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The role of polyploidy in epithelial tissue development

Principal Supervisor: Dr Kristen Panfilio, School of Life Sciences

Co-supervisor: Dr Andre Pires da Silva, School of Life Sciences

PhD project title: The role of polyploidy in epithelial tissue development

University of Registration: University of Warwick

Project outline:

Epithelial tissues are essential structures in animals, creating compartments and barriers such as the skin and lining of the gut. Often such protective tissues cease mitosis and switch to endoreplication, leading to highly polyploid nuclei. Hypotheses on the relevance of polyploidy include: (a) larger nuclei support larger cell sizes that help maintain barrier tissue integrity, (b) simultaneous transcription from multiple gene copies can support rapid synthesis of important proteins. This project uses developmental genetic approaches to test the relevance of these two hypotheses in an excellent experimental model of polyploidy: the extraembryonic epithelia of insect embryos.

Insect eggs are laid externally in a range of environments, and their extraembryonic (EE) tissues protect and support the developing embryos. There are two EE tissues, the outer serosa and the inner amnion, where the latter forms a fluid-filled cavity around the embryo in an analogous way to its namesake in amniote vertebrates (including humans). The serosa and amnion are each polyploid to characteristic levels, with especially large nuclei in the serosa. Given the developmental and physiological requirements of the EE tissues, both large cell size and rapid transcription could be relevant to their function.

This project will use a range of techniques, including functional testing by RNA interference (RNAi) and live cell imaging, to functionally test key genes’ roles in the development of EE tissue polyploidy. The primary research organism for this work is the red flour beetle, Tribolium castaneum, where we have established an excellent genetic toolkit, including transgenic GFP labelling of each EE tissue. This supports detailed, quantitative analyses of cell and tissue structure from multi-dimensional bioimaging data. Furthermore, our recent RNA-seq analyses and pilot functional testing in Triboliumhave identified a number of candidate genes to examine in testing hypotheses on tissue-specific polyploidy. Complementing the in vivoimaging work, ploidy dynamics will also be directly measured with techniques such as RT-qPCR, flow cytometry (FACS), and next generation sequencing methods.

References:

  1. Lee, H.O., Davidson, J.M., and Duronio, R.J. (2009). Endoreplication: polyploidy with purpose. Genes Dev. 23, 2461-2477.
  2. Orr-Weaver, T.L. (2015). When bigger is better: the role of polyploidy in organogenesis. Trends Genet. 31, 307-315.
  3. Hilbrant, M., Horn, T., Koelzer, S., and Panfilio, K.A. (2016). The beetle amnion and serosa functionally interact as apposed epithelia. eLife 5, e13834.

BBSRC Strategic Research Priority: Molecules, Cells and Systems

Techniques that will be undertaken during the project:

  • Multi-dimensional live cell imaging microscopy
  • RNA interference (RNAi)
  • Transgenesis
  • (Fluorescent) histology for gene expression and cellular structure
  • Computational work for image processing and quantitative analysis
  • RT-qPCR
  • FACS
Contact: Dr Kristen Panfilo, University of Warwick