May 20, 1999. Mitosis is the process that ensures that all cells during divison are genetically identical to each other and to the original fertilized egg. This microscopic dance, essentially the engine of living things, is driven by many forces. Zheng's lab is interested in the microtubules, which are tiny filaments composed of protein that help cells to keep their shape. They are found in cells in the stages between mitosis.
Chromosomes attach to the spindle by their centromeres.
Exactly what the signal is that stimulates the microtubules to assemble is the mystery that is being elucidated by Zheng and Wilde. Previous experiments have shown that the signals for microtubules to assemble come from a signal that results when the cell's nuclear membrane ruptures. Up to now, the nature of the signal has not been known. Chronologically, this makes sense, GTPase Ran is stored within the nucleus. It is only once the nucleus ruptures that the signals are released into the cell and come in contact with the microtubules and centrosomes.