Pluripotent mouse embryonic stem cells (ESCs) can differentiate to all germ layers and serve as an in vitro model of embryonic development. To better understand the differentiation paths traversed by ESCs committing to different lineages, we track individual differentiating ESCs by timelapse imaging followed by multiplexed high-dimensional Imaging Mass Cytometry (IMC) protein quantification. This links continuous live single-cell molecular NANOG and cellular dynamics quantification over 5-6 generations to protein expression of 37 different molecular regulators in the same single cells at the observation endpoints. Using this unique data set including kinship history and live lineage marker detection, we show that NANOG downregulation occurs generations prior to, but is not sufficient for neuroectoderm marker Sox1 upregulation. We identify a developmental cell type co-expressing both the canonical Sox1 neuroectoderm and FoxA2 endoderm markers in vitro and confirm the presence of such a population in the post-implantation embryo. RNASeq reveals cells co-expressing SOX1 and FOXA2 to have a unique cell state characterized by expression of both endoderm as well as neuroectoderm genes suggesting lineage potential towards both germ layers.

miR-31 is a highly conserved microRNA that plays crucial roles in cell proliferation, migration and differentiation. We discovered that miR-31 and some of its validated targets are enriched on the mitotic spindle of the dividing sea urchin embryo and mammalian cells. Using the sea urchin embryo, we found that miR-31 inhibition led to developmental delay correlated with increased cytoskeletal and chromosomal defects. We identified miR-31 to directly suppress several actin remodeling transcripts, including β-actin, Gelsolin, Rab35 and Fascin. De novo translation of Fascin occurs at the mitotic spindle of sea urchin embryos and mammalian cells. Importantly, miR-31 inhibition leads to a significant a increase of newly translated Fascin at the spindle of dividing sea urchin embryos. Forced ectopic localization of Fascin transcripts to the cell membrane and translation led to significant developmental and chromosomal segregation defects, highlighting the importance of the regulation of local translation by miR-31 at the mitotic spindle to ensure proper cell division. Furthermore, miR-31-mediated post-transcriptional regulation at the mitotic spindle may be an evolutionarily conserved regulatory paradigm of mitosis.

miR-31, an evolutionarily conserved microRNA, has been studied in different contexts, such as myogenesis, skeletogenesis and cancer; however, its role in post-transcriptional regulation during development is still unclear. In a new study, Jia Song and colleagues find that miR-31 regulates local translation of cytoskeletal remodelling transcripts at the mitotic spindle to ensure proper cell division during sea urchin embryogenesis. To find out more about the story behind the paper, we caught up with first author Carolyn Remsburg and Jia Song, Associate Professor at the University of Delaware, USA.

We point out the issue of differential diagnosis regarding the finding of ectopically localised thymic tissue (a thymic cyst) in the neck. Thymic tissue can be found anywhere along its developmental tract of descent, from the angle of the mandible to the upper mediastinum. Disruption of the thymic descent can result in ectopically/abnormally localised islets of accessory thymic tissue, which may undergo cystic changes, as described in a case report by Sun et al. This anatomical variation of the thymus may be clinically misinterpreted as a neoplasm or other congenital anomalies as a branchial cyst, lymphatic malformation or cystic hygroma. The present editorial focuses on the challenge of establishing a diagnosis of ectopically localised tissue of thymus often presented as a lateral cervical mass, especially in the case of cystic variation/degeneration of this thymic tissue. We summarise hypotheses on the origin of such congenital cervical thymic cysts from the point of view of evolutionary history and embryology. We also discuss lesser-known facts about the anatomy, histopathology and developmental biology of the thymus as one of the most enigmatic organs in the human body.

Mouse (Mus musculus) models have been heavily utilized in developmental biology research to understand mammalian embryonic development, as mice share many genetic, physiological, and developmental characteristics with humans. New explorations into the integration of temporal (stage-specific) and transcriptional (tissue-specific) data have expanded our knowledge of mouse embryo tissue-specific gene functions. To better understand the substantial impact of synonymous mutational variations in the cell-state-specific transcriptome on a tissue\'s codon and codon pair usage landscape, we have established a novel resource-Mouse Embryo Codon and Codon Pair Usage Tables (Mouse Embryo CoCoPUTs). This webpage not only offers codon and codon pair usage, but also GC, dinucleotide, and junction dinucleotide usage, encompassing four strains, 15 murine embryonic tissue groups, 18 Theiler stages, and 26 embryonic days. Here, we leverage Mouse Embryo CoCoPUTs and employ the use of heatmaps to depict usage changes over time and a comparison to human usage for each strain and embryonic time point, highlighting unique differences and similarities. The usage similarities found between mouse and human central nervous system data highlight the translation for projects leveraging mouse models. Data for this analysis can be directly retrieved from Mouse Embryo CoCoPUTs. This cutting-edge resource plays a crucial role in deciphering the complex interplay between usage patterns and embryonic development, offering valuable insights into variation across diverse tissues, strains, and stages. Its applications extend across multiple domains, with notable advantages for biotherapeutic development, where optimizing codon usage can enhance protein expression; one can compare strains, tissues, and mouse embryonic stages in one query. Additionally, Mouse Embryo CoCoPUTs holds great potential in the field of tissue-specific genetic engineering, providing insights for tailoring gene expression to specific tissues for targeted interventions. Furthermore, this resource may enhance our understanding of the nuanced connections between usage biases and tissue-specific gene function, contributing to the development of more accurate predictive models for genetic disorders.

Trogocytosis is the intercellular transfer of membrane and membrane-associated proteins between cells. Trogocytosis is an underappreciated phenomenon that has historically routinely been dismissed as an artefact. With a greater understanding of the process and the implications it has on biological systems, trogocytosis has the potential to become a paradigm changer. The presence on a cell of molecules they don\'t endogenously express can alter the biological activity of the cell and could also lead to the acquisition of new functions. To better appreciate this phenomenon, it is important to understand how these intercellular membrane exchanges influence the function and activity of the donor and the recipient cells. In this chapter, we will examine how the molecules acquired by trogocytosis influence the biology of a variety of systems including mammalian fertilization, treatment of hemolytic disease of the newborn, viral and parasitic infections, cancer immunotherapy, and immune modulation.

Riboflavin deficiency (RD) induces liver damage, abnormal embryonic development, and high mortality. We hypothesized that the phenotype could be rescued by inhibiting ER stress. The objectives of the present study were to investigate the underlying molecular mechanisms of RD-induced embryonic defects using in vitro and in vivo models. Primary duck embryonic hepatocytes were treated with an ER stress inhibitor (4-PBA) or transfected with CHOP siRNA, and cultured in RD medium and riboflavin-sufficient (CON) medium for 8 days. Laying ducks (n = 20 cages/diet, 1 bird/cage) were fed an RD diet or CON diet for 14 wk, and the eggs were collected for hatching. At day 7 of incubation, the fertilized RD eggs were injected with or without 4-PBA into the yolk. RD decreased cell number and cell viability compared to the CON group, induced oxidative stress and apoptosis in primary duck embryonic hepatocytes. However, after being treated with an ER stress inhibitor (4-PBA) or transfected with CHOP siRNA, the apoptosis rate in RD hepatocytes decreased by 60.6% and 86.1%, respectively, being equal to the CON. These results indicated that RD-induced hepatocyte apoptosis is mediated by ER stress and the CHOP pathway. In vivo, RD embryos showed low hatchability, abnormal development, liver damage, ER stress, and apoptosis compared to the CON group. However, 4-PBA administration, as a model of ER stress inhibition, substantially restored embryonic development and alleviated liver damage in the RD group, including ER stress and apoptosis. Notably, hatchability in the RD group increased from 21.7% to 72.7% after 4-PBA treatment, though it remained less than the CON group (87.7%). These results implicated ER stress-CHOP-apoptosis pathway as molecular mechanisms underlying RD-induced abnormal embryonic development and death, this target with potential for therapy or intervention.

Pre-implantation embryonic development occurs in the oviduct during the first few days of pregnancy. The presence of oviductal extracellular vesicles (oEVs, also called oviductosomes) is crucial for pre-implantation embryonic development in vivo as oEVs often contain molecular transmitters such as proteins. Therefore, evaluating oEV cargo during early pregnancy could provide insights into factors required for proper early embryonic development that are missing in the current in vitro embryo culture setting. In this study, we isolated oEVs from the oviductal fluid at estrus and different stages of early embryonic development. The 2306-3066 proteins in oEVs identified at the different time points revealed 58-60 common EV markers identified in exosome databases. Oviductal extracellular vesicle proteins from pregnant samples significantly differed from those in non-pregnant samples. In addition, superovulation changes the protein contents in oEVs compared to natural ovulation at estrus. Importantly, we have identified that embryo-protectant proteins such as high-mobility protein group B1 and serine (or cysteine) peptidase inhibitor were only enriched in the presence of embryos. We also visualized the physical interaction of EVs and the zona pellucida of 4- to 8-cell stage embryos using transmission electron microscopy as well as in vivo live imaging of epithelial cell-derived GFP-tagged CD9 mouse model. All protein data in this study are readily available to the scientific community in a searchable format at https://genes.winuthayanon.com/winuthayanon/oviduct_ev_proteins/. In conclusion, we identified oEVs proteins that could be tested to determine whether they can improve embryonic developmental outcomes in vivo and in vitro setting.

Anthropogenically induced changes to the natural world are increasingly exposing organisms to stimuli and stress beyond that to which they are adapted. In aquatic systems, it is thought that certain life stages are more vulnerable than others, with embryos being flagged as highly susceptible to environmental stressors. Interestingly, evidence from across a wide range of taxa suggests that aquatic embryos can hatch prematurely, potentially as an adaptive response to external stressors, despite the potential for individual costs linked with underdeveloped behavioural and/or physiological functions. However, surprisingly little research has investigated the prevalence, causes and consequences of premature hatching, and no compilation of the literature exists. Here, we review what is known about premature hatching in aquatic embryos and discuss how this phenomenon is likely to become exacerbated with anthropogenically induced global change. Specifically, we (1) review the mechanisms of hatching, including triggers for premature hatching in experimental and natural systems; (2) discuss the potential implications of premature hatching at different levels of biological organisation from individuals to ecosystems; and (3) outline knowledge gaps and future research directions for understanding the drivers and consequences of premature hatching. We found evidence that aquatic embryos can hatch prematurely in response to a broad range of abiotic (i.e. temperature, oxygen, toxicants, light, pH, salinity) and biotic (i.e. predators, pathogens) stressors. We also provide empirical evidence that premature hatching appears to be a common response to rapid thermal ramping across fish species. We argue that premature hatching represents a fascinating yet untapped area of study, and the phenomenon may provide some additional resilience to aquatic communities in the face of ongoing global change.

Assessing fertilized human embryos is crucial for in vitro fertilization, a task being revolutionized by artificial intelligence. Existing models used for embryo quality assessment and ploidy detection could be significantly improved by effectively utilizing time-lapse imaging to identify critical developmental time points for maximizing prediction accuracy. Addressing this, we develop and compare various embryo ploidy status prediction models across distinct embryo development stages. We present BELA, a state-of-the-art ploidy prediction model that surpasses previous image- and video-based models without necessitating input from embryologists. BELA uses multitask learning to predict quality scores that are thereafter used to predict ploidy status. By achieving an area under the receiver operating characteristic curve of 0.76 for discriminating between euploidy and aneuploidy embryos on the Weill Cornell dataset, BELA matches the performance of models trained on embryologists\' manual scores. While not a replacement for preimplantation genetic testing for aneuploidy, BELA exemplifies how such models can streamline the embryo evaluation process.