The role of the TOB1 protein in gametogenesis
AffiliationAnatomy and Neuroscience
Document TypePhD thesis
Access StatusThis item is embargoed and will be available on 2020-07-30.
© 2018 Farnaz Shapouri
Previous studies indicate that TOB1 plays important roles in some cellular processes such as cell proliferation, apoptosis and tumour suppression. Gametogenesis in mammals relies on a series of complex processes that involve hormonal and local control of gene expression via transcriptional and post-transcriptional regulators. Existing data on the Tob1 gene demonstrate its expression in many adult tissues in mouse and human including the reproductive system. However, the specific cell types that express TOB1 in gonads and its function in gametogenesis were unknown. In this study, I investigated the role of TOB1 during gametogenesis in Drosophila and mouse, and its expression in human ovarian and testicular cancers. Utilising droplet digital PCR, I showed a significant increase in Tob1 gene expression during female germ cell development, but its expression was low in developing male germ cells. The presence of TOB1 protein in the mouse oocyte and round spermatids and its association with DCP2 in both cell types by immunofluorescence staining suggested that TOB1 is involved with mRNP granules and plays an important role in post-transcriptional regulation during gametogenesis. Analyses of Tob1-/- ovaries, suggest that TOB1 is associated with regulation of oocyte growth during folliculogenesis, since deletion of Tob1 resulted in atretic follicles of smaller size compared to wild type controls. A proposed mechanism by which TOB1 regulates oocyte growth, which remains to be tested, is that it interacts with SMAD3 function in oocyte and thus regulates TGFβ signals to control follicle maturation or atresia. By contrast, in the mouse testis, TOB1 appears to be involved in acrosome biogenesis, since lack of TOB1 resulted in fragmented acrosomes. Based on similarity with phenotypes in other mouse models it is suggested that TOB1 plays a role in membrane trafficking from the Golgi to the acrosome. Consistent with the role of TOB1 in mouse spermiogenesis, Drosophila Tob expression was shown in investments cones of the individualization complex (IC) by immunofluorescence. Knockdown experiments in fly demonstrated a requirement of Tob in the individualisation of sperm and a defect in the mitochondrial derivatives. The similarity of the phenotypes in TOB-deficient models of fly and mouse suggest some level of evolutionary conservation for TOB genes in spermatogenesis. Finally, my quantitative analyses of TOB1 expression in human ovarian and testicular cancers showed no significant changes in normal ovary versus serous and mucinous ovarian cancers, but decreased expression in seminoma and mixed germ cell tumours. This data suggests that TOB1 plays a role in human testicular but not ovarian cancer. Overall the studies provide evidence for TOB1 playing an important roles in gametogenesis from Drosophila to human.
- Click on "Export Reference in RIS Format" and choose "open with... Endnote".
- Click on "Export Reference in RIS Format". Login to Refworks, go to References => Import References