“Some of the participants in the study also took the Wechsler Adult
Intelligence Scale-Revised, a traditional IQ test. In all, members of 200
families, including more than 2,150 individuals, took the Wechsler test, and those results were matched to differences in individuals’ DNA.
By comparing individual differences embedded in DNA, the team zeroed in on CHRM2, the neuronal receptor gene on chromosome 7. The CHRM2 gene activates multitude of signaling pathways in the brain involved in learning, memory and other higher brain functions. The research team doesn’t yet understand how the gene exerts its effects on intelligence.”
Dick’s team is not the first to notice a link between intelligence and the CHRM2 gene. In 2003, a group in Minnesota looked at a single marker in the gene and noted that the variation was related to an increase in IQ. A more recent Dutch study looked at three regions of DNA along the gene and also noticed influences on intelligence. In this new study, however, researchers tested multiple genetic markers throughout the gene.
“If we look at a single marker, a DNA variation might influence IQ scores between two and four points, depending on which variant a person carries,” Dick explains. “We did that all up and down the gene and found that the variations had cumulative effects, so that if one person had all of the ‘good’ variations and another all of the ‘bad’ variations, the difference in IQ might be 15 to 20 points. Unfortunately, the numbers of people at those extremes were so small that the finding isn’t statistically significant, but the point is we saw fairly substantial differences in our sample when we combined information across multiple regions of the gene.”
Dick says the next step is to look at the gene and its numerous variants to learn what is going on biologically that might affect cognitive performance. Presently, she says it’s too early to predict how small changes in the gene might be influencing communication in the brain to affect intelligence, and she says it’s nearly certain CHRM2 is not the only gene involved.
Prior GNXP references to CHRM2: