Schizophrenia is genetically complex but patterns are emerging

Genetic mutations implicated in autism and intellectual
difficulties may also underlie schizophrenia, say researchers after a study comparing the DNA of schizophrenia patients with that of their parents.

Professor Mick O'Donovan, from Cardiff University,
who co-led the research, said it suggested that several psychiatric and
developmental disorders 'might share some common mechanisms and lends further
weight to calls for research that integrates findings across multiple disorders'.

Previous studies have shown that common
psychiatric disorders share genetic risk factors (see BioNews 695). Traditionally, however, research into
these conditions has been guided by the clinical picture, where, for example, autism
and schizophrenia are seen as very different, possibly entirely unrelated disorders.

The study looked at the DNA of 623 Bulgarian schizophrenia patients
and compared it with their parents' DNA. The scientists were particularly interested in 'de novo' mutations - genetic mutations that are found
in affected people but not in their parents.

They identified de novo mutations that appeared to be
linked to schizophrenia and compared their results with previous similar
studies on autism and intellectual disability. There was
considerable overlap.

Many of the affected genes work in pathways involved in establishing
and maintaining connections between nerve cells and are important for brain
development.

Professor Mike Owen, also a study co-lead at Cardiff University, said: 'For the
first time we have a handle on one of the core brain processes that is
disrupted in the disorder'.

The study was published alongside another in the journal Nature,
in which scientists looked at the genes of over 2,500 people with
schizophrenia, and a similar number of controls. Both studies suggest that
rather than being explained by a single 'schizophrenia gene', a large number of
rare genetic mutations contribute to risk for the disease.

The two studies are among the largest DNA sequencing studies
to be performed on schizophrenia.

Dr Shaun Purcell, head of the Center for Statistical
Genetics at Mount Sinai Hospital in New York, who led the second study, admitted
that 'the complexity of the genetics is sobering' but the work should help
researchers develop better treatments 'than the one-size-fits-all approach
currently used'.

Schizophrenia is one of the most common serious
mental health conditions, affecting about one percent of the
population at some point in their lifetime. The exact cause is unknown but many
scientists think it emerges through a combination of genetic predisposition and
environmental factors.