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Families with severe form of bipolar disorder help scientists narrow the search for disease genes

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  • Ian Pitchford
    Public release date: 1-Apr-2003 Contact: Trent Stockton tstockt1@jhmi.edu 410-955-8665 Johns Hopkins Medical Institutions Families with severe form of bipolar
    Message 1 of 1 , Apr 1, 2003
      Public release date: 1-Apr-2003
      Contact: Trent Stockton tstockt1@... 410-955-8665
      Johns Hopkins Medical Institutions

      Families with severe form of bipolar disorder help scientists narrow the search
      for disease genes

      After years of frustrating searches for genes that contribute to mental
      illness, researchers at Johns Hopkins studying families with a severe form of
      manic depressive illness, called psychotic bipolar disorder, may be one step
      closer to finding the genetic underpinnings of both bipolar disorder and

      "Finding a gene for bipolar disorder is like finding a needle in a haystack,
      but by focusing our search on families with a distinctive form of the illness
      we were able to pinpoint a region of the genome where disease genes are likely
      to be found," said James Potash, M.D., assistant professor of psychiatry at
      Johns Hopkins and lead author of a report on the study in the April issue of
      the American Journal of Psychiatry.

      Although genes are unlikely to tell the whole story of major psychiatric
      diseases, the persistent frequency of mental illness in about 1 percent of the
      global human population, regardless of cultural or ethnic differences, and its
      tendency to run in families have always pointed to a strong genetic role. "But
      pinning down that role is complicated by the many variations in symptoms, even
      within the same family," says Potash. "There are probably many different genes
      and environmental factors that can cause any given mental illness."

      Motivated by previous suggestions that certain broad regions of the DNA
      sequence, especially on human chromosomes 13 and 22, may contain genes that
      contribute to both bipolar disorder and schizophrenia, Potash and colleagues
      focused on those families with the psychotic form of bipolar disorder. Like
      bipolar disorder, psychotic bipolar disorder is characterized by see-sawing
      episodes of depression and mania, but it is distinctive because these mood
      changes often are accompanied by such psychotic symptoms as hallucinations and

      The concept for the new study is that of two slightly overlapping circles,
      explains Potash. In one circle are all of the genes that contribute to
      schizophrenia. The other circle has all of the genes that contribute to bipolar
      disorder, while the intersection of the two circles contains genes that are
      common to both diseases as well as for psychotic bipolar disorder.

      The researchers carefully evaluated and took blood samples from 65 patients
      with bipolar disorder and from their extended families. They extracted blood
      cell DNA and scanned it with DNA probes, looking for matching sequences that
      are more likely to appear in those with mental illness than in those without
      it. By noting where these markers lay on chromosomes, the researchers were able
      to narrow in on where the genes were located.

      Out of 65 bipolar disorder families studied, the 10 families in which 3 or more
      members had psychotic bipolar disorder showed strong genetic "linkage" to
      specific regions on chromosomes 13 and 22. These results differed significantly
      from those for all 65 families, which showed little or no linkage evidence in
      these two regions.

      "These results confirmed our expectation that genes for the psychotic form of
      bipolar disorder are likely to be found in the same regions that show linkage
      to both bipolar disorder as a whole and to schizophrenia," says Potash.

      One important implication of the study is that these "overlap genes" may
      contribute to brain abnormalities that are shared by bipolar disorder and
      schizophrenia, and could help explain why the same anti-psychotic medications
      are effective treatments for both diseases, says Potash.

      Authors on the report are Potash, Dean MacKinnon, Sylvia Simpson, Francis
      McMahon, J. Raymond DePaulo, Melvin McInnis, Peter Zandi, Virginia Willour,
      Tsuo-H. Lan, Yuqing Huo, Dimitrios Avramopoulos, Yin Shugart.

      The study was funded by the National Institute of Mental Health, the National
      Alliance for Research on Schizophrenia and Depression, the Stanley Medical
      Research Institute, the Dana Foundation, the Alexander Wilson Schweizer Fund,
      the Affective Disorders Fund and the George Browne Laboratory Fund.

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