Genes involved in cell shape offer clues on lefthandedness
Why are some people lefthanded while most are righties? This is an area of active research, and a new study sheds light on a genetic component of lefthandedness in some people. Researchers identified rare variants of a gene involved in controlling the shape of cells and found them to be 2.7times more common in lefthanded people.
While these genetic variants account for only about 0.1% of lefthandedness, the researchers said 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.
In most people, the two halves, or hemispheres, of the brain have slightly different anatomies and are dominant for different functions.
“For example, most people have lefthemisphere dominance for language and righthemisphere dominance for tasks that require directing visual attention to a location in space,” said neurobiologist Clyde Francks of the Max
The identification of rare mutations in TUBB4B that are more common in lefthanders suggests that it is responsible for setting up the brain’s normal asymmetries
Planck Institute for Psycholinguistics in the Netherlands, senior author of the study published on April 2 in the journal Nature Communications.
“In most people, the left hemisphere also controls the dominant right hand. The relevant nerve fibres cross from left to right in the lower part of the brain. In lefthanders, the right hemisphere is in control of the dominant hand. The question is: what causes the asymmetry of the brain to develop differently in lefthanders?”
TUBB4B controls a protein that gets integrated into filaments called microtubules that provide internal structure for cells. The identification of rare mutations in this gene that are more common in lefthanders suggests that microtubules are involved in setting up the brain’s normal asymmetries, Mr. Francks said.
The two cerebral hemispheres start to develop differently in the human embryo, though the mechanism has remained unclear.
“Rare genetic variants in just a handful of people can pinpoint genes that give clues to developmental mechanisms of brain asymmetry in everyone. TUBB4B could be a good example of this,” Mr. Francks added.
The findings were based on genetic data covering more than 350,000 middleaged to older adults in Britain in a dataset called the U.K. Biobank. About 11% were lefthanded.
For most people, the determination of which hand is dominant may come down to chance.
“We think that most instances of lefthandedness occur simply due to random variation during development of the embryonic brain, without specific genetic or environmental influences. For example, random fluctuations in the concentrations of certain molecules during key stages of brain formation,” Mr. Francks said.