Meiosis is a special kind of cell division whereby one cycle of chromosome duplication is followed by two rounds of segregations to reduce the chromosome number by half, and thereby create the haploid sperm and eggs. This is accomplished by one round of chromosome replication followed by two consecutive chromosome segregations. In the first meiotic division (meiosis I) homologous chromosome segregate, while in the second division (meiosis II) sister chromatid segregate.
During the prophase stage of meiosis I, the chromosome undergo unique interactions which include homologous chromosome paring, forming of the synaptonemal complex, DNA double strand break induction and repair into crossover recombination, and dramatic restructuring that enable monopolar attachments of the kinetochores.
In humans, all oocytes begin their development in-utero but arrest for decades in the middle of this process, leading to a rapid age related increase in meiotic division failure. This failure is the leading cause for naturally occurring miscarriages and birth defects (e.g. Down syndrome). The oocytes arrest while undergoing dramatic structural changes, termed chromosome remodeling. The chromosome are restructured from a tangled, elongated, and spread conformation that look like this:
In the Tzur lab we focus on the study of chromosome remodeling, trying to understand what facilitates this necessary part of meiosis.
We have already identified several genes encoding for structural proteins, as well as for proteins involved in gene expression, which are required for proper chromosome remodeling. In our research we make use of genetic tools, biochemical assays and high resolution microscopy to study the mechanism of operation of these genes. We are also using novel tools we developed for genome engineering and single nuclei transcriptome analysis.
to highly condensed resolved bodies, with distinct chromosomal domains, which are arranged at the metaphase plate: