Barker, D.J.; (2010) Junctional complexes and cell-cell signalling in zebrafish morphogenesis. Doctoral thesis , UCL (University College London).

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Abstract

Intercellular junctions are composed of tight, gap and adherens junctions and have been shown to play many roles in embryonic morphogenesis. I have been studying the role that intercellular junctions play in zebrafish development. First I have studies the organisation of apical neuroepithelial junctions in the developing brain. By quantifying size and segmental patterning of the junctional arrangement in the hindbrain and elsewhere I have described a level of organisation that is characteristic of compartment boundaries. I describe a distinct pattern of apical junctions in both boundary and non-boundary regions. This pattern appears to be in part regulated by the Notch signalling pathway since apical junctions distribution is different in hdac1-/- zebrafish, which have deficient Notch-Delta signalling. Second I have established that boundary cells prevent the exchange of small molecular weight, gap junction permeable dyes between adjacent CNS compartments, suggesting that the compartments are separate developmental units. Third I have studies the role of gap junction mediated intercellular communication in the propagation of calcium waves and in the coordination of cell divisions in the zebrafish blastocyst. Calcium activity is cyclical, with cells producing a greater number of calcium transients and intercellular waves during cytokinesis than during interphase. In control conditions distinct waves of cell divisions spread across the embryo in an animal to vegetal progression. I show that both the calcium activity and the cell division waves require gap junction communication because pharmacological blockade of coupling reduces the frequency of calcium activity and disrupts cell division waves.

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