Analyzing multigenerational effects of the Piwi/piRNA pathway in zebrafish.

• Applicant: Dr. Holger Dill
• Subject Area: Developmental Biology
• Term: from 2014 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 263669966

Novel integration of mobile DNA elements and amplification of these elements contributes substantially to eukaryotic genome evolution. Nevertheless, transposon insertions can in many cases be harmful for host organisms. To counteract the proliferation of transposons, the animal germ line has developed an adaptive, RNAi based immune system, the Piwi-interacting RNA (piRNA) pathway, to silence transposable elements (TEs) and keep genomes intact. In contrast to other small regulatory RNAs, only little is known about biogenesis, target silencing mechanisms and cell type specific functions of piRNAs. The overall aim of this project is to learn more about the mechanisms of TE silencing by piRNAs and cross-generational maintenance of this silencing, especially in vertebrates.To analyze the basic functions of vertebrate piRNAs, we will set up a unique piRNA/target gene system in vivo. To this end, transgenic zebrafish (Danio rerio) lines expressing distinct piRNAs from EGFP-modified TEs as well as an exogenous target sequence, the germ cell specific vasa::EGFP, will be generated. The zebrafish piRNA machinery closely resembles the ones described for Drosophila melanogaster and mouse. Its known advantages, like fast embryonic development and transparency of embryos, combined with well-established methods to introduce new TE copies into the zebrafish genome makes it a particularly suitable model organism for the proposed project. By using this in vivo system, we are going to investigate (1) piRNA synthesis from unique genomic loci, (2) how the piRNA response to recently introduced transposons is initiated and (3) the possible functions of different Piwi pathway components in long term silencing of target genes. This work will substantially increase our knowledge about TE silencing and protection of genomic integrity in vertebrate species.

• DFG Programme: Research Grants