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Title: Studying centrosome formation and the consequences of centrosome loss in Drosophila melanogaster
Author: Baumbach, Janina
ISNI:       0000 0004 5349 5318
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2014
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Centrioles are conserved microtubule-based structures that are required for the formation of two important cellular organelles, centrosomes and cilia. Centrosomes form the poles of the mitotic spindle and consist of a pair of centrioles surrounded by a matrix of pericentriolar material (PCM) that has the ability to nucleate and organise microtubules. Centrosome defects are implicated into a variety of human diseases including cancer, microcephaly, and ciliopathies. Therefore it is of great interest to understand the mechanisms that lead to centrosome formation and the consequences that centrosome defects have in cells. I have analysed the roles of several centrosomal proteins in centrosome assembly in Drosophila. My results indicate that Sak/PLK4 is only required for the initial step of centriole duplication, but has no further role in recruitment of PCM. I show that two proteins important for PCM recruitment, Asterless (Asl) and Spd-2, are preferentially phosphorylated when they are integrated into the centrosome and I identified these phosphorylation sites using a phosphoproteomic screen. A phosphorylation site in Asl is specifically phosphorylated in mitosis, and the phosphorylation state of Spd-2 regulates its maintenance at the centrosome, suggesting that phosphorylation of PCM proteins is an important mechanism to ensure PCM assembly specifically at the centrosome and in mitosis. I have performed a global transcriptional analysis of flies lacking centrosomes or having extra centrosomes to investigate the effects of centrosomal defects on a cellular level. Surprisingly, my results indicate that centrosome defects per se do not dramatically alter cellular physiology. Finally, I demonstrate that in the absence of centrioles acentrosomal microtubule-organising centres (aMTOCs) are formed in an Asl- and Cnn-dependent fashion, and I show that these aMTOCs can contribute to spindle focusing in acentrosomal cells.
Supervisor: Raff, Jordan Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Cell Biology ; Genetics ; Biochemistry ; centrosomes ; centrioles ; mitotic spindle assembly