Scientists have discovered a gene that may play a role in determining whether a person is left-handed or right-handed. The rare genetic variant, called the TUBB4B gene, was identified in a large genetic study of over 350,000 people published on April 2 in the journal “Nature Communications.” Interestingly, this variant is more common in left-handers.
Approximately 90% of the population is right-handed, while 10% are left-handed. The preference for using one hand over the other is a result of brain asymmetry – studies show that the right side of the brain dominates hand control in left-handers, while it is the left side in right-handers.
This asymmetry forms in the womb and manifests in different ways. According to Clyde Francks, a co-author of the study and a Max Planck geneticist, the left hemisphere of most people’s brains dominates in language, while the right hemisphere excels in tasks requiring visual attention on spatial locations.
The mechanism driving the development of the two hemispheres in different ways is still unclear. Francks mentioned that identifying genes related to brain or behavioral asymmetry, such as handedness, can provide valuable clues.
Previous studies have found several genes associated with left-handedness, some of which are related to proteins called tubulins that have the ability to build cells’ microtubules, essential for cell structure. The TUBB4B gene found in this new study is also connected to tubulin proteins.
Unlike past studies that focused on common genetic variants, this research delved into rarer variants encoding proteins, as opposed to non-coding variants. The TUBB4B variant, present in less than 1% of the population, was 2.7 times more likely to be found in left-handers compared to right-handers.
Sebastian Ocklenburg, a neuroscientist at the University Medical Center Hamburg-Eppendorf who was not part of the new study, called it a significant research effort that supports the role of tubulins in determining brain hemisphere asymmetry.
The authors of the study stated that these findings further demonstrate the association between microtubules and a person’s hand preference. They proposed a possible explanation: microtubules support structures and movements of cilia, hair-like cell organelles that guide fluid flow around cells. The researchers suggested that uneven fluid movement might play a role in the development of brain asymmetry.
Francks informed “Nature News” that while rare gene variants affect only a few individuals, they “can provide clues about the mechanisms of brain asymmetry development for each person.”
In reality, left-handedness and right-handedness might often be mere chance results. “We believe that in most cases, the formation of left-handedness is simply due to random variations in brain development in embryos, without specific genetic or environmental influences,” Francks told Reuters.