The Mr. Mom Switch

Erin O'Donnell in Harvard Magazine:

In the mouse world, virgin male mice are not known as nurturers. They’re aggressive and infanticidal, regularly injuring or killing newborn mice fathered by other males. But research led by Catherine Dulac, Higgins professor of molecular and cellular biology, reveals that these murderous mice can be turned into doting dads simply by stimulating a set of neurons, shared by both males and females, that appears to drive parental behavior. Dulac examines control of instinctive behavior in animal brains, particularly social actions such as courtship and parenting. Previous work in her lab revealed that mouse brains hold circuits that determine whether the animals adopt stereotypical male or female behavior: Dulac discovered that the vomeronasal organ (VNO), a set of chemical-sensing receptors in the nasal septa of mice, dictates which of the two circuits is activated. (Female mice lacking a functional VNO engaged in “very bizarre male-like behaviors,” Dulac reports, emitting ultrasonic vocalizations normally sung by males to attract mates.)

In the most recent research, first described in the journal Nature last year, the investigators set out to learn if male mice had a similar capacity to match females’ parenting abilities. A female mouse that has never encountered a male or babies will nonetheless spring into action if pups are placed in her cage. “She will immediately build a nest, retrieve the pups, groom them, and crouch around them,” Dulac explains. “This is very robust, stereotyped behavior. If you do the same experiment with virgin males, they will immediately attack the pups.” Yet when the researchers removed the VNO of virgin male mice, changing the way they sensed the pups, the normally hostile males became “perfect dads,” Dulac reports. The infanticidal instinct vanished; the males built nests and placed the pups in them, groomed the pups, and huddled by them protectively. These findings, she says, suggest that there are “circuits in the male brain that underlie parental behavior,” but those behaviors are “normally repressed.”

More here.