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Drosophila myosin VI function in dorsal closure

Ezeigwe, Ifeoma Daramfon (2012) Drosophila myosin VI function in dorsal closure. Doctor of Philosophy (PhD) thesis, University of Kent. (doi:10.22024/UniKent/01.02.94335) (KAR id:94335)

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Myosin VI is a minus-end directed actin-based motor protein. In vertebrate cells, myosin VI is of importance in endocytic and exocytic-membrane trafficking pathways, and in regulating Golgi morphology. Myosin VI is also implicated in genetic diseases and is transcriptionally regulated upon DNA damage in a p53-dependent manner and shown to be over-expressed in cancer types. In Drosophila, myosin VI encoded by the jaguar (jar) gene is implicated in a range of cellular processes including dorsal closure. Although understanding of its cellular function is developing, little is known about the mechanisms regulating myosin VI. In vitro studies on vertebrate myosin VI have demonstrated that it is phosphorylated within its motor domain by the serine/threonine kinase P AK and that alters its function in a similar manner to that which occurs in myosin I. More importantly,jar has a Pak phosphorylation site in the same location as the vertebrate myosin VI. Expression of either a dominant negative Jar or a dominant negative Pak causes if not exact, overlapping dorsal phenotypes in Drosophila. The aim of this study was to investigate a working model that Jar functions during dorsal closure are dependent on Pak-mediated phosphorylation. During my thesis research a published report concluded that jar is required but not essential for Drosophila development as 40% null jar mutants survived. On the contrary, I report here that jar is of importance for development as RNA i-mediated knockdown of Jar protein level is lethal and is found to cause abnormal dorsal closure. Further delineation of jar322 mutant allele showed varied phenotypes including wing defects that implicates jar in Notch signalling and in integrin function and signalling. Importantly, I found that Jar is directly regulated by JNK transcriptional activation pathway and down-regulated by the RhoGTPase pathway. Together this work emphasises the multi functional nature of myosin VI. Further the work suggests that the pro-survival function of vertebrate myosin VI is conserved in Drosophila.

Item Type: Thesis (Doctor of Philosophy (PhD))
Thesis advisor: Bloor, Jim
DOI/Identification number: 10.22024/UniKent/01.02.94335
Additional information: This thesis has been digitised by EThOS, the British Library digitisation service, for purposes of preservation and dissemination. It was uploaded to KAR on 25 April 2022 in order to hold its content and record within University of Kent systems. It is available Open Access using a Creative Commons Attribution, Non-commercial, No Derivatives ( licence so that the thesis and its author, can benefit from opportunities for increased readership and citation. This was done in line with University of Kent policies ( If you feel that your rights are compromised by open access to this thesis, or if you would like more information about its availability, please contact us at and we will seriously consider your claim under the terms of our Take-Down Policy (
Subjects: Q Science
Divisions: Divisions > Division of Natural Sciences > Biosciences
SWORD Depositor: SWORD Copy
Depositing User: SWORD Copy
Date Deposited: 16 Sep 2022 15:34 UTC
Last Modified: 16 Sep 2022 15:34 UTC
Resource URI: (The current URI for this page, for reference purposes)

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