Centrosome splitting in neutrophils: an unusual phenomenon related to cell activation and motility.

Detergent-extracted whole mount preparations of human neutrophilic polymorphonuclear leukocytes (neutrophils) were used to study centrosome position and microtubule organization during random, chemokinetic and chemotactic locomotion. Chemotaxing neutrophils have a polarized external and internal morphology, with centrosomes between the anterior lamellipod and the nucleus. In randomly locomoting cells centrosome position is highly variable with respect to these two cell organelles. Stimulation of randomly locomoting cells with a chemoattractant (chemokinesis) rapidly (within 1 min) induces pronounced spreading and ruffling and concomitantly initiates, in up to 55% of the cells, transient separation of the centrosome into two solitary centrioles, each surrounded by an aster of microtubules. In addition, about 10% of the cells with separated centrosomes have a third, centriole-free aster of microtubules radiating from an accumulation of dense material. Neutrophil activation also leads to an increase in the number of microtubules and an approximately twofold increase in polymer length. This unusual response of the centrosome supports a correlation between cell movement and microtubule organization.