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What do Lady Gaga, Barack Obama, Bill Gates, Paul McCartney and Justin Bieber have in common with Jimi Hendrix, Judy Garland and David Bowie? They are all left-handed, a trait common to about 10% of people. But why are some people left-handed while most people are right-handed? This is an area of active research, and a new study sheds light on the genetic component of left-handedness in some people. Researchers identified rare variants of genes involved in controlling the size of cells and found that they were 2.7 times more common in left-handed people.
While these genetic variants account for only a small fraction — perhaps 0.1% — of left-handedness, the researchers said the study suggests that this gene, called TUBB4B, may play a role in the development of the brain abnormality. Which underlines the determination of one. dominant hand.
In most people, the two halves or hemispheres of the brain have slightly different physical structures and are effective for different functions.
Senior author, neurobiologist Clyde Franks of the Max Planck Institute for Psycholinguistics in the Netherlands, said, “For example, most people have left hemisphere dominance for language, and right hemisphere dominance for tasks that require space. “A place requires visual attention.” According to the study published on Tuesday in the journal Nature Communications.
“In most people, the left hemisphere also controls the dominant right hand. Related nerve fibers cross from left to right in the lower part of the brain. In left-handed people, the right hemisphere is under control of the dominant hand. The question is What causes brain abnormalities to develop differently in left-handed people?”
TUBB4B regulates a protein that integrates into filaments called microtubules that provide internal structure to cells. The identification of a rare mutation in this gene, which is more common in left-handed people, suggests that microtubules are involved in setting up common brain abnormalities, Franks said.
The two cerebral hemispheres begin to develop differently in the human embryo, although the mechanism remains unclear.
“Rare genetic variants in a handful of people may point to genes that hold clues to the developmental mechanisms of brain asymmetry in everyone. TUBB4B may be a good example of this,” Franks said.
These findings were based on genetic data covering more than 350,000 middle-aged to older adults in Britain in a dataset called UK Biobank. About 11% were left-handed.
For most people, determining which hand is dominant can be determined by chance.
“We believe that most cases of left-handedness are caused by simply random variation during fetal brain development, without specific genetic or environmental influences. For example, the production of certain molecules during key stages of brain formation Random fluctuations in concentrations,” Franks said.
Over the centuries, many cultures condemned using the left hand and tried to force lefties to become right-handed. In English, the word “right” also means “right” or “proper”. The word “sinister” derives from a Latin word meaning “to the left.” And “praise the left hand” means an insult masquerading as praise.
The prevalence of left-handedness varies in different parts of the world, Franks said, with rates lower in Africa, Asia and the Middle East than in Europe and North America.
“This probably reflects the suppression of left-handedness in some cultures – moving left-handed children toward right-handedness, which also happened in Europe and North America,” Franks said.
The new findings may be relevant to the field of psychiatry. While most left-handed people do not have either of these conditions, people with schizophrenia are about twice as likely to be left-handed or ambidextrous and people with autism are about three times as likely, Franks said.
“Certain genes that function in the developing brain during early life may be involved in both brain abnormalities and psychiatric symptoms. Our study found suggestive evidence of this, and we have also seen this in previous studies where we have looked at more common genetic variants. in the population,” Franks said.
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