Left-handedness is genetic

In the case of nerve cells, which can be as long as 3 feet, microtubules may need to cater for some large distances.

Links to language regions in the brain

The researchers also studied detailed brain scans of about 9,000 of the participants whose DNA they had analysed.

They found that the left and right side of the brain that deals with language works in a more coordinated way in people who are left-handed.

The researchers suggest that this finding raises questions for future research into whether people who are left-handed may be better at carrying out verbal tasks.

Combining the imaging and genetic results, the team found that some of the genetic effects related to handedness linked to differences in the brain’s white matter that contains the cytoskeleton that joins language regions together.

“For the first time in humans, we have been able to establish that these handedness-associated cytoskeletal differences are actually visible in the brain,” says co-senior study author Gwenaëlle Douaud, an associate professor at the Wellcome Centre for Integrative Neuroimaging at the University of Oxford.

“We know from other animals,” Douaud continues, “such as snails and frogs, that these effects are caused by very early genetically guided events, so this raises the tantalising possibility that the hallmarks of the future development of handedness start appearing in the brain in the womb.”

The team also found links between the genetic regions tied to left-handedness and a very slightly reduced risk of Parkinson’s disease and a slightly increased risk of schizophrenia.

The researchers emphasize, however, that because their findings have only established links, they do not mean that having these gene variants actually drives lower or higher risks of the conditions. The findings are valuable in that they point to new directions for genetic studies of these diseases.

“Here, we have demonstrated that left-handedness is a consequence of the developmental biology of the brain, in part driven by the complex interplay of many genes”, says co-senior author Dominic Furniss, a professor in the Nuffield Department of Orthopaedics, Rheumatology, and Musculoskeletal Science at the University of Oxford.

“It is part of the rich tapestry of what makes us human,” he adds.

“Many researchers have studied the biological basis of handedness, but using large datasets from UK Biobank has allowed us to shed considerably more light on the processes leading to left-handedness”.

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Source: Medical news today