Cells without centrosomes lack radial arrays of astral microtubules. Dynactin is also required for microtubule anchoring at centrosomes and centrosome integrity. As mitosis progresses, both centrosomes separate to generate the mitotic spindle. As mitosis progresses, both centrosomes separate to establish the mitotic spindle. During interphase, PLK1 localizes to centrosomes. The two centrosomes polymerize tubulin to help form a microtubule spindle apparatus. Nonkinetochore microtubules lengthen, pushing the centrosomes farther apart. The mitotic spindle then forms between the two centrosomes. Motor proteins then push the centrosomes along these microtubules to opposite sides of the cell. Aurora A associates with centrosomes and is believed to regulate mitotic entry. OFD1 localizes to both centrosomes and basal bodies within the human genetic cellular structure. Microtubules involved in the interphase scaffolding break down as the replicated centrosomes separate. Cells divide along the line connecting two centrosomes of the spindle apparatus. Sperm with mutant or absent centrosomes fail to establish a posterior pole. Aberrant numbers of centrosomes in a cell have been associated with cancer.