Abnormal spindle protein, asp, and the integrity of mitotic centrosomal microtubule organizing centers

The product of the abnormal spindle (asp) gene was found to be an asymmetri cally Localized component of the centrosome during mitosis, required to foc us the poles of the mitotic spindle in vivo. Removing Asp protein function from Drosophila melanogaster embryo extracts, either by mutation or immunod epletion, resulted in Loss of their ability to restore microtubule-organizi ng center activity to salt-stripped centrosome preparations. This was corre cted by addition of purified Asp protein. Thus, Asp appears to hold togethe r the microtubule-nucleating gamma-tubulin ring complexes that organize the mitotic centrosome.