A functional analysis of chromatin reorganisation during sperm morphogenesis in Drosophila

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Chromatin remodelling during spermiogenesis leads to an extreme condensed state of the haploid genome in the sperm by a switch from the nucleosomal configuration to a protamine based doughnut structure in mammals. After fertilization and before zygote formation a reorganization of the paternal genome takes place to resume the nucleosomal configuration. Not much is known about this process in Drosophila, therefore we address questions of the displacement and degradation of histones, the possible role of tran sition proteins and protamines in an in vivo context in Drosophila spermiogenesis. GFP tagged versions of chromatin proteins are an excellent tool to follow chromatin reorganisation in vivo, such as the use of ahistone H2a-GFP carrying fly strain. We began to study if the mechanism of histone degradation is dependent on ubiquitin-conjugating enzymes present in the testes. As candidates for transient chromosomal proteins we analyse Don Juan, Don Juan like and CG1988. We showed the presence of a protamine lik e molecule in the chromatin at the end of spermiogenesis by an eGPF-tagged version. This and functional approaches, like screening for mutants in the respective genes, ectopic expression studies and protein analysis, will help to understand chromatin reorganization of the entire genome, needed for male fertility.