Distinct changes often occur in morphology during the formation of cellular polarity. During directed migration, cells form a distinct front and rear as they migrate towards or away from migratory cues. In many cell types, the microtubule organizing center and nucleus take up discrete localizations relative to one another in migrating cells. During the directed migration that takes place in cellular aggregation, the early process in fruiting body development, Dictyostelium discoideum cells reorganize many components, including their actin and microtubule cytoskeletons. We have discovered that the contractile network also polarizes during migration, moving towards the cell back. Observations with light microscopy of rearward contractile vacuole movement were confirmed by imaging cells expressing the fluorescently-tagged contractile vacuole marker dajumin. Mutants lacking the huntingtin protein (htf) were found to lack a detectable contractile vacuole or network. htf cells have previously been shown to have an inability to regulate their osmotic pressure, and this loss of the contractile vacuole causes this phenotype. Importantly, htf cells made very weak cAMP waves and didn’t stream. Taken together, these results demonstrate that the contractile vacuole redistributes to the rear of migrating cells, plays a vital role in streaming, and likely contributes to cAMP secretion.
|Advisor:||Janetopoulos, Christopher J., Pearce, Margaret M.|
|Commitee:||Klase, Zachary, Myers, Kenneth A.|
|School:||University of the Sciences in Philadelphia|
|School Location:||United States -- Pennsylvania|
|Source:||MAI 56/05M(E), Masters Abstracts International|
|Subjects:||Biology, Developmental biology|
|Keywords:||Chemotaxis, Contractile vacuole, Dictyostelium discoideum, Streaming|
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