ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Tuesday, January 2, 1996 TAG: 9601020188
SECTION: NATIONAL/INTERNATIONAL PAGE: A1 EDITION: METRO
SOURCE: NATALIE ANGIER THE NEW YORK TIMES
note: below
Maybe it is appropriate that the first gene that scientists have found linked to an ordinary human personality trait is a gene involved in the search for new things.
Two teams of researchers have reported detecting a partial genetic explanation for a personality trait called ``novelty seeking.'' People high in a novelty-seeking quotient tend to be extroverted, impulsive, extravagant, quick-tempered, excitable and exploratory - your flamboyant Uncle Milton who shows up with an armload of presents, bellows his hellos, pretends to pull coins from your ear, knows all the latest disaster jokes and then sits around after the family dinner looking faintly bored.
Reporting Monday in the journal Nature Genetics, the scientists have discovered that novelty seekers tend to have a particular variant of a gene that allows the brain to respond to dopamine, an essential chemical-communication signal.
The gene encodes the instructions for the so-called D4 dopamine receptor, one of five receptors known to play a role in the brain's response to dopamine. As it turns out, novelty seekers possess a version of the D4 receptor gene that is slightly longer than the receptor of more-reserved and deliberate individuals.
In theory, the long gene generates a comparatively long receptor protein, and somehow that outsized receptor influences how the brain reacts to dopamine.
Dr. Richard P. Ebstein and his colleagues at Herzog Memorial Hospital in Jerusalem and at Ben-Gurion University in Beersheva, Israel, wrote one of the papers. The other comes from Dr. Jonathan Benjamin, Dr. Dean H. Hamer and their colleagues at the National Institutes of Health in Bethesda, Md.
Dopamine is only one of many so-called neurotransmitters found coursing through the brain, sharing its chemical-communication duties with such other renowned neurotransmitters as serotonin and norepinephrine. However, dopamine is the chemical most strongly linked to pleasure and sensation seeking.
Recreational drugs such as cocaine, nicotine and alcohol are thought to act through the brain's dopamine system. Conversely, people with Parkinson's disease, in which the dopamine-producing cells of the brain gradually degenerate, have been shown to be unusually low in novelty-seeking behavior. Hence, the dopamine system has long been proposed as an actor in impulsive, extravagant behavior.
The new report of the genetic link to the D4 receptor, though, is the first clear evidence of a connection between the neurotransmitter and the personality type.
It is also the first known report of a link between a specific gene and a specific normal personality trait, Ebstein said in an interview. Other reports have tentatively linked genes to behavioral pathologies such as schizophrenia or alcoholism, but a taste for the novel is neither good nor bad, merely a color on the prism of ordinary human complexity.
The gene does not entirely explain the biological basis for novelty seeking. Research on animals, as well as extensive studies of human twins of both the identical and fraternal variety, indicate that about half of novelty-seeking behavior is attributable to genes, the other half to as-yet ill-defined environmental circumstances.
Scientists say the dopamine receptor accounts for perhaps 10 percent of the difference in novelty-seeking behavior between one person and the next.
``If we assume there are other genes out there that we haven't looked at yet, and that each gene exerts more or less the same influence as the D4 receptor,'' Ebstein said, ``then we would expect maybe four or five genes are involved in the trait.''
The influence of the receptor variance on behavior may be modest, but the strength of the new finding is considerable. Not only did the two groups find the same correlation between receptor length and novelty seeking, but they found it in different ethnic groups - the Israeli subjects being mostly Ashkenazi and Sephardic Jews of both sexes, and the group in the United States made up mainly of white American (and presumably genetically diverse) men.
``This is a very credible finding, given the strength of replication by different groups in different countries,'' said Dr. C. Robert Cloninger of the Washington University School of Medicine, who first proposed a link between dopamine and novelty-seeking behavior 10 years ago.
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