Population Genetics of Transposable Element Copy Number in Drosophilia

转座因子（transposable elements，TE）是一种通过插入新的DNA位置而增殖的DNA序列。TE转座是包括人类在内的高等真核生物中突变的主要来源。然而，人们对转座活动是如何调节的知之甚少。 Nuzhdin博士将推断自然选择和宿主-TE共同进化在维持宿主基因组中TE拷贝数量稳定方面的相对贡献。TE活动通常受到宿主的限制;然而，许多基因组都有TE突然爆炸的证据。 Nuzhdin博士将首先检验TE表达有害的假设。如果自然选择对表达的TEs的作用比对那些缺乏启动子的作用更强烈，那么这一假设将得到支持。第二个具体的目的是推断是什么原因TE爆炸模型实验果蝇种群。 为此，将鉴定负责限制copia转座的宿主基因，并对其允许转座的变体进行分子表征。结果将揭示TE活动的决定因素，以及它们在自然种群中的维持和传播。这一知识将有助于防止未来可能发生的TE爆炸事件，这些事件可能发生在圈养的逃避自然选择的物种以及人类身上。

Nuzhdin9815621Transposable elements (TEs) are DNA sequences that multiply by inserting themselves into new DNA positions. TE transpositions are a major source of mutation in higher eukaryotes including humans. Little is known, however, of how transpositional activity is regulated. Dr. Nuzhdin will infer the relative contribution of natural selection and host-TE co-evolution in maintaining a stable number of TE copies in a host genome. TE activity is normally restricted by the host; however, many genomes have evidence of sudden TE explosions. Dr. Nuzhdin will first test the hypothesis that TE expression is deleterious. This hypothesis will be supported if natural selection acts more strongly against expressing TEs than against those lacking promoters. The second specific aim is to infer what causes TE explosions in model experimental Drosophila populations. For this, the host genes responsible for the restriction of copia transposition will be identified, and their variants permitting transpositions will be molecularly characterized. Results will shed light on the factors determining TE activity, and their maintenance and spread in natural populations. This knowledge will help to prevent possible future instances of TE explosions, which are likely in species escaping natural selection in captivity, as well as in humans.