Biology subjects

England, S. K.

Publications and source records attributed to England, S. K..

10 recordsLinked to original sources

bioRxiv2026

Activation of Vasopressin Receptor 1A by Vasopressin Enhances Myometrial Smooth Muscle Cell Excitability by Inhibiting the Potassium Channel SLO2.1

Arginine vasopressin (AVP) increases excitability of myometrial smooth muscle cells (MSMCs) through Gq-coupled AVP receptors. Although excitability requires membrane depolarization, the mechanisms linking AVP receptor activation to membrane depolarization and Ca{superscript 2} signaling are incompletely understood. Here, we show that AVPR1 is the predominant AVP receptor in primary MSMCs. In Xenopus oocytes, AVP signals through AVPR1 to inhibit SLO2.1-mediated potassium currents, reducing current amplitude to approximately 60% of control currents. Consistent with suppression of a hyperpolarizing conductance, AVP depolarized a myometrial cell line (hTERT-HM) and increased intracellular Ca{superscript 2} signaling. Analysis of Ca{superscript 2} dynamics revealed that the initial Ca{superscript 2} peak was largely preserved under conditions limiting extracellular Ca{superscript 2} entry, consistent with intracellular store release. Conversely, the oscillatory phase depended on extracellular Ca{superscript 2} influx and was reduced by SLO2.1 knockdown. Together, these findings support a model in which AVP preferentially signals through AVPR1A to inhibit SLO2.1, depolarize myometrial cells, enhance VDCC-dependent Ca{superscript 2} entry, and promote excitability, enhancing conditions for uterine contraction.

physiology↗

bioRxiv2026

Effects of Maternal Obesity on Fetal Cerebral Glucose Transporter Expression

Emerging evidence indicates that the maternal in utero environment has enduring effects on offspring neurodevelopment. The obesity epidemic in the United States affects nearly one-third of women before pregnancy, potentially predisposing offspring to harmful developmental conditions. Glucose, the primary energy source for the brain, is highly regulated by facilitative diffusion glucose transporters (GLUTs). However, our understanding of how maternal obesity influences perinatal cerebral glucose metabolism remains limited. We hypothesized that maternal obesity is associated with altered expression of key GLUTs and dysregulated energy-sensing mechanisms in the fetal brain. Female C57BL/6J mice were randomly assigned to either a control diet (CON) or an obesogenic diet (DIO) (60% kcal from fat, 17.5% kcal from sucrose) for 10 weeks, time-mated with control males, and fed their respective diets throughout gestation. At 18.5 days post coitum, fetal brain tissue was collected for protein analysis. DIO diet did not affect litter size, offspring body weight, or brain weight when compared to CON. Whole brain GLUT1 expression was elevated only in female DIO offspring, while GLUT3 and GLUT4 expression was increased in all DIO offspring without modification by sex. However, maternal diet was not associated with differences in the activation of energy regulatory pathways adenosine monophosphate-activated protein kinase (AMPK) or the nutrient-sensing pathway mechanistic target of rapamycin (mTOR) in the fetal brain. These findings suggest that maternal obesogenic diet alters glucose transporter expression in the fetal brain, indicating a potential disruption in cerebral glucose metabolism during critical periods of perinatal development.

developmental biology↗

bioRxiv2025

Fetoplacental circadian rhythms develop and then synchronize to the mother in utero

Circadian rhythms in gene expression and hormones are ubiquitous across species and differentiated cell types, yet their developmental origins remain poorly understood. This study aimed to determine if daily rhythms can be detected in utero and if they synchronize to the mother. We developed methods to longitudinally monitor PERIOD2 (PER2), a core circadian clock protein, from embryonic day (E)8.5 to E17.5 by restricting PER2::LUCIFERASE (PER2::LUC) expression to the mouse fetoplacental unit (fetus and fetal-derived tissues). In utero fetoplacental bioluminescence imaging showed that PER2 levels rose exponentially during pregnancy, with variable daily peak times that stabilized to dusk by E15.5. Interestingly, pregnancies that did not exhibit daily in utero PER2 variation were more likely to fail. Because maternal glucocorticoids have been implicated in fetal development and synchronizing other circadian tissues, we tested its capability to shift fetoplacental PER2 rhythms in utero. Daily subcutaneous glucocorticoid injections over five days of late pregnancy phase-dependently shifted the fetoplacental PER2 rhythms in utero. Blocking glucocorticoid signaling in vitro reduced synchrony between maternal and fetal placenta by [~]40%. We conclude that in utero daily rhythms gradually develop and synchronize with the mother prior to birth, potentially through glucocorticoid signaling.

developmental biology↗

bioRxiv2025

PIEZO channels link mechanical forces to uterine contractions in parturition

AbstractMechanical forces are extensively involved in pregnancy and parturition, but their precise roles and mechanisms remain poorly understood. Here, we identify mechanically activated ion channels PIEZO1 and PIEZO2 as key mechanotransducers required for labor progression. Genetic deletion of Piezo1 and Piezo2 in mice resulted in weakened uterine contractions and severe parturition defects. Tissue-specific knockouts revealed that deletion in either the uterus or sensory neurons alone caused modest defects, whereas combined loss significantly impaired labor, demonstrating additive effects. Single-nuclei sequencing showed that loss of PIEZO reduced expression of connexin43 (Gja1), a gap junction protein in uterine smooth muscle cells, suggesting a mechanistic link to impaired contraction. These findings highlight the critical role of PIEZO channels in mechanotransduction during parturition and suggest therapeutic targets for labor dysfunction.

physiology↗

bioRxiv2024

SLO2.1/NALCN Functional Complex Activity in Mouse Myometrial Smooth Muscle Cells During Pregnancy.

At the end of pregnancy, the uterus transitions from a quiescent to a highly contractile state. This is partly due to depolarization of the resting membrane potential in uterine (myometrial) smooth muscle cells (MSMCs). In human MSMCs, the membrane potential is regulated by a functional complex between the sodium (Na+)-activated potassium (K+) channel SLO2.1 and the Na+ Leak Channel Non-Selective (NALCN). Na+ entering through NALCN activates SLO2.1, leading to K+ efflux, membrane hyperpolarization (cells become more negative inside), and reduced contractility. Decreased SLO2.1/NALCN activity results in reduced K+ efflux, leading to membrane depolarization, Ca2+ influx via voltage-dependent calcium channels, and increased MSMC contractility. However, all of these data are from MSMCs isolated from women at term, so the role of the SLO2.1/NALCN complex early in pregnancy was speculative. To address this question here, we examined the role of the SLO2.1/NALCN complex in regulating mouse MSMC membrane potential across pregnancy. We report that Slo2.1 and Nalcn are more highly expressed in MSMCs from non-pregnant and early pregnant mice than in those from late-pregnant mice. Functional studies revealed that SLO2.1 channels mediate a significant portion of the K+ current in mouse MSMCs, particularly in cells from non-pregnant and early pregnant mice. Activation of SLO2.1 by Na+ influx through NALCN led to membrane hyperpolarization in MSMCs from early pregnancy but not in MSMCs from later pregnancy. Moreover, the NALCN/SLO2.1 complex regulates intracellular Ca2+ responses more in MSMCs from non-pregnant and early pregnancy mice than in MSMCs from late pregnancy. Together, these findings reveal that the SLO2.1/NALCN functional complex is conserved between mouse and humans and functions throughout pregnancy. This work could open avenues for targeted pharmacological interventions for pregnancy-related complications.

physiology↗

bioRxiv2024

Understanding the effects of oxytocin receptor variants on OXT-OXT receptor binding: A mathematical model

Approximately half of U.S. women giving birth annually receive Pitocin, the synthetic form of oxytocin (OXT), yet its effective dose can vary significantly. This variability presents safety concerns due to unpredictable responses, which may lead to adverse outcomes for both mother and baby. To address the need for improved dosing, we developed a data-driven mathematical model to predict OXT receptor (OXTR) binding. Our study focuses on five prevalent OXTR variants (V45L, P108A, L206V, V281M, and E339K) and their impact on OXT-OXTR binding dynamics in two distinct cell types: human embryonic kidney cells (HEK293T), commonly used in experimental systems, and human myometrial smooth muscle cells, containing endogenous OXTR. We parameterized the model with cell-specific OXTR surface localization measurements. To strengthen the robustness of our study, we conducted a comprehensive meta-analysis of OXT- OXTR binding, enabling parameterization of our model with cell-specific OXT-OXTR binding kinetics (myometrial OXT-OXTR Kd = 1.6 nM, kon = 6.8 x 105 M-1 min-1, and koff = 0.0011 min-1). Our meta-analysis revealed significant homogeneity in OXT-OXTR affinity across experiments and species with a Kd = 0.52 - 9.32 nM and mean Kd = 1.48 {+/-} 0.36 nM. Our model achieves several valuable insights into designing dosage strategies. First, we predicted that the OXTR complex reaches maximum occupancy at 10 nM OXT in myometrial cells and at 1 {micro}M in HEK293T cells. This information is pivotal for guiding experimental design and data interpretation when working with these distinct cell types, emphasizing the need to consider effects for specific cell types when choosing OXTR-transfected cell lines. Second, our model recapitulated the significant effects of genetic variants for both experimental and physiologically relevant systems, with V281M and E339K substantially compromising OXT-OXTR binding capacity. These findings suggest the need for personalized oxytocin dosing based on individual genetic profiles to enhance therapeutic efficacy and reduce risks, especially in the context of labor and delivery. Third, we demonstrated the potential for rescuing the attenuated cell response observed in V281M and E339K variants by increasing the OXT dosage at specific, early time points. Cellular responses to OXT, including Ca2+ release, manifest within minutes. Our model indicates that providing V281M- and E339K-expressing cells with doubled OXT dose during the initial minute of binding can elevate OXT-OXTR complex formation to levels comparable to wild-type OXTR. In summary, our study provides a computational framework for precision oxytocin dosing strategies, paving the way for personalized medicine.

systems biology↗

bioRxiv2024

Mapping changes in uterine contractility during the ovulatory cycle with wide-area calcium imaging in live mice.

Uterine contraction patterns vary during the ovulatory cycle and throughout pregnancy but prior measurements have produced limited and conflicting information on these patterns. We combined a virally delivered genetically encoded calcium reporter (GCaMP8m) and ultra-widefield imaging in live nonpregnant mice to characterize uterine calcium dynamics at organ scale throughout the estrous cycle. Prior to ovulation (proestrus and estrus) uterine excitations primarily initiated in a region near the oviduct, but after ovulation (metestrus and diestrus), excitations initiated at loci homogeneously distributed throughout the organ. The frequency of excitation events was lowest in proestrus and estrus, higher in metestrus and highest in diestrus. These results establish a platform for mapping uterine activity, and show that the question of whether there is an anatomically localized trigger for uterine excitations depends on the estrous cycle phase.

physiology↗

bioRxiv2023

Fetal daily rhythms develop during pregnancy and entrain to the maternal circadian system

Circadian rhythms in gene expression and hormones are ubiquitous across species and differentiated cell types. This study aimed to determine when daily rhythms begin in the fetus and synchronize to the mother. We developed methods to monitor the expression of fetal PERIOD2 (PER2), a core circadian clock protein, in mice longitudinally from embryonic day (E)8.5 to E17.5 through in utero bioluminescence imaging. We found that embryonic PER2 expression increased rapidly throughout pregnancy and exhibited day-night rhythms from the start of our recordings at E8.5. The daily peak time of PER2 varied between pregnancies until it reliably peaked at night and synchronized to the mother starting around E15.5. Loss of fetal circadian rhythms associated with pregnancies that ultimately failed. Because maternal glucocorticoids have been implicated in fetal development and synchronizing circadian tissues, we tested their sufficiency to shift fetal daily rhythms in utero. Daily glucocorticoids injections over five days of late pregnancy advanced fetal PER2 rhythms in utero and blocking glucocorticoid signaling in vitro reduced PER2 synchrony between the maternal and fetal placenta by [~]40%. We conclude that fetal daily rhythms arise early in pregnancy and then synchronize with the maternal rhythm prior to birth depending, in part, on glucocorticoid signaling.

developmental biology↗

bioRxiv2021

A NOVEL PREGNANT RAT MODEL FOR LABOR INDUCTION AND AUGMENTATION WITH OXYTOCIN

BackgroundDespite the widespread use of oxytocin for induction of labor, mechanistic insights into maternal and neonatal wellbeing are lacking because of the absence of an animal model that recapitulates modern obstetric practice. ObjectiveThe objectives of this research were to create and validate a hi-fidelity animal model that mirrors labor induction with oxytocin in parturients and to assess its translational utility. Study DesignThe study was performed in timed-pregnant Sprague Dawley dams. The model consisted of a subcutaneously implanted microprocessor-controlled infusion pump on gestational day 18 that was pre-programmed to deliver an escalating dose of intravenous oxytocin on gestational day 21 to induce birth. Once predictable delivery of healthy pups was achieved, we validated the model with molecular biological experiments on the uterine myometrium and telemetry-supported assessment of changes in intrauterine pressure. Finally, we applied this model to test the hypothesis that labor induction with oxytocin was associated with oxidative stress in the newborn brain with a comprehensive array of biomarker assays and oxidative stress gene expression studies. ResultsDuring the iterative model development phase, we confirmed the optimal gestational age for pump implantation, the concentration of oxytocin, and the rate of oxytocin administration. Exposure to anesthesia and surgery during pump implantation was not associated with significant changes in the cortical transcriptome. Activation of pump with oxytocin on gestational day 21 resulted in predictable delivery of pups within 8-12 hours. Increased frequency of change of oxytocin infusion rate was associated with dystocic labor. Labor induction and augmentation with oxytocin was associated with increased expression of the oxytocin receptor gene in the uterine myometrium, decreased expression of the oxytocin receptor protein on the myometrial cell membrane, and cyclical increases in intrauterine pressure. Examination of the frontal cortex of vaginally delivered newborn pups born after oxytocin-induced labor did not reveal an increase in oxidative stress compared to saline-treated control pups. Specifically, there were no significant changes in oxidative stress biomarkers involving both the oxidative stress (reactive oxygen/nitrogen species, 4-hydroxynonenal, protein carbonyl) and the antioxidant response (total glutathione, total antioxidant capacity). In addition, there were no significant differences in the expression of 16 genes emblematic of the oxidative stress response pathway. ConclusionsCollectively, we provide a viable and realistic animal model for labor induction and augmentation with oxytocin. We demonstrate its utility in addressing clinically relevant questions in obstetric practice that could not be mechanistically ascertained otherwise. Based on our findings, labor induction with oxytocin is not likely to cause oxidative stress in the fetal brain. Adoption of our model by other researchers would enable new lines of investigation related to the impact of perinatal oxytocin exposure on the mother-infant dyad.

pharmacology and toxicology↗

bioRxiv2020

SLO2.1 and NALCN form a functional complex to modulate myometrial cell excitability

Depolarization of the myometrial smooth muscle cell (MSMC) resting membrane potential is necessary for the transition of the uterus from a quiescent state to a contractile state. The molecular mechanisms involved in this transition are not completely understood. Here, we report a novel coupled system between the Na+-activated K+ channel (SLO2.1) and the non-selective Na+ leak channel (NALCN) which determines the MSMC membrane potential. We show that SLO2.1 currents are activated by an inward Na+ leak current carried by the NALCN channel leading to MSMC hyperpolarization. These results show an unanticipated role for the Na+ leak currents in activating a negative feedback system countering the excitable effects of Na+ currents. This is a novel role for the NALCN channel in which Na+ acts as an intracellular signaling molecule. In fact, we report here that the net effect of Na+ entry through NALCN channels is a hyperpolarization of the MSMCs plasma membrane because of the activation of SLO2.1 K channel. Importantly, we also report that a decrease in NALCN/SLO2.1 activity triggers both Ca2+ entries through VDCCs, promoting myometrial contraction. Consistently, with a functional coupling, our data show that NALCN and SLO2.1 are in proximity to one another in human MSMCs. We propose that the spatial arrangement of SLO2.1 and NALCN permits these channels to functionally interact in order to regulate human MSMC membrane potential and cell excitability to modulate uterine contractile activity.

cell biology↗