Nerve regrows after injury in a soil-living worm
doi:10.1038/nindia.2021.93 Published online 29 June 2021
Axons, the long cable-like carriers of electrical impulses in the nerve cells, can regrow after injury, neuroscientists show in experiments with a soil-living roundworm1.
Scientists at the National Brain Research Centre (NBRC) in Gurgaon, India, found that the axons made connections with other neurons (nerve cells) on the underside of the worm's body. They also discovered the molecular mechanisms behind this process of axon regeneration. These findings could provide leads for developing therapies to correct injured nerves in humans, they say.
Among the six touch-receptor neurons in the posterior part of the worm Caenorhabditis elegans, two are responsible for sensing gentle touch. The scientists, led by Anindya Ghosh-Roy, severed the axon of a single-touch receptor neuron by applying extremely short and focused pulses of laser. The injury caused the worms to lose touch sensation. Over two days, they saw that the proximal end of the injured axon regrew towards the ventral side of the body. On reaching the ventral nerve cord, the growing axon made a new synapse, a connection between two neurons.
After the formation of the synapse, the animals regained their lost touch sensation. The team identified a cascade of molecular events that led to the axon's regeneration resulting in recovery of the touch sensation.
“Injury to the axon increased the levels of UNC-40/DCC, a key protein that regulates the navigation of the axon towards the ventral nerve cord,” Ghosh-Roy said.
1. Basu, A. et al. Regulation of UNC-40/DCC and UNC-6/Netrin by DAF-16 promotes functional rewiring of the injured axon. Development. 148 (2021) Doi: 10.1242/dev.198044