Governing cell lineage formation in cloned mouse embryos
Governing cell lineage formation in cloned mouse embryos
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DOI：
10.1016/j.ydbio.2010.04.012
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发表时间：
2010-07-01
影响因子：
2.7
通讯作者：
Boiani, M.
中科院分区：
文献类型：
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作者：
Balbach, S. T.;Esteves, T. C.;Boiani, M.
植入前小鼠胚胎的卵裂球通过需要转录因子Tead4、Cdx2、Oct4和Nanog的过程形成滋养外胚层和内细胞团。在小鼠桑椹胚克隆体细胞核移植，我们观察到，滋养外胚层转录因子Cdx2的表达非常不同的蛋白质水平相比，时间和阶段匹配的受精。当绘制成直方图时，克隆胚胎中Cdx2的蛋白质水平出现“不稳定”，即广泛分布。与Cdx 2相反，上游因子Tead 4以及内细胞团转录因子Oct 4和Nanog的蛋白水平在克隆和受精胚胎中相似。这些观察结果表明，滋养外胚层的形成开始，但没有正确地维持在克隆小鼠桑椹胚，这是一致的克隆囊胚的有限植入和植入后的成功。因为如果细胞被更多以相同方式分化的细胞包围，细胞的分化能力会大大增强，这是古尔登命名的群体效应的概念，我们推断，在克隆胚胎中经常观察到的细胞数量不足可能导致过早的Cdx 2表达和卵裂球分化为滋养外胚层。因此，我们通过在4细胞阶段聚集它们来创建更大的克隆胚胎。同源凝集刺激多种信号通路的组分的表达，并导致克隆胚胎中Cdx2的水平与受精胚胎相似。大多数所得的桑椹胚和囊胚由所有三个创始人的细胞组成，表明聚集增加了所有单个组分的稳定性。我们的结论是，诱导克隆胚胎的多能性比以前假设的更有效，我们建议，一个最小的细胞数量是必要的，以稳定多能性和抑制过早表达的Cdx2在克隆小鼠胚胎。(C)2010年爱思唯尔公司All rights reserved.
Blastomeres of the pre-implantation mouse embryo form trophectoderm and inner cell mass via a process that requires the transcription factors Tead4, Cdx2, Oct4 and Nanog. In mouse morulae cloned by somatic cell nuclear transfer, we observed that the trophectoderm transcription factor Cdx2 is expressed very differently at the protein level compared to time- and stage-matched fertilized counterparts. Protein levels of Cdx2 in cloned embryos appear 'erratic,' i.e. are widely distributed, when plotted as histograms. In contrast to Cdx2, protein levels of the upstream factor Tead4 and of inner cell mass transcription factors Oct4 and Nanog are similar in cloned and fertilized embryos. These observations suggest that trophectoderm formation is initiated but not maintained correctly in cloned mouse morulae, which is consistent with cloned blastocysts' limited implantation and post-implantation success. Because a cell's ability to differentiate is greatly enhanced if it is surrounded by more cells differentiating the same way, a concept designated community effect by Gurdon, we reasoned that the insufficient cell numbers often observed in cloned embryos might lead to premature Cdx2 expression and differentiation of blastomeres into trophectoderm. Therefore, we created larger cloned embryos by aggregating them at the 4-cell stage. Homologous aggregation stimulates expression of multiple signaling pathways' components and results in cloned embryos with levels of Cdx2 similar to fertilized embryos. Most of the resultant morulae and blastocysts consist of cells of all three founders, indicating that aggregation increases stability of all of the individual components. We conclude that the induction of pluripotency in cloned embryos is more efficient than previously assumed, and we propose that a minimum cell number is necessary to stabilize pluripotency and inhibit premature expression of Cdx2 in cloned mouse embryos. (C) 2010 Elsevier Inc. All rights reserved.