Dissecting the role of molecular motors in the mitotic spindle.

Accurate segregation of genetic material during both mitosis and meiosis is essential for the viability of future cellular generations. Genetic material is packaged in the form of chromosomes during cell division, and chromosomes are segregated equally into two daughter cells by a dynamic, microtubule-based structure known as the spindle. Molecular motor proteins of the kinesin and dynein superfamilies are essential players in the functional microanatomy of cell division. They power various aspects of spindle assembly and function, including establishing spindle bipolarity, spindle pole organization, chromosome alignment and segregation, regulating microtubule dynamics, and cytokinesis. This review highlights the roles that various members of the kinesin and dynein motor superfamilies play during mitosis and meiosis. Understanding how microtubule motors function during cell division will unravel how the spindle precisely segregates chromosomes, and may offer insights into the molecular basis of disease states that arise from spindle malfunctions. For example, chromosome non-disjunction during meiosis causes such disorders as Klinefelter, Turner, and Down Syndromes. Chromosome non-disjunction during mitosis is an important contributing mechanism for tumor progression. In addition, since motor proteins are essential for spindle assembly and function, they provide obvious targets for intervention into the cell division cycle, and compounds that specifically block motor functions during mitosis may prove to be valuable chemotherapeutic agents. Anat Rec (New Anat) 261:14-24, 2000.