AUG 09, 2021 6:59 AM PDT

Muscle Cells Revealed Contracting at the Subcellular Level

WRITTEN BY: Carmen Leitch

Muscle cells were once thought to be the smallest units that experienced contraction. But new research has suggested that smaller sections of muscles cells can experience localized calcium signaling and contractions. The findings have been reported in eLife.

Roundworms squirm around agar plates in lab hoovering up scrumptious bacteria. / Credit: Raleigh McElvery

The roundworm Caenorhabditis elegans, a common research model, does not have eyes. But it's known to be able to sense short-wavelength light, which it avoids. A graduate student in the H. Robert Horvitz lab, Nikhil Bhatla, thought that the worms weren't only reacting to the light by moving away; they also stopped eating. Research indicated that the sightless worms were trying to get away from chemicals generated by the light, like hydrogen peroxide. Further work revealed that the worms were tasting these chemicals and spitting them back out.

Now the researchers have identified the spitting mechanism in the roundworm. Incredibly, the work showed that neurons were stimulating a part of a muscle cell to generate motion. Single muscle cells were thought to be the smallest unit that a neuron could control; this work suggests that subcellular contractions in muscle cells are possible.

The pharnyx of C. elegans has a contractiing movement that basically traps food in the worm's mouth as it moves, then chews and ingests the food with pumping actions.

Study leader Steve Sando Ph.D. "made the remarkable discovery that the contraction of a small region of a particular muscle cell can be uncoupled from the contraction of the rest of the same cell," said senior study author H. Robert Horvitz, the David H. Koch Professor of Biology at MIT and Howard Hughes Medical Institute Investigator. "Furthermore, Steve found that such subcellular muscle compartments can be controlled by neurons to dramatically alter behavior."

The researchers found that as the worm eats, three muscles cells relax in pulses. When the worm tastes the light, subregions of these cells at the front of the mouth contact continuously, propelling material out; feeding reverses and becomes spitting. One neuron at the rear of the worm mouth seems to be in control of this phenomenon. This neuron causes calcium to rush into the muscle, which is likely the cause of the subcellular action.

"The discovery that the worms were spitting was quite surprising to us, because the mouth seemed to be moving just like it does when it's chewing," Sando said. The researchers determined that they had to zoom in really close on the action to see what was happening since the roundworms are so tiny and their movements are so rapid. Each C. elegans roundworm is about one millimeter long.

In this study, the researchers used a tiny laser to remove individual neurons and muscle cells to see how the spitting motion was impacted. The scientists used fluorescent reporter proteins to illuminate the cells.

"We've essentially found a new way for a neuron to move a muscle," Sando said. "Neurons orchestrate the motions of muscles, and this could be a new tool that allows them to exert a sophisticated kind of control. That's pretty exciting."

Sources: Phys.org via Massachusetts Institute of Technology, eLife

About the Author
  • Experienced research scientist and technical expert with authorships on over 30 peer-reviewed publications, traveler to over 70 countries, published photographer and internationally-exhibited painter, volunteer trained in disaster-response, CPR and DV counseling.
You May Also Like
AUG 31, 2021
Health & Medicine
Your metabolism does slow down as you age, but not until you're over 60
AUG 31, 2021
Your metabolism does slow down as you age, but not until you're over 60
A new study shows that, yes, your metabolism does slow down as you age, but not until you're over 60
SEP 27, 2021
Cell & Molecular Biology
Optical Imaging in Tissue with Near-Infrared Dyes
SEP 27, 2021
Optical Imaging in Tissue with Near-Infrared Dyes
Optical Imaging in Tissue with Near-Infrared Dyes Written By Christopher Pratt, PhD   Go Long to See Deeper Imaging ...
SEP 24, 2021
Cell & Molecular Biology
A Human Embryo Model is Made From Stem Cells
SEP 24, 2021
A Human Embryo Model is Made From Stem Cells
This photo by Sozen & Jorgensen et al., Nature Communications, shows an embryo-like structure made from human stem cells ...
OCT 07, 2021
Neuroscience
Unclogged: Constipation Drug May Stimulate Memory and Cognition
OCT 07, 2021
Unclogged: Constipation Drug May Stimulate Memory and Cognition
A drug commonly prescribed for constipation shows promise for memory and cognition
OCT 09, 2021
Cell & Molecular Biology
The Anti-Cancer, Copper-Binding Compounds Found in Fish
OCT 09, 2021
The Anti-Cancer, Copper-Binding Compounds Found in Fish
In the world's waterways, fish are confronted with endless challenges. For example, they have to defend themselves from ...
OCT 18, 2021
Cell & Molecular Biology
New Climatic Data from China Sheds Light on the Emergence of the Dinosaurs
OCT 18, 2021
New Climatic Data from China Sheds Light on the Emergence of the Dinosaurs
The climate is hot and muggy with the world's oceans as hot as a sauna. Also, it just started raining and it will not st ...
Loading Comments...