By harnessing the power of fruit fly genetics, Cullen et al. (page 1005) have isolated a new microtubule-associated protein involved in mitotic spindle formation. This finding also demonstrates the feasibility of using Drosophila genetics to study microtubule-associated proteins (MAPs) in vivo in higher eukaryotes.
MAPs have been studied extensively in vitro, but genetic studies on these proteins in living cells have been done primarily in yeast, whose mitotic machinery differs from that of higher eukaryotes. In this new work, the researchers screened fly mutants for defects in mitosis, and isolated a mutant, subsequently named mini spindles (msps), in which the integrity of mitotic spindles is disrupted. Molecular cloning demonstrated that the mutated gene encodes a MAP that is conserved among eukaryotes. The Msps protein localizes to mitotic spindles and centrosomal regions in a cell cycle-dependent manner. The...
