Identifying the male meiotic functions of the spindle matrix protein Megator : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Biochemistry, School of Fundamental Sciences, Massey University, Palmerston North, New Zealand

Abstract

Male infertility is an emerging global concern and investigating the molecular events accountable for healthy sperm formation is crucial to the design of diagnostic assays and curative therapeutics. The work here proposed provides the first characterisation of the nucleopore protein Megator - the Drosophila homologue of the human Tpr - throughout the meiotic divisions responsible for sperm formation. Megator/Tpr performs highly conserved roles at the nuclear pore complex during interphase. In somatic cells mitosis is also part of the spindle matrix, a structure that surrounds the spindle and promotes accurate chromosome segregation as a crucial component of the spindle assembly checkpoint (SAC). Through genetic crossing, a combination of antibodies and fluorescent protein-expressing cells, Megator was found to localise in the spindle during meiosis I, consistent with forming a matrix. Moreover, Megator depletion by in vivo RNAi led to chromosome segregation defects suggesting loss of spindle assembly checkpoint function, as it has been seen in depleted mitotic cells. Remarkably, Megator was not detectable beyond background levels in meiosis II cells. Protein depletion in these cells induced abnormal chromatin masses and some cells were entirely devoid of nuclei. Examination of other spindle matrix proteins revealed that their distributions were altered by Megator depletion. These data suggest that Megator’s roles in male meiosis are semi-conserved with mitosis