Genetic regions linked to schizophrenia by two Chinese studies

Two Chinese genome wide association studies (GWAS) have identified genomic regions linked to the incidence of schizophrenia. The papers, published in Nature, are some of the first GWAS to look at Chinese as opposed to Western populations.

'[These findings] represent new potential targets to help understand schizophrenia. As we have only a relatively small number [of targets], this represents an important increase', said Dr Pamela Sklar, head of psychiatric genomics at the Mount Sinai School of Medicine in New York, who was not involved in the studies.

The first paper, by a team at Shanghai Jiao Tong University, looked at 3,750 people with schizophrenia, and 6,468 without. They also looked at a further 4,383 schizophrenia patients and 4,539 control samples in a second, independent set. The second study was a collaboration between groups at the Chinese National Human Genome Centre in Shanghai and Peking University in Beijing.

The papers identified a number of chromosomal regions strongly linked to incidence of schizophrenia. Previously unknown variations in a region of chromosome 11 - 11p11.2 - were linked with the condition and associations were also found at chromosome loci 8p12, 1q24.2 and 6p21-p22.1.

The findings reinforced studies in European populations that linked genes on chromosome 6 involved in the major histocompatibility complex (MHC), a cluster of genes essential to the immune system, to schizophrenia.

Schizophrenia affects approximately one percent of the world's population. There is no known single cause of the disorder but researchers believe it commonly has a genetic component. People who have a close relative with schizophrenia are shown to be more likely to develop the disorder than are people who have no relatives with the condition.

However, much work remains to be done to discover which specific genes are involved. Researchers have to date identified around twenty variations in DNA that appear to influence schizophrenia but have not yet been able to find a molecular basis for the disorder.

'None of the studies by themselves pinpoint specific genes or causal alleles in this large, complex region', said Dr Shaun Purcell, who has developed statistical and computational tools for genetic analysis at Massachusetts General Hospital, Boston, USA. 'The next step might be to integrate the Chinese and European data. It would be great to see these large data sets combined'.

More work is needed to determine how much overlap there is between the genetics of the disorder in Asian and European populations.