DNA links reported for schizophrenia.

A new DNA investigation of more than 100 families suggests that a gene located on chromosome 13 contributes to at least some cases of schizophrenia, a severe mental disorder that usually first appears in young adults.

A specific sequence on chromosome 8 also shows signs of boosting susceptibility to schizophrenia for some people who possess the signature sequence on chromosome 13, reports a research team headed by genetic epidemiologist Ann E. Pulver of the Johns Hopkins Medical Institutions in Baltimore.

"What's exciting is that we have the first evidence to support the theory that different sets of genes can create a susceptibility to schizophrenia," Pulver says.

Earlier efforts to locate susceptibility genes for schizophrenia have had mixed results. Some evidence indicates that an unidentified gene on chromosome 6 contributes to the disorganized thinking, delusions, and hallucinations typical of this mental ailment (SN: 2/7/98, p. 91).

Pulver's group recruited families with predominantly European backgrounds to diminish genetic variation in the sample. The team employed a narrow definition of schizophrenia, so as not to include people with related disorders, and consulted long-term clinical records to confirm the schizophrenia diagnoses.

The researchers obtained DNA from blood samples collected from 54 people diagnosed with schizophrenia and 309 members of their extended families, who also completed psychiatric interviews. Molecular markers tagged DNA sequences on chromosomes 1 through 22.

A particular sequence on chromosome 13 appeared markedly more often in those diagnosed with schizophrenia, the scientists report in the September NATURE GENETICS. A "suggestive" statistical link emerged for a chromosome 8 region, they say.

A second study consisted of an additional 51 adults diagnosed with schizophrenia and 248 of their family members. A genetic link to the chromosome 13 and 8 areas was found in families in which some members had schizophrenia and others showed eccentric and withdrawn habits diagnosed as schizophrenia spectrum personality disorder. A genetic link only to chromosome 13 characterized the families in which several members had mood disorders, as well as hallucinations and delusions.

The latter finding coincides with an unpublished study directed by psychiatric geneticist Sevilla D. Detera-Wadleigh of the National Institute of Mental Health in Bethesda, Md. It finds the same chromosome 13 sequence often in family members diagnosed with bipolar disorder, or manic depression. Schizophrenia and bipolar disorder may share some susceptibility genes, Detera-Wadleigh holds.

Pulver's data suggests that a gene on chromosome 13 increases the likelihood of schizophrenia, but her study does not definitively show that it sometimes combines with a chromosome 8 gene to promote the disorder, comments psychiatrist Elliot S. Gershon of the University of Chicago Pritzker School of Medicine.