Knockdown of KIF9 leads to defects in mitotic entry and progression in mammalian cells

Kinesin motors bind to microtubules and function in mitosis and intracellular transport depending on the position of the motor domain within the primary sequence (Hirokawa and Noda 2008). KIF9 has recently been shown to be involved in MTOC positioning and mitotic entry in Dictyostelium (Tikhonenko et al. 2009). To determine if a similar role for KIF9 exists in mammalian cells, we are using siRNA-mediated knockdown of KIF9 in COS-7 cells. Analysis of unsynchronized and cell-cycle synchronized cells treated with siRNA to KIF9 reveal that the transition from G2 to M phase is delayed and that mitotic progression is also affected. Additionally, our data indicates that spindle pole function during anaphase may be abnormal in cells treated with siRNA, suggesting a role for KIF9 during that stage.