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Title: The role of Xenopus D1x5 in the establishment of the neural/epidermal boundary
Author: Day, P.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2002
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An early step in the development of the nervous system is the establishment of clearly defined neural and epidermal territories. The neural territory consists of the neural plate proper and placodal/neural crest derivatives that surround the neural plate. Using the frog Xenopus laevis as a model system I have investigated the formation of the boundary between the epidermal and neural territories. It has been observed through gene expression mapping of the early neural plate that D1x5, a homeobox-containing putative transcription factor, is the border marker located furthest away from the neural midline, and that it marks the edge of the neural ectoderm in both layers of the ectoderm. Due to this pattern of endogenous expression, D1x5, is a candidate for a role in the formation of the neural/epidermal boundary. Overexpression of D1x5 by RNA injection results in suppression of marker genes from neural, epidermal, placodal and neural crest cell fates, suggesting that D1x5 via suppression, demarcates the boundary between the neural-fated cells and those epidermal derivatives surrounding the neural ectoderm. To further support these observations, loss of function of D1x5 through the use of antisense morpholino oligonucleotides results in an expansion of the neural plate. D1x5 upregulation can be achieved by Bone morphogenetic proteins (BMPs), however in Xenopus, this induction is restricted to the anterior neural plate. Notch ICD, an activated form of X-Notch-1, can also cause D1x5 upregulation, although this occurs conversely in the epidermis and at the neural/epidermal boundary. When used in conjunction, X-Notch-1 and BMP signalling cooperate to induce D1x5 not only in the epidermis and anterior neural plate, but also in the posterior neural plate. To conclude, D1x5 is induced at the perimeter of the neural ectoderm through combined BMP and X-Notch-1 signalling, and defines a neural/epidermal boundary through suppression of cell fates present on opposing sides of this frontier.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available