Histone deacetylase 1 and 2 drive differentiation and fusion of progenitor cells in human placental trophoblasts

Cell fusion occurs when several cells combine to form a multinuclear aggregate (syncytium). In human placenta, a syncytialized trophoblast (syncytiotrophoblast) layer forms the primary interface between maternal and fetal tissue, facilitates nutrient and gas exchange, and produces hormones vital for pregnancy. Syncytiotrophoblast development occurs by differentiation of underlying progenitor cells called cytotrophoblasts, which then fuse into the syncytiotrophoblast layer. Differentiation is associated with chromatin remodeling and specific changes in gene expression mediated, at least in part, by histone acetylation. However, the epigenetic regulation of human cytotrophoblast differentiation and fusion is poorly understood. In this study, we found that human syncytiotrophoblast development was associated with deacetylation of multiple core histone residues. Chromatin immunoprecipitation sequencing revealed chromosomal regions that exhibit dynamic alterations in histone H3 acetylation during differentiation. These include regions containing genes classically associated with cytotrophoblast differentiation (TEAD4, TP63, OVOL1, CGB), as well as near genes with novel regulatory roles in trophoblast development and function, such as LHX4 and SYDE1. Prevention of histone deacetylation using both pharmacological and genetic approaches inhibited trophoblast fusion, supporting a critical role of this process for trophoblast differentiation. Finally, we identified the histone deacetylases (HDACs) HDAC1 and HDAC2 as the critical mediators driving cytotrophoblast differentiation. Collectively, these findings provide novel insights into the epigenetic mechanisms underlying trophoblast fusion during human placental development

Epigenetic alterations in sperm associated with male infertility

The most common form of male infertility is a low sperm count, known as oligozoospermia. Studies suggest that oligozoospermia is associated with epigenetic alterations. Epigenetic alterations in sperm, which may arise due to the exposure of gametes to environmental factors or those that pre-exist in the sperm of infertile individuals, may contribute to the increased incidence of normally rare imprinting disorders in babies conceived after assisted reproductive technology using the sperm of infertile men. Genomic imprinting is an important developmental process whereby the allelic activity of certain genes is regulated by DNA methylation established during gametogenesis. The aberrant expression of several imprinted genes has been linked to various diseases, malignant tumors, lifestyle and mental disorders in humans. Understanding how infertility and environmental factors such as reproductive toxicants, certain foods, and drug exposures during gametogenesis contribute to the origins of these disorders via defects in sperm is of paramount importance. In this review, we discuss the association of epigenetic alterations with abnormal spermatogenesis and the evidence that epigenetic processes, including those required for genomic imprinting, may be sensitive to environmental exposures during gametogenesis, fertilization and early embryonic development. In addition, we review imprinting diseases and their relationships with environmental factors. While the plasticity of epigenetic marks may make these more susceptible to modification by the environment, this also suggests that aberrant epigenetic marks may be reversible. A greater understanding of this process and the function of epidrugs may lead to the development of new treatment methods for many adult diseases in the future

Genome-wide microRNA expression profiling in placentae from frozen-thawed blastocyst transfer

Abstract Background Frozen-thawed embryo transfer (FET) is increasingly available for the improvement of the success rate of assisted reproductive technologies other than fresh embryo transfer (ET). There have been numerous findings that FET provides better obstetric and perinatal outcomes. However, the birth weight of infants conceived using FET is heavier than that of those conceived via ET. In addition, some reports have suggested that FET is associated with perinatal diseases such as placenta accreta and pregnancy-induced hypertension (PIH). Results In this study, we compared the microRNA (miRNA) expression profiles in term placentae derived from FET, ET, and spontaneous pregnancy (SP). We identified four miRNAs, miR-130a-3p, miR-149-5p, miR-423-5p, and miR-487b-3p, that were significantly downregulated in FET placentae compared with those from SP and ET. We found that DNA methylation of MEG3-DMR, not but IG-DMR, was associated with miRNA expression of the DLK1-DIO3 imprinted domain in the human placenta. In functional analyses, GO terms and signaling pathways related to positive regulation of gene expression, growth, development, cell migration, and type II diabetes mellitus (T2DM) were enriched. Conclusions This study supports the hypothesis that the process of FET may increase exposure of epigenome to external influences

Trophoblast stem cell-based organoid models of the human placental barrier

Abstract Human placental villi have essential roles in producing hormones, mediating nutrient and waste exchange, and protecting the fetus from exposure to xenobiotics. Human trophoblast organoids that recapitulate the structure of villi could provide an important in vitro tool to understand placental development and the transplacental passage of xenobiotics. However, such organoids do not currently exist. Here we describe the generation of trophoblast organoids using human trophoblast stem (TS) cells. Following treatment with three kinds of culture medium, TS cells form spherical organoids with a single outer layer of syncytiotrophoblast (ST) cells that display a barrier function. Furthermore, we develop a column-type ST barrier model based on the culture condition of the trophoblast organoids. The bottom membrane of the column is almost entirely covered with syndecan 1-positive ST cells. The barrier integrity and maturation levels of the model are confirmed by measuring transepithelial/transendothelial electrical resistance (TEER) and the amount of human chorionic gonadotropin. Further analysis reveals that the model can be used to derive the apparent permeability coefficients of model compounds. In addition to providing a suite of tools for the study of placental development, our trophoblast models allow the evaluation of compound transfer and toxicity, which will facilitate drug development

Association of four imprinting disorders and ART

Abstract Background Human-assisted reproductive technologies (ART) are a widely accepted treatment for infertile couples. At the same time, many studies have suggested the correlation between ART and increased incidences of normally rare imprinting disorders such as Beckwith-Wiedemann syndrome (BWS), Angelman syndrome (AS), Prader-Willi syndrome (PWS), and Silver-Russell syndrome (SRS). Major methylation dynamics take place during cell development and the preimplantation stages of embryonic development. ART may prevent the proper erasure, establishment, and maintenance of DNA methylation. However, the causes and ART risk factors for these disorders are not well understood. Results A nationwide epidemiological study in Japan in 2015 in which 2777 pediatrics departments were contacted and a total of 931 patients with imprinting disorders including 117 BWS, 227 AS, 520 PWS, and 67 SRS patients, were recruited. We found 4.46- and 8.91-fold increased frequencies of BWS and SRS associated with ART, respectively. Most of these patients were conceived via in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), and showed aberrant imprinted DNA methylation. We also found that ART-conceived SRS (ART-SRS) patients had incomplete and more widespread DNA methylation variations than spontaneously conceived SRS patients, especially in sperm-specific methylated regions using reduced representation bisulfite sequencing to compare DNA methylomes. In addition, we found that the ART patients with one of three imprinting disorders, PWS, AS, and SRS, displayed additional minor phenotypes and lack of the phenotypes. The frequency of ART-conceived Prader-Willi syndrome (ART-PWS) was 3.44-fold higher than anticipated. When maternal age was 37 years or less, the rate of DNA methylation errors in ART-PWS patients was significantly increased compared with spontaneously conceived PWS patients. Conclusions We reconfirmed the association between ART and imprinting disorders. In addition, we found unique methylation patterns in ART-SRS patients, therefore, concluded that the imprinting disorders related to ART might tend to take place just after fertilization at a time when the epigenome is most vulnerable and might be affected by the techniques of manipulation used for IVF or ICSI and the culture medium of the fertilized egg

Genome-Wide Analysis of DNA Methylation Dynamics during Early Human Development

<div><p>DNA methylation is globally reprogrammed during mammalian preimplantation development, which is critical for normal development. Recent reduced representation bisulfite sequencing (RRBS) studies suggest that the methylome dynamics are essentially conserved between human and mouse early embryos. RRBS is known to cover 5–10% of all genomic CpGs, favoring those contained within CpG-rich regions. To obtain an unbiased and more complete representation of the methylome during early human development, we performed whole genome bisulfite sequencing of human gametes and blastocysts that covered>70% of all genomic CpGs. We found that the maternal genome was demethylated to a much lesser extent in human blastocysts than in mouse blastocysts, which could contribute to an increased number of imprinted differentially methylated regions in the human genome. Global demethylation of the paternal genome was confirmed, but SINE-VNTR-Alu elements and some other tandem repeat-containing regions were found to be specifically protected from this global demethylation. Furthermore, centromeric satellite repeats were hypermethylated in human oocytes but not in mouse oocytes, which might be explained by differential expression of <i>de novo</i> DNA methyltransferases. These data highlight both conserved and species-specific regulation of DNA methylation during early mammalian development. Our work provides further information critical for understanding the epigenetic processes underlying differentiation and pluripotency during early human development.</p></div