Adaptation of tissue polarity to regenerative outcomes in planaria
Day, Margot E.
2019
- Abstract: The process of regeneration requires that the correct structures are grown, in the correct orientation, with the same functionality as the tissues that have been lost. To achieve this, polarity at two levels must be reconciled: organismal polarity ensures that the proper structures are grown, while cellular polarity ensures that those structures are oriented properly. When a regeneration ... read moreevent occurs, however, an inevitable mismatch between organismal and cellular polarity is created. This is resolved through a process called repatterning, during which newly regenerated tissue undergoes changes in polarity at the cellular level in order to align properly with the rest of the organism. I explored both the mechanism and the signaling by which repatterning occurs in planaria, a favorite model organism to study regeneration. Double-headed planaria show a large degree of mismatch between organismal and cellular polarity, allowing for easier observation of repatterning. Using the orientation of cilia beat as a readout of cell polarity, I observed that repatterning is a slow process that lasts significantly longer than regeneration and occurs independently of cell turnover. This indicates that it acts by modifying existing structures rather than replacing them. Disrupting various components of cilia structure and function, I observed that depolymerization of the actin network resulted in faster repatterning. Of the two brains in a double-head animal, the one that regenerated on the once ‘tail’ end appears to play a critical role in initiating the repatterning signal, while the brain in the original head position sends out signals that slow down repatterning. These signals are transmitted from the brain through the body along the ventral nerve cords. Once the midpoint of the animal is established however, the brain is no longer required for its positional maintenance. These findings show that repatterning to adjust polarity following a drastic change in target morphology is a slow process and that tissue polarity is regulated by signals from the brain.read less
- ID:
- w6634g71w
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- TARC Citation Guide EndNote
