Unravelling the role of beta-catenin in ground state pluripotency

干细胞由两个特性定义：它们可以无限增殖，产生与自身相同的细胞(自我更新特性)，以及可以专门化(分化)为成熟细胞类型(多能性特性)。在成人中，干细胞，例如在骨髓中发现的干细胞，在受伤的情况下主要具有修复功能。成人干细胞目前也被用于医学治疗；一个典型的例子是用于白血病治疗的骨髓移植。将成体干细胞用于医疗目的的主要限制是可获得性低，以及难以在培养时保持其特征不变。此外，成体干细胞的再生能力很差，因为它们不能分化为所有需要的细胞类型。由于胚胎干细胞(ESCs)的发现，这些问题被克服了：从囊胚中分离出来的ESCs可以在体外无限培养，并在适当的条件下分化为每种细胞类型。此外，2006年诺贝尔奖获得者山中也有了一个惊人的发现：体细胞可以重新编程回到干细胞状态，获得所谓的诱导多能干细胞(IPSCs)。ESCs和IPSCs被认为是一个巨大的希望：许多人认为他们的发现将在短期内推动再生医学、基因疗法和个性化医学领域令人印象深刻的扩张，最终导致许多与健康相关的问题的解决。到目前为止，这一承诺只实现了一部分，主要是因为我们对使这些细胞如此特殊的基本生物学过程知之甚少。在这项研究中，我们旨在提高我们对协调多能性的分子过程的理解，重点是β-连环蛋白(b-连环蛋白)，这是一种维持茎干的关键蛋白质。事实上，我们和其他人报道了b-连环蛋白在体内体细胞重编程、分化、多能性和组织再生中的核心作用。尽管如此，b-连环蛋白控制胚胎干细胞多能性的机制仍然存在很大争议。我们将使用跨学科的方法来揭示这种复杂性。利用尖端技术，我们将设计出小鼠胚胎干细胞(MESCs)，其中b-连环蛋白可以通过多种方式进行调节(蛋白质含量、时间动力学、调节其他基因的能力)。随后，我们将进行实验，将特定的b-连环蛋白扰动行为与mESCs的自我更新和分化能力联系起来。最后，我们将使用强大的计算方法来了解b-catenin如何与其他对多能性至关重要的基因相互作用。该项目将为胚胎干细胞生物学领域提供重要的创新和知识步骤：结果将揭示b-catenin如何调节多能性和分化之间的平衡，并指示如何在体外驱动特定的细胞命运。未来，拟议的项目的输出可以扩展到控制b-catenin依赖的人ESCs和iPSCs的自我更新和分化，缩短多能干细胞与其应用靶点之间的距离。此外，开发的技术还可以用于其他涉及b-连环蛋白的生物过程，包括发育和癌症。

Stem cells are defined by two properties: they can proliferate indefinitely producing cells identical to themselves (self-renewal property), and can specialise (differentiate) into mature cells types (pluripotency property). In adults, stem cells, found for example in the bone marrow, have mainly a repair function in case of injury. Adult stem cells are currently used also in medical therapy; a typical example is bone marrow transplant for leukemia treatment. The major limit of using adult stem cells for medical purposes is the low availability, and the difficulty to expand them in culture maintaining their features intact. Moreover, adult stem cells have a poor regeneration range, as they are unable to differentiate into all desired cell types.Such issues were overcome thanks to the discovery of embryonic stem cells (ESCs): isolated from blastocysts, ESCs can be cultured in vitro indefinitely, and can give rise, under the appropriate conditions, to every cell type. Also, in 2006 the Nobel Prize winner Yamanaka made an astonishing discovery: somatic cells can be reprogrammed back to a stem-like state, obtaining the so-called induced pluripotent stem cells (iPSCs). ESCs and iPSCs were thought to be a great promise: many believed that their discovery would have fuelled an impressive expansion of regenerative medicine, gene therapy and personalised medicine fields in the short term, ultimately leading to the solution of many health-related problems. So far, only a part of this promise has been fulfilled, mainly because of the scarce knowledge we have about the basic biological processes that make these cells so special. In this research, we aim at improving our understanding of the molecular processes that orchestrate pluripotency focusing on beta-catenin (b-catenin), a pivotal protein in stemness maintenance. Indeed, we and others reported a central role of b-catenin in somatic cell reprogramming, differentiation, pluripotency and tissue regeneration in vivo. Still, the mechanisms through which b-catenin controls pluripotency of embryonic stem cells are highly debated.We will unfold this complexity using an interdisciplinary approach. Using cutting-edge technology, we will engineer mouse ESCs (mESCs) in which b-catenin can be modulated in a number of way (amount of protein, temporal dynamics, ability to regulate other genes). Subsequently, we will perform experiments to link specific b-catenin perturbed behaviours to mESCs self-renewal and differentiation ability. Finally, we will use potent computational approaches to understand how b-catenin interacts with other genes important for pluripotency.The project will provide a vital step of innovation and knowledge to the embryonic stem cells biology field: the results will reveal how b-catenin regulates the balance between pluripotency and differentiation, and indicate how to drive specific cell-fates in vitro.In the future, the output of the proposed project could be extended to control b-catenin dependent self-renewal and differentiation of human ESCs and iPSCs, shortening the distances between pluripotent stem cells and their applicative targets. Also, the developed techniques could be used in other biological processes in which b-catenin is involved, including development and cancer.