Free centrosomes: Where do they all come from?

Centrosomes act as major microtubule-organizing centers in most cell types. Their functions in interphase and mitosis are usually facilitated by their association with the nucleus. This may be particularly true in very large cells. Several papers report free centrosomes in syncytial Drosophila embryos. However, this phenotype often remains little explored. Yet, free centrosomes can occur by multiple mechanisms, including functional defects of the mitotic spindle, detachment of centrosomes from the nuclear envelope, centrosome inactivation upon DNA damage, and de novo centrosome genesis. Deciphering the cellular mechanism leading to free centrosomes upon a given perturbation such as a mutation or injection of a drug, can provide valuable clues regarding the nature of the molecular pathway affected. To this end, genetic and cytological tests, as well as time-lapse imaging are available. These studies can inform on the biology of centrosomes, cell cycle regulation and cytoskeletal dynamics. Here we briefly discuss what to make of free centrosomes in the fly embryo.