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A rare gene variant is thought to play a role in understanding why people are left-dominant

What do Lady Gaga, Barack Obama, Bill Gates, Paul McCartney and Justin Bieber have in common with Ronald Reagan, Jimi Hendrix, Judy Garland, Fidel Castro and David Bowie? They are all left-handed, a trait shared by about 10% of people.

But why are some people left-handed while most are right-handed? This is an area of ​​active research, and a new study sheds light on a genetic component to left-handedness in some people. Researchers identified rare variants of a gene involved in controlling cell shape and found they were 2.7 times more common in left-handed people.

While these genetic variants account for only a tiny fraction – perhaps 0.1% – of left-handedness, the researchers say the study shows that this gene, called TUBB4B, may play a role in the development of the brain asymmetry that underlies the determination of a dominant hand.

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In most people, the two halves or hemispheres of the brain have slightly different anatomies and are dominant for different functions.

A gene involved in cell shape could explain left-handedness

There is a rare gene variant involved in cell shape that is thought to be linked to left-handedness. (REUTERS/Carlos Jasso/File Photo)

“For example, most people have left hemisphere dominance for language and right hemisphere dominance for tasks that require directing visual attention to a location in space,” said neurobiologist Clyde Francks of the Max Planck University. Institute for Psycholinguistics in the Netherlands, lead author of the study published Tuesday in the journal Nature Communications.

“For most people, the left hemisphere also controls the dominant right hand. The relevant nerve fibers cross from left to right in the lower part of the brain. In left-handed people, the right hemisphere controls the dominant hand.” The question is: What causes the asymmetry of the brain to develop differently in left-handed people?”

TUBB4B controls a protein that integrates into filaments called microtubules that give cells internal structure. The identification of rare mutations in this gene that are more common in left-handed people suggests that microtubules are involved in the formation of the brain’s normal asymmetries, Francks said.

The two hemispheres of the brain begin to develop differently in the human embryo, but the mechanism is still unclear.

“Rare genetic variants in just a handful of people can identify genes that provide clues to developmental mechanisms of brain asymmetry in everyone. TUBB4B could be a good example of this,” added Francks.

The findings were based on genetic data from more than 350,000 middle-aged to older adults in the UK in a data set called the UK Biobank. About 11% were left-handed.

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For most people, deciding which hand is the dominant hand is a matter of chance.

“We believe that most cases of left-handedness are simply due to random variations during embryonic brain development, without specific genetic or environmental influences. “For example, random fluctuations in the concentration of certain molecules during important phases of brain formation,” Francks said.

Over the centuries, many cultures have denigrated left-handedness and attempted to force left-handed people to become right-handed. In English, the word “right” also means “correct” or “correct”. The word “sinister” comes from a Latin word that means “on the left.” And a “left-handed compliment” means an insult disguised as praise.

The prevalence of left-handedness varies in different parts of the world, with rates lower in Africa, Asia and the Middle East than in Europe and North America, Francks said.

“This likely reflects the suppression of left-handedness in some cultures, leading to left-handed children transitioning to right-handedness, which was also previously the case in Europe and North America,” Francks added.

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The new findings could be important in the field of psychiatry. While the vast majority of left-handed people have neither 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 more likely, Francks said.

“Some of the genes that function in the developing brain during early life may be involved in both brain asymmetry and psychiatric traits. Our study found evidence of this, and we have also seen it in previous studies where we looked at more common genetic variants in the population,” Francks added.

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