Schizophrenia is a fairly common mental disease that causes the breakdown of normal human thought processes. In 2011 alone, over 24 million people from around the world have been diagnosed with this disease. Aside from the usual mental symptoms, schizophrenia has also been known to significantly reduce a person's life expectancy. Due to the commonality of the disease as well as the numerous problems it causes for patients, medical experts and scientists have been trying to understand the underlying mechanisms that lead to the development of schizophrenia. Two new studies have now been published that shed light on the probable genetic causes that may partially be responsible for the onset of schizophrenia.
While scientists are already aware of the existence of certain genetic triggers that can lead to schizophrenia, the exact mechanisms for these triggers are still currently being explored. The two new studies, which were conducted by researchers from Broad Institute's Stanley Center for Psychiatric Research and several partnering institutions, and published in the online journal Nature, indicate that the underlying genetic factors behind the disease may be more complex than what scientists initially believed. The combined result of these studies comprises the largest study ever conducted on the genetic mechanisms of schizophrenia.
The first study involved the analysis of the sequenced genomes of over 5,000 people, half of whom have been diagnosed with schizophrenia. The other half of the genomes was taken from healthy individuals. The study shows that large-scale genome analysis of both affected and healthy individuals may yield important information about specific genes that may lead to a predisposition to schizophrenia.
"Taken together, these data suggest that population-based exome sequencing can discover risk alleles and complements established gene-mapping paradigms in neuropsychiatric disease," said the research team who conducted the first study.
On the other hand, the second study looked at new or "de novo" gene mutations in the genes responsible for coding proteins in schizophrenic individuals. While the second study looked for these "de novo" mutations in over 600 schizophrenic individuals, the study also involved analyzing the gene sequences of both the mothers and the fathers of the 600 schizophrenics in the sample group. The second study showed that the gene mutations responsible for schizophrenia predisposition might also be closely related to the mutations that cause intellectual disability and autism.
"Genes affected by mutations in schizophrenia overlap those mutated in autism and intellectual disability, as do mutation-enriched synaptic pathways," said the researchers involved in the second study. "Aligning our findings with a parallel case-control study, we demonstrate reproducible insights into aetiological mechanisms for schizophrenia and reveal pathophysiology shared with other neurodevelopmental disorders."
New information brought to light by both studies can now help medical professionals understand the causal relationships between specific mutations and schizophrenia. Moreover, the results of these studies may lead to early diagnosis of individuals with predispositions to certain mental diseases, in the future.
"Despite the considerable sample sizes, no individual gene could be unambiguously implicated in either study. Taken as a group, however, genes involved in neural function and development showed greater rates of disruptive mutations in patients," said Broad senior associate member Shaun Purcell, who played key roles in both studies.
Agrees Harvard Medical School professor in genetics, Steven McCarroll, who has authored both the papers. "From a scientific standpoint, it's reassuring to see different methods of studying the genetics of schizophrenia converge on the same sets of genes. These varied approaches are pointing toward the same underlying biology, which can be followed up in future research," said McCarroll, who is also the director of genetics for the Broad's Stanley Center for Psychiatric Research.
