Analysing the mechanisms of spindle formation in C. elegans oocytes.

Cell division, which exists in two forms, mitosis and meiosis, involves the precise segregation of the chromosomes among the daughter cells. Segregation of chromosomes involves a sophisticated microtubule-based spindle. During somatic cell division and spermatogenesis, spindle microtubules are assembled from two microtubule-organising centres, termed the centrosomes. In contrast, during female meiosis, centrosomes are eliminated early-on and an acentrosomal spindle is assembled via atypical mechanisms. My project aims at dissecting the mechanisms of acentrosomal spindle assembly in the oocyte of the soil worm nematode Caenorhabditis elegans. I focus on the specific function of the CLS-2 protein in spindle microtubule assembly. CLS-2 is a conserved microtubule-associated protein (MAP) which promotes spindle microtubule assembly by controlling their dynamics parameters. I developed an optogenetic approach, based on the LOV2-Zdk1 system, to inactivate CLS-2 in a temporally-controlled manner during oocyte meiosis. Once spindle microtubules are assembled, their organisation into a bipolar spindle relies in large part on the activities of microtubule motor proteins. These include Kinesin-like Proteins (KLPs), microtubule motors that promote microtubule sliding and organisation. I analysed the presence or absence of various KLPs in the C. elegans oocyte. Overall my project will bring insight into the fundamental mechanisms of acentrosomal spindle assembly. It will potentially help understanding defects in chromosome segregation during oogenesis and their detrimental impact on fertility.