Sex-specific alternative splicing in the head of Drosophila melanogaster and its underlying regulatory mechanisms
Final Report Abstract
95 % of human and 60 % of Drosophila genes are alternatively spliced. However, in general, little is known about the impact of AS on developmental processes, about regulatory mechanisms underlying AS, and about the biological role of alternative transcripts. In this project, Drosophila was used as a model organism to explore the level of sex-specific transcripts in the neural system, to investigate the regulation of AS, and to explore the biological relevance of these transcripts. For this purpose, genome-wide approaches were combined with in vivo genetic and molecular studies. Whole-transcriptome RNA-Sequencing (RNA-Seq) analyses revealed that many more genes besides the classical sex determination factors are sex-specific alternatively spliced in the adult fly head. Further experiments showed that these AS changes are not significantly influenced by signals of the germline or factors which are transferred during mating. Because we could not establish mutants for the master regulators of sex-determination, SXL and TRA, RNASeq using those lines could not be performed. Instead, we looked at sex-specific transcripts in third instar larval brains. Surprisingly, at this stage, only a few mRNAs are sex-specifically spliced further supporting the idea of a functional relevance of sex-specific transcripts in adult fly heads. We further analyzed sex-specific isoforms of one of our candidate genes, tango13. Firstly, we showed that tango13 transcripts encode two sexspecific protein isoforms. Next, we illustrated the potential of alternative Tango13 isoforms to influence the behavior of the fly in a sex-specific manner. To study expression of transcript isoforms in vivo we established Gal4/UAS-dependent dualfluorescence reporter minigenes for 7 of our candidate genes. While we could not detect sexspecific isoform bias with this system, we did observe a very pronounced tissue-specific regulated isoform expression. Often, one isoform was exclusively expressed in a restricted pattern in the Drosophila brain, whereas the alternative isoform was expressed in a complete different pattern. Another part of the project was the investigation of SF in the development of a neuronal structure, the mushroom bodies, using RNAi and MARCM. We identified 9 SF that affect mushroom body development.
Publications
- Alternative splicing in Drosophila neuronal development. J Neurogenet. 2014 Sep-Dec;28(3-4):199-215
Mohr C, Hartmann B
(See online at https://doi.org/10.3109/01677063.2014.936437) - PhD-Thesis, 2015 Sex-specific transcript complexity in the neural system of Drosophila melanogaster
Carmen Mohr
(See online at https://dx.doi.org/10.6094/UNIFR/10809) - Sex-Specific Transcript Diversity in the Fly Head Is Established during Pupal Stages and Adulthood and Is Largely Independent of the Mating Process and the Germline. Sex Dev. 2017;11(2):94-108
Mohr C, Kleiner S, Blanchette M, Pyrowolakis G, Hartmann B
(See online at https://doi.org/10.1159/000456022) - The Role of Splice Factors in Neuronal Development in Drosophila melanogaster. Dissertation Albert-Ludwigs-Universität Freiburg im Breisgau 2019. VI, 125 S.
Sarah Kleiner (formerly Ortolf)
(See online at https://doi.org/10.6094/UNIFR/155351 )
