Ultrastructural Insights into Augmin-Dependent Microtubule Nucleation in the Spindle

Abstract

The mitotic spindle is a highly organized microtubule-based structure that is required for accurate chromosome segregation. It is generally known that the centrosomes and the chromosomes function as scaffolds for microtubule generation during spindle formation. In addition, emerging evidence suggests that the microtubules within the spindle are important for the spindle microtubule supplementation.  An eight-subunit protein complex augmin plays a pivotal role in the microtubule-dependent microtubule generation during spindle formation, but the molecular basis of augmin’s functions remains unclear. Our latest research, which uses electron tomography and 3-D modeling, revealed that microtubule branching occurs within the spindle in an augmin-dependent fashion, demonstrating the ultrastructural basis of the microtubule-dependent microtubule generation during functional spindle formation.