Resumen de Using genetic mosaics to understand the role of polyamine biosynthesis in cellular competition and segregation during angiogenesis
Recombinase genetic tools are extensively used in biomedical research to label cells and tissues or to modify the genotype of a cell and are very useful to understand development and disease progression. There are recombinase-reporters that allow us to label specific tissues/ cell-types; there are floxed lines that allow us to induce deletion of genes; and driver lines that induce the expression of recombinases to delete a gene or recombine a reporter only in the tissue of interest and at a specific time point. These lines are powerful tools when combined but, as we describe in the first chapter of this thesis, can caused misinterpretation of results if misused. We show here why Cre-reporters should not be used as indicators of gene deletion and present a new set of ratiometric multispectral mosaic genetic tools, called iFlpMosaics¸ as an alternative for reliable KO and WT labelling of cells, which will be of broad interest for the research community.
In the second part of this thesis we apply iFlpMosaics as well as classical genetic tools, to understand the role of polyamines in cellular competition and segregation during angiogenesis. Polyamines are small cationic peptides synthesised by ODC1 enzyme and are implicated in several cellular processes such as proliferation and migration which are important for angiogenesis. Thanks to the iFlpMosaics we can study how different cell types respond to mosaic Odc1 deletion. While some cell types are capable of adapting and compensating over time others cell types cannot adapt and KO cells are outcompeted by WT cells. We demonstrate how this compensation in endothelial cells (ECs) could be driven by import of polyamines from extracellular sources and how cells with abnormally low or high levels of polyamines, despite their competitive nature, behave different when they are not in a mosaic situation. Finally, we also compare the deletion of Odc1 with the deletion of its direct activator c-Myc, both negatively regulated by Notch in angiogenesis, and
