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Title: The development of cilia on the Ciona intestinalis embryo and the evolution of chordate left-right asymmetry
Author: Thompson, Helen
ISNI:       0000 0004 2723 8668
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2011
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Most multicellular organisms have body plans that exhibit an element of symmetry; either radial or bilateral symmetry. Bilateral symmetry refers to organisms which have a single plane of symmetry with each side a mirror image of the other. Although externally these species appear symmetrical, internally, the organs are positioned in an asymmetric manner. This left-right axis is the last axis established after the A-P axis and D-V axis and recent research has analysed how this asymmetry is established. In the mouse it has been shown that monocilia on the organiser region, the mouse ventral node, rotate and generate a leftward fluid flow across the node. This flow, termed nodal flow, is essential for the left-sided localised expression of nodal, lefty and pitx2 and subsequent asymmetric patterning of organs. Nodal flow is highly conserved in the vertebrates but, although the conservation of asymmetric gene expression extends into the invertebrates, whether this is established through directional flow remains unknown. This research has investigated the extent of nodal flow conservation in a basal chordate, the urochordate, Ciona intestinalis. Here I have shown, through Electron Microscopy and immunofluorescence, that cilia are present, at the posterior of each cell of the Ciona intestinalis embryo, at the time point indicative to a role in the establishment of left-right asymmetry. They do not appear to be homologous to the cilia of the mouse ventral node because they are not motile and have a disorganised microtubule structure. However, the cilia may still have an important role in the development of left-right asymmetry in a sensory capacity or provide the site for H+/K+-ATPase channels already known to be involved in Ciona intestinalis left-right asymmetry.
Supervisor: Shimeld, Sebastian ; Dawe, Helen Sponsor: Biotechnology and Biological Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Evolution (zoology) ; Biology ; Development (zoology)