Making more microtubules by severing: a common theme of noncentrosomal microtubule arrays?

Two related enzymes, katanin and spastin, use the energy from ATP hydrolysis to sever microtubules. Two new studies (one in this issue; see McNally et al., p. 881) show that microtubule severing by katanin provides a means for increasing microtubule density in meiotic spindles. Interestingly, loss of spastin leads to a sparser microtubule array in axons and synaptic boutons. Together, these studies hint at a wider role for microtubule-severing enzymes in the formation and organization of noncentrosomal microtubule arrays by generating new seeds for microtubule growth.