Microscopic mysteries of nematodes resolved

Editorial

Rebecca Pool

Wednesday, March 6, 2019 - 18:00
C. elegans: With a body length of 1 mm, all cells can be observed through its transparent body, while living. [OIST]
 
Japan-based researchers have discovered new information that contradicts perceived wisdom on how the brain of the Caenorhabditis elegans nematode functions.
 
Analyses from Professor Ichiro Maruyama from the Information Processing Biology Unit (IPBU) at Okinawa Institute of Science and Technology Graduate University (OIST), and colleagues, revealed that the worm's neurons fire action potentials.
 
Prior to these results, researchers believed that C. elegans neurons only responded in a graded way with analogue signals.
 
The new information could lead to better understanding of how nerve signals are transmitted in the organism and serve as a future model for neuronal information processing in other animals, including humans.
 
The video shows scientists extracting a cell from C. elegans in order to conduct whole-cell recording. [OIST]
 
To observe sensory processing in C. elegans, Maruyama and colleagues applied salt to the tip of a genetically modified nematode's nose, increasing and decreasing concentration to assess different reactions while monitoring the neuron electroactivity.
 
Research revealed that an increase in concentration first affected a neuron on the left side of the brain, then triggered signals causing the worm to move forward. 
 
Meanwhile, a decrease in concentration caused a neuron on the right side to send signals for the worm to move backwards.
 
As part of this research, Maruyama and colleagues created a glass needle, less than one micron in size, to extract a GFP-labeled cell from the C. elegans.
 
A small number of nerve cell bodies were excised out from the animal’s brain through a tiny hole made by incision of an extremely small needle tip.[OIST]
 
Using a whole-cell patch-clamp technique, they then recorded the neuronal response of the cell when different salt concentrations were added to the worm's nose.
 
By measuring the voltage change in cells, the researchers could track neuron activation.
 
Meanwhile calcium imaging with a Zeiss LSM 510 confocal microscope supported results and produced additional data.
 
"Whole-cell patch-clamp recordings in vivo showed supralinear depolarization of [the sensory neuron] upon current injection," he explains. "Furthermore, stimulation of animal’s nose with NaCl evoked all-or-none membrane depolarization in [the neuron]
 
All in all, the research took seven years; four years of trial and error to create the right techniques, and three more for collecting data.
 
As Maruyama's colleague, Professor Jeff Wickens, Head of the Neurobiology Research Unit at OIST says: "Unlike complex nervous systems, such as mouse brains, C. elegans has a very simple nervous system consisting of 302 nerve cells."
 
"It will lead to better and efficient understandings of how more complex neural circuits function," he adds.
 
Research is published in Nature Scientific Reports.
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