Left-handed people have a curious relationship with this disease.

It’s quite normal for us to exist left-handed, but not as interesting as it actually is. It is clear that humans are capable of adapting to the use of either of our hands. It is clear that right-handers who for some reason have lost their right hand eventually learn to use their left hand with ease. But the amazing thing is that, naturally, most of us predominantly use the right. Only 10% of people are left-handed. This is a percentage that is maintained throughout the world and has been constant throughout history. It is independent of culture and appears to have no predisposing factors other than genes. However, new research suggests it may be due to something apparently unrelated: autism.

Of course, the study does not conclude that all autistic people are left-handed or that all left-handers are autistic. However, when analyzing genes more than 350,000 peoplefound that there appears to be a genetic predisposition to neurodevelopmental disorders and a direct link to genes associated with autism.

The cause-and-effect relationship is not entirely clear, although certain hypotheses exist. Of course, what they did not find a connection with was neurodegenerative diseases. It was previously thought that they might also be associated with left-hand dominance, but the present study did not find any association in this regard.

Genetics of left-handers

It has long been thought that left-handedness may be linked to genes. After all, you can often see how it is inherited from parents to children. However, only recently have the first genes involved been identified. Today some are known 41 different genetic variants which, apparently, are characteristic of left-handers. Genetic variants refer to fixed changes in the DNA that most often makes up a gene.

Of these 41 variants, many appear to be associated with genes associated with the synthesis of tubulin. It is the main protein of structures called microtubules that make up the cytoskeleton that supports cells.

All cells have cytoskeleton. However, in the case of neurons, they have unique qualities compared to other types of cells. This is mainly due to the fact that brain microtubules contain tubulins of different isotypes. In addition, the composition of microtubules varies depending on location within the neuron. For example, line neuron, called an axon, and its small branches headdendrites have different tubulin compositions, so their microtubules may have different specializations.

All this suggests that mutations, better called variants, in the genes encoding tubulins may particularly alter neuron function.

What does all this have to do with autism?

We have already seen that the most common genetic variants in left-handers may be related to neurodevelopmental disorders due to disruption of tubulin function.

To find out exactly what these neurodevelopmental disorders are and whether there really is a connection, a team of scientists from Max Planck Institute for Psycholinguistics recently conducted a study in which they took part 38,043 left-handed and 313,271 right-handed.

By analyzing their genes, they found that left-handers were 2.7% more likely to have changes in brain composition. TUBB4B geneassociated with tubulin synthesis. In addition, some variations in DSCAM and FOXP1 genespreviously associated with autism.

We must remember that autism is not a disorder per se. This is a whole spectrum with varying degrees of affectation. In some cases, it may not even be detected, so some left-handers may be on the autism spectrum and not know it. But there are also many left-handers who do not have any neurodevelopmental disorders at all.

This study helps to better understand lateral preferences of our brain and how they relate to other problems that appear to have no connection. No one would think that left-handedness would be associated with autism, but there is evidence that makes us think so.