The “template” flatworm, G. dorotocephala, can be seen in the top left. The rest of the top row shows the worms whose heads were grown onto the template worm. The bottom row shows the results.
It’s not quite the Esquilax of flatworms, but it’s way more interesting. A team of biologists at Tufts University have induced one species of flatworm to grow the head and brain of another species of flatworm, without tampering with the genomic sequence. Instead, they manipulated electrical synapses in the worm’s body.
The research shows that large-scale anatomy is not hard-wired in the genome, but can also be affected by physiological circuits outside the genes (at least in flatworms). It has been published this week in the International Journal of Molecular Sciences.
“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,” said senior and corresponding author Michael Levin.
The team conducted their experiments on Girardia dorotocephala, a type of flatworm with advanced regenerative capabilities. To induce the head change, the team interrupted the electrical signals that travel along protein channels between cells. What they found was that the head just didn’t change shape, the brain shape and the distribution of the worm’s stem cells were also altered.
This was easier to accomplish depending on how close to G. dorotocephala the target worm was on the evolutionary timeline. This suggests that these physiological circuits may play a role in evolution.
Interestingly, the changes were not permanent. After a few weeks, the worms began reverting back to their original head shapes and eventually returned to normal. More research is needed to understand this process.
Why would you want worms to grow the heads of different worms? Aside from helping gain some insight into the evolutionary process, it could also help improve understanding of both birth defects and regeneration.
“We’ve demonstrated that the electrical connections between cells provide important information for species-specific patterning of the head during regeneration in planarian flatworms,” said first author Maya Emmons-Bell.
“This kind of information will be crucial for advances in regenerative medicine, as well as a better understanding of evolutionary biology.”