( eceptor gene. It was considered jun...)Rodent social behavior encoded in junk DNA

"It was considered junk DNA because it didn't seem to have any function," noted Hammock.

Each animal species has its own signature microsatellites; for example, the repeating letter sequences are much longer in monogamous than in polygamous vole species. But even within a species, there are differences in the number of letters in the sequence among individuals.

The researchers first showed in cell cultures that the vole vasopressin receptor microsatellites could modify gene expression. Next, they bred two strains of a monogamous species, the prairie vole ?one with a long version of the microsatellites and the other with a short version. Adult male offspring with the long version had more vasopressin receptors in brain areas involved in social behavior and parenting (olfactory bulb and lateral septum). They also checked out female odors and greeted strangers more readily and were more apt to form pair bonds and nurture their young.

"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," added 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."

Prairie voles with the long version have more receptors in circuits for social recognition, so release of vasopressin during social encounters facilitates social behavior. If such familial traits are adaptive in a given environment, they are passed along to future generations through natural selection.

Variability in vasopressin receptor microsatellite length could help account for differences in normal human personality traits, such as shyness, and perhaps influence disorders of sociability like autism and social anxiety disorders, suggest the r
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Source:NIH/National Institute of Mental Health