Search Results (32)

Human preimplantation embryo arrest (PREMBA) represents a significant clinical hurdle in assisted reproductive technology (ART), in which approximately 10% of in vitro fertilized (IVF) embryos arrest at the cleavage stages. Whole-exome sequencing (WES) studies have discovered numerous genetic mutations associated with preimplantation embryo arrest. These mutations often disrupt critical biological milestones such as maternal mRNA clearance (BTG4, ZFP36L2, ZAR1), subcortical maternal complex (TLE6, PADI6, OOEP, NLRP2, NLRP5, NLRP7, KHDC3L), DNA double-strand break formation and homologous recombination (REC114, TOP6BL, MEI1, MEI4, TRIP13), spindle assembly (TUBB8 and TUBA4A) and cell cycle and checkpoints (FBXO43, MOS, CHEK1, TRIP13, CDC20), as well as nuclear transport and translational regulation (KPNA7, DDOST). However, the cause of most clinical cases remains genetically unexplained. Studies investigating these unexplained arrests have uncovered widespread multi-omics abnormalities, including transcriptional arrest, DNA hypermethylation, higher chromatin accessibility, aberrant histone modification, chromosomal aneuploidy and senescent-like states. This review provides a comprehensive overview of the molecular mechanisms underlying PREMBA, categorized into those that are attributable to known genetic mutations and those with unexplained reasons. Full article

The rhesus macaque is one of the closest evolutionary relatives to humans, making the study of alternative splicing (AS) during its early embryonic development highly valuable for understanding human embryogenesis and related diseases. However, systematic studies in this context remain limited. Here, a comprehensive bioinformatic analysis of AS was performed using RNA-seq data spanning early rhesus macaque embryogenesis. We identified multiple previously unannotated zygotic genome activation (ZGA) genes, thereby refining the rhesus macaque ZGA gene repertoire. The landscape of AS and differential AS events (DASEs) across early stages was characterized, revealing dynamic and stage-specific regulation, with a marked increase in AS events from the 8-cell to morula stages. In addition, weighted gene co-expression network analysis identified 35 key splicing factors (SFs) involved in regulating early rhesus macaque embryonic development. Finally, we calculated the correlation between differentially expressed SFs and DASEs during the ZGA process, and identified potential regulatory relationships between several SFs (TRA2B, IGF2BP1, HNRNPAB, and MATR3) and specific DASEs. Collectively, this study provides the first systematic analysis of AS dynamics and regulation in early rhesus macaque embryogenesis, highlighting its critical role in development and offering a valuable reference for understanding AS in early human embryos. Full article

Foam acidification is often employed as a clean and efficient method to remove blockages from wells and promote oil and gas production. In order to effectively control the diffusion of H⁺ in the acid solution into the rock surface, reduce the acid–rock reaction rate, and achieve deep acidification, a foam-retarding acid with foam stability, temperature and salt resistance, and excellent retarding performance was prepared by studying the synergistic effect of the foaming agent and foam stabilizer. ZG-A was used as the foaming agent, and ZG-B was added as a foam stabilizer to achieve foam stabilization. When the ZG-A/ZG-B ratio was 0.67%/0.33%, the foam exhibited the best comprehensive performance. By measuring and comparing the acid–rock reaction rate under different conditions, the results showed that the average acid–rock reaction rate of the 10% compound acid was 1.412 × 10⁻³ mg/(cm²·s), while the average acid–rock reaction rate of the foam-retarding acid system was reduced to 6.622 × 10⁻⁵ mg/(cm²·s), representing a reduction of two orders of magnitude, and the slow rate reached 95.31%. Foam fluid diversion experiments were carried out on cores with different permeabilities. The results showed that the foam could increase the diversion flow rate of low-permeability cores and reduce the diversion flow rate of high-permeability cores. Thus, the foam fluid could be uniformly propelled in cores with different permeabilities. Based on this principle, foam acid acidification can increase the amount of acid injection into the low-permeability layer and reduce the amount of acid absorption in the high-permeability layer, thereby improving the acidification effect. Full article

Zygotic genome activation (ZGA) represents one of the most vulnerable periods to environmental perturbations. The objective of this study was to investigate the formation of stress granules in mouse embryos in response to temperature reduction during ZGA, preimplantation embryo mortality, and long-term phenotypic outcomes. These outcomes included the evaluation of expression noise in bilateral right/left limbs of offspring as an indicator of developmental instability, behavioral deviation, hippocampal volume, and metabolomics profiling in adult offspring. Exposure to hypothermia during ZGA was associated with an increased number and inter-blastomere variability of stress granules, extended duration of the second embryonic division, and elevated embryonic mortality during the second and third cleavage stages. The embryonic response to hypothermic stress correlated with phenotypic traits indicative of increased pathology risk. Expression noise, serving as an indicator of developmental instability, was reduced in adult offspring derived from two-cell embryos incubated at 35 °C compared to those at 37 °C, while showing no significant difference relative to the control group. These results suggest that embryos surviving hypothermic exposure (35 °C) possess enhanced resilience to the adverse effects commonly associated with embryo transfer procedures. Furthermore, increased hippocampal volume and augmented auditory startle reflex observed in offspring that endured hypothermia during ZGA imply reduced risks of cognitive-related pathologies and reduced risks of pathologies associated with cognitive functions. Full article

Grass carp is an economically important cultured species in China. Triploid embryo production is widely applied in aquaculture to achieve reproductive sterility, improve somatic growth, and reduce ecological risks associated with uncontrolled breeding. In this study, a simple cold shock method for inducing triploid grass carp was developed. The triploid induction rate of 71.73 ± 5.00% was achieved by applying a cold treatment at 4 °C for 12 min, starting 2 min after artificial fertilization. Flow cytometry and karyotype analysis revealed that triploid individuals exhibited a 1.5-fold increase in DNA content compared to diploid counterparts, with a chromosomal composition of 3n = 72 (33m + 36sm + 3st). Additionally, embryonic transcriptome analysis demonstrated that, in the cold shock-induced embryos, genes associated with abnormal mesoderm and dorsal–ventral axis formation, zygotic genome activation (ZGA), and anti-apoptosis were downregulated, whereas pro-apoptotic genes were upregulated, which may contribute to the higher abnormal mortality observed during embryonic development. Overall, this study demonstrates optimized conditions for inducing triploidy in grass carp via cold shock and provides insights into the transcriptomic changes that take place in cold shock-induced embryos, which could inform future grass carp genetic breeding programs. Full article

Zygotic genome activation (ZGA) marks the critical transition from reliance on maternal transcripts to the initiation of embryonic transcription early in development. Despite extensive characterization in model species, the regulatory framework of ZGA in sheep remains poorly defined. Here, we applied single-cell RNA sequencing (Smart-seq2) to in vivo- and in vitro-derived sheep embryos at the 8-, 16-, and 32-cell stages. Differential expression analysis revealed 114, 1628, and 1465 genes altered in the 8- vs. 16-, 16- vs. 32-, and 8- vs. 32-cell transitions, respectively, with the core pluripotency factors SOX2, NANOG, POU5F1, and KLF4 upregulated during major ZGA. To uncover coordinated regulatory modules, we constructed a weighted gene co-expression network using WGCNA, identifying the MEred module as most tightly correlated with developmental progression (r = 0.48, p = 8.6 × 10⁻¹⁴). The integration of MERed genes into the STRING v11 protein–protein interaction network furnished a high-confidence scaffold for community detection. Louvain partitioning delineated two discrete communities: Community 0 was enriched in ER–Golgi vesicle-mediated transport, transmembrane transport, and cytoskeletal dynamics, suggesting roles in membrane protein processing, secretion, and early signaling; Community 1 was enriched in G2/M cell-cycle transition and RNA splicing/processing, indicating a coordinated network for accurate post-ZGA cell division and transcript maturation. Together, these integrated analyses reveal a modular regulatory architecture underlying sheep ZGA and provide a framework for dissecting early embryonic development in this species. Full article

The mouse genome is transcribed at different rates in both directions from the newly formed genome after fertilization. During embryonic genomic activation (EGA/ZGA), the first RNA metabolism creates heterogeneity between blastomeres. Indeed, ZGA-dependent maternal RNA degradation is crucial to regulate gene expression and enable the initiation and acquisition of full developmental competence. Subsequently, from the new genome, in addition to mRNAs, a wide range of regulatory ncRNAs are also transcribed. Regulatory ncRNAs (non-coding RNAs) have profoundly influenced fields ranging from developmental biology to RNA-mediated non-Mendelian inheritance, exhibiting sequence-specific functions. To date, the database cataloging ncRNA is not exhaustive, but their high sequence diversity, length and low expression level can vary within the same genome depending on environmental conditions, making understanding their functions often ambiguous. Indeed, during transcription control, cellular RNA content varies continuously. This phenomenon is observed in genetically identical organisms studied—bacteria, flies, plants and mammals—due to changes in transcription rates, and therefore, it impacts cellular memory. Importantly, experimental data regarding the simple modification of RNAs levels by microinjection into fertilized mouse eggs suggest that they certainly play a driving role in establishing and transmitting newly formed expression information. The idea here is that, even in a stable genome, transcripts can vary rapidly and significantly in response to environmental changes, initiated by transcriptional variations in the genome, thus altering cellular memory. Full article

At the early developmental stage, embryos are susceptible to environmental factors, which modulate development trajectories. In our study, we examined how different incubation temperatures (35 °C, 37 °C, and 39 °C) in vitro during the first embryonic cleavage affect the morphology, cell division rate, and DNA methylation in two-, four-, and eight-cell embryos and the viability of these two-cell embryos transferred to recipient females. Embryos kept at 35 °C for the first 24 h after in vitro fertilization in two- and four-cell embryos at 37 °C showed enhanced variability in the size of blastomeres and DNA 5mC level among blastomeres, as compared to the groups kept at 37 °C and 39 °C. This was associated with the highest rate of embryo death in four- and eight-cell embryos and the highest viability of newborns. In contrast, incubation at 39 °C did not significantly impact developmental dynamics and viability in vitro but led to a notably higher rate of gestation failure compared to other groups. The indicators of the 37 °C group fell within an intermediate range. Therefore, we conclude that a decrease in temperature during zygotic genome activation (ZGA) highlights the adaptive potential of embryos during their initial cleavages, while an increase in temperature does not show clear effects on their fate. Full article

During embryonic development, zygotic genome activation (ZGA) is a critical event that determines the rational process and the fate of embryonic cells. The tricarboxylic acid cycle (TCA cycle) provides necessary reactants and energy for biological activities such as genome activation, chromatin opening, and epigenetic modifications during ZGA. Recent studies have shown that during ZGA, core enzymes associated with TCA briefly enter the nucleus and participate in initiating the ZGA process. However, the regulatory relationship between ZGA factors, such as Dux, Dppa2, and Dppa4, and the core enzymes of the TCA cycle remains unknown. In this study, we found that Dppa2 plays a key role in ZGA by directly determining the localization of TCA core enzymes, thereby affecting the early embryonic development. To further investigate the effect of Dppa2 on the localization of pyruvate dehydrogenase (PDH), we followed the establishment of an inducible Dppa2 transgenic mouse model. We found that the “chronoectopic” expression of Dppa2 prior to normal ZGA time could lead to the advanced nuclear localization of PDH. In summary, Dppa2 plays a key role in ZGA, directly determining the location of TCA core enzymes in early embryos. This study provides a theoretical basis for early embryonic development at the metabolic regulation level. Full article

Early embryonic development relies on intricately regulated gene expression, and miRNAs influence zygotic genome activation (ZGA), cleavage, and cell fate determination through post-transcriptional regulatory mechanisms. miR-192 is expressed in early pig embryos and participates in various reproductive processes. However, its role in pre-implantation pig embryo development remains poorly understood. In this study, we microinjected the miR-192 agonist (miR-192 agomir) into parthenogenetically activated pig embryos to evaluate its effects on early pig embryo development. Our findings indicate that compared to the control group (agomir NC), miR-192 agomir impairs the developmental capacity of parthenogenetic pig embryos to reach the 2-cell, 4-cell, and blastocyst stages. This impairment leads to imbalances in the oxidative–reductive system and abnormalities in mitochondrial function during the 4-cell stage, resulting in the significant accumulation of ROS, notable decreases in the expression of antioxidant enzymes CAT and SOD1 mRNA, reduction in mitochondrial membrane potential, and induction of apoptosis in pig blastocysts. Additionally, the overexpression of miR-192 inhibits the expression of its target genes YY1 and the pluripotency factor NANOG mRNA. In conclusion, this study reveals that the overexpression of miR-192 adversely affects early pig embryo development, providing new evidence for understanding the role miR-192 plays in reproduction. Full article

Zygotic genome activation (ZGA) is critical for early embryo development and is meticulously regulated by epigenetic modifications. H3K4me3 is a transcription-permissive histone mark preferentially found at promoters, but its distribution across genome features remains incompletely understood. In this study, we investigated the genome-wide enrichment of H3K4me3 during early embryo development and embryonic stem cells (ESCs) in both sheep and mice. We discovered that broad H3K4me3 domains were present in MII stage oocytes and were progressively diminished, while promoter H3K4me3 enrichment was increased and correlated with gene upregulation during ZGA in sheep. Additionally, we reported the dynamic distribution of H3K4me3 at the transposable elements (TEs) during early embryo development in both sheep and mice. Specifically, the H3K4me3 distribution of LINE1 and ERVL, two subsets of TEs, was associated with their expression during early embryo development in sheep. Furthermore, H3K4me3 enrichment in TEs was greatly increased during ZGA following Kdm5b knockdown, and the distribution of RNA polymerase II (Pol2) in TEs was also markedly increased in Kdm5b knockout ESCs in mice. These findings suggest that H3K4me3 plays important roles in regulating TE expression through interaction with RNA Pol2, providing valuable insights into the regulation of ZGA initiation and cell fate determination by H3K4me3. Full article

Zygotic genome activation (ZGA) is a pivotal event in mammalian embryogenesis, marking the transition from maternal to zygotic control of development. During the ZGA process that is characterized by the intricate cascade of gene expression, who tipped the first domino in a meticulously arranged sequence is a subject of paramount interest. Recently, Dux, Obox and Nr5a2 were identified as pioneer transcription factors that reside at the top of transcriptional hierarchy. Through co-option of retrotransposon elements as hubs for transcriptional activation, these pioneer transcription factors rewire the gene regulatory network, thus initiating ZGA. In this review, we provide a snapshot of the mechanisms underlying the functions of these pioneer transcription factors. We propose that ZGA is the starting point where the embryo’s own genome begins to influence development trajectory, therefore in-depth dissecting the functions of pioneer transcription factors during ZGA will form a cornerstone of our understanding for early embryonic development, which will pave the way for advancing our grasp of mammalian developmental biology and optimizing in vitro production (IVP) techniques. Full article

Commencing with sperm–egg fusion, the early stages of metazoan development include the cleavage and formation of blastula and gastrula. These early embryonic events play a crucial role in ontogeny and are accompanied by a dramatic remodeling of the gene network, particularly encompassing the maternal-to-zygotic transition. Nonetheless, the gene expression dynamics governing early embryogenesis remain unclear in most metazoan lineages. We conducted transcriptomic profiling on two types of gametes (oocytes and sperms) and early embryos (ranging from the four-cell to the gastrula stage) of an economically valuable flatfish–the Chinese tongue sole Cynoglossus semilaevis (Pleuronectiformes: Cynoglossidae). Comparative transcriptome analysis revealed that large-scale zygotic genome activation (ZGA) occurs in the blastula stage, aligning with previous findings in zebrafish. Through the comparison of the most abundant transcripts identified in each sample and the functional analysis of co-expression modules, we unveiled distinct functional enrichments across different gametes/developmental stages: actin- and immune-related functions in sperms; mitosis, transcription inhibition, and mitochondrial function in oocytes and in pre-ZGA embryos (four- to 1000-cell stage); and organ development in post-ZGA embryos (blastula and gastrula). These results provide insights into the intricate transcriptional regulation of early embryonic development in Cynoglossidae fish and expand our knowledge of developmental constraints in vertebrates. Full article

In vitro-fertilized (IVF) and parthenogenetically activated (PA) embryos, key to genetic engineering, face more developmental challenges than in vivo-developed embryos (IVV). We analyzed single-cell RNA-seq data from the oocyte to eight-cell stages in IVV, IVF, and PA porcine embryos, focusing on developmental differences during early zygotic genome activation (ZGA), a vital stage for embryonic development. (1) Our findings reveal that in vitro embryos (IVF and PA) exhibit more similar developmental trajectories compared to IVV embryos, with PA embryos showing the least gene diversity at each stage. (2) Significant differences in maternal mRNA, particularly affecting mRNA splicing, energy metabolism, and chromatin remodeling, were observed. Key genes like SMARCB1 (in vivo) and SIRT1 (in vitro) played major roles, with HDAC1 (in vivo) and EZH2 (in vitro) likely central in their complexes. (3) Across different types of embryos, there was minimal overlap in gene upregulation during ZGA, with IVV embryos demonstrating more pronounced upregulation. During minor ZGA, global epigenetic modification patterns diverged and expanded further. Specifically, in IVV, genes, especially those linked to H4 acetylation and H2 ubiquitination, were more actively regulated compared to PA embryos, which showed an increase in H3 methylation. Additionally, both types displayed a distinction in DNA methylation. During major ZGA, IVV distinctively upregulated genes related to mitochondrial regulation, ATP synthesis, and oxidative phosphorylation. (4) Furthermore, disparities in mRNA degradation-related genes between in vivo and in vitro embryos were more pronounced during major ZGA. In IVV, there was significant maternal mRNA degradation. Maternal genes regulating phosphatase activity and cell junctions, highly expressed in both in vivo and in vitro embryos, were degraded in IVV in a timely manner but not in in vitro embryos. (5) Our analysis also highlighted a higher expression of many mitochondrially encoded genes in in vitro embryos, yet their nucleosome occupancy and the ATP8 expression were notably higher in IVV. Full article

Mammalian fertilization initiates the reprogramming of oocytes and sperm, forming a totipotent zygote. During this intricate process, the zygotic genome undergoes a maternal-to-zygotic transition (MZT) and subsequent zygotic genome activation (ZGA), marking the initiation of transcriptional control and gene expression post-fertilization. Histone modifications are pivotal in shaping cellular identity and gene expression in many mammals. Recent advances in chromatin analysis have enabled detailed explorations of histone modifications during ZGA. This review delves into conserved and unique regulatory strategies, providing essential insights into the dynamic changes in histone modifications and their variants during ZGA in mammals. The objective is to explore recent advancements in leading mechanisms related to histone modifications governing this embryonic development phase in depth. These considerations will be useful for informing future therapeutic approaches that target epigenetic regulation in diverse biological contexts. It will also contribute to the extensive areas of evolutionary and developmental biology and possibly lay the foundation for future research and discussion on this seminal topic. Full article