A new study has, for the first time, identified regions of the genome associated with left-handedness in the general population and linked their effects with brain architecture. The study linked these genetic differences with the connections between areas of the brain related to language. It was already known that genes have a partial role in determining handedness - studies of twins have estimated that 25% of the variation in handedness can be attributed to genes - but which genes these are had not been established in the general population. The new study, led by researchers at the University of Oxford who were funded by the Medical Research Council and Wellcome, was published online on September 5, 2019 in Brain. The study identified some of the genetic variants associated with left-handedness by analyzing the genomes of approximately 400,000 people from UK Biobank, which included 38,332 left-handers. The open-access article is titled “'Handedness, Language Areas, and Neuropsychiatric Diseases: Insights from Brain Imaging and Genetics,” Of the four genetic regions the scientists identified, three of these were associated with proteins involved in brain development and structure. In particular, these proteins were related to microtubules, which are part of the scaffolding inside cells, called the cytoskeleton, which guides the construction and functioning of the cells in the body. Using detailed brain imaging from approximately 10,000 of these participants, the researchers found that these genetic effects were associated with differences in brain structure, in white matter tracts - which contain the cytoskeleton of the brain - that joins language-related regions.
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