Project 3: Control of Differentiation and Dedifferentiation in Human Development

干细胞生物学的前景是基于这些细胞将被用于再生医学和模拟体外组织的发育和疾病的想法。虽然通过对体细胞进行重编程使其成为多能状态，在产生患者特异性干细胞方面取得了惊人的进展，但对这些细胞的基本生物学以及它们是否能够在再生医学、发育和疾病方面兑现其承诺知之甚少。我们发现hESCs和hiPSCs的体外分化并不能准确反映人体组织的体内分化。我们已经确定了这种差异的分子基础，初步数据表明，事实上，从人类多能干细胞分化可以反映人类的发育，但是从非常早期的胚胎阶段。我们发现LIN28/let-7能够在早期胎儿发育过程中控制人类分化，这与秀丽隐杆线虫中该回路所显示的一致。我们建议操纵这一重要的基因表达回路，以确定适当控制这一回路是否对人类细胞的成熟至关重要。该项目还将开发工具，以允许操纵该电路和简化的方法来驱动体外细胞成熟。最后，我们将使用全基因组方法来了解这个回路是如何正常调节的，以及它是否代表了对人类发育重要的一组共调节基因。

The promise of stem cell biology is predicated on the idea that these cells will be utilized in regenerative medicine and to model development and disease of tissues in vitro. While fantastic progress has been made in the generation of patient-specific stem cells through the use of reprogramming of somatic cells to a pluripotent state, little is known about the basic biology of these cells and whether they will be able to live up to their promise in regenerative medicine, development and disease. We have found that in vitro differentiation from hESCs and hiPSCs does not accurately reflect in vivo differentiation in human tissue. We have identified a molecular basis for this discrepancy and preliminary data suggest that in fact differentiation from human pluripotent stem cells could reflect human development but from a very early embryonic stage. We identified LIN28/let-7 as able to control human differentiation during early fetal development, in congruence with what has been shown for this circuit in C. Elegans. We propose to manipulate this important gene expression circuit to determine whether proper control of this circuit is vital to allow for maturation of human cells. This project will also develop tools that will allow for manipulation of this circuit and a simplified method for driving cellular maturation in vitro. Finally, we will use genome-wide approaches to understand how this circuit is normally regulated and whether it is representative of a cohort of co-regulated genes important for human development. This project will significantly contribute to our limited knowledge of human development, and the control of cell fate with human pluripotent stem cells. There will be no human subjects or animal experimentation with the proposed work.