Our ‘junk’ DNA makes us uniquely human

Researchers at the Mount Sinai School of Medicine have found evidence that ‘junk’ DNA could hold the key to understanding how the human mind works and the risk of developing neurological diseases like Alzheimer’s disease and autism.

The researchers were looking at DNA sequences that differ in humans and non-human primates.  There are nearly 40 million differences, making the task of finding which ones are important a challenge.  Dr Schahram Akbarian and his team at the Mount Sinai School of Medicine tried to find the critical differences, not by looking at the individual strands of DNA, but by looking at the chromatin: the protein structure that surrounds and controls the expression of DNA.

They isolated strands of DNA from chromatin in the prefrontal cortex, a region of the brain that controls complex emotional and cognitive behaviour, including self-control.  They analysed these small sections of DNA and found that many of the sequences that were specific to humans were ‘junk DNA’, thought to have no function. ‘Junk’ sequences in DNA were thought to be unimportant because they don’t code directly for a protein, but they are increasingly being thought of as having a regulatory role.  Dr Akbarian’s team analysed the chromatin rather than the DNA because they were investigating the epigenetic properties of the DNA, which is how the expression of DNA is regulated by other factors (like action of chromatin).  This emerging field of epigenomics (which deals with epigenetics on a whole genome level) can “help us identify previously overlooked or discarded sequences that are key to understanding disease,” according to Dr. Akbarian.

Finding the uniquely human parts of the genome may help us learn more about uniquely human diseases like Alzheimer’s disease, autism and depression, which may help devise better treatments, and the field of epigenomics looks to hold answers in the years to come.