The astonishing regeneration experiment

Now, a team of Massachusetts researchers has discovered that the regenerative powers of planarian flatworms are even more astounding than previously believed.

Without altering their genomic sequence, these worms can also grow the heads and brains of entirely different species.

The findings of the Tufts University biologists reveal that information outside of genomic sequence can determine large-scale anatomy. 

This understanding could be applied to correcting birth defects or grow new biological structures after an injury.

The researchers were able to induce free-living flatworms, Girardia dorotocephala, to grow specific head shapes and brains characteristic of other species of flatworm, and the changes were beyond skin deep.

By interrupting protein channels called gap junctions, which pass electrical signals between cells, the researchers changed the distribution of the worm's adult stem cells, along with the shape of the head and brain.

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,' says the paper's senior and corresponding author Michael Levin, Ph.D.

Levin holds the Vannevar Bush Chair in biology and directs the Center for Regenerative and Developmental Biology in the School of the Arts and Sciences at Tufts.

'By 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,' he says.

'These findings raise significant questions about how genes and bioelectric networks interact to build complex body structures.'

Researchers found that the ease in generating different head shapes was closely tied to proximity on the evolutionary timeline. 

The G. dorotocephala flatworm was more easily able to form the head and brain shapes of a closely related species, which suggests that physiological circuits may be exploited during evolution to alter an animal's body plan.

'We've demonstrated that the electrical connections between cells provide important information for species-specific head regeneration in planarian flatworms,' says Maya Emmons-Bell, first author on the paper and a senior majoring in biology.

'This kind of information will be crucial for advances in regenerative medicine, as well as a better understanding of evolutionary biology. 

'As an undergraduate, it's been an extraordinary experience to conduct and author important research with leading biologists.'

Though revolutionary, the new heads of the flatworms turned out to be temporary fixtures. After a few weeks, the planaria flatworms regrew their own heads. 

(dailymail.co.uk)