New genetic variations linked to schizophrenia

By Dr Matt Wilkinson

- Last updated on GMT

Related tags: Genetics

Researchers have used Affymetrix Genome-Wide Human SNP (single nucleotide polymorphism) arrays to discover genetic variations that increase the risk of schizophrenia.

Schizophrenia is a chronic and disabling brain disorder that affects around one per cent of the world’s population and can lead to hallucinations, delusions, cognitive deficits and apathy.

While current treatments enable many sufferers to live in the community and not institutions, the majority do not recover sufficiently to hold a job leaving their families to care for them.

The link between schizophrenia and genetics is not new, with around 40 per cent of disease instances believed to be inherited.

However, the latest studies are among the first large-scale genome-wide schizophrenia surveys and they discovered a number of new copy number variants (CNV), the number of copies of a certain gene a person possesses, which lead to increased risk of developing schizophrenia.

The results were published in three separate articles, one in the journal Nature Genetics​ entitled “Strong association of de novo​ copy number mutations with sporadic schizophrenia”, and two in the journal Nature​ entitled “Rare chromosomal deletions and duplications increase risk of schizophrenia” and “Large recurrent microdeletions associated with schizophrenia”.

“The Affymetrix SNP Array 6.0 enables researchers to perform the most powerful whole-genome association and copy number studies ever by genotyping more markers across more individuals at a lower cost per sample,”​ said Kevin King, president of Affymetrix.

“Scientists around the world are using this power to discover rare genetic variations associated with complex diseases. These three recent schizophrenia discoveries are great examples of research breakthroughs that should bring us closer to a day when we can diagnose, treat and potentially cure this debilitating disorder.”

The first study used the Affymetrix SNP Array 5.0 to uncover a clear link between 17 rare de novo​ CNVs in patients with schizophrenia in an African population, a number of the genes are members of pathways previously associated with neural development and RNA binding and processing.

“This is the first high-resolution, family-based study which examined in a systematic manner whether rare copy number mutations contribute to sporadic schizophrenia,”​ said Dr Maria Karayiorgou, professor of psychiatry at Columbia University Medical Center and lead author of the report.

“The Affymetrix technology made it possible for us to discover that de novo​ copy number mutations account for at least 10 percent of the non-familial cases of this devastating disease. Now that we better understand what brain development pathways are involved with schizophrenia, we can look at better ways of treating it in the future.”

The other two studies, one conducted by the International Schizophrenia Consortium (ISC) and one by the SGENE collaboration, used the Affymetrix SNP Array 6.0 to detect genetic deletions associated with schizophrenia in chromosomes 1, 15 and 22.

“Identifying these genetic deletions provides us with rich clues to follow up in future research on schizophrenia,​” said Dr Pamela Sklar, associate director, Psychiatric and Neurodevelopmental Genetics Unit in the Center for Human Genetic Research at Massachusetts General Hospital, and a member of the ISC.

“Recent advances in high-quality genotyping, such as the newest chip technologies from Affymetrix, enabled us to determine the importance of copy number variations through true genome-wide surveys.”

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