Search

Stem cell-based mammalian embryo models facilitate the discovery of developmental mechanisms because they are more amenable to genetic and epigenetic perturbations than natural embryos. Here, we highlight exciting recent advances that have yielded a plethora of models of embryonic development. Imperfections in these models highlight gaps in our current understanding and outline future research directions, ushering in an exciting new era for embryology., Competing Interests: Declaration of Competing Interest The authors are inventors on the following patents: 1. Patent applicant: Caltech. Inventors: Magdalena Zernicka-Goetz, Berna Sozen, and Victoria Jorgensen. Application number: 17/692,790. Specific aspect of the paper covered in patent application: Reconstructing human early embryogenesis in vitro with pluripotent stem cells. 2. Patent applicant: Caltech and Cambridge Enterprise Limited. Inventors: Magdalena Zernicka-Goetz, Gianluca Amadei, and Charlotte Handford. Application number: 63/397,630. Specific aspect of the paper covered in patent application: Synthetic embryos. 3. Patent Applicant: Caltech and Cambridge Enterprise Limited. Inventors: Magdalena Zernicka-Goetz, Bailey Weatherbee, and Carlos Gantner. Application number: 63/403,684. Specific aspect of the paper covered in patent application: Stem cell-derived model of the human embryo., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

In this chapter, we detail the experimental protocol leading to the generation of stem cell-based mouse embryo-like structures termed "ETiX-embryoids." ETiX-embryoids are formed from combined embryonic stem cells, trophoblast stem cells, and embryonic stem cells transiently induced to express Gata4. Cells are seeded into AggreWell dishes where they form aggregates that develop to resemble post-implantation mouse embryos following 4 days of culture. ETiX-embryoids establish an anterior signaling center and undergo gastrulation over the following 2 days. By day 7, ETiX-embryoids undergo neurulation and form an anterior-posterior axis with head folds at one end and a tail bud on the other. On day 8, they develop a brain and form a heart-like structure and a gut tube., (© 2023. Springer Science+Business Media, LLC.)

Droplet microfluidic methods have massively increased the throughput of single-cell sequencing campaigns. The benefit of scale-up is, however, accompanied by increased background noise when processing challenging samples and the overall RNA capture efficiency is lower. These drawbacks stem from the lack of strategies to enrich for high-quality material or specific cell types at the moment of cell encapsulation and the absence of implementable multi-step enzymatic processes that increase capture. Here we alleviate both bottlenecks using fluorescence-activated droplet sorting to enrich for droplets that contain single viable cells, intact nuclei, fixed cells or target cell types and use reagent addition to droplets by picoinjection to perform multi-step lysis and reverse transcription. Our methodology increases gene detection rates fivefold, while reducing background noise by up to half. We harness these properties to deliver a high-quality molecular atlas of mouse brain development, despite starting with highly damaged input material, and provide an atlas of nascent RNA transcription during mouse organogenesis. Our method is broadly applicable to other droplet-based workflows to deliver sensitive and accurate single-cell profiling at a reduced cost., (© 2023. Springer Nature Limited.)

Embryonic stem (ES) cells can undergo many aspects of mammalian embryogenesis in vitro 1-5 , but their developmental potential is substantially extended by interactions with extraembryonic stem cells, including trophoblast stem (TS) cells, extraembryonic endoderm stem (XEN) cells and inducible XEN (iXEN) cells 6-11 . Here we assembled stem cell-derived embryos in vitro from mouse ES cells, TS cells and iXEN cells and showed that they recapitulate the development of whole natural mouse embryo in utero up to day 8.5 post-fertilization. Our embryo model displays headfolds with defined forebrain and midbrain regions and develops a beating heart-like structure, a trunk comprising a neural tube and somites, a tail bud containing neuromesodermal progenitors, a gut tube, and primordial germ cells. This complete embryo model develops within an extraembryonic yolk sac that initiates blood island development. Notably, we demonstrate that the neurulating embryo model assembled from Pax6-knockout ES cells aggregated with wild-type TS cells and iXEN cells recapitulates the ventral domain expansion of the neural tube that occurs in natural, ubiquitous Pax6-knockout embryos. Thus, these complete embryoids are a powerful in vitro model for dissecting the roles of diverse cell lineages and genes in development. Our results demonstrate the self-organization ability of ES cells and two types of extraembryonic stem cells to reconstitute mammalian development through and beyond gastrulation to neurulation and early organogenesis., (© 2022. The Author(s).)

Human embryogenesis entails complex signalling interactions between embryonic and extra-embryonic cells. However, how extra-embryonic cells direct morphogenesis within the human embryo remains largely unknown due to a lack of relevant stem cell models. Here, we have established conditions to differentiate human pluripotent stem cells (hPSCs) into yolk sac-like cells (YSLCs) that resemble the post-implantation human hypoblast molecularly and functionally. YSLCs induce the expression of pluripotency and anterior ectoderm markers in human embryonic stem cells (hESCs) at the expense of mesoderm and endoderm markers. This activity is mediated by the release of BMP and WNT signalling pathway inhibitors, and, therefore, resembles the functioning of the anterior visceral endoderm signalling centre of the mouse embryo, which establishes the anterior-posterior axis. Our results implicate the yolk sac in epiblast cell fate specification in the human embryo and propose YSLCs as a tool for studying post-implantation human embryo development in vitro., Competing Interests: KM, BW, VS, CH, GH, TC, LP, SB, LV, MS, MZ No competing interests declared, (© 2021, Mackinlay et al.)

Embryo polarization is critical for mouse development; however, neither the regulatory clock nor the molecular trigger that it activates is known. Here, we show that the embryo polarization clock reflects the onset of zygotic genome activation, and we identify three factors required to trigger polarization. Advancing the timing of transcription factor AP-2 gamma (Tfap2c) and TEA domain transcription factor 4 (Tead4) expression in the presence of activated Ras homolog family member A (RhoA) induces precocious polarization as well as subsequent cell fate specification and morphogenesis. Tfap2c and Tead4 induce expression of actin regulators that control the recruitment of apical proteins on the membrane, whereas RhoA regulates their lateral mobility, allowing the emergence of the apical domain. Thus, Tfap2c, Tead4, and RhoA are regulators for the onset of polarization and cell fate segregation in the mouse., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Milk in its natural form has a high food value, since it is comprised of a wide variety of nutrients which are essential for proper growth and maintenance of the human body. In recent decades, there has been an upsurge in milk consumption worldwide, especially in developing countries, and it is now forming a significant part of the diet for a high proportion of the global population. As a result of the increased demand, in addition to the growth in competition in the dairy market and the increasing complexity of the supply chain, some unscrupulous producers are indulging in milk fraud. This malpractice has become a common problem in the developing countries, which lack strict vigilance by food safety authorities. Milk is often subjected to fraud (by means of adulteration) for financial gain, but it can also be adulterated due to ill-informed attempts to improve hygiene conditions. Water is the most common adulterant used, which decreases the nutritional value of milk. If the water is contaminated, for example, with chemicals or pathogens, this poses a serious health risk for consumers. To the diluted milk, inferior cheaper materials may be added such as reconstituted milk powder, urea, and cane sugar, even more hazardous chemicals including melamine, formalin, caustic soda, and detergents. These additions have the potential to cause serious health-related problems. This review aims to investigate the impacts of milk fraud on nutrition and food safety, and it points out the potential adverse human health effects associated with the consumption of adulterated milk., (© 2015 Institute of Food Technologists®.)

Pesticide use is important in agriculture to protect crops and improve productivity. However, pesticides have the potential to cause adverse human health or environmental effects, depending on exposure levels. This review examines existing pesticide legislation worldwide, focusing on the level of harmonization and impacts of differing legislation on food safety and trade. Pesticide legislation varies greatly worldwide, because countries have different requirements, guidelines, and legal limits for plant protection. Developed nations have more stringent regulations than developing countries, which lack the resources and expertise to adequately implement and enforce legislation. Global differences in pesticide legislation act as a technical barrier to trade. International parties such as the European Union (EU), Codex Alimentarius Commission (Codex), and North American Free Trade Agreement (NAFTA) have attempted to harmonize pesticide legislation by providing maximum residue limits (MRLs), but globally these limits remain variable. Globally harmonized pesticide standards would serve to increase productivity, profits, and trade and also enhance the ability to protect public health and the environment., (© 2015 SETAC.)

The metabotropic glutamate receptor 5 (mGlu5) and N-methyl-D-aspartate (NMDA) receptor are critical for processes underlying synaptic plasticity, such as long-term potentiation. mGlu5 signaling increases neuronal excitability and potentiates NMDA receptor currents in the amygdala and the hippocampus. The present study examined the involvement of mGlu5 in the acquisition and consolidation of conditioned fear to a tone and context in mice, and explored the functional relationship between mGlu5 and NMDA receptors in this regard. Experiment 1 showed that systemic administration of the mGlu5 negative allosteric modulator 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine (MTEP) prior to conditioning significantly attenuated cue-elicited freezing during fear conditioning, which suggests that mGlu5 is necessary for the formation of a tone-shock association. This effect was dose-related (Experiment 2) and not due to any effects of MTEP on shock sensitivity or state-dependency (Experiment 3). Post-conditioning injection of MTEP had no effects (Experiment 4). Although post-conditioning injection of the NMDA receptor partial agonist D-cycloserine (DCS) alone facilitated consolidation of conditioned fear (Experiment 6), it was not able to rescue the acquisition deficit caused by MTEP (Experiment 5). Taken together, these findings indicate a crucial role for mGlu5 signaling in acquisition and NMDA receptor signaling in consolidation of conditioned fear.