The role of the centrosome in mitotic spindle formation.

During cell division, correct chromosome segregation between the two daughter cells is important to maintain the genetic balance in the organism. A bipolar mitotic spindle consisting of microtubules is formed to generate force to separate the chromosomes. For a long time the centrosome has been described to be the main microtubule organizing center in the cell during mitotic spindle formation. Meiotic cell divisions however, do not require the centrosomes for chromosome segregation. Currently, several papers show that mitotic spindle formation can also occur in the absence of the centrosome. This review discusses the role of the centrosomes during the formation of the microtubule spindle. We propose that although the centrosomes are important to increase the fidelity of bipolar spindle formation and microtubule organization, they are not essential to form the bipolar spindle. Furthermore, we will highlight the alternative mechanisms that can order non-centrosomal microtubules into a functional spindle. We conclude that the cell possesses sufficient cellular machinery to form the bipolar spindle in the absence of the centrosomes.