Characterization of the Derlin protein, CUP-2, in promoting stem cell proliferation in the C. elegans germ line
Date
2018-03-27
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Abstract
Understanding of how tissue homeostasis is maintained is not only essential for furthering our understanding of a fundamental area in Biology, but also has important implications for regenerative medicine and the design of therapeutics for human health. The germline of the C. elegans nematode serves as an excellent model to study adult stem cells and how the balance between proliferation and differentiation is maintained in this vital tissue. GLP-1/Notch signalling is the principal pathway that promotes proliferation of Germline Stem Cells (GSCs) in this system. In this thesis, the role of a Derlin (Degradation in the ER) protein, CUP-2, in promoting GLP-1/Notch signalling-mediated proliferation of GSCs is presented. Reducing cup-2 activity strongly suppresses germline tumours caused by increased Notch signalling. However, cup-2(0) is unable to suppress Notch-independent germline tumours, which suggests that cup-2 promotes Notch signalling specifically and not cell proliferation in general. This is further supported by cup-2’s ability to influence the expression of a read-out for Notch signalling, SYGL-1. The cup-2 gene was tagged using CRISPR/Cas9 editing with an epitope tag and CUP-2 was found to be expressed in the germ line, which is consistent with its role in promoting Notch signalling. The ability of cup-2 to promote GLP-1/Notch signalling likely represents a conserved function, since der-2, a Derlin homolog, was also found to contribute to the development of Notch-dependent germ line tumours. In fact, cup-2 and der-2 appear to additively promote GLP-1/Notch signalling. Derlin proteins are known to function in Endoplasmic Reticulum-Associated Degradation (ERAD) of proteins. Therefore, this work sheds light on the importance of ERAD in maintaining the balance between proliferation and differentiation in stem cells.
Investigation into the mechanism by which cup-2 promotes GLP-1/Notch signalling led to the discovery that cup-2 is involved in anchoring the niche cell, the Distal Tip Cell, in place in the aging gonad. This is a novel phenotype not reported before in the literature. The CRISPR/Cas9 tagged cup-2 alleles developed as part of this thesis could serve as a useful reagent for further studies in determining the mechanism by which cup-2 promotes GLP-1/Notch signalling.
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Keywords
C. elegans, Developmental Biology
Citation
Singh, R. (2018). Characterization of the Derlin protein, CUP-2, in promoting stem cell proliferation in the C. elegans germ line (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/31769