Kessler, Jeannette

My research is focused on meiosis and recombination in Drosophila, including the epigenetic control of recombination and its dependence on different factors like temperature and female age. Recent studies showed that different epigenetic factors are essential for successful oogenesis. For example, the Drosophila histone lysine methyltransferase eggless which catalyzes methylation of Histone H3 lysine 9 is required for multiple stages in oogenesis, like germ cell survival  past stage 5 of oogenesis  and early egg chamber budding. To identify epigenetic factors that cause changes on recombination frequency I use isogenic strains containing mutations or additional genomic copies of important epigenetic modulators. The assay allows a chromosome wide analyzation of crossover frequency. I also investigate the epigenetic indexing of synaptonemal complexes in this isogenic strains and the role of diapause on chromatin state in oogenesis.

Recombination is a prominent feature of meiosis and not only plays an important role in increasing genetic diversity during inheritance but also mediates the pairing and segregation of homologous chromosomes at the first meiotic division. In Drosophila recombination is initiated by MeiW68-dependent DNA double strand breaks (DSBs).  This occurs within the context of a proteinaceous structure the synaptonemal complex (SC). The SC is highly conserved among different organisms; it consists of two lateral elements held together by transverse elements and the central element. The lateral elements are associated with chromatin loops arise from the sister chromatid axes. DSBs are repaired by using the homologous chromosome as template and generate crossover or noncrossover products. The number and distribution of crossovers is regulated.