Canonical and Non-canonical modes of Chromosome Segregation in Oocyte Meiosis

ended

Cell division is crucial for the development of complex organisms, for the homeostasis of tissues, and for the reproductive capacity of individuals. While most somatic cells are diploid and proliferate through mitosis, multiplication of sexually reproducing species relies on haploid gametes that are generated through a specialized cell division process called meiosis. To achieve this reduction in ploidy, two rounds of chromosome segregation follow a single phase of genome replication. Inaccuracy in this process leads to gametes that carry an incorrect number of chromosomes and to aneuploid embryos after fertilization. In their vast majority, these are non-viable and lead to spontaneous abortion: defective meiotic division is therefore a major obstacle in achieving reproduction. However, the key principles that drive this process are still poorly understood, one main reason being the diversity of the molecular scenarios that have been adopted across evolution to regulate oocyte chromosome segregation. To dissect the key components of oocyte meiotic chromosome segregation, we propose to carry out a multi-disciplinary approach, combining several nematode species with the use of high-resolution live and electron microscopy, cutting edge genomic and proteomic technologies, and biochemistry coupled to in silico modeling. In Work Package 1 (WP1), we will analyze the molecular mechanisms controlling the self-assembly of the chromosome segregation machinery -the meiotic spindle- in the oocyte. WP2 will focus on defining how chromosome segregation is achieved in oocytes with non-canonical kinetochore geometry. WP3 aims at analyzing meiotic divisions in parthenogenetic nematodes with specific meiotic constraints, such as centrosomal oogenesis and unichromosomal genomes. By considering the wealth of mechanisms that can drive chromosome segregation in oocytes, this project will provide decisive steps towards understanding the essential and universal features of female meiosis.