WHY SOME PEOPLE ARE LEFT-HANDED? A STUDY EXAMINES THE REASONS BEHIND IT

Wed 03 April 2024:

The ability of some people to use their left hand to complete all main daily duties, including writing, always attracts the curiosity of right-handed persons. This inquisitiveness has also left many scientists scratching their heads, as there is no confirmed the theory of how certain people acquire left-handedness or whether their brain wiring differs from their right-handed counterparts.

A new study reveals that left-handedness is linked to several unusual mutations in specific genes.

Researchers from the Max Planck Institute for Psycholinguistics in the Netherlands analyzed genetic data from over 350,000 people. They obtained the data from the UK Biobank, which contained 38, 043 left-handed and 313, 271 right-handed individuals.

The research was published in Nature Communications.

The team came across some potential similarities and differences between brain-related disorders that contribute to left-handedness.

The team searched for specific genes that might have a link to left-handedness and observed whether these rare genes have any say in influencing it. The team found that the inheritability of left-handedness with these rare coding variants was only about 1 per cent.

The team deduced that left-handed people are 2.7 times more likely to have rare coding variants in a gene called TUBB4B that codes for tubulins that make microtubules. These microtubules are responsible for forming the major part of the cytoskeleton which gives cells their shape. The microtubules are also important for neuron development, migration and plasticity.

“It is not known how microtubules affect inter-individual variation in human handedness,” write the authors, “but it has been suggested that they may contribute to cellular chirality early in brain development, and thereby to organ-intrinsic formation of the brain’s left-right axis.”

Researchers did not find any link between left-handedness and any nine genes implicated in neurogenerative diseases by large-scale exome studies.

However, what they found during the study came as a surprise to the team as well. They discovered that people with two variations in genes previously are related to autism, DSCAM and FOXP1; potentially also having higher chances of being left-handed.

“This study reveals a role for rare, protein-altering variants in left-handedness, providing further evidence for the involvement of microtubules and disorder-relevant genes,” the authors write.

Put another way, the majority of left-handed individuals do not have autism, but the higher rate of left-handedness could be brought on by these uncommon gene alterations. The authors suggest that DSCAM or FOXP1 mutations that cause autism may also have an impact on alterations in the brain’s left-right axis development.

SOURCE: INDEPENDENT PRESS AND NEWS AGENCIES

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