Context-specific regulation of Wnt/beta-catenin target genes

生物学中最重要的问题之一是我们的身体是如何构建的。胚胎中的许多细胞相互交流，首先安排一般的身体计划，然后调节专门细胞的形成以构建我们的器官。这些胚胎细胞使用分子细胞间信号传导机制相互通信。这个过程在出生后持续存在，当器官被修复时，组织通过从驻留的成体干细胞继续形成这种专门的细胞而再生。与胚胎中相同的细胞间信号传导途径在成人中调节这一过程。因此，信号机制的缺陷不仅会导致婴儿的出生缺陷，还会导致成人的疾病，例如癌症。具体研究问题：Wnt信号传导是我们最重要的分子细胞到细胞信号传导机制之一。我们已经对线性分子Wnt信号级联有了很好的了解，它的功能是打开或关闭在我们的功能器官中建立专门细胞所需的特定基因。然而，我们还不知道Wnt信号是如何在不同的组织和器官中找到正确的基因来打开或关闭的。我们显然需要揭示这些重要的机制，这些机制允许Wnt信号在胚胎发育期间和不同的干细胞中重复发挥作用，同时可靠地打开或关闭每种类型细胞中的正确基因组。实验系统：我们最近利用了最先进的分子分析方案，这使我们能够以全面的方式识别在特定细胞组中通过Wnt信号转导而开启的所有基因。我们已经在一个可访问的实验系统中建立了这些方法，在该系统中，我们已经知道Wnt信号调节早期胚胎细胞的方式与稍微年长的细胞相比在短时间内发生了巨大的变化。通过这些新方法，我们现在已经发现，Wnt信号确实在后期细胞中打开了非常不同的基因，而不是我们已经知道的早期细胞中的少数基因。1.特殊要求：既然我们现在已经非常清楚地了解了在后来的细胞中开启的基因组，我们现在想与在早期细胞中开启的基因组进行一个适当的比较。2.因为我们通常知道哪组分子在开关打开或关闭时会接触开关，所以我们现在想研究不同的个体分子是否会接触不同组织中的不同开关，这可能会使不同的基因组在早期与晚期细胞相比被打开。当我们知道早期和晚期细胞中的特定开关以及在早期和晚期细胞中接触这些开关的分子时，我们将研究这些分子被引导到正确开关的分子机制。结果和益处：我们的实验模型系统现在使我们能够解决这些科学问题。然而，我们的实验结果将不仅仅与这个实验模型系统相关。同样的Wnt信号级联也控制着成年人的干细胞，例如疾病中的癌细胞。我们的实验还将开发分子工具和实验方法，这些工具和方法将被证明对其他人有用，因为他们需要识别在特定细胞群中通过某种分子途径打开的所有基因;或者一组特定的分子如何找到、接触并转动开关来激活这些基因。

GENERAL RESEARCH QUESTION: One of the most important questions in biology asks how our body is built. The many cells in the embryo communicate with each other, first to arrange the general body plan and then to regulate formation of specialised cells to build our organs. These embryonic cells communicate with each other using molecular cell-to-cell signalling mechanisms. This process persists after birth when organs are repaired and tissues regenerated by continued formation of such specialised cells from resident adult stem cells. The same cell-to-cell signalling pathways as in the embryo regulate this process in the adult. Defects in signalling mechanisms consequently do not only lead to birth defects in babies but also to diseases in adults, such as cancer.SPECIFIC RESEARCH QUESTION: Wnt signalling is one of our most important molecular cell-to-cell signalling mechanisms. We already have a good understanding of the linear molecular Wnt signalling cascade, which functions to switch on or off specific genes that are needed to build specialised cells in our functional organs. However, we do not yet understand how Wnt signalling manages to find the correct genes to switch on or off in different tissues and organs. We clearly need to uncover these important mechanisms that allow Wnt signalling to function repeatedly during embryonic development and in different stem cells, while nonetheless reliably switching on or off the correct set of genes in each of these types of cells. EXPERIMENTAL SYSTEM: We have recently taken advantage of state-of-the-art molecular analysis protocols, which allow us to identify in a comprehensive manner all the genes that are switched on by Wnt signalling in a particular group of cells. We have established these methods in an accessible experimental system where we knew already about a dramatic change happening in a short time in the way Wnt signalling regulates early embryonic cells compared to slightly older cells. With these new methods we have now uncovered that Wnt signalling indeed switches on very different genes in later cells than the few we already knew about in early cells. SPECIFIC OBJECTIVES:1. Since we are now getting to know very well the set of genes switched on in later cells, we now want to carry out a proper comparison with an equally well analysed set of genes switched on in earlier cells. 2. Because we know generally which group of molecules touch switches as they are turned on or off, we now want to investigate whether different individual molecules touch different switches in different tissues, which may then allow different sets of genes to be switched on in early as compared to later cells.3. When we know the particular switches in early and in later cells and the molecules touching these switches in early and later cells, we will investigate the molecular mechanisms by which these molecules are guided to the correct switches. OUTCOMES AND BENEFITS: Our experimental model system allows us now to address these scientific questions. However, the findings from our experiments are going to be relevant not just for this experimental model system. The same Wnt signalling cascade also controls stem cells in the adult and for instance cancer cells in disease. A wide range of scientific fields will therefore benefit from our results about how different specific genes can be switched on or off by Wnt signalling in different tissues.Our experiments will also develop molecular tools and experimental approaches that will prove useful to others as they need to identify all the genes that are switched on by a certain molecular pathway in a particular group of cells; or how a specific group of molecules finds, touches and turns switches to activate these genes.