Predictive molecular features of developmental competence in mouse embryos bisected at the 2-cell stage

从2011年到2014年，我们在MPI和CeRA的两个小组联合起来，在辅助生殖技术（ART）的小鼠模型中研究培养条件对胚胎质量的影响。出乎意料的是，在临床使用的培养基中裂解后，受精的小鼠卵母细胞呈现出不同的发育轨迹，其特征在于胚泡的培养基特异性比例和基因表达的培养基特异性模式。DFG的这一更新申请促进了对体外条件下胚胎发育的新理解，这与估计ART程序的任何潜在风险有关，也为预测ART程序的结果和最大限度地减少卵母细胞的损失以及ART周期的数量提供了线索。我们的重点是培养基，因为它们可以在实验生物学的其他领域重新编程细胞的命运;那么，在ART中呢？鉴于人类胚胎的异质性，到目前为止，很难区分受精后培养环境的贡献与配子的内在质量（自然与培育）。虽然在小鼠中模拟这种异质性是不切实际的，但几乎完全消除它是可行的。利用小鼠2-细胞期胚胎二等分的方法，我们可以在给定的环境（培养基）的条件下，追求使2-细胞胚胎成为发育或非发育的分子性状：二等分后，一个细胞提供分子信息，该分子信息可以与另一个细胞的发育信息相匹配。此外，我们可以使用两个同卵双胞胎来测试两种不同的培养基是否会从相同的基因型中引出不同的发育轨迹。从生物信息学比较的转录组的双胞胎胚胎生长在不同的媒体，我们将了解环境的信号分子转导（胚胎质量的外在调节剂，如信号通路）。通过比较不同培养基中发育正常的卵裂球与发育不正常的卵裂球的转录组，我们将了解对环境线索不太敏感的基因的核心。我们的工作可以将胚胎研究向前推进，因为孪生模型将应用于ART培养基的研究，从而发现新的终点，为哺乳动物发育的最早阶段提供洞察力。与我们之前的DFG项目一样，本次更新申请将为着床前发育的关键步骤提供科学证据。此外，它应该有助于理解卵母细胞是否更适合在受精后但胚胎基因组激活前在某种培养基中培养，而不是在另一种培养基中培养。我们MPI和CeRA之间的合作企业将产生有效的数据，以阐明哺乳动物生命中最早的个体特征。

From 2011 to 2014 our two groups at MPI and CeRA joined strengths to investigate the effects of culture conditions on embryo quality in the mouse model of assisted reproductive technologies (ART). Unexpectedly, upon cleavage in culture media that are used in the clinics, fertilized mouse oocytes took on different developmental trajectories, characterized by medium-specific proportions of blastocysts and medium-specific patterns of gene expression. This renewal application to the DFG fosters new understanding of embryo development under in vitro conditions which are relevant to estimate any potential risks of ART procedures, and also provides clues to anticipate the outcome of ART procedures and to minimize the loss of oocytes and thereby the number of ART cycles. Our focus is on culture media, because they can reprogram cell fate in other fields of experimental biology; so, what about in ART?Given the heterogeneity of human embryos, until now it proved difficult to distinguish the contribution of the postfertilization culture environment from that of the intrinsic quality of the gametes (nature vs nurture). While it is utopic to mimic such heterogeneity in mice, it is feasible to eliminate it almost completely. Taking advantage of the method of mouse embryo bisection at the 2-cell stage, we can pursue the molecular traits that make a 2-cell embryo a developer or a non-developer under the provisions of a given environment (medium): after bisection, one cell provides the molecular information, which can be matched with the developmental information of the other cell. Further, we can use the two monozygotic twins to test if two different media elicit different developmental trajectories from the same genotype. From the bioinformatic comparison of the transcriptomes of twin embryos grown in different media we shall learn about the molecular transductors of environmental cues (extrinsic modulators of embryo quality e.g. signaling pathways). From the comparison of the transcriptomes of developmentally competent vs incompetent blastomeres across culture media we shall learn about the core of genes that are less sensitive to environmental cues.Our work can bring embryo research forward as the model of twinning will be applied to the study of ART culture media, leading to discover novel endpoints providing insight into the earliest stages of mammalian development. As in our previous DFG project, this renewal application will provide scientific evidence for critical steps of preimplantation development. Also, it should help to understand whether oocytes would be more suited for culture in a certain medium as opposed to another medium, after fertilization but before embryonic genome activation. Our collaborative enterprise between MPI and CeRA shall generate valid data to illuminate the earliest features of individuality in mammalian life.