The work presented in this thesis is a study of human pancreas development. The principle goal of this work is to provide information that can be used in the development of treatments for Type 1 Diabetes and in pancreas regeneration methodologies. The transcription factor (TF) sex determining region Y homeobox gene 9 (SOX9) has been identified as a key factor in human pancreas development but its role has not been well characterized. The expression of SOX9 during early pancreas development was analyzed by immunostaining of fixed embryonic and fetal sections in the context of other developmentally important TFs. Modulators of SOX9 function, downstream targets and upstream regulatory pathways were investigated in human cell lines using coimmunoprecipitation, small interfering RNA (siRNA) knockdown, quantitative polymerase chain reaction (qPCR), luciferase assays and small molecule signaling pathway inhibitors. SOX9 was expressed in epithelial progenitors from initial human pancreas specification, but became excluded from the periphery of the epithelium and developing islet cells as differentiation proceeded. It was co-expressed with important endocrine and exocrine differentiation factors during the early stages of development. Some factors, such as Nirenberg and Kim 2, homeobox family member, drosophila, homolog of, 2 (NKX2.2) showed differing expression profile compared to murine development, while the widespread expression of endocrine factors before expression of the pro-endocrine gene neurogenin 3 (NGN3) suggested that these factors play an important role in initiating endocrine specification. Two transcription factors, GATA-binding protein 4 (GATA4) and neurogenic differentiation 1 (NEUROD1), were found to interact with SOX9 in potentially developmentally relevant complexes. This prompted the search for downstream targets of these transcriptional complexes by in silico analysis, which identified an array of novel potential downstream targets. Luciferase assay analysis of a subset of these genes showed SOX9 to activate a regulatory region of NGN3, and inhibit the regulatory regions of carboxy peptidase A6 (CPA6), v-ets avian erythroblastosis virus E26 oncogene homolog1 (ETS1) and SPONDIN1. An additional target of SOX9, osteopontin (OPN), was identified from a microarray of Sox9 knockout mouse pancreata. Investigation of SOX9 and OPN regulation by the Hedgehog signalling pathway (HH) identified both factors to be regulated by the pathway, suggesting SOX9 may act as a mediator of HH signalling. This is the first study to identify a range of SOX9 targets relevant to human pancreas development. While further characterization is required this work has provided essential clues to the function of SOX9, and provides a detailed framework of SOX9 expression and targets for future pancreatic studies to build upon.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:549036 |
| Date | January 2011 |
| Creators | Roberts, Neil Alistair |
| Contributors | Piper Hanley, Karen ; Hanley, Neil |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/the-role-of-sox9-during-human-pancreas-development(dab5d8da-4c02-4592-b05e-471984461dcc).html |
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