Figure 5.

Mitotic spindle abnormalities in PS-1 transfected cells. (A) hTERT cells were transfected for 48 hours with either the WT or M146L PS-1 plasmid or the empty vector and then stained with anti-α-tubulin monoclonal antibody and DAPI as a co-stain. Typical examples of cells in metaphase and anaphase are shown. Note the well-formed spindles, the correctly-positioned DNA and the clearly-defined microtubule organizing centers/centrosomes in the vector-transfected cells (a,b). In contrast, cultures transfected with PS-1-expressing plasmids developed numerous cells with abnormal mitotic spindles by 48 hours (c,d). For example, the first cell (c) appears to be in metaphase, however, there is no evidence that any centrosome or microtubule organizing center (MOC) has begun to develop, although the DNA is tightly arrayed along a metaphase plate. The next cell (d) appears to be in anaphase, but again the microtubule array and centrosomes are not well defined. Note also the apparent presence of lagging chromosomes left at the metaphase plate as the rest of the DNA has begun to move to opposite poles of the cell. (B) Quantification of the abnormal mitotic figures in cells transiently transfected with WT or mutant (M146L) PS-1 show more mitotic abnormalities (abnormal spindle appearance and lagging chromosomes) than cells transfected with the empty vector.