Darnell has been studying the protein – called NOVA1 and known to be crucial to brain development – since the early 1990s. For the latest research, scientists in his lab at New York's Rockefeller University used CRISPR gene editing to replace the NOVA1 protein found in mice with the exclusively human type to test the real-life effects of the genetic variant. To their surprise, it changed the way the animals vocalized when they called out to each other.
Baby mice with the human variant squeaked differently than normal littermates when their mom came around. Adult male mice with the variant chirped differently than their normal counterparts when they saw a female in heat.
Both are settings where mice are motivated to speak, Darnell said, "and they spoke differently" with the human variant, illustrating its role in speech.