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Manic depression: a new gene defect.

Manic depression: A new gene defect

There have been a spate of recentstudies concerned with the genetic basis of manic depression, and the latest effort indicates that either of at least two genetic defects may predispose individuals to this severe disorder.

Scientists who studied five large familiesin Jerusalem report in the March 19 NATURE that cases of manic depression or related mood disorders were linked to genetic markers near one tip of the X chromosome. Researchers recently linked manic depression among three Amish families in Pennsylvania to a defect on chromosome 11 (SN: 2/28/87, p.132), although the same defect did not show up in two other studies of non-Amish families. The critical gene in both the Israeli and Amish families has not been identified.

The possibility that manic depressionis influenced by a gene on the X chromosome has been suggested previously, since more women than men are affected and family studies have documented that both fathers and sons seldom have the disorder. The 23rd and final pair of human chromosomes consists of two X chromosomes for females and one X and one Y chromosome for males. The Y chromosome is inherited from the father.

Miron Baron of Columbia University inNew York City and his colleagues at Yale University School of Medicine and Hebrew University-Hadassah Medical School in Jerusalem isolated genetic material from 161 adults, 47 of whom had manic depression or related disorders, in five Jewish families. DNA-cutting enzymes were used to locate two genetic markers at one tip of the X chromosome linked to color blindness and a chemical deficiency that causes anemia. The genetic mutations occurred overwhelmingly among subjects with the psychiatric diagnoses.

Further analysis confirmed this patternamong the four families of Mediterranean and Asian origin, but not among the one family of Eastern European descent. X-linked inheritance of manic depression may be more pronounced among Jews and other groups in the former regions, suggest the researchers.

The findings do not indicate that manicdepression is more common in those populations, note the scientists. Nor is there evidence that color blindness or the genetically caused anemia are accompanied by manic depression in the population at large.

The investigators estimate, however,that perhaps one-third of all manic depressives carry the X-linked gene.
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Author:Bower, Bruce
Publication:Science News
Date:Mar 28, 1987
Words:375
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