A genetic study led by the University of St Andrews has identified a biological process that influences whether we are right handed or left handed.
In the new study, the team found correlations in developing embryos between handedness and a network of genes involved in establishing left-right asymmetry.
In the report published in the journal PLOS Genetics, the researchers suggest that the genes may also help establish left-right differences in the brain, which in turn influences handedness.
The work was led by Dr Silvia Paracchini of St Andrews alongside scientists at the Universities of Oxford and Bristol and the Max Plank Institute in Nijmegen, the Netherlands.
Dr Paracchini, a Royal Society Research Fellow in the School of Medicine, said, “The genetics of handedness have been investigated for a long time, but this is the first study that show robust results at both statistical and biological levels”.
Dr Paracchini and her team were interested in understanding which genes might have an influence on handedness, in order to gain an insight into the causes and evolution of handedness. Humans are the only species to show such a strong bias in handedness, with around 90% of people being right-handed. The cause of this bias remains largely a mystery.
The researchers carried out a genome-wide association study to identify any common gene variants that might correlate with which hand people prefer using.
The most strongly associated, statistically significant, variant with handedness is located in the gene PCSK6, which is involved in the early establishment of left and right in the growing embryo.
‘The genes are involved in the biological process through which an early embryo moves on from being a round ball of cells and becomes a growing organism with an established left and right side,’ explained first author William Brandler, a PhD student in the MRC Functional Genomics Unit at Oxford University.
The researchers then made full use of knowledge from previous studies (done elsewhere) into what PCSK6 and similar genes do in mice to reveal more about the biological processes involved.
When genes responsible for left-right defects were disrupted, there was increased likelihood of an association with relative hand skills than you would expect by chance.
While the team has identified the role of genes in establishing left from right in embryo development, they say that the results do not completely explain the variation in handedness seen among humans.
William Brandler explained, “As with all aspects of human behaviour, nature and nurture go hand-in-hand. The development of handedness derives from a mixture of genes, environment, and cultural pressure to conform to right-handedness.”
The research was supported by the University of St Andrews, the UK Medical Research Council, the Wellcome Trust, the Max Plank Society, and the EU 6th Framework Programme, using data from the Avon Longitudinal Study of Parents and Children (ALSPAC).
The paper ‘Common variants in left-right asymmetry genes and pathways are associated with relative hand skill’ is published by the journal PLOS Genetics. It is available online.
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