Voles shed light on genetics of fidelity and shyness

Research on voles could help explain some human behaviour and disorders such as autism, US scientists say. The researchers, based at Emory University in Atlanta, have shown that differences in the length of a piece of 'junk' DNA found in a vole gene affect the animals' behaviour. The study, published in the journal Science, suggests a biological basis for traits such as monogamy, good parenting and shyness in voles.

Previous research showed that different versions of the gene that makes a key hormone receptor are linked to differences in the promiscuity of different vole species. Prairie voles, which have a longer version of the vasopressin receptor (V1aR) gene, are more monogamous than meadow voles, which have a shorter version. Last year, the Emory University team showed they could make meadow voles behave like faithful prairie voles by adding extra copies of the V1aR gene to part of their brains.

In the latest study, the researchers have shown that the difference is down to a section of non-coding microsatellite DNA (previously known as 'junk' DNA), buried within the 'control region' of the gene, which affects how many vasopressin receptor proteins it makes. The scientists first showed that in cells grown in the laboratory, the length of the vole vasopressin receptor microsatellites could change the amount of protein made by the gene. Next, they bred two strains of the monogamous prairie vole - one with a long version of the microsatellites and the other with a short version.

Adult male voles with the long version had more vasopressin receptors in brain areas involved in social behaviour and parenting. They also responded to female odours and greeted strangers more readily, and were more likely to form pair bonds and nurture their young, according to a press release. 'If you think of brain circuits as locked rooms, the vasopressin receptor as a lock on the door, and vasopressin as the key that fits it, only those circuits that have the receptors can be 'opened' or influenced by the hormone', said first author Elizabeth Hammock. 'An animal's response to vasopressin thus depends upon which rooms have the locks and our research shows that the distribution of the receptors is determined by the length of the microsatellites', she added.

Hammock says that differences in the same microsatellite could account for some of the diversity in human social personality traits. 'For example, it may help explain why some people are naturally gregarious while others are shy', she said. The authors also think different versions of the gene could influence human conditions like autism and social anxiety disorders. Two studies have already found weak links between alterations in this microsatellite and autism in some families. Far from being junk, says lead author Larry Young, these segments of DNA may interact with other genes to produce individual differences and social diversity.