated with velocity of control rats in Barnes maze. Findings suggest BPA exposure induced non-EE-like gene expression and epigenetic changes in adult rat hippocampi, a region involved in spatial navigation.

Hypothalamic transcriptomic alterations in male and female California mice (Peromyscus californicus) developmentally exposed to bisphenol A or ethinyl estradiol

Bisphenol A (BPA) is an endocrine‐disrupting chemical (EDC) prevalent in many household items. Rodent models and human epidemiological studies have linked this chemical to neurobehavior impairments. In California mice, developmental exposure to BPA results in sociosexual disorders at adulthood, including communication and biparental care deficits, behaviors that are primarily regulated by the hypothalamus. Thus, we sought to examine the transcriptomic profile in this brain region of juvenile male and female California mice offspring exposed from periconception through lactation to BPA or ethinyl estradiol (EE, estrogen present in birth control pills and considered a positive estrogen control for BPA studies). Two weeks prior to breeding, P₀ females were fed a control diet, or this diet supplemented with 50 mg BPA/kg feed weight or 0.1 ppb EE, and continued on the diets through lactation. At weaning, brains from male and female offspring were collected, hypothalamic RNA isolated, and RNA‐seq analysis performed. Results indicate that BPA and EE groups clustered separately from controls with BPA and EE exposure leading to unique set of signature gene profiles. Kcnd3 was downregulated in the hypothalamus of BPA‐ and EE‐exposed females, whereas Tbl2, Topors, Kif3a, and Phactr2 were upregulated in these groups. Comparison of transcripts differentially expressed in BPA and EE groups revealed significant enrichment of gene ontology terms associated with microtubule‐based processes. Current results show that perinatal exposure to BPA or EE can result in several transcriptomic alterations, including those associated with microtubule functions, in the hypothalamus of California mice. It remains to be determined whether these genes mediate BPA‐induced behavioral disruptions.

Multigenerational effects of bisphenol A or ethinyl estradiol exposure on F2 California mice (Peromyscus californicus) pup vocalizations

Rodent pups use vocalizations to communicate with one or both parents in biparental species, such as California mice (Peromyscus californicus). Previous studies have shown California mice developmentally exposed to endocrine disrupting chemicals, bisphenol A (BPA) or ethinyl estradiol (EE), demonstrate later compromised parental behaviors. Reductions in F1 parental behaviors might also be due to decreased emissions of F2 pup vocalizations. Thus, vocalizations of F2 male and female California mice pups born to F1 parents developmentally exposed to BPA, EE, or controls were examined. Postnatal days (PND) 2-4 were considered early postnatal period, PND 7 and 14 were defined as mid-postnatal period, and PND 21 and 28 were classified as late postnatal period. EE pups showed increased latency to emit the first syllable compared to controls. BPA female pups had decreased syllable duration compared to control and EE female pups during the early postnatal period but enhanced responses compared to controls at late postnatal period; whereas, male BPA and EE pups showed greater syllable duration compared to controls during early postnatal period. In mid-postnatal period, F2 BPA and EE pups emitted greater number of phrases than F2 control pups. Results indicate aspects of vocalizations were disrupted in F2 pups born to F1 parents developmentally exposed to BPA or EE, but their responses were not always identical, suggesting BPA might not activate estrogen receptors to the same extent as EE. Changes in vocalization patterns by F2 pups may be due to multigenerational exposure to BPA or EE and/or reduced parental care received.

Mapping Molecular Datasets Back to the Brain Regions They are Extracted from: Remembering the Native Countries of Hypothalamic Expatriates and Refugees

This article focuses on approaches to link transcriptomic, proteomic, and peptidomic datasets mined from brain tissue to the original locations within the brain that they are derived from using digital atlas mapping techniques. We use, as an example, the transcriptomic, proteomic and peptidomic analyses conducted in the mammalian hypothalamus. Following a brief historical overview, we highlight studies that have mined biochemical and molecular information from the hypothalamus and then lay out a strategy for how these data can be linked spatially to the mapped locations in a canonical brain atlas where the data come from, thereby allowing researchers to integrate these data with other datasets across multiple scales. A key methodology that enables atlas-based mapping of extracted datasets-laser-capture microdissection-is discussed in detail, with a view of how this technology is a bridge between systems biology and systems neuroscience.

Reproductive Impacts of Endocrine-Disrupting Chemicals on Wildlife Species: Implications for Conservation of Endangered Species

Wildlife have proven valuable to our understanding of the potential effects of endocrine-disrupting chemicals (EDCs) on human health by contributing considerably to our understanding of the mechanisms and consequences of EDC exposure. But the threats EDCs present to populations of wildlife species themselves are significant, particularly for endangered species whose existence is vulnerable to any reproductive perturbation. However, few studies address the threats EDCs pose to endangered species owing to challenges associated with their study. Here, we highlight those barriers and review the available literature concerning EDC effects on endangered species. Drawing from other investigations into nonthreatened wildlife species, we highlight opportunities for new approaches to advance our understanding and potentially mitigate the effects of EDCs on endangered species to enhance their fertility.