MECHANISTIC INSIGHTS INTO THE DEVELOPMENTAL-STAGE SPECIFIC ACTIVITY OF A UBIQUITOUSLY EXPRESSED TRANSCRIPTION FACTOR

我们所有的细胞都来自一个受精卵细胞，该受精卵细胞进行多次分裂，产生我们体内所有复杂的细胞类型。这种发育过程最吸引人的方面是，不同细胞形成的时间总是相同的，从而确保我们的器官在正确的顺序和正确的时间发育。这种同步的原因是，我们身体计划的所有信息都编码在我们的DNA中，其中包含关于我们的基因何时应该表达以及何时应该沉默的指令。其结果是，人类是用一个计划建造的，而灵长类动物是由另一个计划建造的。然而，人类和灵长类动物的DNA有99%相同，因此问题是这两个物种之间有什么不同。答案很可能在调控其他基因表达的基因表达顺序的微妙变化中找到，这些基因就是所谓的转录因子。这些蛋白质可以“读取”遗传密码，它们与许多其他调节蛋白质一起工作，以确保基因在正确的细胞和正确的时间表达。在过去的几年中，人们发现有不同类型的转录因子：一种只存在于一种细胞类型中，另一种存在于多种细胞类型中。所有类型的因素共同作用来调节特定的基因。当细胞特异性因子缺失时，通常不会形成这种细胞类型。当每个细胞中存在的一个因子缺失时，其影响可能是戏剧性的，而且往往是生物体无法发育。在这项建议中，我们希望研究后一类转录因子Sp1的成员。我们已经证明，如果没有它，血细胞发育会受到越来越多的影响，成熟的血细胞无法形成。现在我们想知道Sp1是如何工作的，什么时候需要它，以及它与哪些其他因素合作。然而，不仅转录因子的表达时间可以不同。此外，在一个给定的细胞中存在多少这些调节剂的水平也是至关重要的，因为调节其他调节器的因子浓度的微小变化将对进一步的发展产生巨大影响。一个重要的例子表明，因子水平的差异可以在唐氏综合症患者身上看到，他们的每个细胞中都有一个额外的染色体。他们有太多来自这条染色体的这些基因的产物，他们的发育受到强烈的干扰。在这项拨款中，我们将改变Sp1的水平和测量，这些变化如何影响其目标基因的表达，进而影响特定类型的细胞的形成。为此，我们将使用一个基于小鼠胚胎干细胞的系统，该系统模仿体外正常发育，在那里我们可以产生足够的细胞来检查许多不同的特征。我们的工作将回答一些基本的问题，如转录因子如何相互作用，以及重要调控基因的平衡和时间是如何控制的。

All our cells originate from one single fertilised egg cell which divides many times and gives rise to all the complex cell types in our body. The most fascinating aspect of such developmental processes is the fact that the timing of how different cells form is always the same, thus ensuring that our organs develop in the right order and at the right time. The reason for this synchrony is that all information for our body plan is encoded in our DNA which contains instructions on when our genes should be expressed and when they should be silent. The result is that humans are built with one plan and primates are built by another. However, humans and primates are 99% identical in their DNA, the question therefore arises what is different between the two species. The answer most likely can be found in subtle changes of the order of expression of genes that regulate the expression of other genes, the so-called transcription factors. These proteins can "read" the genetic code and they work together with many other regulator proteins to make sure that a gene is expressed in the right cell and at the right time. In the last years it was found that there are different types of transcription factors: those which are only found in one cell type, and those who are present in many cell types. All types of factors work together to regulate specific genes. When cell-specific factors are missing, usually this cell type does not form. When a factor is missing that is present in every cell, the effects can be dramatic, and often the organism is unable to develop. In this proposal we wish to study a member of the latter class of transcription factors, Sp1. We have shown that without it, blood cell development gets more and more compromised and mature blood cells cannot form. Now we want to know, how Sp1 works, when exactly it is needed and with which other factors it cooperates.However, not only the timing of expression of transcription factors can be different. Also the levels of how much of these regulators is present in a given cell is critical since small changes in the concentration of a factor that regulates other regulators will have a huge effect in further development. An important example of what differences in factor levels can make is seen in people with Down's syndrome who have an extra chromosome in each cell. They have too much of the products of these genes from this chromosome and their development is strongly perturbed. In this grant, we will change the levels of Sp1 and measure, how such changes impact of the expression of its target genes and how this, in turn, then impacts of how many cells of a given type are formed.To this end, we will use a system based on mouse embryonic stem cells that mimics normal development in vitro and where we can generate enough cells to examine many different features. Our work will answer a number of fundamental questions on how transcription factors interact with each other and how the balance and timing of important regulator genes is controlled.