18 Feb

2nd Regensburg – Canberra Symposium on RNP Biology

On February 14th and 15th, the second Regensburg – Canberra Symposium on RNP Biology took place at the John Curtin School of Medical Research at the Australian National University (ANU) in Canberra with the aim to further strengthen our collaborations and to pave the way for establishment of an international PhD program. It was great to meet down under and to hear about the exciting research on RNA biology at the ANU.

I would like to thank our colleagues in Canberra very much for organization of this wonderful meeting and for their generous hospitality.

John Curtin School of Medical Research at the Australian National University

25 Jan

How to stabilize a sex-specific gene expression pattern in male flies

New manuscript from the lab published in Nucleic Acids Research: Drosophila Sister-of-Sex-lethal reinforces a male-specific gene expression pattern by controlling Sex-lethal alternative splicing.

In a collboration with the labs of Stefan Schneuwly, Gunter Meister (both at the University of Regensburg), Michael Krahn (Westfälische Wilhelms-Universität Münster), and Oliver Rossbach (Justus-Liebig-University Giessen), we could demonstrate that the protein Sister-of-sex-lethal (Ssx) is required in male flies to suppress production of Sex-lethal (Sxl).

 

Genomic tagging of the Sex-lethal (Sxl) locus in flies to reveal Sxl protein mis-expression (arrowheads) in male flies mutant for Sister-of-Sex-lethal. Arrows mark expression of a Sxl isoform in neural cell bodies and projections.

 

Most higher eukaryotes reproduce sexually, increasing the variability in the offspring. This allows e.g. rapid adaption to a new (or changing) environment or the cleansing of harmful mutations from a population. Sexual reproduction in higher eukaryotes usually involves individuals of different sex: males and females. Not surprisingly, the genetic programs that determine sex and control sexual differentiation need to be particularly robust in order to ensure survival of the population.

In Drosophila, a single protein, the master regulator Sex-lethal (Sxl), governs female development by controlling the expression of key factors involved in female morphology and behaviour. Once expressed, it engages in an auto-regulatory, positive feedback loop to ensure its sustained expression. This stably ‘flips the switch’ and commits to female development.

In contrast, in males Sxl expression needs to be shut-off which is achieved by alternative splicing that generates RNA isoforms encoding truncated, non-functional Sxl protein. Fluctuations inherent to gene expression can, however, produce small amounts of functional Sxl protein. When left unchallenged, this protein can trigger a self-enforcing cascade resulting in Sxl protein expression snowballing out of control. Until now, however, it remained unclear how males completely shut off the Sxl expression cascade and protect themselves against runaway protein production to ensure robust sex-specific development.

We have discovered a safeguard mechanism that prevents Sxl production in adult male flies. We identified the protein Sister of Sex-lethal (Ssx) as the first antagonist of Sxl-mediated auto-regulatory splicing that defines a precise threshold level for activation of the auto-regulatory, positive feedback loop that controls Sxl expression. We could show that Ssx exerts function by competing with Sxl for the same RNA regulatory elements thus preventing Sxl from triggering the self-enforcing expression cascade in adult male animals.

 

1 Nov

Methods course on RNP analyses – from ensembles to single molecules

From October 8th to 10th 2018, a hands-on methods course took place at the University of Regensburg, aimed at training PhD students in the latest methods of ribonucleoprotein (RNP) analysis. Topics included the quantification of protein-RNA interactions, single molecule analyses of RNPs by fluorescence resonance energy transfer (FRET) or fluorescence in situ hybridization (FISH), RNA structure probing, and comprehensive capture of RNA-binding proteins by interactome profiling from cultured cells. The course attracted PhD students from labs around the globe, some travelling from as far as Canberra, Australia, to get insight in and training on a variety of biophysical and biochemical methods. The design of the course was also aimed at fostering interactions between the participants, allowing them to build networks with peers working on related topics. Besides the lectures and the practical hands-on training, it was particularly the vivid and intense discussions among the participants that made this course a big success.

We are extremely grateful for the support of many expert speakers and trainers that delivered lectures on the latest methodological developments and that supervised the experimental work. In particular we want to thank the invited speakers from industry and academia that travelled to Regensburg to provide expert guidance: Rastislav Horos (European Molecular Biology Laboratory, EMBL, Heidelberg), Agatha Korytowski (Malvern Panalytical), Stefanie Nunes Rosa (Swedish University of Agricultural Sciences, Uppsala), Joel Perez-Perri (EMBL Heidelberg), Bruno Sargueil (CNRS/Paris Descartes University), and Ralf Seidel (Peter Debye Institute for Soft Matter Physics, Universität Leipzig).

The course was organized by the Graduate Research Academy RNA Biology of the Collaborative Research Centre 960 (SFB960, Ribosome formation: principles of RNP biogenesis and control of their function) that also provided financial support.

picture courtesy of Kinga Ay