Morphological changes in the nucleus and actin cytoskeleton in the processof Fas-induced apoptosis in Jurkat T cells

To investigate the early event of apoptosis, we monitored the morphological changes in the early stage of Fas-induced apoptosis in the human T-cell ly mphoma cell line Jurkat, using confocal microscopy. Morphological changes i n the nuclei were observed from 30 min after stimulation, and preceded the changes in the cytoskeleton. This kind of change was enhanced in the presen ce of EGTA but decreased in the presence of dihydrocytochalasin B, without any changes in caspase-3 activation. During the changes in shape of the cel ls, the actin cytoskeleton collapsed and shrank in the center. Even though nuclei also changed their shapes in apoptotic cells, they were partially TU NEL-negative, suggesting that they were not yet damaged at the DNA level. O ur results suggest that, in the process of apoptosis in Jurkat cells, cell nuclei and cytoskeleton are changed first, then membrane blebbing and caspa se-3 activation occur, and fragmentation of chromosomal DNA is last.