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August

SGENE Consortium discover deletions in the Human Genome linked to risk of Schizophrenia

AUGUST 05, 2008

In a major paper published today in the online edition of the journal Nature, a consortium led by Decode genetics and including scientists from the Institute of Psychiatry report the discovery of three rare deletions in the human genome, known as copy number variants, that confer risk of schizophrenia. Such deletions are gaps in the normal sequence of the genome that can arise spontaneously during the recombination or reshuffling of the genome that takes place in the creation of sperm and eggs. The deletions reported in today’s study are located on chromosomes 1q21, 15q11 and 15q13, and confer, respectively, 3, 15 and 12 times greater than average risk of schizophrenia. These are the first such deletions to be associated with risk of mental illness using large sample sizes and validated across many populations. The substantial increase in risk they confer make them a valuable basis upon which to develop molecular diagnostic tests to complement standard clinical diagnosis.

This discovery was made possible by an international consortium, SGENE, put together by deCODE genetics and the University of Iceland, along with academic colleagues from the Institute of Psychiatry, The University of Aberdeen, Helsinki University, Finland, Ludwig-Maximilians-University, Munich, Germany and the University of Verona. The SGENE consortium was initially funded by a £2.5 M grant from the European Commission, and put together a sample of 1400 patients from five countries. The group expanded to collaborate with investigators from the University of Copenhagen, the University of Oslo, the University of Heidelberg, the University of Bonn, the University Medical Centre of Utrecht, Nijmegen Medical Centre, the Duke University Center for Population Genomics and Pharmacogenetics, GlaxoSmithKline and the Sichuan University, China.

The local principal investigator, David Collier, of the Medical Research Council- funded Social, Genetic and Developmental Psychiatry Centre, said “Although schizophrenia is a disorder with a strong genetic component, it has proved difficult to identify the genes which increase an individual's risk of developing the disorder, despite over 20 years of effort. This may mean that there are either many vary rare risk variants, or if common risk genes exist, these have a very small effect and are therefore difficult to detect. The discovery of new deletions occurring in people with schizophrenia has important implications of research and treatment of this illness. The deletions found so far have only been found in a small proportion of people with schizophrenia, but might account for 10% or more of cases overall.”

“The reason we want to identify the genes involved is to improve treatment for the patient, and may allow early identification of those affected, so that effective treatment may be given before the illness takes hold. In addition it may allow us to better diagnose mental illness through genetic tests, and develop a new generation of better pharmaceutical compounds, or identify the best non-pharmacological treatments for specific types of illness. And of course it is a major benefit to research and clinical treatment if the basic aetiology of a disorder is better understood.” 

“Participation in this landmark research was made possible by the dedication and effort over many years of researchers in the Division of Psychological Medicine and the Social, Genetic and Developmental Psychiatry Centre. The efforts of clinical staff in SLAM and Psychological Medicine, especially Robin Murray, Tao Li, Marta Di Forti, Timothea Toulopoulou and Elvira Bramon led to the recruitment of hundreds of volunteer patients for genetic studies, including the SLAM-funded Genetics and Psychosis study, the Maudsley Family Study and a twin study of schizophrenia. The state of the art laboratory facilities and support of the MRC-funded Social Genetic and Developmental Psychiatry Centre made the molecular genetic research possible.”

In order to identify novel CNVs, deCODE first analyzed the genomes of a total of approximately 15,000 parents and children taking part in deCODE gene discovery programs and who had been genotyped with the more than 300,000 SNPs on the HumanHap300 chip. The deCODE team discovered 66 de novo CNVs, that is, CNVs present in the genomic DNA of the children but not in that of their parents. deCODE then tested these variants for association with schizophrenia in more than 1400 schizophrenics and 33,000 control subjects, including volunteer patients from SE London. The deletions on chromosomes 1q21, 15q11 and 15q13 were suggestively associated with schizophrenia in this first phase, and then validated in 3,300 cases and 8,000 controls.

deCODE and the SGENE consortium gratefully acknowledge the participation in this study of the thousands of patients, family members and control subjects from these eleven countries. This study was supported by the European Union through the SGENE consortium (www.SGENE.eu), by grants LSHM-CT-2006-037761 and PIAP-GA-2008-218251.

The contribution of deCODE genetics and the SGENE consortium to this statement is acknowledged.
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