Gene That suppresses tissue growth, planarian flatworm
Results from a Northwestern University study of the planarian flatworm could have ramifications for novel tissue engineering methods. Credit: Northwestern University

Gene That Suppresses Tissue Growth – Gene puts brakes on tissue growth

Scientists have identified the beginnings of a genetic signaling pathway that puts the brakes on the growth of animal.

Planarian flatworm is a simple animal with a highly and mighty unusual ability of being able to regenerate itself even from decapitation and from nearly every imaginable injury. Any missing cell or tissue—epidermis, neurons, muscle, even a new brain can be regrown by these tiny worms. With around a million cells, planarian are 2 to 20 millimeters in size having complex anatomy. There are found all around the world and they live in streams and freshwater ponds. Planarians are popular with scientists as their genome has been sequences and its basic biology is well-characterized.

To understand the fundamental principles of natural regeneration and repair better, scientists have studied these worms to get the information that could provide insights into tissue healing and cancer since the late 1800s. However, the mechanism of how organisms like these control the proportional scaling of tissue during regeneration still remains unknown.

Now, the beginnings of a genetic signaling pathway that puts brakes on the growth of animal has been identified by two Northwestern University

molecular biologists. In these highly regenerative animals, the appropriate amount of tissue growth is ensured by this important process.

In Northwestern’s Weinberg College of Arts and Sciences, an associate professor of molecular bio-sciences and the research lead, Christian Petersen conducted the study with a graduate student in his lab, Erik G. Schad. Schad is the paper’s first author and Petersen is the corresponding author. The journal Current Biology published the results.

Petersen said, “These worms through their evolution, have essentially discovered a natural form of regenerative medicine. Their whole lives, planarians are able to regenerate, but how do they limit their growth has not been understood. The organizing principles and the molecular components that goven perfect tissue restoration can be understood better through our discovery.”

Ultimately, the findings may have important ramifications for new tissue engineering strategies or methods to promote natural repair mechanisms in humans.

A new mechanism to explain how stem cells can influence growth and a control system for limiting regeneration has been identified by the researchers. Particularly, a gene called mob4 which suppresses tissue growth in the animals was discovered by Petersen and Schad. In their experiments, the animal was seen to grow twice its normal size when they inhibited the gene.

The researchers found that the gene they discovered works in a rather surprising way: by preventing the descendants of stem cells from producing a growth factor, a protein released from cells to communicate across distances, called Wnt. In cancer cell regeneration, the Wnt signaling pathway is known to play a role.