January 2001

From Weizmann Institute

Blood test for diagnosing schizophrenia

Rehovot, Israel--January 16, 2001--A relatively simple blood test for diagnosing the mental illness schizophrenia has been proposed by researchers at the Weizmann Institute of Science. The study, conducted by Prof. Sara Fuchs and graduate student Tal Ilani of the Immunology Department, appears in the January 16th issue of the Proceedings of the National Academy of Sciences, (PNAS).

Schizophrenia, which affects approximately 1 percent of the population, is characterized by disturbances in the person's emotional functioning, perception of reality and thought processes. Because the biological basis of this disease is still a mystery, diagnosis is based on psychiatric and behavioral assessment. Still, numerous research findings suggest a possible connection between the disease and an excessive activity of dopamine, a chemical messenger, or neurotransmitter, involved in communication between nerve cells in the brain. This activity is dependent, among other factors, on the number of dopamine receptors on the surface of nerve cells. In fact, postmortem studies of the brains of schizophrenic patients, as well as PET scans of the brains of live patients, have suggested that the number of these receptors is increased in schizophrenia. Therefore, by measuring this number it may be possible to diagnose the disease. Unfortunately, however, it is impossible to assess the number and location of dopamine receptors in the brains of live schizophrenic patients with sufficient precision. Prof. Sara Fuchs and Tal Ilani propose a way of getting around this problem. They suggest evaluating the presence of dopamine receptors on the surface of white blood cells called lymphocytes as a potential diagnostic test for schizophrenia. To examine this possibility, the scientists compared blood samples taken from people with schizophrenia in mental hospitals in Israel with blood samples from healthy individuals.

Since identifying dopamine receptors on the surface of white blood cells is extremely difficult, the scientists focused on an earlier stage in receptor formation -- the stage at which messenger RNA molecules convey the genetic information needed for making dopamine receptors from the cell nucleus to the ribosome, the small cellular "factory" where the receptors are manufactured.

A statistical analysis showed that the blood of patients with schizophrenia contains, on average, 3.6 times more messenger RNA molecules of dopamine receptors of a particular kind, called D3, than the blood of healthy people. The high levels were observed in patients treated with a variety of drugs, as well as in patients who received no medications. On the basis of these findings, the scientists propose to use the blood test determining the levels of mRNA that encode D3 receptors on the membranes of white blood cells as a test for schizophrenia.

The research team included Dr. Dorit Ben-Shachar from the Rambam Medical Center and B. Rappaport Faculty of Medicine at the Technion-Israel Institute of Technology; Drs. Rael D. Strous and Moshe Kotler of Beer Yaakov Mental Health Center; and Drs. Marina Mazor and Ala Sheinkman of the Mental Health Center in Tirat Hacarmel, Haifa.

Professor Sara Fuchs holds the Professor Ernst N. Chain Chair of Neuro-Immunology. Her research is supported by the Abramson Family Foundation, the Wood-Byer Foundation, the Crown Endowment Fund for Immunological Research, the Irwin Green Research Fund in the Neurosciences, the Levine Center for Applied Research, the Edward D. and Anna Mitchell Research Fund and the Cemach and Anna Oiserman Research Fund.












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