Laboratory of Mammalian Molecular Embryology, RIKEN Center for Developmental Biology, Kobe, Japan.
EMBO J. 2011 May 4;30(9):1841-51. doi: 10.1038/emboj.2011.92. Epub 2011 Apr 5.
Transcriptome regionalization is an essential polarity determinant among metazoans, directing embryonic axis formation during normal development. Although conservation of this principle in mammals is assumed, recent evidence is conflicting and it is not known whether transcriptome asymmetries exist within unfertilized mammalian eggs or between the respective cleavage products of early embryonic divisions. We here address this by comparing transcriptome profiles of paired single cells and sub-cellular structures obtained microsurgically from mouse oocytes and totipotent embryos. Paired microsurgical spindle and remnant samples from unfertilized metaphase II oocytes possessed distinguishable profiles. Fertilization produces a totipotent 1-cell embryo (zygote) and associated spindle-enriched second polar body whose paired profiles also differed, reflecting spindle transcript enrichment. However, there was no programmed transcriptome asymmetry between sister cells within 2- or 3-cell embryos. Accordingly, there is transcriptome asymmetry within mouse oocytes, but not between the sister blastomeres of early embryos. This work places constraints on pre-patterning in mammals and provides documentation correlating potency changes and transcriptome partitioning at the single-cell level.
转录组区域化是后生动物中一个重要的极性决定因素,指导正常发育过程中的胚胎轴形成。尽管人们假设哺乳动物中存在这一原则的保守性,但最近的证据存在矛盾,并且尚不清楚未受精的哺乳动物卵内或早期胚胎分裂的各自分裂产物之间是否存在转录组不对称性。我们通过比较从小鼠卵母细胞和全能胚胎中微手术获得的配对单细胞和亚细胞结构的转录组谱来解决这个问题。来自未受精的中期 II 卵母细胞的配对微手术纺锤体和残余样本具有可区分的图谱。受精产生全能的 1 细胞胚胎(受精卵)和相关的富含纺锤体的第二极体,其配对图谱也不同,反映了纺锤体转录物的富集。然而,在 2 或 3 细胞胚胎中的姐妹细胞之间没有程序化的转录组不对称性。因此,在小鼠卵母细胞内存在转录组不对称性,但在早期胚胎的姐妹卵裂球之间不存在。这项工作限制了哺乳动物的预模式化,并提供了在单细胞水平上与潜能变化和转录组分区相关的文档。