Characterisation of a RhoBTB3 deficient mouse model

Lutz, Julia Babette

October 2012

Thesis or dissertation

© 2012 Julia Babette Lutz. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder.

RhoBTB proteins are atypical members of the Rho-family of small GTPases with a characteristic domain architecture: a GTPase-domain is followed by a proline-rich region, a tandem of two BTB domains and a C-terminal region. RhoBTB3 is the most divergent member of the RhoBTB family and has been shown to have ATPase instead of GTPase activity. Its precise roles at a cellular and organismal level are unknown. In order to investigate the functions of RhoBTB3 in vivo a RhoBTB3 knockout mouse was characterised in this study. The expression pattern of rhobtb3 was studied with the help of a β-galactosidase reporter gene and confirmed in a number of cases by studying protein expression. The overall strong expression in embryos was highest in bone, cartilage, smooth muscle and heart followed by skeletal muscle, skin and localised areas of the nervous system. The expression declines during late development but remains visible in cartilage, heart, kidneys, smooth muscle cells of blood vessels, testes and ovaries of adult animals. Important phenotypic changes in RhoBTB3 knockout animals are reduced survival as well as growth and fertility defects. Testes of knockout animals are smaller than wildtype controls. Proliferation of primary lung fibroblasts and the integrity of the intestinal tract appear not to be affected by knockout of RhoBTB3. RhoBTB3 appears to have a completely novel role in haemostasis and platelets of RhoBTB3 knockout animals have defects in aggregation stimulated by collagen and thrombin as well as in adhesion to fibrinogen and collagen. They express higher numbers of α2β1 and αIIbβ3 integrins which might relate to the molecular origin of the observed defects. Platelet morphology and in vivo tail bleeding times were appeared unaffected by loss of RhoBTB3. A two-hybrid screening yielded Kindlins as potential binding partners of RhoBTB3 and the interaction has been verified in this study by co-immunoprecipitation. Kindlins are mediators of integrin activation and have been implicated in various human diseases of the skin, the intestine and haematopoietic tissue.

Hull York Medical School, The University of Hull and University of York
Rivero-Crespo, Francisco
Sponsor (Organisation)
University of Hull
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