Identification of novel transcription factors in the development and function of the Drosophila renal tubule

The formation and development of an organ is a complex process which involves several programmed events, including changes in cell shape and adhesion, proliferation, and differentiation. Defects in any of them lead to malformations and lethality. Investigating these processes can lead to a mechanistic understanding of organ development in health and disease conditions. They are defined by the expression and combination of specific Transcription Factors (TFs). These are active during the development of the Malpighian Tubules (MTs), of Drosophila melanogaster, which perform equivalent functions to the human kidney. Therefore, research using Drosophila proved very useful for understanding the processes of cell differentiation, proliferation, and development. To investigate which novel TFs could be involved in the development and physiology of the Drosophila kidney, an initial genetic screen of candidate TFs was performed. These selection criteria included the identification of candidate TFs regarding their patterns of expression, previous literature and human homologues involved in renal diseases. This resulted in the selection GATAe, a member of the GATA family of TFs, as the focus of this project. The effects of GATAe downregulation and overexpression were studied in the context of the MTs employing diverse genetic manipulation techniques. Silencing GATAe in any of the three main cell-types of the MTs occasioned a diverse range of phenotypes. GATAe in the MT Principal Cells (PCs) is not required for the embryonic development of the tubule, but is crucial in to ensure the correct morphology and maintenance of the adult tubule from metamorphosis. As a consequence, loss of GATAe in PCs results in a reduced lifespan, less tolerance to diverse kinds of stress, and liquid retention. Further preliminary ChIP-Sequencing analysis using a tagged line of GATAe revealed potential downstream targets of GATAe in the PCs, reinforcing its roles in cell-to-cell communication, tissue maintenance and stress response in the MTs. In Stellate Cells (SCs), GATAe is required for their survival through metamorphosis. Therefore, loss of GATAe in SCs induces a sharp reduction in this cell population in the adult stage, and impairing their secretion capabilities. Furthermore, GATAe is necessary in the Renal and Nephritic Stem Cells (RNSCs) for their migration into the ureters and lower tubules during metamorphosis. Overall, the findings reported in this PhD thesis reveal the novel functions of GATAe as a potential master regulator in the events of tissue maintenance, cell survival and cell migration. Apart from GATAe, additional TFs were identified in this project, which could serve as a base for future investigation of their possible novel roles in the fly renal system. Altogether, the data showed here provides new insights into the molecular pathways involved in the formation and maintenance of a functional organ