A maternal effectrough dealmutation suggesting multiple pathways regulating Drosophila RZZ kinetochore recruitment

Proper kinetochore recruitment and regulation of Dynein and the Mad1-Mad2 complex requires the Rod-Zw10-Zwilch (RZZ) complex. We describe rodZ3, a maternal-effect Drosophila mutation changing a single residue in the Rough Deal (Rod) subunit of RZZ. Although RZ3ZZ complex is present in early syncytial stage embryos laid by homozygous rodZ3 mothers, it is not recruited to kinetochores. Consequently, the embryos have no spindle assembly checkpoint (SAC), and syncytial mitoses are profoundly perturbed. The polar body (residual meiotic products) cannot remain in its SAC-dependent metaphase-like state, and decondenses into chromatin. In neuroblasts of homozygous rodZ3 larvae, RZ3ZZ recruitment is only partially reduced, the SAC is functional and mitosis is relatively normal. RZ3ZZ nevertheless behaves abnormally: it does not further accumulate on kinetochores when microtubules are depolymerized; it reduces the rate of Mad1 recruitment; and it dominantly interferes with the dynein-mediated streaming of RZZ from attached kinetochores. These results suggest that the mutated residue of rodZ3 is required for normal RZZ kinetochore recruitment and function and moreover that the RZZ recruitment pathway may differ in syncytial stage embryos and post-embryonic somatic cells.