New data challenge personality gene - D4 dopamine receptor shows no link to novelty-seeking behavior in Finnish men - Brief Article

Science News, Nov 2, 1996 by Bruce Bower

In a pair of reports released earlier this year, scientists asserted that the presence of a particular gene increases the likelihood that someone will have an excitable, adventurous personality. Closer scrutiny raises questions about whether researchers have cornered this so-called personality gene, according to two new studies.

A version of the D4 dopamine receptor gene, or D4DR, cited as a key factor in producing novelty-seeking behavior (SN: 1/6/96, p. 4) shows no sign of eliciting this personality characteristic in Finnish men, contend psychiatrist Anil K. Malhotra of the National Institute of Mental Health in Bethesda, Md., and his coworkers. Moreover, the same D4DR variation occurs frequently in some parts of the world and rarely in others, making it an unlikely candidate for regulating such a widespread trait, asserts a team directed by geneticist Kenneth K. Kidd of Yale University School of Medicine.

"It's unacceptably speculative to claim that large, heterogeneous populations would have an average difference in novelty-seeking behavior just because they differ dramatically in the frequencies of [this gene]," Kidd argues.

The D4DR gene regulates a protein involved in the transmission between brain cells of messages carried by dopamine. The gene contains a region that is repeated from 2 to 11 times in different individuals. Earlier data suggested that a 7-repeat form of the gene occurs mainly in avid novelty seekers, identified by their answers to a questionnaire.

Malhotra's investigation, published in the November Molecular Psychiatry, yields no association between the 7-repeat version of D4DR and novelty seeking in a group of 193 Finnish men. None of the volunteers suffered from psychiatric disorders.

In an additional examination of 138 alcoholic Finnish men, many of whom displayed high levels of novelty seeking, the D4DR variation appeared slightly more often among those with the lowest scores on that personality trait, the researchers hold.

Kidd's team, which presented its findings this week at the American Society of Human Genetics annual meeting in San Francisco, assessed D4DR variations in 14 populations from Africa, Europe, the Middle East, East Asia, North America, and South America.

The 7-repeat form appeared far more often in some regions, such as the Middle East, than in others, such as East Asia, the researchers note. Studies that discerned a link between this D4DR form and novelty seeking took place in Israel and the United States, where the gene is relatively frequent, they state.

Preliminary data gathered by Kidd's team indicate that chimpanzees, gorillas, and orangutans exhibit other DNA variations in a region that corresponds to the part of the human D4DR gene where repeated sequences are found. This suggests that natural selection has not preserved stable, functional variations of D4DR in primates, in his view.

The 7-repeat form of D4DR may still affect personality, argues geneticist Dean H. Hamer of the National Cancer Institute in Bethesda, who directed one of the studies linking it to novelty seeking. In that analysis, the gene showed an even stronger association with a measure of general happiness, Hamer contends. A dopamine-mediated reward system in the brain may strongly influence a happy outlook on life and have a weaker effect on novelty seeking, he theorizes.