Dimorphic Regulation Research Articles

A theoretical composite model for population sex-specific shell size dynamics in Strombidae (Gastropoda, Neostromboidae)

ABSTRACT Modelling sexual dimorphism has important implications for understanding the evolution of size relationships among and within organisms. We present a composite model for the regulation and evolution of sex-specific inter-population shell size in a family of herbivorous marine molluscs, the Strombidae. In particular, this model postulates that gene flow acts as a size regulator that limits inter-population divergence by not allowing the mean size of each sex to deviate significantly between disparate populations. The mean shell size of individuals within populations is affected by the ecological setting in which the animal is growing. The model considers niche divergence as inconsequential in the regulation of sexual dimorphism, whereas environmental regulation for the mean size of a population is considered a significant driving factor. Sexual competition, where males may dislodge other males during copulation, is also considered a non-significant driver of male body size because of the open mating system. In such a system, smaller males can simply mate before larger males have matured. Selection for earlier mating in males so as to maximise lifetime fecundity favours male maturation at small body sizes. Conversely, greater fecundity at larger body size in females argues for larger females. The postulated composite model presented here fills a knowledge gap by graphically illustrating the factors affecting inter-and intra-specific variation. These differences include the modelling of mean inter-population shell size, as well as the regulation of intra-population sex size ratios. The components of this new model can be applied to a wider range of sexually dimorphic organisms to explain the evolutionary factors involved in regulating the observed sexual dimorphism.

Voluntary running attenuates behavioural signs of low back pain: dimorphic regulation of intervertebral disc inflammation in male and female SPARC-null mice

To examine the effect of running exercise on behavioral measures of pain and intervertebral disc (IVD) inflammation in the SPARC-null mouse model. Male and female 8-month old SPARC-null and age-matched control mice received a home cage running wheel or a control, fixed wheel for 6 months. Behavioral assays were performed to assess axial discomfort (grip test) and radiating leg pain (von Frey, acetone tests) and voluntary running was confirmed. Expression of inflammatory mediators (TNF-α, IL-1β, IL-2, IL-10, CCL5, CXCL1, CXCL5, RANKL, M-CSF, and VEGF) in IVDs was determined. Additional inflammatory (IL-1β, IL-1Ra, CXCR1, CXCR2) and macrophage phenotypic markers (ITGAM, CD80, CD86, CD206, Arg1) in IVDs were investigated by qPCR. Voluntary running attenuated behavioral measures of pain in male and female SPARC-null mice. Increases in mediators including IL-1β, CXCL1 and CXCL5 were observed in SPARC-null compared to control IVDs. After 6 months of running, increases in M-CSF and VEGF were observed in male SPARC-null IVDs. In females, pro-inflammatory mediators, including CXCL1 and CXCL5 were downregulated by running in SPARC-null mice. qPCR analysis further confirmed the anti-inflammatory effect of running in female IVDs with increased IL-1Ra mRNA. Running induced upregulation of the macrophage marker ITGAM mRNA in males. Voluntary running reversed behavioral signs of pain in male and female mice and reduced inflammatory mediators in females, but not males. Thus, the therapeutic mechanism of action may be sex-specific.

Sex-dependent dynamics of metabolism in primary mouse hepatocytes

The liver is one of the most sexually dimorphic organs. The hepatic metabolic pathways that are subject to sexual dimorphism include xenobiotic, amino acid and lipid metabolism. Non-alcoholic fatty liver disease and hepatocellular carcinoma are among diseases with sex-dependent prevalence, progression and outcome. Although male and female livers differ in their abilities to metabolize foreign compounds, including drugs, sex-dependent treatment and pharmacological dynamics are rarely applied in all relevant cases. Therefore, it is important to consider hepatic sexual dimorphism when developing new treatment strategies and to understand the underlying mechanisms in model systems. We isolated primary hepatocytes from male and female C57BL6/N mice and examined the sex-dependent transcriptome, proteome and extracellular metabolome parameters in the course of culturing them for 96 h. The sex-specific gene expression of the general xenobiotic pathway altered and the female-specific expression of Cyp2b13 and Cyp2b9 was significantly reduced during culture. Sex-dependent differences of several signaling pathways increased, including genes related to serotonin and melatonin degradation. Furthermore, the ratios of male and female gene expression were inversed for other pathways, such as amino acid degradation, beta-oxidation, androgen signaling and hepatic steatosis. Because the primary hepatocytes were cultivated without the influence of known regulators of sexual dimorphism, these results suggest currently unknown modulatory mechanisms of sexual dimorphism in vitro. The large sex-dependent differences in the regulation and dynamics of drug metabolism observed during cultivation can have an immense influence on the evaluation of pharmacodynamic processes when conducting initial preclinical trials to investigate potential new drugs.

Male-Biased microRNA Discovery in the Pea Aphid.

Simple SummaryMales and females develop from a genome that is largely similar, yet the sexes have dramatically different traits. How this happens has driven interest in the role of epigenetic mechanisms—i.e., changes in gene function that are not due to changes in the DNA—in regulating sexual dimorphisms. Our focus here is on differences between the sexes in one epigenetic mechanism, the downregulation of gene expression by small RNAs called microRNAs. Typical genomes code for hundreds of microRNAs and each one can target many protein-coding RNAs, ultimately causing them to produce fewer protein copies. Here, we focus on microRNAs in male versus female pea aphids. We use small RNA sequence data to identify all the microRNAs in the pea aphid genome and to find microRNAs that are highly biased towards expression in males. This work is foundational for future studies of the epigenetic basis of sex differences in the pea aphid.Epigenetic mechanisms modulate gene expression levels during development, shaping how a single genome produces a diversity of phenotypes. Here, we begin to explore the epigenetic regulation of sexual dimorphism in pea aphids (Acyrthosiphon pisum) by focusing on microRNAs. Previous analyses of microRNAs in aphids have focused solely on females, so we performed deep sequencing of a sample containing early-stage males. We used this sample, plus samples from Genbank, to find 207 novel pea aphid microRNA coding loci. We localized microRNA loci to a chromosome-level assembly of the pea aphid genome and found that those on the X chromosome have lower overall expression compared to those on autosomes. We then identified a set of 19 putative male-biased microRNAs and found them enriched on the X chromosome. Finally, we performed protein-coding RNA-Seq of first instar female and male pea aphids to identify genes with lower expression in males. 10 of these genes were predicted targets of the 19 male-biased microRNAs. Our study provides the most complete set of microRNAs in the pea aphid to date and serves as foundational work for future studies on the epigenetic control of sexual dimorphism.

588 Regulation of sexual dimorphism in dermal fat by the THY1-TGFBR pathway axis

588 Regulation of sexual dimorphism in dermal fat by the THY1-TGFBR pathway axis

The role of epigenetics, particularly DNA methylation, in the evolution of caste in insect societies.

Eusocial insects can be defined as those that live in colonies and have distinct queens and workers. For most species, queens and workers arise from a common genome, and so caste-specific developmental trajectories must arise from epigenetic processes. In this review, we examine the epigenetic mechanisms that may be involved in the regulation of caste dimorphism. Early work on honeybees suggested that DNA methylation plays a causal role in the divergent development of queen and worker castes. This view has now been challenged by studies that did not find consistent associations between methylation and caste in honeybees and other species. Evidence for the involvement of methylation in modulating behaviour of adult workers is also inconsistent. Thus, the functional significance of DNA methylation in social insects remains equivocal. This article is part of the theme issue 'How does epigenetics influence the course of evolution?'

Fetal sex modulates placental microRNA expression, potential microRNA-mRNA interactions, and levels of amino acid transporter expression and substrates: INFAT\xa0study subpopulation analysis of n-3 LCPUFA intervention during pregnancy and associations with offspring body composition

BackgroundPreviously, we revealed sexually dimorphic mRNA expression and responsiveness to maternal dietary supplementation with n-3 long-chain polyunsaturated fatty acids (LCPUFA) in placentas from a defined INFAT study subpopulation. Here, we extended these analyses and explored the respective placental microRNA expression, putative microRNA-mRNA interactions, and downstream target processes as well as their associations with INFAT offspring body composition.ResultsWe performed explorative placental microRNA profiling, predicted microRNA-mRNA interactions by bioinformatics, validated placental target microRNAs and their putative targets by RT-qPCR and western blotting, and measured amino acid levels in maternal and offspring cord blood plasma and placenta. microRNA, mRNA, protein, and amino acid levels were associated with each other and with offspring body composition from birth to 5 years of age. Forty-six differentially regulated microRNAs were found. Validations identified differential expression for microRNA-99a (miR-99a) and its predicted target genes mTOR, SLC7A5, encoding L-type amino acid transporter 1 (LAT1), and SLC6A6, encoding taurine transporter (TauT), and their prevailing significant sexually dimorphic regulation. Target mRNA levels were mostly higher in placentas from control male than from female offspring, whereas respective n-3 LCPUFA responsive target upregulation was predominantly found in female placentas, explaining the rather balanced expression levels between the sexes present only in the intervention group. LAT1 and TauT substrates tryptophan and taurine, respectively, were significantly altered in both maternal plasma at 32 weeks’ gestation and cord plasma following intervention, but not in the placenta. Several significant associations were observed for miR-99a, mTOR mRNA, SLC7A5 mRNA, and taurine and tryptophan in maternal and cord plasma with offspring body composition at birth, 1 year, 3 and 5 years of age.ConclusionsOur data suggest that the analyzed targets may be part of a sexually dimorphic molecular regulatory network in the placenta, possibly modulating gene expression per se and/or counteracting n-3 LCPUFA responsive changes, and thereby stabilizing respective placental and fetal amino acid levels. Our data propose placental miR-99, SLC7A5 mRNA, and taurine and tryptophan levels in maternal and fetal plasma as potentially predictive biomarkers for offspring body composition.

SNPC-1.3 is a sex-specific transcription factor that drives male piRNA expression in C. elegans.

Piwi-interacting RNAs (piRNAs) play essential roles in silencing repetitive elements to promote fertility in metazoans. Studies in worms, flies, and mammals reveal that piRNAs are expressed in a sex-specific manner. However, the mechanisms underlying this sex-specific regulation are unknown. Here we identify SNPC-1.3, a male germline-enriched variant of a conserved subunit of the small nuclear RNA-activating protein complex, as a male-specific piRNA transcription factor in Caenorhabditis elegans. SNPC-1.3 colocalizes with the core piRNA transcription factor, SNPC-4, in nuclear foci of the male germline. Binding of SNPC-1.3 at male piRNA loci drives spermatogenic piRNA transcription and requires SNPC-4. Loss of snpc-1.3 leads to depletion of male piRNAs and defects in male-dependent fertility. Furthermore, TRA-1, a master regulator of sex determination, binds to the snpc-1.3 promoter and represses its expression during oogenesis. Loss of TRA-1 targeting causes ectopic expression of snpc-1.3 and male piRNAs during oogenesis. Thus, sexually dimorphic regulation of snpc-1.3 expression coordinates male and female piRNA expression during germline development.

InSexBase: an annotated genomic resource of sex chromosomes and sex-biased genes in insects.

Sex determination and the regulation of sexual dimorphism are among the most fascinating topics in modern biology. As the most species-rich group of sexually reproducing organisms on Earth, insects have multiple sex determination systems. Though sex chromosomes and sex-biased genes are well-studied in dozens of insects, their gene sequences are scattered in various databases. Moreover, a shortage of annotation hinders the deep mining of these data. Here, we collected the chromosome-level sex chromosome data of 49 insect species, including 34 X chromosomes, 15 Z chromosomes, 5 W chromosomes and 2 Y chromosomes. We also obtained Y-linked contigs of four insects species—Anopheles gambiae, Drosophila innubila, Drosophila yakuba and Tribolium castaneum. The unannotated chromosome-level sex chromosomes were annotated using a standard pipeline, yielding a total of 123 030 protein-coding genes, 2 159 427 repeat sequences, 894 miRNAs, 1574 rRNAs, 5105 tRNAs, 395 snoRNAs (small nucleolar RNA), 54 snRNAs (small nuclear RNA) and 5959 other ncRNAs (non-coding RNA). In addition, 36 781 sex-biased genes were identified by analyzing 62 RNA-seq (RNA sequencing) datasets. Together with 5707 sex-biased genes from the Drosophila genus collected from the Sex-Associated Gene Database, we obtained a total of 42 488 sex-biased genes from 13 insect species. All these data were deposited into InSexBase, a new user-friendly database of insect sex chromosomes and sex-biased genes. Database URL: http://www.insect-genome.com/Sexdb/.

Androgen Receptor Is Dispensable for X-Zone Regression in the Female Adrenal but Regulates Post-Partum Corticosterone Levels and Protects Cortex Integrity.

Adrenal androgens are fundamental mediators of ovarian folliculogenesis, embryonic implantation, and breast development. Although adrenal androgen function in target tissues are well characterized, there is little research covering the role of androgen-signaling within the adrenal itself. Adrenal glands express AR which is essential for the regression of the X-zone in male mice. Female mice also undergo X-zone regression during their first pregnancy, however whether this is also controlled by AR signaling is unknown. To understand the role of the androgen receptor (AR) in the female adrenal, we utilized a Cyp11a1-Cre to specifically ablate AR from the mouse adrenal cortex. Results show that AR-signaling is dispensable for adrenal gland development in females, and for X-zone regression during pregnancy, but is required to suppress elevation of corticosterone levels post-partum. Additionally, following disruption to adrenal AR, aberrant spindle cell development is observed in young adult females. These results demonstrate sexually dimorphic regulation of the adrenal X-zone by AR and point to dysfunctional adrenal androgen signaling as a possible mechanism in the early development of adrenal spindle cell hyperplasia.

Allodynia by Splenocytes From Mice With Acid-Induced Fibromyalgia-Like Generalized Pain and Its Sexual Dimorphic Regulation by Brain Microglia.

Fibromyalgia (FM), a disease of unknown etiology characterized by chronic generalized pain, is partly recapitulated in an animal model induced by repeated acid saline injections into the gastrocnemius muscle. Here, we attempted to investigate the sex difference in pain hypersensitivity (mechanical allodynia and hypersensitivity to electrical stimulation) in the repeated acid saline-induced FM-like generalized pain (AcGP) model. The first unilateral acid injection into gastrocnemius muscle at day 0/D0 and second injection at D5 (post day 0, P0) induced transient and long-lasting mechanical allodynia, respectively, on both sides of male and female mice. The pretreatment with gonadectomy did not affect the first injection-induced allodynia in both sexes, but gradually reversed the second injection-induced allodynia in male but not female mice. Moreover, the AcGP in male mice was abolished by intracerebroventricular minocycline treatments during D4–P4 or P5–P11, but not by early treatments during D0–D5 in male but not female mice, suggesting that brain microglia are required for AcGP in late-onset and sex-dependent manners. We also found that the intravenous treatments of splenocytes derived from male but not female mice treated with AcGP caused allodynia in naive mice. In addition, the purified CD4+ T cells derived from splenocytes of acid-treated male mice retained the ability to cause allodynia in naive mice. These findings suggest that FM-like AcGP has multiple sexual dimorphic mechanisms.

Significant down-regulation of growth hormone receptor expression revealed as a new unfavorable prognos- tic factor in hepatitis C virus-related hepatocellular carcinoma

Background/AimsGrowth hormone (GH) is the main regulator of somatic growth, metabolism, and gender dimorphism in the liver. GH receptor (GHR) signaling in cancer is derived from a large body of evidence, although the GHR signaling pathway involved in the prognosis of hepatocellular carcinoma (HCC) in patients with hepatitis C virus (HCV)-related HCC, remains unclear. We aimed to explore the expression of GHR and analyze its association with clinicopathologic features and prognosis of patients with chronic hepatitis C and HCC.MethodsThe expression of GHR mRNA was investigated by quantitative real-time polymerase chain reaction in paired tumors and adjacent non-tumorous (ANT) liver tissues of 200 patients with chronic hepatitis C and HCC. Western blotting and immunofluorescence assays using the HCV-infected Huh7.5.1 cell model was performed.ResultsGHR mRNA was significantly lower in HCV-HCC tissues than in corresponding ANT liver tissues. GHR mRNA and protein levels also decreased in the HCV-infected Huh7.5.1 cell model. Notably, lower GHR expression was associated with age of >60 years (P=0.0111) and worse clinicopathologic characteristics, including alpha-fetoprotein >100 ng/mL (P=0.0403), cirrhosis (P=0.0075), vascular invasion (P=0.0052), pathological stage II–IV (P=0.0002), and albumin ≤4.0 g/dL (P=0.0055), which were linked with poor prognosis of HCC. Most importantly, the high incidence of recurrence and poor survival rates in patients with a low ratio of tumor/ANT GHR (≤0.1) were observed, indicating that low expression levels of GHR had great risk for development of HCC in patients with chronic hepatitis C.ConclusionsOur study demonstrates a significant down-regulation of GHR expression as a new unfavorable independent prognostic factor in patients with chronic hepatitis C and HCC.

Targeting Bone Cells During Sexual Maturation Reveals Sexually Dimorphic Regulation of Endochondral Ossification.

ABSTRACTIn endochondral ossification, chondroblasts become embedded in their matrix and become chondrocytes, which are mature cells that continue to proliferate, eventually becoming hypertrophic. Hypertrophic chondrocytes produce cartilage that is then resorbed by osteoclasts prior to bone matrix replacement via osteoblasts. Although sexually dimorphic bone phenotypes have long been characterized, specific modulation of the growth plate during a critical window in sexual maturation has not been evaluated. Here we report that specific depletion of osteocalcin‐ (OCN‐) expressing cells in vivo during sexual maturation leads to dimorphic bone phenotypes in males and females. At 6 to 8 weeks of age, OCN‐Cre;iDTR (inducible diphtheria toxin receptor‐expressing) mice were treated with diphtheria toxin (DT) for 2 weeks to deplete OCN+ cells. At the end of the study, long bones were collected for μCT and histomorphometry, and serum was collected for proteomic and lipidomic analyses. Ablation of OCN+ cells in mice leads to consistent trends for weight loss after 2 weeks of treatment. Females exhibited decreased skeletal parameters in response to OCN+ cell ablation treatment, as expected. However, OCN+ cell ablation in males uniquely displayed an expansion of hypertrophic chondrocytes, a widening of the growth plate, and an abnormal “clubbing” anatomy of the distal femur. Following DT treatment, mice from both sexes also underwent metabolic cage analysis, in which both sexes exhibited decreased energy expenditure. We conclude that skewing endochondral bone formation during longitudinal growth has a profound effect on body weight and energy expenditure with sex‐specific effects on developing bone. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

One template, two outcomes: How does the sex-shared nervous system generate sex-specific behaviors?

Sex-specific behaviors are common in nature and are crucial for reproductive fitness and species survival. A key question in the field of sex/gender neurobiology is whether and to what degree the sex-shared nervous system differs between the sexes in the anatomy, connectivity and molecular identity of its components. An equally intriguing issue is how does the same sex-shared neuronal template diverge to mediate distinct behavioral outputs in females and males. This chapter aims to present the most up-to-date understanding of how this task is achieved in C. elegans. The vast majority of neurons in C. elegans are shared among the two sexes in terms of their lineage history, anatomical position and neuronal identity. Yet a substantial amount of evidence points to the hermaphrodite-male counterparts of some neurons expressing different genes and forming different synaptic connections. This, in turn, enables the same cells and circuits to transmit discrete signals in the two sexes and ultimately execute different functions. We review the various sex-shared behavioral paradigms that have been shown to be sexually dimorphic in recent years, discuss the mechanisms that underlie these examples, refer to the developmental regulation of neuronal dimorphism and suggest evolutionary concepts that emerge from the data.

Diabetes-related sex differences in the brain endothelin system following ischemia in vivo and in human brain endothelial cells in vitro.

The endothelin (ET) system has been implicated to contribute to the pathophysiology of cognitive impairment and stroke in experimental diabetes. Our goals were to test the hypotheses that (1) circulating and (or) periinfarct ET-1 levels are elevated after stroke in both sexes and this increase is greater in diabetes, (2) ET receptors are differentially regulated in the diabetic brain, (3) brain microvascular endothelial cells (BMVEC) of female and male origin express the ETA receptor subtype, and (4) diabetes- and stroke-mimicking conditions increase ET-1 levels in BMVECs of both sexes. Control and diabetic rats were randomized to sham or stroke surgery. BMVECs of male (hBEC5i) and female (hCMEC/D3) origin, cultured under normal and diabetes-mimicking conditions, were exposed to normoxia or hypoxia. Circulating ET-1 levels were higher in diabetic animals and this was more pronounced in the male cohort. Stroke did not further increase plasma ET-1. Tissue ET-1 levels were increased after stroke only in males, whereas periinfarct ET-1 increased in both control and diabetic females. Male BMVECs secreted more ET-1 than female cells and hypoxia increased ET-1 levels in both cell types. There was sexually dimorphic regulation of ET receptors in both tissue and cell culture samples. There are sex differences in the stroke- and diabetes-mediated changes in the brain ET system at the endothelial and tissue levels.

Current Aspects in the Biology, Pathogeny, and Treatment of Candida krusei, a Neglected Fungal Pathogen.

Fungal infections represent a constant and growing menace to human health, because of the emergence of new species as causative agents of diseases and the increment of antifungal drug resistance. Candidiasis is one of the most common fungal infections in humans and is associated with a high mortality rate when the fungi infect deep-seated organs. Candida krusei belongs to the group of candidiasis etiological agents, and although it is not isolated as frequently as other Candida species, the infections caused by this organism are of special relevance in the clinical setting because of its intrinsic resistance to fluconazole. Here, we offer a thorough revision of the current literature dealing with this organism and the caused disease, focusing on its biological aspects, the host-fungus interaction, the diagnosis, and the infection treatment. Of particular relevance, we provide the most recent genomic information, including the gene prediction of some putative virulence factors, like proteases, adhesins, regulators of biofilm formation and dimorphism. Moreover, C. krusei veterinary aspects and the exploration of natural products with anti-C. krusei activity are also included.

Sexually Dimorphic Regulation of Gut Microbiota and Body Weight by a Naturally Occurring Flavonoid

Abstract Objectives 7,8-Dihydroxyflavone (DHF) is a naturally occurring flavonoid that is being actively investigated as a therapeutic modality in the treatment of neurological disorders. A recent study also indicated that oral DHF supplementation protected female but not male mice from diet-induced obesity. However, the mechanisms underlying this sexually-dimorphic effects of DHF were not known. The aim of the work is to investigate the mechanisms underlying sex-specific effects of flavonoid. Methods Age-matched male and female mice were given ad libitum access to high fat-diet and drinking water containing vehicle or DHF for 12 weeks. Body weights, body composition, food, and water intake, were assessed. Immunohistological analysis, immunohistochemistry staining, plasma triglycerides, plasma bile acids, and hepatic lipids were investigated. Fresh fecal samples were collected, genomic DNA was extracted and hypervariable region V4 of the 16S rRNA gene was amplified. Gut microbiota structure was evaluated using alpha diversity indices and beta diversity distance metrices. Principal coordinates analysis (PCoA) was performed using the R “ape” package to visualize differences in gut microbiota structure between treatment groups along principal coordinates that accounted for most of the variations. Results Oral administration of DHF, remodels the intestinal microbiome of female, but not male, prior to divergence in body weight. This is concomitant with increase in brown adipose tissue thermogenesis, mediated by increased expression of UCP1 and Pgc -1α protecting the female mice from diet-induced obesity. Conclusions This study demonstrates sexually-dimorphic effects of a clinically relevant natural compound. Importantly, it points to a role for sex-dependent remodeling of the intestinal microbiome as a mechanism for weight control in females. Thus, our discoveries pave the way for personalized nutrition strategies that account for sex differences in metabolism. Funding Sources NIH.

Spatiotemporal Expression of Foxl2 and Dmrt1 before, during, and after Sex Determination in the Sea Turtle Lepidochelys olivacea

The sex of sea turtles is determined by temperature during egg incubation. Thus, climate change affects the sex ratio, exacerbating their vulnerability to extinction. Understanding spatiotemporal effects of temperature on sex determination at the gonadal level may facilitate the design of strategies to mitigate the effects of global warming. Here, we used qRT-PCR and immunofluorescence to analyze the spatiotemporal expression of Dmrt1 and Foxl2 in developing gonads of Lepidochelys olivacea incubated at male-producing temperature (MPT, 26°C) or female-producing temperature (FPT, 33°C). Although both transcription factors are expressed in bipotential gonads up to stage 25, the timing of their sexually dimorphic regulation differs. Whereas the dimorphic expression of Dmrt1 protein initiates at stage 24, Foxl2 protein was expressed specifically in females at stage 25. Interestingly, whereas Dmrt1 colocalizes with Sox9 in cell nuclei of primary medullary cords to form the testis cords, Foxl2 protein is first detected in Sox9-negative cells of primary medullary cords, prior to its substantial expression in the ovarian cortex. Thus, results suggest that the temperature-dependent regulation of sexual pathways is stochastic among the cells of primary medullary cords in undifferentiated bipotential gonads of the olive ridley.

OR29-04 TGFβ Regulates Bone Perilacunar/Canalicular Remodeling in a Sexually Dimorphic Manner

Sexual dimorphism in the material properties of bone extracellular matrix (ECM) and geometry, which are parameters of bone quality have been recognized (Alswat, 2017; Nieves et al., 2005). However, the molecular mechanisms responsible for dimorphic bone quality remain unclear, limiting our ability to therapeutically target fragility, which is determined by bone quality. Recently, using male mice, we found that systemic or osteocyte-intrinsic inhibition of TGFβ signaling (TβRIIocy-/-), suppresses perilacunar/canalicular remodeling (PLR) and compromises bone quality (Dole et al., 2017). Since we previously demonstrated that female bone mass is more sensitive to TGFβ (Mohammad et al., 2009), we hypothesized that loss of osteocytic TGFβ in females will lead to more severe deterioration of PLR and bone quality.Analysis of female bones, however, surprisingly revealed sexual dimorphism in the TGFβ regulation of osteocyte function. While the male TβRIIocy-/- mice demonstrated reduced trabecular bone mass and repression in expression of requisite PLR genes, including matrix metalloproteinases (Mmp2, Mmp13, and Mmp14), cathepsin K (Ctsk), and tartrate-resistant acid phosphatase (Acp5/TRAP) (Qing et al., 2012), the female TβRIIocy-/- bones were intact. With absence of osteocytic TGFβ signaling, the canaliculi of male TβRIIocy-/- osteocytes were truncated and a severe deterioration of lacuno-canalicular network (LCN) was observed. Unlike the male TβRIIocy-/- mice that exhibited poor bone quality, female TβRIIocy-/- bones were completely protected from bone quality defects and macromechanical bone fragility. Thus, TGFβ-dependent regulation PLR and bone quality is sexually dimorphic.Since, lactation is a potent PLR agonist, we also evaluated the lactation-induced PLR response of TβRIIocy-/- female mice. Compared to WT, lactation-induced bone loss and upregulation of PLR genes was significantly attenuated in the TβRIIocy-/- female mice. Lactation-mediated increases in osteocyte lacunar volume were suppressed in TβRIIocy-/- bones as well. This mitigation in PLR of lactating TβRIIocy-/- mice was analogous to that observed in mice with osteocyte-specific ablation of parathyroid hormone type I receptor (PTHR1) (Qing et al., 2012). Remarkably, lactation-inducible PTHR1 expression was also diminished in TβRIIocy-/- osteocytes. Therefore, osteocyte-intrinsic TGFβ signaling is critical for the maximal induction of PLR during lactation, and TGFβ is an upstream regulator of PTHR1-dependent activation of osteocytic PLR. Indeed, we also found sexual dimorphism in the regulation of osteocytic PTHR1 expression by TGFβ, such that male, but not female, TβRIIocy-/- mice had reduced PTHR1 compared to WT.In summary, we identify a novel PTH-dependent mechanism that protects female bone against the severe bone fragility that results from suppressed TGFβ signaling in osteocytes.

SUN-LB41 The Role of Androgen Receptors in Female Mouse X-Zone Loss During Aging and Pregnancy

Introduction: Sex differences are prevalent in the risk and manifestation of numerous human diseases as well as in the response to most therapeutic interventions. While marked sexual dimorphism is observed in the development, homeostasis and most diseases of the adrenal cortex, the impact of these differences on adrenal function remains poorly understood. Sex differences include the timing of adrenal fetal zone (X-zone) regression, which occurs during male mouse puberty but only after pregnancy or advanced age in females. The mechanisms driving regression, particularly in females, are unknown. A potential regulator of adrenal sexual dimorphism and X-zone regression is androgen exposure. Through adrenocortical-specific deletion of the androgen receptor (AR), we tested the hypothesis that androgen signaling is responsible for X-zone post-pubertal regression in male mice and post-pregnancy/aging related regression in female mice. Methods: Adrenocortical-targeted Ar deletion was accomplished by crossing heterozygous aldosterone synthase-Cre mice to mice with a floxed exon 2 of Ar (ARΔAdr). Mice were sacrificed at 25 or 50 weeks of age and compared to ARf/f littermates (controls). Adrenals were processed for histology (H&E), immunofluorescence (IF) and whole adrenal mRNA RT-PCR to detect AR and X-zone specific markers Akr1c18 (20αHSD) and Pik3c2g. Results: In all mice, Ar mRNA expression was significantly decreased in ARΔAdr mice compared to control littermates. As expected, 25 week control females had higher expression of Akr1c18 (6740-fold) and Pik3c2g (198-fold) compared to 25 week control males. 25 week ARΔAdr males retained expression of Akr1c18 (20864-fold) and Pik3c2g (2802-fold) compared to controls, and also exhibited positive 20αHSD staining, confirming X-zone retention. 50 week control females exhibited histologic loss of the X-zone with negligible expression of Akr1c18 and Pik3c2g compared with 25 week control females. However, 50 week female ARΔAdr mice exhibited a histologic X-zone retention and concomitant high expression of X-zone genes (Akr1c18 67-fold, Pik3c2g 75-fold) compared to female control littermates. Furthermore, 20αHSD IF demonstrated undetectable levels in controls and positive staining in ARΔAdr, indicating that age-associated X-zone loss may be AR-mediated. Post-pregnant 25 week control mice had ~99% lower expression of both X-zone markers compared to virgin female controls. Post-pregnant ARΔAdr mice displayed higher expression of Akr1c18 (19-fold) and Pik3c2g (5-fold) compared to post-pregnant controls, though neither group had detectable 20αHSD by IF. Conclusion: Our findings indicate that AR signaling not only causes post-pubertal X-zone loss in males, but also plays a major role in the loss of the X-zone observed in aged female mice. Conversely, AR signaling may only play a minor role in X-zone regression following pregnancy.