Social sense may heed uneven inheritance.
The X chromosome apparently contains a still-unidentified gene that contributes to one's ability to gauge others' social reactions and to inhibit impulsive acts, contends psychiatrist David H. Skuse of the Institute of Child Health in London and his coworkers. The suspected gene appears to influence social thinking in different ways, depending on the gene's parental source.
"We're going to continue hunting for what I suspect is a single gene with many actions that in some way influence social cognition," Skuse says. That gene undoubtedly interacts with others on different chromosomes, he adds.
Women typically have two X chromosomes, one inherited from each parent; men receive an X chromosome from their mother and a Y chromosome from their father. Skuse and his colleagues studied 80 females age 6 to 25 who lack all or part of one X chromosome.
This condition, known as Turner's syndrome, affects 1 in 2,500 females. It is characterized by short stature and stunted sexual development at puberty. Problems with social adjustment often occur, although scores on intelligence tests fall within the normal range.
The researchers divided their volun-teers into two groups: 55 with a complete X chromosome inherited from their mother and 25 with an undamaged X chromosome from their father.
Marked social difficulties and academic failure occurred far more often in the group with a maternally inherited X chromosome, the researchers report in the June 12 Nature. These females also scored lower on a test of word knowledge and reading comprehension and on a parent-completed questionnaire about the extent to which they displayed social insight and adeptness.
Both groups of volunteers achieved lower scores on those measures than previously established standards for females with two complete X chromosomes, the researchers note.
Maternal-X females scored particularly poorly on a "behavioral inhibition" task that assessed their ability to suppress familiar responses. Volunteers saw a random series of the numbers 1 and 2 and had to say "one" in response to 2 and "two" in response to 1. Paternal-X females did as well on this task as females with both X chromosomes. Males typically score lower than females on behavioral inhibition tests of this type.
Finally, Skuse's team found that another eight Turner's syndrome volunteers, each lacking much of the short arm of the paternally inherited X chromosome, performed as well on social and verbal tests as the other group of paternal-X females. This suggests that the gene implicated in social intelligence lies elsewhere on that chromosome, Skuse holds.
His report represents the first evidence that a gene on the X chromosome works differently depending on which parent it's inherited from, according to an accompanying commentary by Peter McGuffin and Jane Scourfield of the University of Wales College of Medicine in Cardiff.
Two other provocative possibilities emerge from these results, Skuse remarks. First, the existence of a gene on the maternally inherited X chromosome that disturbs social skills may explain why males prove more vulnerable to some developmental disorders, such as autism and attention-deficit disorder. Second, this X-linked gene may contribute to sex differences in aggressiveness and social skill often attributed solely to cultural influences and child rearing.
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|Title Annotation:||research on genetics of social intelligence|
|Date:||Jun 14, 1997|
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