U. Chicago Scientists Implicate Genetic Duo in Bipolar Disorder
Researchers at the University of Chicago last week said they have tied bipolar disorder to a pair of overlapping genes, making their finding the second of its kind to link a gene to the disorder.
Though it is widely known that multiple genes are implicated in the disorder, the bipolar genes found on chromosome 13 by the University of Chicago team have a “weak effect,” which serves to increase susceptibility to the disease by about 25 percent, according to Elliot Gershon, professor and chairman of psychiatry at the University of Chicago and a co-author of the study.
Gershon’s team, which is widely considered to be on the vanguard of bipolar disorder research, used positional cloning to discover the genes, named G30 and G72. Led by research associates Eiji Hattori and Chunyu Liu, the group studied 174 families in which 845 members have bipolar disorder. The researchers found that one version of a stretch of DNA comprising G30 and G72 was associated with bipolar disorder. Their study appears in the May issue of the American Journal of Human Genetics.
G30 and G72 are “rather strange genes,” Hattori said, adding that they are expressed only in primates and have “no counterpart in mice. They have no known function. They reside in a sort of ‘gene desert’ near the end of the chromosome, with no other genes nearby, and they overlap on complementary chromosome strands.”
The G72/G30 gene complex was originally discovered at Genset, which associated the genes with schizophrenia in the fall of 2002. “These two reports are the first consistent demonstration of a gene complex associated with both bipolar illness and schizophrenia,” the University of Chicago said in a statement. “These disorders were thought to be inherited separately. In the past few years, however, the possibility that the same genes contribute to both disorders has gained favor.”
One other gene has been implicated in the disorder: In 2002, researchers linked brain-derived neurotrophic factor, a candidate gene.
“The discovery of susceptibility genes for psychiatric disorders has been one of the most intractable problems in human genetics,” said Gershon. “In the past two years, we seem to have reached a watershed for psychiatric gene discovery, with the identification of genes that increase risk of bipolar disorder and schizophrenia. After years of false starts and unfulfilled promises, we have begun to make real progress.”
Iceland Genomics Identifies Loci for Increased Cancer Risk
The Iceland genomics company that’s not DeCode Genetics has used data in the Iceland Cancer Project to identify several chromosomal loci for genes linked to an increased risk of breast, prostate, and other cancers.
The company, Iceland Genomics, is part of a collaboration called the Icelandic Cancer Project, which also counts as members the Iceland Cancer Clinicians group, the Icelandic Cancer Society, and the two main hospitals in Iceland.
The project has been performing a population-wide association study with samples from 2,500 cancer patients and 1,500 healthy controls. So far, it has mapped five loci in which genetic variations are believed to contribute to an increased risk of cancer. The groups are now planning to validate their results in other populations and isolate the specific genes, IGC said in a statement last week.
“It has been known for a long time that Iceland is particularly suitable for genetic studies but the emphasis has usually been on linkage analysis of large families, “ Snorri Thorgeirsson, chairman of IGC’s scientific advisory board, said in the statement. “This is concrete evidence that our approach … is also valid for the identification of genes which contribute to cancer susceptibility in this population.”
Thorunn Rafnar, director of cancer research at Iceland Genomics, told SNPtech Reporter in an e-mail message that the company “is working very hard on isolating the genes involved and hopes to isolate the first target gene within a year. Development of diagnostic tests and further characterization of drug targets will follow,” he said.
Icelandic Cancer Project collaborators do not have a direct stake in any revenue, he stressed, but added that Iceland Genomics “will donate a portion of its future income to a non-profit research fund which is jointly governed by the company and its clinical collaborators.” He declined to define “a portion.”
This is the first round of news for Reykjavik-based IGC since June, when the privately held company said that Myriad Genetics has asked for help to hunt cancer-causing genes.
Under that deal, IGC will use Myriad’s batch of genetic markers together with its own sample-collection tools to identify the genes. In exchange, Myriad will award IGC research and milestone payments and royalties on any products that might be developed.