BACKGROUND:

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I started my career at the University of York where I completed an Integrated Masters in Biology. During my final year, I studied the embryo development of an extremophile fish, Orechromis alcalicus. I then started my PhD at the University of Exeter in 2020, where I transitioned to the well-established zebrafish model. 

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In my PhD I am researching the role of the Wnt/β-catenin signalling pathway in neural crest development. The neural crest is an extraordinary population of cells that emerge at the interface of the neural plate and epidermis in vertebrate embryos. NC cells (NCCs) are multipotent and form pigment cells, peripheral neurons, cardiomyocytes and the craniofacial skeleton. During their development, NCCs receive different environmental signals instructing them to adopt specific fates.

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One of the signals received by NCCs is Wnt proteins activating the Wnt/β -catenin pathway. Wnts act as long-range morphogens, providing concentration-dependent positional information to tissues. NCCs that receive high levels of Wnt form melanocytes as opposed to other fates. The objective of my research is to gain mechanistic insight into Wnt/β -catenin signalling to NCCs. I aim to identify the source of Wnt proteins and their mechanisms of transport to NCCs.

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My research will provide further insight into fundamental mechanisms that regulate embryonic development, and increase our understanding of Wnt/β-catenin signalling, a pathway implicated in cancers and Alzheimer’s disease.

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METHODOLOGY:

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During my PhD I have used a variety of tools to regulate Wnt/β -catenin signalling during development. I started treating zebrafish embryos with chemical inhibitors that over-activate or inhibit Wnt/β -catenin signalling at specific time periods. I have also used CRISPR/Cas9 to knockout Wnt genes expressed midbrain-hindbrain boundary (MHB). The MHB acts as a signalling centre to pattern adjacent brain regions, and may also signal to NCCs. The knockouts proved more difficult than expected as zebrafish have 20 Wnt genes, there appears to be a lot of redundancy!

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I have been generating transgenic zebrafish to label the MHB and to express fluorescently-tagged Wnt proteins in this region. Furthermore, to observe the transport of Wnt proteins between cells, I use confocal microscopy. More recently I started working with a light-sheet microscope with which I can take image stacks at high speed. I hope to use this to take time-series of the transport of Wnt proteins.

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RESULTS:

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Although I have not yet identified how Wnt proteins are transported from the MHB, my hypothesis is that Wnts are transported along specialised signalling protrusions known as cytonemes. I have some preliminary data from the early zebrafish embryo, where I co-expressed an eGFP-tagged Wnt3a and mCherry membrane marker. In these cells, I see eGFP-Wnt3a puncta localising with membrane protrusions.

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eGFP-Wnt3a and mCherry expression in the gastrulating zebrafish embryo. eGFP-wnt3a puncta can be found on protrusions, known as cytonemes. Scale bar 20µm.