Studies on cell division in mammalian cells. VII. A temperature-sensitive cell line abnormal in centriole separation and chromosomemovement

摘要

A temperature-sensitive Syrian hamster mutant cell line, ts-745, exhibiting novel mitotic events has been isolated. The cells show normal growth and mitosis at 33 degrees C, the permissive temperature. At the nonpermissive temperature of 39 degrees C, mitotic progression becomes aberrant. Metaphase cells and those cells still able to form a metaphase configuration continue through and complete normal cell division. However, cells exposed to 39 degrees C for longer than 15 min can not form a normal metaphase spindle. Instead, the chromosomes are distributed in a spherical shell, with microtubules (MT) radiating to the chromosomes from four closely associated centrioles near the center of the cell. The cells progress from the spherical monopolar state to other monopolar orientations conical in appearance with four centrioles in the apex region. Organized chromosome movement is present, from the spherical shell state to the asymmetrical orientations. Chromosomes remain in the metaphase configuration without chromatid separation. Prometaphase chromosome congression appears normal, as the chromosomes and MT form a stable monopolar spindle, but bipolar spindle formation is apparently blocked in apremetaphase state. When returned from 39 degrees to 33 degrees C, thedefective phenotype is readily reversible. At 39 degrees C, the mitoticabnormality lasts 3-5 h, followed by reformation of a single nucleus andcell flattening in an interphase- like state. Subsequent cell cycle eventsappear to occur, as the cells duplicate chromosomes and initiate a secondround of abnormal mitosis. Cell cycle traversion continues for at least 5 din some cells despite abnormal mitosis resulting in cells accumulatingseveral hundred chromosomes.