Department of Anatomy and Developmental Biology, Monash University, Clayton, Victoria, Australia.
Development and Stem Cells Program, Monash Biomedicine Discovery Institute, Clayton, Victoria, Australia.
Nature. 2020 Oct;586(7827):101-107. doi: 10.1038/s41586-020-2734-6. Epub 2020 Sep 16.
The reprogramming of human somatic cells to primed or naive induced pluripotent stem cells recapitulates the stages of early embryonic development. The molecular mechanism that underpins these reprogramming processes remains largely unexplored, which impedes our understanding and limits rational improvements to reprogramming protocols. Here, to address these issues, we reconstruct molecular reprogramming trajectories of human dermal fibroblasts using single-cell transcriptomics. This revealed that reprogramming into primed and naive pluripotency follows diverging and distinct trajectories. Moreover, genome-wide analyses of accessible chromatin showed key changes in the regulatory elements of core pluripotency genes, and orchestrated global changes in chromatin accessibility over time. Integrated analysis of these datasets revealed a role for transcription factors associated with the trophectoderm lineage, and the existence of a subpopulation of cells that enter a trophectoderm-like state during reprogramming. Furthermore, this trophectoderm-like state could be captured, which enabled the derivation of induced trophoblast stem cells. Induced trophoblast stem cells are molecularly and functionally similar to trophoblast stem cells derived from human blastocysts or first-trimester placentas. Our results provide a high-resolution roadmap for the transcription-factor-mediated reprogramming of human somatic cells, indicate a role for the trophectoderm-lineage-specific regulatory program during this process, and facilitate the direct reprogramming of somatic cells into induced trophoblast stem cells.
人类体细胞重编程为初始或幼稚的诱导多能干细胞，再现了早期胚胎发育的阶段。这些重编程过程的分子机制在很大程度上仍未被探索，这阻碍了我们的理解，并限制了对重编程方案的合理改进。在这里，为了解决这些问题，我们使用单细胞转录组学重建了人类皮肤成纤维细胞的分子重编程轨迹。这表明，向初始和幼稚多能性的重编程遵循不同的、独特的轨迹。此外，对可及染色质的全基因组分析显示，核心多能性基因的调控元件发生了关键变化，并在时间上协调了染色质可及性的全局变化。对这些数据集的综合分析揭示了与滋养外胚层谱系相关的转录因子的作用，以及在重编程过程中存在进入滋养外胚层样状态的细胞亚群。此外，这种滋养外胚层样状态可以被捕获，从而能够衍生出诱导滋养层干细胞。诱导滋养层干细胞在分子和功能上与从人类囊胚或第一 trimester 胎盘中衍生的滋养层干细胞相似。我们的研究结果为人类体细胞的转录因子介导重编程提供了高分辨率路线图，表明在这个过程中滋养外胚层谱系特异性调控程序发挥了作用，并促进了体细胞向诱导滋养层干细胞的直接重编程。
