Fluorescent Speckle Microscopy of the Kinetochore/Microtubule Interface
Ted Salmon, University of North Carolina, Chapel Hill

Lecture Abstract:
To ensure that each daughter cell inherits an accurate complement of the genome, the mitotic and meiotic spindle machinery must segregate the chromosomes correctly. Loss or gain of a chromosome in daughter cells, "aneuploidy," can lead to birth defects (e.g., Down's syndrome) and may play a critical role in tumor development. We have previously shown that merotelically oriented kinetochores can lead to anaphase "lagging" chromosomes, a source of aneuploidy in mammalian tissue cells (Cimini et al. 2001, J. Cell Biol.). Merotelic kinetochores are attached by microtubules to both spindle poles. Thus they have pulling forces in opposing directions, which can result in the chromosome lagging behind the rest of the complement during anaphase. During cytokinesis lagging chromosomes are frequently included in the "wrong" daughter cell. The error of merotelic orientation is not detected by the mitotic checkpoint nor does it prevent metaphase alignment (Cimini et al., 2002, J. Cell Sci.). The cell has correction mechanisms, however. There are 100 times as many cells with merotelic kinetochores in early mitosis and 16 times as many entering anaphase as there are cells with lagging chromosomes in late anaphase   (Cimini et al., 2003, J. Cell Sci.). In my talk, I will show how Daniela Cimini and Lisa Cameron in my lab have used spinning disk confocal fluorescence microscopy to discover how anaphase spindle mechanics and the kinetochore/microtubule interface prevent most anaphase merotelic kinetochores from producing lagging chromosomes. Shinya Inoue was a pioneer in the use of this technology for live cell imaging (Maddox et al., 1999, Biol. Bull.)