Scientists Rewired The Brain of a Mutant Worm Using Parts From a Hydra

Because of their intricate wiring and subtle whisperings of neurotransmitter messages, brains can be difficult to study. This research could be a lot easier if we discovered that we can swap critical chemical systems without the host animal knowing.
A team of US researchers conducted a proof of concept study on the microscopic worm Caenorhabditis Elegans. They took genetically-gifted pieces from Hydra, a curious freshwater organism.

It was not like teaching a particular brain circuit a foreign tongue, and it still does its job as before.

Josh Hawk, a neuroscientist at the Marine Biological Laboratory in Massachusetts, says that there is a lot of synaptic connectivity in every animal's brain.

"Being able pick and choose the things we put in other organisms will help us understand and untangle how and why brains do what it does."

Like us, C. elegans is governed by neurotransmitters (chemical messengers) and has a tightly connected nervous system. Different circuits use different kinds of neurotransmitters, which are released into tiny gaps between neurons called synapses.

These narrow voids are, for the most part where the brain does its majority of its work. Synapses are the logic gates in the brain's computer circuitry that block some signals and enhance others. They transform chemical fluctuations into something more profound.

Neuroscientists can learn a lot about the nervous system's functions by playing with it using a variety drugs, genetic tweaks and light-operated switches.

You can learn a lot about the nervous system by turning things on and off, and by watching the chaos unfold. A lot of neuroscience's knowledge has been derived from studying the effects of a brain that isn't working properly.

"But, to truly understand their workings, you need to be able to rebuild them and fix them after they have been damaged. That is not easy," Daniel Coln-Ramos, Yale University School of Medicine's senior author of the study, said.

This case involved fixing a broken circuit in nematodes using parts taken from another organism. Hydra aren’t worms. Hydra are closely related to the sea anemone. They have tiny tentacled bodies that are controlled by a loosely connected spread of neurons, arranged in a net-like structure.

Stranger still, cells that make up the neural mesh communicate with each other by sending out peptides. These peptides then diffuse through the body of the Hydra, activating the matching receptors on the other cells.

Hawk says that there are many neural peptides found in Hydra. Each could be a different channel for communication.

"That's what I find most exciting. This will open up an area that has never been explored before.

Hawk and his collaborators genetically modified C. elegans specimens to test the theory. They made them feel hungry, which was a good thing. The researchers were able to see a clear pattern in the mutants' foraging behavior, regardless of how much food they had consumed.

They created two lines from this group of worms, one with the gene to make a hydra-neuropeptide and the other with the receptor gene.

They were able to bring together their two families' offspring, resulting in a single nervous system. They had to rely upon the hydra neuropeptides for signalling that it was time to stop eating, as their normal 'I'm full" brain circuit was not in use.

The swap is only the beginning. It is possible to seperate the neuropeptides of hydra and allow them to communicate long distance.

Coln-Ramos says, "It gives me more flexibility as an researcher to manipulate neurons which are not adjacent each other."

HySyn is a combination of messengers and receptors. Researchers could use this to create a wide range of replacement transmitters to help them understand the intricate details of neural circuitry.

Nature Communications published this research.