Cell type divergence in Dictyostelium - delineation of the signalling pathway that leads to prespore cell differentiatio

动植物是由数以百万计的单个细胞组成的，根据它们的形式和功能，这些细胞可以分为数百种不同的细胞类型。细胞类型在这两个基本属性上有所不同，因为每种细胞都会读出写入特定有机体基因集中的不同信息子集。细胞在以蛋白质形式表达的信息子集中彼此分化的过程称为分化。分化不良会导致多种人类疾病，如胚胎发育异常、儿童和成人癌症等。研究哺乳动物胚胎的分化是很困难的，因为同时产生了如此多的细胞类型，它们往往很难获得，而且某些类型的遗传分析也是不可能的。因此，发育生物学家发现研究更简单的模型是非常有价值的。像果蝇这样的生物。展示细胞命运选择的最简单的模式生物是生活在土壤中的网囊阿米巴。在短短24小时内，网柄柄细胞聚集在一起，分化为柄细胞或孢子细胞。在发育的中间阶段，段塞阶段，柄和孢子细胞前体沿着段塞排列成线性阵列，在那里它们可以被分析和操纵。前柄细胞占前五分之一，前孢子细胞占后五分之四。基因是什么？阅读吗？当被称为转录因子的蛋白质识别与基因相邻的DNA中的特定信号序列时。指导分化为柄前细胞所需基因的转录因子具有部分特征。然而，目前还不知道是什么转录因子直接读取成为前孢子细胞所必需的基因。该项目的目的是确定这些因素。虽然它的发育模式与动植物略有不同，但网柄菌的基因组序列表明，它与它们分享了许多基因产物。因此，在网柄苔藓中发现的基因和遗传途径往往与高等有机体和困扰它们的疾病有关。

Animals and plants are built up of millions of individual cells that can be classified into many hundreds of different cell types by their form and function. The cell types differ in these two fundamental properties because each kind of cell reads out a different sub-set of the messages that are written within the gene set of that particular organism. The process whereby cells diverge from one another, in the sub-set of messages that they express as proteins, is called differentiation. Improper differentiation leads to many kinds of human diseases, e.g. developmental abnormalities in embryos and cancer in children and adults. Studying differentiation as it occurs in a mammalian embryo is difficult, because so many cell types are being simultaneously generated, they are often not easily accessible and certain kinds of genetic analysis are not possible.Therefore, developmental biologists have found it immensely valuable to study simpler, ?model? organisms such as the fruit fly. The simplest model organism to display a choice of cell fate is the soil-living amoeba Dictyostelium. In just 24 hours, Dictyostelium cells aggregate together and differentiate as either stalk cells or spore cells. At an intermediate stage of development, the slug stage, the stalk and spore cell precursors are arranged in a linear array along the slug, where they can be analysed and manipulated. Prestalk cells occupy the front one-fifth of the slug and prespore cells occupy the rear four-fifths. Genes are ?read? when proteins, known as transcription factors, recognise specific signal sequences in the DNA adjacent to the gene. The Dictyostelium transcription factors that direct the reading of genes necessary to differentiate as a prestalk cell are partially characterised. However, the transcription factors that direct reading of the genes necessary to become a prespore cell are unknown. The aim of this project is to identify such factors. Although it has a somewhat different mode of development to that of plants and animals, the genome sequence of Dictyostelium show that it shares many gene products with them. Therefore, genes and genetic pathways discovered in Dictyostelium are often relevant to higher organisms and to the diseases that beset them.