Functional characterization of DNA methylation in Drosophila

DNA甲基化在高等真核生物如植物和哺乳动物的表观遗传基因调控中起着重要作用。这些生物体中甲基化的丢失(或减少)会导致戏剧性的但鲜为人知的发育问题。我们最近发现果蝇基因组DNA在早期胚胎发育过程中发生了特异的甲基化。果蝇的基因组序列包含一个候选基因dDnmt2，该基因被预测为编码(胞嘧啶-5)DNA甲基转移酶。DNMT2基因是真核细胞中分布最广泛的DNA甲基转移酶基因，在表观遗传基因调控中起着重要作用。为了详细描述dDnmt2，我们将彻底分析该基因的功能组织，然后产生携带该基因的靶向缺失或可诱导过度表达的转基因果蝇。对突变果蝇的详细分子分析将提供重要的结果，重新认识dDnmt2的作用以及DNA甲基化在果蝇发育过程中的作用。这些实验将得到对果蝇发育过程中亚核dDnmt2分布和基因组5-甲基胞嘧啶的分析的补充。果蝇的实验可及性将产生大量丰富的数据，这些数据将极大地加深我们对表观遗传的理解，并建立果蝇作为DNA甲基化研究的中心模式系统。

DNA methylation plays an important role in epigenetic gene regulation of higher eukaryotes like plants and mammals. Loss (or reduction) of methylation in these organisms results in dramatic but little understood developmental problems. We have shown recently that genomic DNA of the fruit fly Drosophila melanogaster is methylated specifically during early embryogenesis. The genome sequence of Drosophila contains a single candidate gene, dDnmt2, that has been predicted to encode a (cytosine-5) DNA methyltransferase. Dnmt2 genes are the most widely distributed eukaryotic DNA methyltransferase genes suggesting an important function in epigenetic gene regulation. For a detailed characterization of dDnmt2 we will thoroughly analyze the functional organization of the gene and then generate transgenic flies that carry either a targeted deletion of the gene or a transgene for inducible overexpression. A detailed molecular analysis of mutant flies will provide important results regading the role of dDnmt2 as well as the function of DNA methylation during Drosophila development. These experiments will be complemented by an analysis of subnuclear dDnmt2 distribution and genomic 5-methylcytosine during fly development. The experimental accessibility of the fly will generate a large wealth of data that will significantly deepen our understanding of epigenetic inheritance and establish Drosophila as a central model system for DNA methylation research.