McCorkindale, Alexandra L (2014) Examination of the Piwi/piRNA pathway in somatic stem cells of the mouse (Restricted until July 2017). PhD thesis, Victor Chang Cardiac Research Institute.
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Abstract
The Piwi proteins are a clade of the Argonaute family specific to animals that bind small RNAs called Piwi-interacting RNAs (piRNAs). The Piwi/piRNA system is indispensable in germ cells, where it has dual roles in germline stem cell self-renewal and the epigenetic silencing of retrotransposons. Although Piwi/piRNA activity is generally assumed to be restricted to the germline, there is mounting evidence that Piwi genes and proteins also have a somatic function. In primitive metazoans, Piwi orthologues appear to be important for self-renewal of somatic stem cells, and Piwi homologues are expressed in multiple mammalian tissues as well as in a variety of cancers.I hypothesised that the Piwi/piRNA system is important for mammalian somatic stem cell self-renewal, in particular, in maintaining pluripotency in embryonic stem cells. I also hypothesised that the Piwi/piRNA pathway is involved in conferring the stem cell-like phenotype of certain cancer cells. To test these hypotheses, I investigated the expression and function of the murine Piwi homologue, Miwi2, in embryonic stem (ES) cells and a panel of breast cancer cell lines.In this thesis, I show that Miwi2 is expressed in the cytoplasm of murine ES cells, and that its expression diminishes along with ES cell differentiation; however, Miwi2 does not appear to be critical for ES cell self-renewal and pluripotency. I also show that Miwi2 is highly expressed in metastatic 4T1 murine breast cancer cells, and that ectopic Miwi2 expression in syngenic, non-metastatic 4TO7 cells causes gene and small RNA expression changes in pathways relevant to metastasis. In ES cells, I find that Miwi2 associates with repeat-derived piRNAs and piRNAs produced from large intergenic clusters, as well from the 3’UTR of genes, including the master regulators of pluripotency, Oct4, Sox2 and Nanog. In 4T1 cells, Miwi2 associates with piRNAs from 3’UTR clusters, as well with 5’ tRNA fragments that are linked to translational control. The function of Miwi2 in ES cells and cancer biology remains unclear, but my data indicate that Miwi2 and its associated piRNAs have a role in the regulation of gene expression in somatic cells.
| Item Type: | Thesis (PhD ) |
|---|---|
| Additional Information: | Supervisor: Suter, Catherine, Victor Chang Cardiac Research Institute, Faculty of Medicine, UNSW; Cropley, Jennifer, Victor Chang Cardiac Research Institute, Faculty of Medicine, UNSW; Romaric, Bouveret, Victor Chang Cardiac Research Institute, Faculty of Medicine, UNSW |
| Subjects: | R Medicine > R Medicine (General) |
| Depositing User: | Repository Administrator |
| Date Deposited: | 28 May 2017 23:22 |
| Last Modified: | 16 Oct 2020 01:10 |
| URI: | https://eprints.victorchang.edu.au/id/eprint/591 |
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