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Tiny Worm Holds Healing Secrets

Gene identified in worm sheds light on phenomenon of tissue regeneration

EVANSTON, Ill. --- By studying the regenerative power of the tiny planarian flatworm, researchers at Northwestern University have discovered a gene that could advance the field of tissue regeneration in humans.

Results of the study will be published today (July 3) in the journal PLOS Genetics.

“We think that our study raises the possibility that using human stem cells to create tissue organizers, such as the one we have discovered in planarians, could some day be a strategy to improve tissue repair in humans,” said Christian Petersen, an assistant professor of molecular biosciences in Northwestern’s Weinberg College of Arts and Sciences and senior author of the study.

Planarians are 2 to 20 millimeters in size and have a complex anatomy with around a million cells. They are famous for their ability to regenerate any body part, even after decapitation, due to stem cells that have properties similar to human embryonic stem cells. The worm’s genome has been sequenced, and its basic biology is well characterized, making planarians popular with scientists studying the mechanisms controlling tissue repair.

In the study, Petersen and Constanza Vásquez-Doorman, a doctoral student in his lab at Northwestern, report that they’ve identified a gene called zic-1 that controls planarian stem cells to turn them into a "signaling center" that coordinates the production of new organs for tissue regeneration in that animal. 

The Northwestern team studied this gene in decapitated planarian worms and found that its product likely acts as a transcription factor to produce cells that secrete a growth-promoting protein, NOTUM, at the tip of the regenerating tissue outgrowth to organize and enable the worm’s head regeneration.

These results suggest that regeneration requires specialized uses of stem cell descendants to orchestrate new tissue production following injury, Petersen said.

“Many studies of human or mammalian stem cells have focused on how such cells can be manipulated to produce new cell types in a dish, but an important long-term challenge for stem cell research remains how to use these cells to create complex tissues for regenerative repair,” Petersen said. “This study identifies Zic proteins as important regulators of tissue regeneration and gives us a better roadmap for using human stem cells to enhance tissue repair in humans.”

The National Institutes of Health, the American Cancer Society and Ellison Medical Foundation funded the study.