zygote arrest

Zygotic genome activation (ZGA) marks the beginning of the embryonic program for a totipotent embryo, which gives rise to the inner cell mass (ICM) where pluripotent epiblast arises, and extraembryonic trophectoderm. However, how ZGA is connected to the first lineage segregation in mammalian embryos remains elusive. Here, we investigated the role of nuclear receptor (NR) transcription factors (TFs), whose motifs are highly enriched and accessible from the 2-cell (2C) to 8-cell (8C) stages in mouse embryos. We found that NR5A2, an NR TF strongly induced upon ZGA, was required for this connection...

In oocyte biology the zona pellucida has long been known to operate three extracellular functions downstream of the secretory pathway, namely, encasing the oocytes in ovarian follicles, mediating sperm-oocyte interaction and preventing premature embryo contact with oviductal epithelium. The present study uncovers a fourth function that is fundamentally distinct from the other three, being critical for embryonic cell survival in mice. Intriguingly, the three proteins of the mouse zona pellucida (ZP1, ZP2, ZP3) were found abundantly present also inside the embryo 4 days after fertilization, as shown by mass spectrometry, immunoblotting and immunofluorescence...

Mammalian oocytes are filled with poorly understood structures called cytoplasmic lattices. First discovered in the 1960s and speculated to correspond to mammalian yolk, ribosomal arrays, or intermediate filaments, their function has remained enigmatic to date. Here, we show that cytoplasmic lattices are sites where oocytes store essential proteins for early embryonic development. Using super-resolution light microscopy and cryoelectron tomography, we show that cytoplasmic lattices are composed of filaments with a high surface area, which contain PADI6 and subcortical maternal complex proteins...

Tubulin beta-8 (TUBB8) is expressed exclusively in the oocyte and early embryo, encoding a beta-tubulin polypeptide that participates in the assembly of microtubules. TUBB8 was first attributed to being responsible for oocyte MI arrest. Further studies have demonstrated that patients with different pathogenic variants have variable phenotypes. We report a TUBB8 variant (c.10 A > C) in two siblings who presented different clinical features of primary infertility. The younger sister showed severe oocyte maturation arrest with abnormal morphology, whereas a few mature oocytes and zygotes could be retrieved from the older sister, but no embryo was available for transfer...

Gram-negative bacteria release of lipopolysaccharide (LPS) endotoxin elicits robust immune responses capable of disrupting normal ovarian function contributing to female infertility. However, effects of subclinical or non-detectable infections on oocyte competence and subsequent embryo development remain to be fully elucidated. The aim of this study was to investigate the effects of exposing bovine oocytes to low LPS doses on oocyte and embryo competence. Bovine oocytes were collected from slaughterhouse-derived ovaries and matured with vehicle-control or increasing doses of LPS (0...

Defects in ribosomal biogenesis profoundly affect organismal development and cellular function, and these ribosomopathies produce a variety of phenotypes. One ribosomopathy, Shwachman-Diamond syndrome (SDS) is characterized by neutropenia, pancreatic exocrine insufficiency, and skeletal anomalies. SDS results from biallelic mutations in SBDS , which encodes a ribosome assembly factor. Some individuals express a missense mutation, SBDS R126T , along with the common K62X mutation. We reported that the sbds -null zebrafish phenocopies much of SDS...

In mammals, many retrotransposons are de-repressed during zygotic genome activation (ZGA). However, their functions in early development remain elusive largely due to the challenge to simultaneously manipulate thousands of retrotransposon insertions in embryos. Here, we employed epigenome editing to perturb the long terminal repeat (LTR) MT2_Mm, a well-known ZGA and totipotency marker that exists in ∼2667 insertions throughout the mouse genome. CRISPRi robustly repressed 2485 (∼ 93%) MT2_Mm insertions and 1090 (∼55%) insertions of the closely related MT2C_Mm in 2-cell embryos...

BACKGROUND: Infertility and pregnancy loss are longstanding problems. Successful fertilization and high-quality embryos are prerequisites for an ongoing pregnancy. Studies have proven that every stage in the human reproductive process is regulated by multiple genes and any problem, at any step, may lead to fertilization failure (FF) or early embryonic arrest (EEA). Doctors can diagnose the pathogenic factors involved in FF and EEA by using genetic methods. With the progress in the development of new genetic technologies, such as single-cell RNA analysis and whole-exome sequencing, a new approach has opened up for us to directly study human germ cells and reproductive development...

In mouse preimplantation development, zygotic genome activation (ZGA), which synthesizes new transcripts in the embryo, begins in the S phase at the one-cell stage, with major ZGA occurring especially at the late two-cell stage. Myc is a transcription factor expressed in parallel with ZGA, but its direct association with major ZGA has not been clarified. In this study, we found that developmental arrest occurs at the two-cell stage when mouse embryos were treated with antisense oligonucleotides targeting Myc or MYC-specific inhibitors from the one-cell stage...

Meiotically competent oocytes in mammals undergo cyclic development during folliculogenesis. Oocytes within ovarian follicles are transcriptionally active, producing and storing transcripts required for oocyte growth, somatic cell communication and early embryogenesis. Transcription ceases as oocytes transition from growth to maturation and does not resume until zygotic genome activation. Although SUMOylation, a post-translational modification, plays multifaceted roles in transcriptional regulation, its involvement during oocyte development remains poorly understood...

UNLABELLED: OVO is required for karyotypically female germ cell viability but has no known function in the male germline in Drosophila. ovo is autoregulated by two antagonistic isoforms, OVO-A and OVO-B. All ovo - alleles were created as partial revertants of the antimorphic ovo D1 allele. Creation of new targeted alleles in an ovo + background indicated that disrupting the germline-specific exon extension of ovo-B leads to an arrested egg chamber phenotype, rather than germ cell death...

Nitrogen (N) and phosphorus (P) are essential elements whose availability promotes successful growth of phytoplankton and governs aquatic primary productivity. In this study, we investigated the effect of N and/or P deficiency on the sexual reproduction of Prorocentrum cordatum, the dinoflagellate with the haplontic life cycle which causes harmful algal blooms worldwide. In P. cordatum cultures, N and the combined N and P deficiency led to the arrest of the cell cycle in the G0 /G1 phases and attenuation of cell culture growth...

OBJECTIVE: Reconstructed oocytes after polar body genome transfer constitute a potential therapeutic option for patients with a history of embryo fragmentation and advanced maternal age. However, the rescue of genetic material from the first polar body (PB1) through introduction into the donor cytoplasm is not yet ready for clinical application. METHODS: Eighty-five oocytes were obtained following in vitro maturation (IVM) and divided into two groups: PB1 nuclear transfer (PB1NT; n=54) and control (n=31)...

During the oocyte growth, maturation and zygote development, chromatin structure keeps changing to regulate different nuclear activities. Here, we reported the role of SMC2, a core component of condensin complex, in oocyte and embryo development. Oocyte-specific conditional knockout of SMC2 caused female infertility. In the absence of SMC2, oocyte meiotic maturation and ovulation occurred normally, but chromosome condensation showed defects and DNA damages were accumulated in oocytes. The pronuclei were abnormally organized and micronuclei were frequently observed in fertilized eggs, their activity was impaired, and embryo development was arrested at the one-cell stage, suggesting that maternal SMC2 is essential for embryonic development...

Centromeres direct genetic inheritance but are not themselves genetically encoded. Instead, centromeres are defined epigenetically by the presence of a histone H3 variant, CENP-A.1 In cultured somatic cells, an established paradigm of cell-cycle-coupled propagation maintains centromere identity: CENP-A is partitioned between sisters during replication and replenished by new assembly, which is restricted to G1. The mammalian female germ line challenges this model because of the cell-cycle arrest between pre-meiotic S phase and the subsequent G1, which can last for the entire reproductive lifespan (months to decades)...

The changes in epigenetic modifications during early embryonic development significantly impact mammalian embryonic genome activation (EGA) and are species-conserved to some degree. Here, we reanalyzed the published RNA-Seq of human, mouse, and goat early embryos and found that Zfp296 (zinc finger protein 296) expression was higher at the EGA stage than at the oocyte stage in all three species (adjusted p -value < 0.05 |log2(foldchange)| ≥ 1). Subsequently, we found that Zfp296 was conserved across human, mouse, goat, sheep, pig, and bovine embryos...

Conventional dogma presumes that protamine-mediated DNA compaction in sperm is achieved by electrostatic interactions between DNA and the arginine-rich core of protamines. Phylogenetic analysis reveals several non-arginine residues conserved within, but not across species. The significance of these residues and their post-translational modifications are poorly understood. Here, we investigated the role of K49, a rodent-specific lysine residue in protamine 1 (P1) that is acetylated early in spermiogenesis and retained in sperm...

Zygotic genome activation (ZGA) is essential for early embryonic development. However, the regulation of ZGA remains elusive in mammals. Here we report that a maternal factor TDP-43, a nuclear transactive response DNA-binding protein, regulates ZGA through RNA Pol II and is essential for mouse early embryogenesis. Maternal TDP-43 translocates from the cytoplasm into the nucleus at the early two-cell stage when minor to major ZGA transition occurs. Genetic deletion of maternal TDP-43 results in mouse early embryos arrested at the two-cell stage...

Zygotic genome activation (ZGA) activates the quiescent genome to enable the maternal-to-zygotic transition1,2 . However, the identity of transcription factors that underlie mammalian ZGA in vivo remains elusive. Here we show that OBOX, a PRD-like homeobox domain transcription factor family (OBOX1-OBOX8)3-5 , are key regulators of mouse ZGA. Mice deficient for maternally transcribed Obox1/2/5/7 and zygotically expressed Obox3/4 had a two-cell to four-cell arrest, accompanied by impaired ZGA...

Oogenesis involves transduction of mechanical forces from the cytoskeleton to the nuclear envelope (NE). In Caenorhabditis elegans , oocyte nuclei lacking the single lamin protein LMN-1 are vulnerable to collapse under forces mediated through LINC (linker of nucleoskeleton and cytoskeleton) complexes. Here, we use cytological analysis and in vivo imaging to investigate the balance of forces that drive this collapse and protect oocyte nuclei. We also use a mechano-node-pore sensing device to directly measure the effect of genetic mutations on oocyte nuclear stiffness...