Spindle assembly: asters part their separate ways

Abstract

Cells have developed diverse ways to separate two microtubule asters to form a mitotic spindle. Here, I focus on two mechanisms used to position asters around chromosomes during mitosis: first, aster migration around the nuclear envelope and, second, aster attachment to a contractile cortex at the plasma membrane after the nuclear envelope has broken down. Although certain cell types use one mechanism predominantly, most rely on both to ensure proper spindle assembly.