People with schizophrenia
have genetic mutations that cluster in specific proteins key to the workings of
the brain, according to research that suggests a fresh way to look at the
illness and links it to other brain disorders such as autism.
In two research papers
published in the Journal Nature, which together made up the largest genetic
study of its kind, scientists analysed new or "de novo" gene
mutations in people with schizophrenia and found they tend to disrupt sets of
proteins which have related functions in the brain.
"De novo" gene
mutations are found in affected people but not in their parents – in other
words they are not inherited.
Overlap with other disorders
As well as identifying how
genetic mutations affect brain function, findings also point to an overlap with
the causes of other brain disorders such as autism and intellectual disability,
the researchers said.
"The fact we've been
able to identify a degree of overlap between the underlying causes of
schizophrenia and those in autism and intellectual disability suggest... these
disorders might share some common mechanisms," said Mick O'Donovan of
Britain's Cardiff University, who jointly led the research.
He said the combined
finding "tells us that for the first time we have a handle on one of the
core brain processes that (are) disrupted in the disorder".
Read: What is schizophrenia?
Schizophrenia is one of the
most common serious psychiatric illnesses, affecting around 1 in 100 people
worldwide. Scientists are not clear exactly what causes it, but believe it
could be a combination of a genetic predisposition to the condition as well as
Connections between nerve cells
Working with teams from the
Icahn School of Medicine at Mount Sinai, New York, the Broad Institute of the
Massachusetts Institute of Technology, from Harvard and from Britain's
Cambridge University, researchers examined DNA blood samples from 623
schizophrenia patients and their parents.
In a separate study, a
second team analysed gene sequences of more than 2 500 people with
schizophrenia and around the same number of controls as a comparison.
Their teams found that de
novo mutations play a role in triggering schizophrenia, and also that they
appear clustered in proteins that are involved in modulating the strength of
connections between nerve cells and that play important roles in brain
development, learning, memory and cognition.
Read: Schizophrenia breakthrough
No individual gene implicated
The Broad Institute's Shaun
Purcell, who worked on both studies, said the result was "sobering but
considerable sample sizes, no individual gene could be unambiguously implicated
in either study," he said.
"It suggests that many
genes underlie risk for schizophrenia and so any two patients are unlikely to
share the same profile of risk genes."
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