The role of MAD2 in mitotic cell cycle regulation

The research being proposed is designed to explore the mechanism of action of a recently identified human mitotic checkpoint gene, hsMAD2, and to determine if defects in the mitotic checkpoint pathway contribute to the generation of neoplasia in mouse models. hsMAD2 is the human homologue of a gene first identified in the budding yeast Saccharomyces cerevisiae (scMAD2) where its product is required for cells to arrest in mitosis if the mitotic spindles are improperly attached to the kinetochores of chromosomes. Yeast cells with defects in scMAD2 are hypersensitive to mitotic spindle inhibitors such as nocodazole and benomyl due to the progression of these cells through mitosis despite incomplete spindle assembly which in turn leads to massive chromosome loss. This project focuses on the importance of hsMAD2 for the execution of the above described mitotic checkpoint in mammalian cells and will determine whether loss of this checkpoint can lead to neoplasia. Embryonic stem (ES) cells and mice .defective for both copies of the MAD2 gene will be created and it will be determined if such defects lead to a loss of mitotic checkpoint control, hypersensitivity to mitotic spindle inhibitors or, in the case of the MAD2 null mice, an increased frequency of tumor progression. This study will allow an assessment of the importance of genomic instability m the generation of neoplasia.