 |
 |
Dahong Zhang
Associate Professor, Zoology
|
 |
||||||||||||||
RESEARCH:
I am a cell biologist interested in cellular mechanics of mitosis and cytokinesis and the control of cell cycle. Every time a eukaryotic cell divides, mitosis has to occur accurately to distribute replicated chromosomes to the spindle poles, and cytokinesis has to initiate in the right place to partition segregated chromosomes into the daughter cells. Inaccurate chromosome distribution and uncontrolled cell division may result in cancer and birth defects or other related diseases.
Methods: My laboratory uses biomechanical techniques to investigate mechanisms underlying chromosome movement and cell cleavage. Our basic strategy is to mechanically dissect and reconstruct spindle apparatus as desired in living grasshopper spermatocytes. The resulting effects on cell division are observed with high-resolution imaging techniques, such as digital-enhanced polarization, DIC, epifluorescence, and confocal. This strategy simplifies the problem of interest in testing and proposing hypotheses.
Mitosis: Our current focus in mitosis is on chromosome congression, a process that governs movement of partner/sister chromosomes to the spindle equator and ensures equapartition of chromosomes. Failure in chromosome congression due to malorientation or misattachment will lead to either the activation of spindle checkpoint that blocks anaphase chromosome segregation or a disastrous chromosome distribution into the daughter cells. We are interested in how chromosomes know the direction to move and the position to stop in the spindle. We investigate the process by inducing congression with micromanipulation, dissecting directional forces with laser ablations, and revealing force generation with cytoskeleton/motility alterations.
Cytokinesis: Our current focus in cytokinesis is on cleavage induction. Cytokinesis ultimately ensures the proper partition of chromosomes and cytoplasm into the daughter cells. In animal cells, this is brought about by the formation of a cleavage furrow that bisects the mitotic (or meiotic) spindle between segregated chromosomes. Failure in, or improper positioning of the cleavage furrow makes faithful DNA replication and precise chromosome distribution all for naught. It is known that the mitotic apparatus defines the cell cleavage plane. However, it is not clear how the mitotic apparatus initiates the cleavage furrow due to our lack of in-depth understanding about the source and nature of the furrow signal. Specifically, it is uncertain about which part of mitotic apparatus is the essential source of the signal and whether all parts act in concert. We dissect which spindle constituent is the essential source of furrow signal by testing furrow induction with each single spindle constituent in the absence of all the others.