Interspecies blastocyst complementation holds great potential to address the global shortage of transplantable organs by growing human organs in animals. However, a major challenge in this approach is the limited chimerism of human cells in evolutionarily distant animal hosts due to various xenogeneic barriers. Here, we reveal that human pluripotent stem cells (PSCs) struggle to adhere to animal PSCs. To overcome this barrier, we developed a synthetic biology strategy that leverages nanobody-antigen interactions to enhance interspecies cell adhesion. We engineered cells to express nanobodies and their corresponding antigens on their outer membranes, significantly improving adhesion between different species\' PSCs during in vitro assays and increasing the chimerism of human PSCs in mouse embryos. Studying and manipulating interspecies pluripotent cell adhesion will provide valuable insights into cell interaction dynamics during chimera formation and early embryogenesis.

The sixth SY-Stem Symposium, jointly organized by the Research Institute of Molecular Pathology and the Institute of Molecular Biotechnology took place in Vienna in March 2024. Again, aspiring new group leaders were given a stage to present their work and vision of their labs. To round up the excellent program, the scientific organizers included renowned keynote speakers. Here, we provide a summary of the talks covering topics such as early embryogenesis, nervous system development and disease, regeneration and the latest technologies.

Constitutive heterochromatin is essential for transcriptional silencing and genome integrity. The establishment of constitutive heterochromatin in early embryos and its role in early fruitfly development are unknown. Lysine 9 trimethylation of histone H3 (H3K9me3) and recruitment of its epigenetic reader, heterochromatin protein 1a (HP1a), are hallmarks of constitutive heterochromatin. Here, we show that H3K9me3 is transmitted from the maternal germline to the next generation. Maternally inherited H3K9me3, and the histone methyltransferases (HMT) depositing it, are required for the organization of constitutive heterochromatin: early embryos lacking H3K9 methylation display de-condensation of pericentromeric regions, centromere-centromere de-clustering, mitotic defects, and nuclear shape irregularities, resulting in embryo lethality. Unexpectedly, quantitative CUT&Tag and 4D microscopy measurements of HP1a coupled with biophysical modeling revealed that H3K9me2/3 is largely dispensable for HP1a recruitment. Instead, the main function of H3K9me2/3 at this developmental stage is to drive HP1a clustering and subsequent heterochromatin compaction. Our results show that HP1a binding to constitutive heterochromatin in the absence of H3K9me2/3 is not sufficient to promote proper embryo development and heterochromatin formation. The loss of H3K9 HMTs and H3K9 methylation alters genome organization and hinders embryonic development.

In recent years, the pursuit of inducing the trophoblast stem cell (TSC) state has gained prominence as a compelling research objective, illuminating the establishment of the trophoblast lineage and unlocking insights into early embryogenesis. In this review, we examine how advancements in diverse technologies, including in vivo time course transcriptomics, cellular reprogramming to TSC state, chemical induction of totipotent stem-cell-like state, and stem-cell-based embryo-like structures, have enriched our insights into the intricate molecular mechanisms and signaling pathways that define the mouse and human trophectoderm/TSC states. We delve into disparities between mouse and human trophectoderm/TSC fate establishment, with a special emphasis on the intriguing role of pluripotency in this context. Additionally, we re-evaluate recent findings concerning the potential of totipotent-stem-like cells and embryo-like structures to fully manifest the trophectoderm/trophoblast lineage\'s capabilities. Lastly, we briefly discuss the potential applications of induced TSCs in pregnancy-related disease modeling.

Phosphatidylinositol 4-kinase beta (PI4KB) is a member of the PI4K family, which is mainly enriched and functions in the Golgi apparatus. The kinase domain of PI4KB catalyzes the phosphorylation of phosphatidylinositol to form phosphatidylinositol 4-phosphate, a process that regulates various sub-cellular events, such as non-vesicular cholesterol and ceramide transport, protein glycosylation, and vesicle transport, as well as cytoplasmic division. In this study, a strain of PI4KB knockout mouse, immunofluorescence, reverse transcription polymerase chain reaction and microinjection were used to characterize the cytological location and biological function of PI4KB in the mouse embryos. we found that knocking down Pi4kb in mouse embryos resulted in embryonic lethality at around embryonic day (E) 7.5. Additionally, we observed dramatic fluctuations in PI4KB expression during the development of preimplantation embryos, with high expression in the 4-cell and morula stages. PI4KB colocalized with the Golgi marker protein TGN46 in the perinuclear and cytoplasmic regions in early blastomeres. Postimplantation, PI4KB was highly expressed in the epiblast of E7.5 embryos. Treatment of embryos with PI4KB inhibitors was found to inhibit the development of the morula into a blastocyst and the normal progression of cytoplasmic division during the formation of a 4-cell embryo. These findings suggest that PI4KB plays an important role in mouse embryogenesis by regulating various intracellular vital functions of embryonic cells.

Protein O-GlcNAcylation is a monosaccharide post-translational modification maintained by two evolutionarily conserved enzymes, O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). Mutations in human OGT have recently been associated with neurodevelopmental disorders, although the mechanisms linking O-GlcNAc homeostasis to neurodevelopment are not understood. Here, we investigate the effects of perturbing protein O-GlcNAcylation using transgenic Drosophila lines that overexpress a highly active OGA. We reveal that temporal reduction of protein O-GlcNAcylation in early embryos leads to reduced brain size and olfactory learning in adult Drosophila. Downregulation of O-GlcNAcylation induced by the exogenous OGA activity promotes nuclear foci formation of Polycomb-group protein Polyhomeotic and the accumulation of excess K27 trimethylation of histone H3 (H3K27me3) at the mid-blastula transition. These changes interfere with the zygotic expression of several neurodevelopmental genes, particularly shortgastrulation (sog), a component of an evolutionarily conserved sog-Decapentaplegic (Dpp) signaling system required for neuroectoderm specification. Our findings highlight the importance of early embryonic O-GlcNAcylation homeostasis for the fidelity of facultative heterochromatin redeployment and initial cell fate commitment of neuronal lineages, suggesting a possible mechanism underpinning OGT-associated intellectual disability.

Determination (inducing) factors, the extracellular matrix, signaling pathways, transcription factors and genes interact in pattern formation and neural induction. Genes can either be activated or repressed. The animalvegetal and dorso-ventral polarities are determined in very early developmental stages. Factors of the TGF-β superfamily in a graded distribution are involved in the determination of endoderm, mesoderm and ectoderm. The differentiation of mesoderm also depends on the animal ectoderm. Neural inducing factors have been partially purified.

During mammalian oocyte-to-embryo transition, before zygotic genome activation, the transcription in oocytes and embryos is silenced, so the post-transcriptional regulation of mRNA plays an essential role in this process. Poly(A) tail is an important post-transcriptional modification that affects mRNA metabolism and translation efficiency. With the development of sequencing technology and analysis tools, especially the methods based on third-generation sequencing technology, the length and composition of poly(A) tails can be accurately measured, greatly expanding our understanding of poly(A) tails in mammalian early embryonic development. This review focuses on the achievements of poly(A) tail sequencing methods and the research progress of poly(A) tail in regulating oocyte-to-embryo transition, discussing the future applications for the investigation of mammalian early embryonic development and infertility related diseases.
在哺乳动物卵子向胚胎转变过程中，卵子和胚胎中的转录在合子基因组激活之前都是沉默的，因此mRNA转录后修饰在此过程发挥着重要的作用。poly(A)尾巴是影响mRNA命运和翻译效率的一种重要的转录后修饰。随着测序技术和分析工具的进步，尤其是三代测序技术的发展，poly(A)尾的长度和组成能够被精确测量，极大地拓展了人们对于poly(A)尾在哺乳动物早期胚胎发育过程中的认识。本文对poly(A)尾研究方法的发展及其在卵子向胚胎转变中的研究进展进行评述，以期为哺乳动物早期胚胎发育和不孕不育相关疾病的研究带来新的思路。.

Mammalian embryogenesis begins with a totipotent zygote. Blastocyst-like structures can be captured by aggregated cells with extended pluripotent properties in a three-dimensional (3D) culture system. However, the efficiency of generating blastoids is low, and it remains unclear whether other reported totipotent-like stem cells retain a similar capacity. In this study, we demonstrated that spliceosomal repression-induced totipotent blastomere-like cells (TBLCs) form blastocyst-like structures within around 80% of all microwells. In addition, we generated blastoids initiating from a single TBLC. TBLC-blastoids express specific markers of constituent cell lineages of a blastocyst and resemble blastocyst in cell-lineage allocation. Moreover, single-cell RNA sequencing revealed that TBLC-blastoids share a similar transcriptional profile to natural embryos, albeit composed of fewer primitive endoderm-like cells. Furthermore, TBLC-blastoids can develop beyond the implantation stage in vitro and induce decidualization in vivo. In summary, our findings provided an alternative cell type to efficiently generate blastoids for the study of early mouse embryogenesis.

It is essential to understand and manage environmental factors for good quail production and welfare. One of the most important environmental stressors that hinder quail productivity is heat stress. This study aimed to evaluate the impact of spraying Japanese quail (Coturnix coturnix japonica) eggs with betaine after exposure to short-term high temperature during early embryogenesis on pre and post-hatch performance of quail. A total of 750 eggs were equally divided into two groups. Eggs in the first group were incubated at normal incubation temperature (37.5 °C/NIT), while those in the second group were incubated at high incubation temperature (39.0 °C/HIT) for 3 h daily from day 4-6 of incubation. Eggs in both groups were subjected to five treatments, NC (negative control), PC sprayed distilled water (positive control), while B0.5, B1, and B2 treatments were sprayed with distilled water supplemented with 500, 1000, and 2000 mg betaine/L, respectively. The chick weight at hatch, slaughter weight, and first egg weight was significantly impaired by the HIT treatment. The HIT group revealed a significant increase in cloacal temperature, H/L ratio, liver enzymes, triglyceride, and cholesterol and a significant decrease in hatchability, T3 hormone, and blood protein levels than the NIT group. Regarding betaine effects, the embryonic mortality rates, hatchability, hatched chick weight, and oviduct percentage in groups treated with 1000 or 2000 mg betaine/L were significantly improved compared with the control. Also, spraying betaine at 1000 or 2000 mg/L significantly increased blood protein and triiodothyronine (T3) hormone levels and significantly decrease liver enzyme levels and total feed consumption compared with the untreated group. The right/total ventricle ratio (RV/TV) of quail in HIT group was significantly increased, while betaine treatment significantly decreased this ratio. Considering these results, it is strongly suggested that spraying of betaine on eggs at 2000 mg/L optimizes Japanese quail performance.