Biologists Induce Flatworms to Grow Heads of Another Flatworm Species

Posted on December 5, 2015

Flatworm head shapes experiment

Biologists from Tufts University say they have succeeded in inducing one species of flatworm to grow the brain and head of another flatworm species during regeneration. This was done without altering genomic sequence. The head shape change was only temporary. Weeks after the planaria completed regeneration to the other species' head shapes, the worms once again began remodeling and re-acquired their original head morphology.

The scientists say the study reveals physiological circuits as a new kind of epigenetics that determines large-scale anatomy. The scientists found that the head shape of the flatworm is not hard-wired by the genome and can be overridden by manipulating electrical synapses in the body. The image above shows the head shapes of the different flatworm species that were induced in G. dorotocephala during the experiment.

The papers senior author is Michael Levin, Ph.D., director of the Center for Regenerative and Developmental Biology in the School of Arts and Sciences at Tufts. Levin says in a statement, "It is commonly thought that the sequence and structure of chromatin - material that makes up chromosomes - determine the shape of an organism, but these results show that the function of physiological networks can override the species-specific default anatomy. y modulating the connectivity of cells via electrical synapses, we were able to derive head morphology and brain patterning belonging to a completely different species from an animal with a normal genome."

The researchers worked with Girardia dorotocephala, a species of planarian flatworm known for its remarkable regenerative capacity. The scientists induced the development of different species-specific head shapes by interrupting gap junctions. These gap junctions are protein channels that enable cells to communicate with each other by passing electrical signals back and forth. It was not just the shape of the head that changed but also the flatworm's brain shape and the distribution of its adult stem cells.

A research paper on the finding was published here in the International Journal of Molecular Sciences.

Photo: Center for Regenerative and Developmental Biology, School of Arts and Sciences, Tufts University