The respective contributions of the mother and daughter centrioles to centrosome activity and behavior in vertebrate cells

We have generated several stable cell lines expressing GFP-labeled centrin. This fusion protein becomes concentrated in the lumen of both centrioles, making them clearly visible in the living cell. Time-lapse fluorescence mic roscopy reveals that the centriole pair inherited after mitosis splits duri ng or just after telophase. At this time the mother centriole remains near the cell center while the daughter migrates extensively throughout the cyto plasm. This differential behavior is not related to the presence of a nucle us because it is also observed in enucleated cells. The characteristic moti ons of the daughter centriole per sist in the absence of microtubules (Mts) , or actin, but are arrested when both Mts and actin filaments are disrupte d. As the centrioles replicate at the G(1)/S transition the movements exhib ited by the original daughter become progressively attenuated, and by the o nset of mitosis its behavior is indistinguishable from that of the mother c entriole. While both centrioles possess associated gamma-tubulin, and nucle ate similar number of Mts in Mt repolymerization experiments, during G(1) a nd S only the mother centriole is located at the focus of the Mt array. A m odel, based on differences in Mt anchoring and release by the mother and da ughter centrioles, is proposed to explain these results.