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San Diego Researchers Offer Insight Into What Makes Humans Social

Williams syndrome-derived neurons in culture.
UC San Diego
Williams syndrome-derived neurons in culture.

Possible new insights into the underlying neurobiology of human social behavior came to light as researchers studied Williams syndrome, a rare genetic disorder that causes hyper sociability, UC San Diego reported Wednesday.

The research involved a variety of disciplines at UC San Diego, the Salk Institute for Biological Studies and other organizations.

The scientists, whose work appears in Wednesday's online edition of the journal Nature, studied Williams syndrome, which is caused by the deletion of one copy of 25 contiguous genes on chromosome 7 out of an estimated 30,000 genes in the brain.


Williams syndrome causes several medical problems for patients, but also tends to make them hyper-social.

"An interesting aspect is their typical hyper-sociability," said study co-author Ursula Bellugi, director of the cognitive neuroscience lab at Salk and an adjunct professor at UCSD who has studied Williams syndrome for many years. "Persons with the WS deletion tend to be overly friendly, overly trusting, drawn to strangers, yet anxious."

They also suffer from a heart defect, developmental delays and severe spatial deficits. Around 20,000 Americans are believed to have the condition.

Study co-author Alysson Muotri, an associate professor of pediatrics and cellular and molecular medicine at UCSD School of Medicine who studies autism, extracted dental pulp cells from baby teeth donated by children with Williams syndrome and reprogrammed them to form functional neuronal networks resembling the developing cortex of the human brain in a dish.

"At the functional level, they make more synapses or connections to other neurons than what you would expect," Muotri said. "That might explain the WS super-social aspect and their gregarious human brain, giving insights into autism and other disorders that affect the social brain."


Muotri said studying Williams syndrome could provide insight into what makes humans social beings — a key development in the evolution of humanity.

"It was our social power that made us a collaborative species capable of dramatic transformation of our environment by creating poetry, music and technology," Muotri said.

The scientists also made findings more specific to Williams syndrome itself, including a discovery that the reprogrammed cells didn't replicate as fast as similar cells because many of them died. That leaves patients with a reduced cortex surface area, according to Muotri.

Scientists in Thailand, Pontifica Universidade Catolica do Parana in Brazil and the University of Utah also participated in the study, which received funding from, among others, the California Institute for Regenerative Medicine, the National Institutes of Health, the Helmsley Foundation and the Royal Thai Government.