| Genetic
research to date fails to identify major gene for schizophrenia Despite promising evidence that a gene linked to schizophrenia would be found on human chromosome number 1, an international team who evaluated the chromosome in more than 1,900 patients has concluded it is not there, according to an article in the April 26th issue of Science. The findings highlight the challenge of identifying the genetic roots of complex diseases. "The bad news is we couldn't find it, but the good news is we can now concentrate on other regions of the genome, such as chromosomes 6, 8 and 13," says Ann Pulver, Sc.D., psychiatrist and co-author of the study. "Schizophrenia is a complex psychiatric disorder," says Pulver. "It can't be explained by either a single altered gene or a single environmental cause. There are clearly genetic components, but they are likely to be varied and to interact in many ways with non-genetic factors." Recent studies had suggested that genes associated with susceptibility to schizophrenia would be found on the long arm of chromosome 1. In their study, Pulver and colleagues searched for associations between genetic markers on chromosome 1 and schizophrenia with use of DNA samples from families that have more than one member with the disease. This approach, called genetic linkage analysis, is used to detect the location on the chromosome where disease genes reside. "By pooling our resources and data, and agreeing on how to attack the problem in a large sample of affected families, we were able to quickly use this type of genetic linkage analysis to tell if we were on the right track," says Pulver. It is still possible that genes on chromosome 1 contribute to the disease, she says, but these would influence only a small proportion of patients. "Biology is complicated, and the search for genes that contribute to large numbers of cases continues," she says. "This paper highlights the difficulty of unraveling complex diseases," says Solomon Snyder, M.D., author with Akira Sawa, M.D., Ph.D., of a review article on schizophrenia research in the same issue. Snyder points out that a variety
of genetic and environmental factors are at play in cancer, cardiovascular
disorders, and diabetes. "Despite the difficulties," says
Snyder, "we are getting closer to understanding the molecular
causes of schizophrenia. Advances in imaging, neuroanatomy, genetic
analysis and psychopharmacology are being applied in earnest to
this debilitating disease." |