Mice, natural loners, can be transformed into gregarious social creatures by receiving a gene transplanted from the prairie vole--proof for the first time that switching genes from one species to another can alter behavior, scientists report today.
The research, conducted by scientists at Emory University in Atlanta, eventually could lead to new treatments for behavioral disorders, including schizophrenia, autism and other diseases that are marked by isolation and difficulty in forming personal attachments, the researchers said.
Largely by studying the personalities of twins who were raised separately, scientists have estimated that about one-third to one-half of human social behaviors have genetic origins. But precisely which genes are involved in human behavior remains unclear, with most probably consisting of a large, complex network of interactions.
In this case, only a single gene was involved, with the researchers creating the cuddling vermin by transplanting a gene from a prairie vole, a small, outgoing rodent.
Mice and many other animals, including humans, have their own version of the gene, called the vasopressin receptor.
Though the gene is very similar among the various species, its chosen stomping grounds within the brain vary wildly. In fact, species that look physically identical can be differentiated purely based on vasopressin receptor patterns.
In their study, reported in today's Nature, the Emory researchers inserted vole vasopressin receptor genes into mice and compared their behavior to that of normal mice.
Normal male mice put in a cage with a female briefly would sniff her and then move on to explore the rest of their environment. Mice with the altered pattern of vasopressin would spend significantly more time with the female, said Larry Young, a psychiatry professor at Emory University.
"The [male mice] became much more interested in the female," he said. "They spent more time with her, smelling her, grooming her and generally being nice to her."
Originally, the Emory scientists observed two kinds of voles, prairie and montane, that have 99% identical DNA. Regardless, the social behaviors of the prairie voles and montane voles couldn't have been more different.
Prairie voles, both males and females, are monogamous mates and devoted parents; if put in a large cage, they will spend more than half their time in contact with each other. The montane voles mated promiscuously and soon abandoned their children, and would spend only about 5% of their time interacting with other voles.
