The Gene for Left-Handedness Has Been Found. It Could be Linked to Madness!

As everything you do (from spitting to nose fishing) is genetically controlled, it is normal to think that left-handedness is also genetic. Now they have found its gene, named LRRTM1, which also presents an increased risk of being prone to some mental illnesses like schizophrenia.

"For right-handed people, the right side of the brain usually controls emotion, while the left side of the brain tends to control speech and language," said lead author Clyde Francks, visiting fellow at the Wellcome Trust Centre for Human Genetics at Oxford University.

Left-handers, roughly 10 % of the world's population, present a reversed pattern.

"We think that this gene affects the symmetry of the brain. LRRTM1 is not essential for left-handedness, but it can be a strong contributing factor." said Francks.

Brain asymmetry has been connected to schizophrenia, a mental disorder affecting 1 % of the world's population, characterized by impaired perception and severe behavioral shifts. That's why it was not a surprise that LRRTM1 was associated with a person's chances of developing schizophrenia.

"But left-handers should not be unduly concerned about this link. There are many factors which make individuals more likely to develop schizophrenia, and the vast majority of left-handers will never develop a problem." said Francks.

His team found the LRRTM1 gene during a research of a hundred families with dyslexic children. The researchers initially looked for a link between dyslexia (a neurological learning disability) and left- or right-handedness in a person. Genetic analysis of samples taken from all the families revealed a link between a certain chromosome and handedness.

"We then started to study the chromosome in detail and found this gene," said Francks.

The gene seems to be transmitted by the father. Now the researchers will try to understand the precise role of the gene.

"We need to find out what role it plays in brain development and at what point it is active, whether it is during fetal development, childhood, or adulthood," said Francks.

LRRTM1 "may turn out to be part of a complex relationship between a range of genes and environmental factors that lead to people developing schizophrenia," said Paul Corry, director of public affairs at Rethink, a U.K.-based mental health charity.
The gene could also give some clues on human evolution. The majority of the species have more symmetric brains than the humans, including our closest relatives, the apes.