About 1 in 10 people worldwide is left-handed. Scientists knew that genetics contributes to our being left- or right-handed, but they did not know exactly which genes were involved. Now, for the first time, a team of experts from the University of Oxford (UK) has identified regions of human DNA that are closely related to left-handedness.
The authors describe in their paper published in the journal Brain, how they found the DNA regions after analyzing the genomes of around 400,000 UK Biobank participants, including more than 38,000 left-handed people. This is the first study to link specific areas of the genome with left-hander in the general population.
“About 90% of people are right-handed,” says Akira Wiberg, a member of the Oxford University Medical Research Council, “and this has been the case for at least 10,000 years.”
Genes and brain
In their genetic analysis, the researchers identified four regions of DNA that were powerfully related to the left-hander. Three of the regions are within or influence genes that encode proteins that are “involved in brain design and development.” These proteins play a key role in creating scaffold-like building blocks called microtubules that guide the construction of cells.
Made up of long-chain molecules, microtubules make up the cytoskeleton, or the physical structure of cells throughout the body, and can assemble and disassemble very quickly in response to cellular signals.
The genes that drive the formation of the cytoskeleton are also responsible for the right and left differences in the growth and development of animals . Microtubules also maintain the transport infrastructure that enzymes use to transport cargo around different parts of the cell.
Linguistic regions in the brain
The researchers also examined detailed brain scans of about 9,000 of the participants whose DNA they had analyzed. They found that the left and right side of the brain that deals with language works in a more coordinated way in left-handed people. Experts suggest that this finding raises questions for future research about whether left-handed people may be better at performing verbal tasks.
Combining the images and the genetic results, the team discovered that some of the genetic effects related to left-hander are linked to differences in the white matter of the brain that contains the cytoskeleton that links the language regions.
“For the first time in humans, we have been able to establish that these cytoskeletal differences are actually visible in the brain”, comments Gwenaëlle Douaud, co-author of the work.
“We know from other animals, such as snails and frogs, that these effects are caused by genetically early events, so this increases the tantalizing possibility that future developmental characteristics of the left-hander will begin to appear in utero, ” he says. Douaud.
Diseases
The scientists also found links between left-hander-related genetic regions and a very slightly reduced risk of Parkinson’s disease and a slightly increased risk of schizophrenia. However, they point out that because their findings have only established links, it does not mean that having these genetic variants actually leads to a lower or higher risk of the conditions ; But the findings are valuable because they point to new directions for genetic studies of these diseases.
“Here, we have shown that left-hander is a consequence of the developmental biology of the brain, in part driven by the complex interplay of many genes,” says Dominic Furniss, professor in the Nuffield Department of Orthopedics, Rheumatology and Musculoskeletal Sciences at the University. of Oxford and leader of the work.
Referencia: Handedness, language areas and neuropsychiatric diseases: insights from brain imaging and genetics . Akira Wiberg, Michael Ng, Yasser Al Omran, Fidel Alfaro-Almagro, Paul McCarthy, Jonathan Marchini, David L Bennett, Stephen Smith, Gwenaëlle Douaud, Dominic Furniss Brain, awz257, DOI: https://doi.org/10.1093/brain/awz257 Published: September 2019
