RESUMO
Human fertility is suboptimal, partly due to error-prone divisions in early cleavage-stages that result in aneuploidy. Most human pre-implantation are mosaics of euploid and aneuploid cells, however, mosaic embryos with a low proportion of aneuploid cells have a similar likelihood of developing to term as fully euploid embryos. How embryos manage aneuploidy during development is poorly understood. This knowledge is crucial for improving fertility treatments and reducing developmental defects. To explore these mechanisms, we established a new mouse model of chromosome mosaicism to study the fate of aneuploid cells during pre-implantation development. We previously used the Mps1 inhibitor reversine to generate aneuploidy in embryos. Here, we found that treatment with the more specific Mps1 inhibitor AZ3146 induced chromosome segregation defects in pre-implantation embryos, similar to reversine. However, AZ3146-treated embryos showed a higher developmental potential than reversine-treated embryos. Unlike reversine-treated embryos, AZ3146-treated embryos exhibited transient upregulation of Hypoxia Inducible-Factor-1A (HIF1A) and lacked p53 upregulation. Pre-implantation embryos develop in a hypoxic environment in vivo, and hypoxia exposure in vitro reduced DNA damage in response to Mps1 inhibition and increased the proportion of euploid cells in the mosaic epiblast. Inhibiting HIF1A in mosaic embryos also decreased the proportion of aneuploid cells in mosaic embryos. Our work illuminates potential strategies to improve the developmental potential of mosaic embryos.
RESUMO
The next 50 years of developmental biology will illuminate exciting new discoveries but are also poised to provide solutions to important problems society faces. Ten scientists whose work intersects with developmental biology in various capacities tell us about their vision for the future.
Assuntos
Biologia do Desenvolvimento , Biologia do Desenvolvimento/tendências , Humanos , Células-Tronco/citologia , Animais , Pesquisa com Células-TroncoRESUMO
The mouse and human embryo gradually loses totipotency before diversifying into the inner cell mass (ICM, future organism) and trophectoderm (TE, future placenta). The transcription factors TFAP2C and TEAD4 with activated RHOA accelerate embryo polarization. Here we show that these factors also accelerate the loss of totipotency. TFAP2C and TEAD4 paradoxically promote and inhibit Hippo signaling before lineage diversification: they drive expression of multiple Hippo regulators while also promoting apical domain formation, which inactivates Hippo. Each factor activates TE specifiers in bipotent cells, while TFAP2C also activates specifiers of the ICM fate. Asymmetric segregation of the apical domain reconciles the opposing regulation of Hippo signaling into Hippo OFF and the TE fate, or Hippo ON and the ICM fate. We propose that the bistable switch established by TFAP2C and TEAD4 is exploited to trigger robust lineage diversification in the developing embryo.
Assuntos
Proteínas de Ligação a DNA , Fatores de Transcrição de Domínio TEA , Fator de Transcrição AP-2 , Fatores de Transcrição , Fator de Transcrição AP-2/metabolismo , Fator de Transcrição AP-2/genética , Animais , Fatores de Transcrição/metabolismo , Fatores de Transcrição/genética , Proteínas de Ligação a DNA/metabolismo , Proteínas de Ligação a DNA/genética , Camundongos , Humanos , Transdução de Sinais , Linhagem da Célula , Regulação da Expressão Gênica no Desenvolvimento , Proteínas Musculares/metabolismo , Proteínas Musculares/genética , Embrião de Mamíferos/metabolismo , Embrião de Mamíferos/citologia , Via de Sinalização Hippo , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Serina-Treonina Quinases/genética , Desenvolvimento Embrionário/genéticaRESUMO
Retrospective lineage reconstruction of humans predicts that dramatic clonal imbalances in the body can be traced to the 2-cell stage embryo. However, whether and how such clonal asymmetries arise in the embryo is unclear. Here, we performed prospective lineage tracing of human embryos using live imaging, non-invasive cell labeling, and computational predictions to determine the contribution of each 2-cell stage blastomere to the epiblast (body), hypoblast (yolk sac), and trophectoderm (placenta). We show that the majority of epiblast cells originate from only one blastomere of the 2-cell stage embryo. We observe that only one to three cells become internalized at the 8-to-16-cell stage transition. Moreover, these internalized cells are more frequently derived from the first cell to divide at the 2-cell stage. We propose that cell division dynamics and a cell internalization bottleneck in the early embryo establish asymmetry in the clonal composition of the future human body.
Assuntos
Blastômeros , Linhagem da Célula , Embrião de Mamíferos , Feminino , Humanos , Blastômeros/citologia , Blastômeros/metabolismo , Divisão Celular , Embrião de Mamíferos/citologia , Embrião de Mamíferos/metabolismo , Desenvolvimento Embrionário , Camadas Germinativas/citologia , Camadas Germinativas/metabolismo , Masculino , Animais , CamundongosRESUMO
The blueprint of the mammalian body plan is laid out during gastrulation, when a trilaminar embryo is formed. This process entails a burst of proliferation, the ingression of embryonic epiblast cells at the primitive streak, and their priming toward primitive streak fates. How these different events are coordinated remains unknown. Here, we developed and characterized a 3D culture of self-renewing mouse embryonic cells that captures the main transcriptional and architectural features of the early gastrulating mouse epiblast. Using this system in combination with microfabrication and in vivo experiments, we found that proliferation-induced crowding triggers delamination of cells that express high levels of the apical polarity protein aPKC. Upon delamination, cells become more sensitive to Wnt signaling and upregulate the expression of primitive streak markers such as Brachyury. This mechanistic coupling between ingression and differentiation ensures that the right cell types become specified at the right place during embryonic development.
Assuntos
Diferenciação Celular , Gastrulação , Camadas Germinativas , Animais , Camundongos , Camadas Germinativas/citologia , Camadas Germinativas/metabolismo , Proteínas com Domínio T/metabolismo , Proteínas com Domínio T/genética , Células-Tronco Pluripotentes/citologia , Células-Tronco Pluripotentes/metabolismo , Linha Primitiva/citologia , Linha Primitiva/metabolismo , Proteínas Fetais/metabolismo , Proteínas Fetais/genética , Via de Sinalização Wnt , Proliferação de Células , Regulação da Expressão Gênica no Desenvolvimento , Embrião de Mamíferos/citologia , Embrião de Mamíferos/metabolismoRESUMO
Development requires coordinated interactions between the epiblast, which generates the embryo proper; the trophectoderm, which generates the placenta; and the hypoblast, which forms both the anterior signalling centre and the yolk sac. These interactions remain poorly understood in human embryogenesis because mechanistic studies have only recently become possible. Here we examine signalling interactions post-implantation using human embryos and stem cell models of the epiblast and hypoblast. We find anterior hypoblast specification is NODAL dependent, as in the mouse. However, while BMP inhibits anterior signalling centre specification in the mouse, it is essential for its maintenance in human. We also find contrasting requirements for BMP in the naive pre-implantation epiblast of mouse and human embryos. Finally, we show that NOTCH signalling is important for human epiblast survival. Our findings of conserved and species-specific factors that drive these early stages of embryonic development highlight the strengths of comparative species studies.