The master transcription factors play integral roles in the pluripotency transcription circuitry of embryonic stem cells (ESCs). How they selectively activate expression of the pluripotency network ...while simultaneously repressing genes involved in differentiation is not fully understood. Here, we define a requirement for the INO80 complex, a SWI/SNF family chromatin remodeler, in ESC self-renewal, somatic cell reprogramming, and blastocyst development. We show that Ino80, the chromatin remodeling ATPase, co-occupies pluripotency gene promoters with the master transcription factors, and its occupancy is dependent on OCT4 and WDR5. At the pluripotency genes, Ino80 maintains an open chromatin architecture and licenses recruitment of Mediator and RNA polymerase II for gene activation. Our data reveal an essential role for INO80 in the expression of the pluripotency network and illustrate the coordination among chromatin remodeler, transcription factor, and histone-modifying enzyme in the regulation of the pluripotent state.
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•INO80 is required for ESC self-renewal, reprogramming, and blastocyst development•INO80 occupies pluripotency gene promoter regions, which is dependent on Wdr5 and Oct4•INO80 maintains an open chromatin structure and recruits Mediator and Pol II•INO80 binding distinguishes active genes from those repressed by master TFs
INO80 is required for ESC self-renewal, reprogramming, and blastocyst development. It activates pluripotency genes by maintaining an open chromatin structure at promoters to recruit Mediator and Pol II.
•Epidemiological and model system studies support an early origin of reproductive dysfunction.•Estrogenic/anti-androgenic chemicals as endocrine disrupting chemicals (EDCs) have vast developmental ...influences on adult reproductive outcomes.•Gestational, perinatal, neonatal, and pubertal periods are “windows of susceptibility” for epigenetic programming.•EDCs induce exposure-specific epigenetic modifications in regulatory genes in organs of the reproductive system.•Germline epigenetic disruption is a mechanism underlying transgenerational inheritance of reproductive disorders.
Sex-specific differentiation, development, and function of the reproductive system are largely dependent on steroid hormones. For this reason, developmental exposure to estrogenic and anti-androgenic endocrine disrupting chemicals (EDCs) is associated with reproductive dysfunction in adulthood. Human data in support of “Developmental Origins of Health and Disease” (DOHaD) comes from multigenerational studies on offspring of diethylstilbestrol-exposed mothers/grandmothers. Animal data indicate that ovarian reserve, female cycling, adult uterine abnormalities, sperm quality, prostate disease, and mating behavior are susceptible to DOHaD effects induced by EDCs such as bisphenol A, genistein, diethylstilbestrol, p,p′-dichlorodiphenyl-dichloroethylene, phthalates, and polyaromatic hydrocarbons. Mechanisms underlying these EDC effects include direct mimicry of sex steroids or morphogens and interference with epigenomic sculpting during cell and tissue differentiation. Exposure to EDCs is associated with abnormal DNA methylation and other epigenetic modifications, as well as altered expression of genes important for development and function of reproductive tissues. Here we review the literature exploring the connections between developmental exposure to EDCs and adult reproductive dysfunction, and the mechanisms underlying these effects.
Phytoestrogens, estrogenic compounds derived from plants, are ubiquitous in human and animal diets. These chemicals are generally much less potent than estradiol but act via similar mechanisms. The ...most common source of phytoestrogen exposure to humans is soybean-derived foods that are rich in the isoflavones genistein and daidzein. These isoflavones are also found at relatively high levels in soy-based infant formulas. Phytoestrogens have been promoted as healthy alternatives to synthetic estrogens and are found in many dietary supplements. The aim of this review is to examine the evidence that phytoestrogen exposure, particularly in the developmentally sensitive periods of life, has consequences for future reproductive health.
In mammalian embryos, proper zygotic genome activation (ZGA) underlies totipotent development. Double homeobox (DUX)-family factors participate in ZGA, and mouse Dux is required for forming cultured ...two-cell (2C)-like cells. Remarkably, in mouse embryonic stem cells, Dux is activated by the tumor suppressor p53, and Dux expression promotes differentiation into expanded-fate cell types. Long-read sequencing and assembly of the mouse Dux locus reveals its complex chromatin regulation including putative positive and negative feedback loops. We show that the p53-DUX/DUX4 regulatory axis is conserved in humans. Furthermore, we demonstrate that cells derived from patients with facioscapulohumeral muscular dystrophy (FSHD) activate human DUX4 during p53 signaling via a p53-binding site in a primate-specific subtelomeric long terminal repeat (LTR)10C element. In summary, our work shows that p53 activation convergently evolved to couple p53 to Dux/DUX4 activation in embryonic stem cells, embryos and cells from patients with FSHD, potentially uniting the developmental and disease regulation of DUX-family factors and identifying evidence-based therapeutic opportunities for FSHD.
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Exposure to naturally derived estrogen receptor activators, such as the phytoestrogen genistein, can occur at physiologically relevant concentrations in the human diet. Soy-based ...infant formulas are of particular concern because infants consuming these products have serum genistein levels almost 20 times greater than those seen in vegetarian adults. Comparable exposures in animal studies have adverse physiologic effects. The timing of exposure is particularly concerning because infants undergo a steroid hormone-sensitive period termed “minipuberty” during which estrogenic chemical exposure may alter normal reproductive tissue patterning and function. The delay between genistein exposure and reproductive outcomes poses a unique challenge to collecting epidemiological data. In 2010, the U.S. National Toxicology Program monograph on the safety of the use of soy formula stated that the use of soy-based infant formula posed minimal concern and emphasized a lack of data from human subjects. Since then, several new human and animal studies have advanced our epidemiological and mechanistic understanding of the risks and benefits of phytoestrogen exposure. Here we aim to identify clinically relevant findings regarding phytoestrogen exposure and female reproductive outcomes from the past 10 years, with a focus on the phytoestrogen genistein, and explore the implications of these findings for soy infant formula recommendations. Research presented in this review will inform clinical practice and dietary recommendations for infants based on evidence from both clinical epidemiology and basic research advances in endocrinology and developmental biology from mechanistic in vitro and animal studies.
Calcium (Ca
) signals initiate egg activation across the animal kingdom and in at least some plants. These signals are crucial for the success of development and, in the case of mammals, health of ...the offspring. The mechanisms associated with fertilization that trigger these signals and the molecules that regulate their characteristic patterns vary widely. With few exceptions, a major contributor to fertilization-induced elevation in cytoplasmic Ca
is release from endoplasmic reticulum stores through the IP3 receptor. In some cases, Ca
influx from the extracellular space and/or release from alternative intracellular stores contribute to the rise in cytoplasmic Ca
. Following the Ca
rise, the reuptake of Ca
into intracellular stores or efflux of Ca
out of the egg drive the return of cytoplasmic Ca
back to baseline levels. The molecular mediators of these Ca
fluxes in different organisms include Ca
release channels, uptake channels, exchangers and pumps. The functions of these mediators are regulated by their particular activating mechanisms but also by alterations in their expression and spatial organization. We discuss here the molecular basis for modulation of Ca
signalling at fertilization, highlighting differences across several animal phyla, and we mention key areas where questions remain.
Egg activation in mammals is triggered by oscillations in egg intracellular calcium (Ca2+) level. Ca2+ oscillation patterns can be modified in vitro by changing the ionic composition of culture media ...or in vivo by conditions affecting mitochondrial function, such as obesity and inflammation. In mice, disruption of Ca2+ oscillations in vitro impacts embryo development and offspring growth. Here we tested the hypothesis that, even without in vitro manipulation, abnormal Ca2+ signaling following fertilization impacts offspring growth. Plasma membrane Ca2+ ATPases (PMCA) extrude cytosolic Ca2+ to restore Ca2+ homeostasis. To disrupt Ca2+ signaling in vivo, we conditionally deleted PMCA1 (cKO) in oocytes. As anticipated, in vitro fertilized cKO eggs had increased Ca2+ exposure relative to controls. To assess the impact on offspring growth, cKO females were mated to wild type males to generate pups that had high Ca2+ exposure at fertilization. Because these offspring would be heterozygous, we also tested the impact of global PMCA1 heterozygosity on offspring growth. Control heterozygous pups that had normal Ca2+ at fertilization were generated by mating wild type females to heterozygous males; these control offspring weighed significantly less than their wild type siblings. However, heterozygous offspring from cKO eggs (and high Ca2+ exposure) were larger than heterozygous controls at 12 week-of-age and males had altered body composition. Our results show that global PMCA1 haploinsufficiency impacts growth and support that abnormal Ca2+ signaling after fertilization in vivo has a long-term impact on offspring weight. These findings are relevant for environmental and medical conditions affecting Ca2+ handling and for design of culture conditions and procedures for domestic animal and human assisted reproduction. Summary Sentence Plasma membrane calcium ATPase 1 (PMCA1) in eggs regulates calcium homeostasis at fertilization, and offspring derived from PMCA1-null eggs (and excess calcium signal at fertilization) weigh more than controls with normal calcium. Graphical Abstract
Chromatin changes in response to estrogen and progesterone are well established in cultured cells, but how they control gene expression under physiological conditions is largely unknown. To address ...this question, we examined in vivo estrous cycle dynamics of mouse uterus hormone receptor occupancy, chromatin accessibility and chromatin structure by combining RNA-seq, ATAC-seq, HiC-seq and ChIP-seq. Two estrous cycle stages were chosen for these analyses, diestrus (highest estrogen) and estrus (highest progesterone). Unexpectedly, rather than alternating with each other, estrogen receptor alpha (ERα) and progesterone receptor (PGR) were co-bound during diestrus and lost during estrus. Motif analysis of open chromatin followed by hypoxia inducible factor 2A (HIF2A) ChIP-seq and conditional uterine deletion of this transcription factor revealed a novel role for HIF2A in regulating diestrus gene expression patterns that were independent of either ERα or PGR binding. Proteins in complex with ERα included PGR and cohesin, only during diestrus. Combined with HiC-seq analyses, we demonstrate that complex chromatin architecture changes including enhancer switching are coordinated with ERα and PGR co-binding during diestrus and non-hormone receptor transcription factors such as HIF2A during estrus to regulate most differential gene expression across the estrous cycle.Chromatin changes in response to estrogen and progesterone are well established in cultured cells, but how they control gene expression under physiological conditions is largely unknown. To address this question, we examined in vivo estrous cycle dynamics of mouse uterus hormone receptor occupancy, chromatin accessibility and chromatin structure by combining RNA-seq, ATAC-seq, HiC-seq and ChIP-seq. Two estrous cycle stages were chosen for these analyses, diestrus (highest estrogen) and estrus (highest progesterone). Unexpectedly, rather than alternating with each other, estrogen receptor alpha (ERα) and progesterone receptor (PGR) were co-bound during diestrus and lost during estrus. Motif analysis of open chromatin followed by hypoxia inducible factor 2A (HIF2A) ChIP-seq and conditional uterine deletion of this transcription factor revealed a novel role for HIF2A in regulating diestrus gene expression patterns that were independent of either ERα or PGR binding. Proteins in complex with ERα included PGR and cohesin, only during diestrus. Combined with HiC-seq analyses, we demonstrate that complex chromatin architecture changes including enhancer switching are coordinated with ERα and PGR co-binding during diestrus and non-hormone receptor transcription factors such as HIF2A during estrus to regulate most differential gene expression across the estrous cycle.
Mammalian fertilization is accompanied by oscillations in egg cytoplasmic calcium (Ca2+) concentrations that are critical for completion of egg activation. These oscillations are initiated by Ca2+ ...release from inositol 1,4,5-trisphosphate (IP3)-sensitive intracellular stores. We tested the hypothesis that Ca2+ influx across the plasma membrane was a requisite component of egg activation signaling, and not simply a Ca2+ source for store repletion. Using intracytoplasmic sperm injection (ICSI) and standard in vitro fertilization (IVF), we found that Ca2+ influx was not required to initiate resumption of meiosis II. However, even if multiple oscillations in intracellular Ca2+ occurred, in the absence of Ca2+ influx, the fertilized eggs failed to emit the second polar body, resulting in formation of three pronuclei. Additional experiments using the Ca2+ chelator, BAPTA/AM, demonstrated that Ca2+ influx is sufficient to support polar body emission and pronucleus formation after only a single sperm-induced Ca2+ transient, whereas BAPTA/AM-treated ICSI or fertilized eggs cultured in Ca2+-free medium remained arrested in metaphase II. Inhibition of store-operated Ca2+ entry had no effect on ICSI-induced egg activation, so Ca2+ influx through alternative channels must participate in egg activation signaling. Ca2+ influx appears to be upstream of CaMKIIγ activity because eggs can be parthenogenetically activated with a constitutively active form of CaMKIIγ in the absence of extracellular Ca2+. These results suggest that Ca2+ influx at fertilization not only maintains Ca2+ oscillations by replenishing Ca2+ stores, but also activates critical signaling pathways upstream of CaMKIIγ that are required for second polar body emission.
Calcium (Ca2+) signals drive the fundamental events surrounding fertilization and the activation of development in all species examined to date. Initial studies of Ca2+ signaling at fertilization in ...marine animals were tightly linked to new discoveries of bioluminescent proteins and their use as fluorescent Ca2+ sensors. Since that time, there has been rapid progress in our understanding of the key functions for Ca2+ in many cell types and of the impact of cellular localization on Ca2+ signaling pathways. In this review, which focuses on mammalian egg activation, we consider how Ca2+ is regulated and stored at different stages of oocyte development and examine the functions of molecules that serve as both regulators of Ca2+ release and effectors of Ca2+ signals. We then summarize studies exploring how Ca2+ directs downstream effectors mediating both egg activation and later signaling events required for successful preimplantation embryo development. Throughout this review, we focus attention on how localization of Ca2+ signals influences downstream signaling events, and attempt to highlight gaps in our knowledge that are ripe for future research. Mol. Reprod. Dev. 79: 742–756, 2012. Published 2012. This article is a US government work and, as such, is in the public domain in the United States of America.
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