A team of researchers found new genetic evidence, published in the journal Schizophrenia, suggests that the condition is an "unwanted side effect" of the evolution of the complex human brain.
At recent times more and more studies have been illuminating the genetic components of schizophrenia, a condition that affects about 1 percent of the world's population.
In the largest twin study of schizophrenia put 79 percent of the risk of the condition down to genes, while another believed that genetic mutations in the brain's glial cells may be responsible for the disorder.
However, a new study conducted by three researchers from the Florey Institute for Neurosciences and Mental Health in Parkville, Australia, finds genetic changes in a frontal brain area commonly linked with schizophrenia traits, supporting the theory that the condition may be an undesired side effect of the human brain's evolution.
One of the scientists Prof. Brian Dean, of Swinburne University's Centre for Mental Health in Hawthorne, Australia, as well as the Florey Institute, is the new study's corresponding author.
Changes in genetic expression found in the frontal pole of the brain
For the study Prof. Dean and colleagues conducted a postmortem examination of the brains of 15 people who had schizophrenia and 15 who did not.
The research team measured the levels of messenger RNA (mRNA) in the frontal pole of the brain, the dorsolateral prefrontal cortex, and the cingulate cortex.Using mRNA levels, the researchers predicted genetic pathways "that would be affected by the changes in gene expression."
In the brains of people who had been diagnosed with schizophrenia, the researchers found 566 instances of changes in genetic expression in the frontal pole of the brain and surrounding areas, which are regions known to be involved in schizophrenia-related traits.
The lead authors explain, "The frontal pole is critical in maintaining the cognitive flexibility that underpins human reasoning and planning abilities," which are two functions "that are impaired in individuals with (schizophrenia)."
Researchers uncovered a genetic pathway (Brodmann area)
Moreover the study uncovered a genetic pathway in the brain's so-called Brodmann area that comprised interactions between 97 genes.
"Abetter understanding of changes in this pathway could suggest new drugs to treat the disorder," says Prof. Dean. He goes on to explain the findings,saying, "It's thought that schizophrenia occurs when environmental factors trigger changes in gene expression in the human brain."
And thus potential environmental triggers for epigenetic changes include pregnancy and delivery complications, as well as psychosocial stressors such as growing up in a dysfunctional family.
"Though this is not fully understood," adds Prof. Dean, "our data suggest the frontal area of the brain is severely affected by such changes."
"There is the argument that schizophrenia is an unwanted side effect of developing a complex human brain and our findings seem to support that argument." Prof. Brian Dean
"A major finding of this study," the authors continue, "is that [........] no gene had altered levels of expression in all three regions of the cortex from subjects with [schizophrenia]."
According to the research team, this means that in terms of gene expression,schizophrenia-related molecular changes are not uniform across the cortex.
"These data also raise the possibility that the symptoms of [schizophrenia] that are thought to result from the dysfunction of different cortical regions could be due to changes in gene expression specific to the cortical region thought to be central to the genesis of a symptom," they say.