Genes identified for left-handedness

Genetic differences are in regions important for brain development

Four loci are noticeably changed in left-handed people. © Creative Family, ho To / iStock
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Found in genetic material: Researchers have identified genes for left-handedness for the first time. In the largest DNA study so far, they found four loci that are significantly altered in left-handers. Three of these gene regions are closely related to brain development and apparently also influence the functional linkage of the speech centers of both halves of the brain, as the scientists report.

About ten percent of the people are left-handed - but what lies behind this preference for the left hand in everyday activities, is so far only partially resolved. Thus, there is evidence that prenatal imprints play a role and even the season of birth. Both may be due to hormonal influences on the unborn child. At the same time, however, twin studies and familial accumulations point to the fact that left-handedness could be about 25 percent hereditary.

DNA comparison with nearly 40, 000 left-handers

But which genes and gene places are behind the left-handedness, was previously unknown. Now, the most comprehensive genetic comparative study to date sheds more light on the subject. Akira Wiberg of the University of Oxford and her colleagues compared differences in individual DNA bases among more than 38, 000 left-handers and around 350, 000 right-handers, whose genetic material is recorded in the UK's UK biobank.

In addition, however, scientists examined brain activity scans of 721 left-handed and 6, 685 right-handed participants. Using functional magnetic resonance tomography (fMRI) images, they were able to draw conclusions as to whether and how the functional linkages in the left-hand brain differed from those of the right-handed person - and whether there was any connection with certain genes.

Four loci are different in left-handers

The result: The researchers discovered four gene loci, which differed significantly from left-handed DNA sequences of right-handed people. Of these four gene regions, three are closely linked to brain development, as reported by Wiberg and her colleagues. "This is the first study to identify genomes of significant loci for expression in the general population, " said the researchers. display

The four loci contain building instructions for proteins that influence, among other things, the structure of the brain and the formation of certain brain cells and their supporting structures, the microtubules. At the same time, however, the four left-handed genes are linked to some neurological diseases. "It is noteworthy that these loci are highly positively correlated with schizophrenia and negative with Parkinson's disease, " the researchers report. This confirms earlier studies that left-shifters have a slightly higher risk of schizophrenia.

Language centers more closely linked

However, this is far more relevant for everyday life: as the researchers discovered, the left-vein loci are closely related to striking differences in the functional linkage of certain brain regions. "We have discovered that the left-and-right-brain linguistic regions of left-handed people communicate with each other in a more coordinated manner than in right-wing countries, " explains Wiberg.

This confirms earlier finds, according to which left-brained brains differ from those of right-wingers, especially in terms of language processing and the division of tasks of language centers. Thus, the asymmetry of the brain halves seems to be less pronounced, at least in some left-handers. The now proven stronger functional link between the language centers of the left and right sides underpin this.

Genes and developmental biology work together

"This raises the exciting possibility that left-handed people could have an advantage when it comes to verbal tasks, " says Wiberg. "However, we have to keep in mind that this is about average differences in a large number of people and not all left-handers are the same." However, future studies have now come to an end Connectivity data and the four loci provide valuable starting points for more in-depth investigations.

"We demonstrated that left-handedness is a consequence of our brain's developmental biology and that it is partly determined by the complex interplay of multiple genes, " says senior author Dominic Furniss of the University of Oxford. "It is part of the rich diversity that makes us human." (Brain, 2019; doi: 10.1093 / brain / awz257)

Source: UK Research and Innovation

- Nadja Podbregar