View Program - 63rd Annual Drosophila Research Conference

Meiosis is a conserved process of cell division occurring in sexually reproducing eukaryotes which produces gametes with half the number of chromosomes. Errors in this process result in infertility, miscarriages, and genetic disorders. One poorly understood protein in meiosis, ROD, is a component of the ROD-ZW10-Zwilch (RZZ) complex and localizes to the kinetochores. The RZZ complex is involved in attachment error correction and the spindle assembly checkpoint (SAC) during mitosis. Error correction involves the selective stabilization and destabilization of kinetochore-microtubule (KT-MT) attachments while the SAC delays entry into anaphase until accurate attachments form. Mitotic evidence suggests that RZZ at the kinetochores prevents the formation of premature stable attachments. Attachment stabilization requires RZZ removal, a process called streaming which is suggested to depend on the microtubule motor protein Dynein and its recruitment factor Spindly. However, the role of ROD in these processes is not well characterized in female meiosis, which is unique in that it lacks the centrosomes and involves the segregation of homologous chromosomes rather than sister chromatids.

To analyze the function of ROD in female meiosis I, we observed ROD behavior in mutant or RNAi oocytes for proteins hypothesized to interact with RZZ. Female Drosophila depleted of ROD in the ovaries are sterile and have chromosome orientation defects, suggesting that ROD is required for correct KT-MT attachments. We found that ROD recruitment to the kinetochores is mediated by amino acids 154-840 of the kinetochore protein SPC105R. Furthermore, while ROD is not required for the creation of the initial KT-MT attachments, it may have a role in preventing or correcting erroneous attachments. Surprisingly, ROD removal may not be required for creating stable attachments, as in mitosis. Therefore, meiotic RZZ streaming may depend on the cell cycle stage rather than attachment status. We also found that ROD streaming in oocytes is at least partly Spindly-independent even though Spindly is required for meiosis I, suggesting potential Dynein-independent mechanisms of RZZ removal in meiosis. In the absence of microtubules, ROD expands around the kinetochores, likely to facilitate microtubule capture and contribute to SAC signaling. Determining how ROD regulates microtubule attachments will provide valuable insight into how pairs of homologous chromosomes segregate to maintain meiotic fidelity.

Regulation of Meiotic Kinetochore-Microtubule Attachments by the RZZ Complex