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Title: A chemical genetic and functional approach to studying cell migration in Xenopus development
Author: Tomlinson, Matthew Leigh
ISNI:       0000 0001 3534 8443
Awarding Body: University of East Anglia
Current Institution: University of East Anglia
Date of Award: 2007
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Xenopus embryos have long been used as a developmental model organism, their potential as an in vivo model for single cell migration has yet to be fully explored. The PhD study presented used two cell types, macrophage and melanophores. Xenopus melanophores were assayed in a chemical genetic screen to identify novel small molecule compounds effecting their migration. With respect to macrophage migration, a set of three identified XMMPs showed expression in the migrating macrophages their functional role was unknown. The function of three Xenopus MMPs was characterised. by loss-of-function. Analysis of each XMMP shows that they are all functional. The MMPs were shown to act synergistically when knocked down with each other. Localisation of the XMMPs in an embryonic wound healing model was also characterised. The highest model organism used in chemical genetic studies to date is the developing zebrafish embryo. Xenopus embryos offer a higher evolutionary model and an alternative to zebrafish embryos. Xenopus embryos were characterised as a potential developmental chemical genetic model. This proof of principle study assayed penetrance, efficacy, genetic variation and throughput. From these studies, a large-scale screen was undertaken to identify novel compounds modulating melanophore migration. Compounds effecting a number of other areas of embryonic development were identified including pigmentation, edema formation, eye development, general morphology and melanophore morphology were also identified. One compound (NCI 84093) has a striking pigment phenotype, causing a vertical banding pattern and effecting only one pigment stripe. The mode of action of NCI 84093 was further characterised. Application of the compound disrupts the formation of the dorsal pigment stripe at an early stage in development, before migration is normally observed. By molecular, biochemical and computational analysis NCI 84093 was discovered to have the pharmacological properties of a matrix metalloproteinase (MMP) inhibitor. A set of novel small molecule compounds effecting melanophore migration was identified and the mode of action of one of the compounds characterised. The set of three macrophage expressed XMMPs are shown to be functional, evidence suggests they act in combination. The application of NCI 84093 and the loss-of-function of an XMMP (XMMP-14) previously identified as being expressed by the migrating melanophores were used to characterise the migration routes of embryonic melanophores.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available