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Curious: Presentations by Young Researchers II

Why Does a Hand Move When We Think of It?

Three young Japanese researchers in Chicago made curious presentations about their studies at the Japan Information Center of the Consulate General of Japan at Chicago on April 13.
The researchers have formed the Japanese Researchers Crossing in Chicago to help each other and held meetings to share their studies. They also have invited people who are interested in learning new things.

Tomoya Kubota, Postdoctoral Scholar ? Department of Biochemistry and Molecular Biology at the University of Chicago, spoke about a process pinpointing the cause of nerve related disease.
A human has a cerebrum, cerebellum, brainstem, and spinal cord, and we can move muscles or feel something on the skin through circuits in our body. The circuit is called neural circuit, which is similar to the electric circuit. Channels, which are consisted of protein, control electronic signals in our bodies.

Looking for a cause of specific symptom

When Kubota was in the Graduate School of Medicine, Osaka University, he encountered a patient who was suffering from myotonic disorder. He had enlarged muscles and was unable to open his hands quickly once he squeezed them. He said if he found a genetic anomaly, he couldn’t say that it was the cause of the disease because a gene had a complicated structure. A gene has exons, which become protein, and other areas. When exons get together, messenger RNA (mRNA), a blueprint copy of protein, is made, then protein is created, and cells, organs, and body are created step by step; therefore, he said that a process to find a cause is difficult.

In his patient’s case, action potential, which transmitted a signal to his muscles from his brain, was continuously firing. It was found by a test with a needle in his muscles.

What is action potential?

The Natrium (sodium) channel, Kalium (potassium) channel, and Chloride channel are responsible to transmit an electronic signal to muscles from a brain. Each of them has specificity, such as Na channel only transmits sodium, and K channel transmits almost only potassium. In this circumstance, the inside of a cell is kept as negative.

When you think that you want to move your hand, an electronic signal reaches your muscle, and potential gradually rises at the cell membrane of muscle. When the potential reaches a certain level, Na channel suddenly opens and natrium (sodium) flows into the inside of a cell. Then the inside of the cell turns to positive. The rise of potential at cell membrane is called generation of action potential
After action potential was generated, Na channel puts on a brake to prevent the inflow of sodium current. This is called inactivation of Na channel. K channel and Cl channel work to pull out positive ions from the cell. All the three channels work together and return back action potential to the original level. Our cells are always doing electronic exchanges in this way.
In Kubota’s patient’s case, action potential didn’t converge and continued to fire; thus his muscle cell membranes were always easily excited.

Two causal genes of myotonic disorder have been discovered. One is Na channel SCN4A, and another is Cl channel CLCN1. Kubota analyzed the genes and found his patient’s had something wrong with Na channel SCN4A. Further study found that the gene would have blueprints for normal and abnormal protein, and their ratio was 2:1. However, he still thought about if he could say that the abnormal protein was cause of the symptom.
Finally, Kubota found the same myotonic discharge with his patient through a computer simulation. The cause of his patient’s symptom was found after so many studies in each step. As a result, he could give curative medicine to his patient.

Kubota said that his purpose of research in Chicago was visualizing action potential, and he would approach it by measuring energy transfer. He also said that he would like to make customized medicine for each patient by finding the real cause of a disease.