Dystroglycan in the uterus: Roles in embryo implantation and endometrial cancer
Creators: name: Sophea Heng
Publisher: name: Monash University
Year: 2017
Subjects: Uncategorized

description: Embryo implantation requires a receptive endometrium. Development of endometrial receptivity involves major cellular and molecular changes in the epithelium. PC6, a member of the proprotein convertase (PC) family, is the only PC that is significantly up-regulated in the endometrial epithelium for receptivity. Dystroglycan (DG) is a large glycoprotein comprised of α-DG and β-DG subunits. The central glycosylated region of α-DG mediates cell adhesion, but this region is obstructed by its N-terminus (α-DG-N). Proteolytic cleavage of α-DG by a PC enzyme at amino acid 312 removes α-DG-N and exposes the central region for cell adhesion. <br> One aim of this thesis was to investigate the importance of post-translational removal of α-DGN by PC6 for endometrial receptivity in cycling women. Chapter 2 established that the PC6-mediated removal of α-DG-N was critical for establishing endometrial receptivity, and that the full-length α-DG was an endometrial barrier for embryo attachment. A single mutation at amino acid 312 prevented α-DG-N removal, retained the full-length α-DG on the cell surface, and reduced cell adhesion and attachment to trophoblast spheroids (blastocyst surrogates). Additionally, the α-DG-N removed from the endometrial tissue was detected in uterine fluids of women, with levels correlating to receptivity. <br> We have previously reported that endometrial PC6 is secreted into the uterine fluid and that the levels are significantly increased at receptivity. Expanding from this knowledge, an ELISA for PC6 was successfully established in Chapter 3 using human specific PC6 monoclonal antibodies. This PC6 ELISA was validated to be able to quantify PC6 in human uterine fluids as a noninvasive method to determine receptivity. <br> The studies in Chapter 2 suggested that the human uterine fluid also contained α-DG-N derived from PC6-cleavage of endometrial tissue α-DG. An ELISA for α-DG-N was thus established in Chapter 4 using commercial antibodies to quantify α-DG-N in human uterine fluids to determine receptivity. With both ELISAs, significantly higher levels of both PC6 and α-DG-N were detected in human uterine fluids in the receptive phase of the menstrual cycle. <br> Endometrial cancer is one of the most common gynecological malignancies in women. Removal of α-DG-N by another PC member, furin, was reported in cancer. Our previous studies have established that furin is the only PC member that is up-regulated in endometrial cancer tissue of post-menopausal women. The work in Chapter 5 thus determined the significance of α-DG-N removal in endometrial cancer. Removal of α-DG-N was found to be important for early stage endometrial cancer development; this removal promoted epithelial-mesenchymal transition and enhanced estrogen-dependent proliferation of endometrial epithelial cells. Furthermore, α-DG-N that was removed from the endometrial cancer tissue was detected in uterine fluids by the α-DGN ELISA, and the levels were significantly higher in early stage cancer patients. <br> In summary, this thesis demonstrated the significance of PC-mediated post-translational removal of α-DG-N in the development of endometrial receptivity in cycling women and endometrial cancer in post-menopausal women. The studies also suggest a potential clinical utility of uterine fluid α-DG-N in non-invasive detection of endometrial receptivity (cycling women) and early stage endometrial cancer (post-menopausal women).