Scientists have uncovered genes that are involved in determining whether a person is left or right-handed, according to a study published in the journal PLOS ONE.
Researchers from the UK and the Netherlands say they have discovered correlations between left and right-handedness and a network of genes present within developing embryos.
According to the researchers, humans are the only species that show a strong preference for which hand they use, with 90% of the population being right-handed.
The team conducted a genome-wide association (GWAS) study of 728 individuals with dyslexia, in order to identify any common gene variants that may determine which hand people prefer to use.
From this, the research team found a number of genes that could be linked to left-right preference, but there was a significantly strong association in the gene PCSK6. This gene is involved in the early establishment of left and right in the growing embryo, and may help to establish left-right differences in the brain which could influence handedness.
The results were then replicated in a general population cohort of around 2,600 individuals without dyslexia.
"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," explains William Brandler of the MRC Functional Genomics Unit at Oxford University and first author of the study.
Previous studies have shown how PCSK6 and similar genes work in mice. Therefore, the research team referred to these studies in order to find out more about their biological process.
"We have performed a genome-wide association study meta-analysis for a quantitative measure of handedness and found association with variants that implicate genes involved in the determination of left/right body asymmetry," the study authors explain.
"To achieve this, we developed a novel approach to GWAS pathway analysis, coupling gene-set enrichment analysis (GSEA) with mouse phenotype data."
They discovered that interfering with the PCSK6 gene in mice causes them to suffer left-right asymmetry defects. For example, this can lead to abnormal positioning of organs in the body.
Further research showed that when PCSK6 and other genes known to cause left or right defects were disrupted in mice, these were highly likely to be linked to relative hand skill.
The researchers say:
"Our findings lead us to propose that handedness is a polygenic trait controlled in part by the molecular mechanisms that establish left-right body asymmetry early in development."
However, William Brandler warns that these results do not completely explain the variation of left and right handedness within the human population:
"As with all aspects of human behavior, 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."