Recombination hotspot activity in Drosophila melanogaster

Sexual reproduction depends on the success of faithful chromosome transmission during meiosis to yield viable gametes. Crucial to proper meiosis is the process of recombination between paternal and maternal chromosomes which ensures normal homologous chromosome segregation. Errors in number and location of the recombination events are known to be one of the leading causes of nondisjunction and aneuploidy. Recombination events tend to cluster in certain regions of the genome where the frequency of recombination is high compared to the average recombination rate. These regions are called recombination hotspots. The identification of these hotspots will bring us closer to understanding the etiology of nondisjunction. We used transposon insertion at defined sites to test for recombination hotspots in Drosophila melanogaster. The first method employs two transposable element bearing fly strains that have the insertion at sites flanking the proposed hotspot. The number of recombination events in the interval between the two transposon insertion sites is used to detect hotspots. The second strategy is to generate a double strand break (DSB) by mobilizing the excision of the transposon from a precise location. By monitoring the outcomes of DSB repair event at these loci, sites that have a higher recombination rates can be detected. Unfortunately, both methods did not reveal hotspot activity. Studies in yeast and mammals have uncovered a few genes that have a large effect on the distribution and pattern of recombination events. In Saccharomyces cerevisiae, Set1 complex (also known as COMPASS complex) has been shown to decreases DSB frequencies at > 80% of DSB sites genome-wide and cause changes in their localization. We want to know if Set1 complex plays a major role in controlling DSB sites in Drosophila Melanogaster also. RNAi mediated knockdowns of subunits of the Set1 complex are used to investigate if these flies show a reduction of DSBs. Although Set1 complex knockdowns did not have a significant effect on the DSBs, they may play a role in the repair of DSBs and oocyte development.M.S.Includes bibliographical referencesby Mahrose Mehd