Prajna Hebbar was studying DNA sequences when she noticed something that other scientists had missed for years — entire chunks of genetic code that were simply missing from the standard map scientists use when studying marmosets. Those gaps mattered because marmosets, small monkeys from South America, are becoming one of the most important animals for understanding human diseases like Alzheimer's. Now Hebbar and her team at the University of California, Santa Cruz have filled in those gaps with the very first complete genome of the common marmoset.
The human genome — all the DNA that makes up a person — was only fully mapped in 2022, and scientists have been working to do the same for other species ever since. A complete genome is important because it gives researchers an accurate blueprint to compare against. Without it, important differences can be overlooked. "It's great to be in an era where we're not stuck with the technical problems — we can go into the biology and make discoveries relevant to human health," Hebbar said.
Hebbar, a Ph.D. student in biomolecular engineering, worked on the project alongside Professor Benedict Paten at the UC Santa Cruz Genomics Institute. Together they are part of a larger group called the Telomere-to-Telomere Consortium, an international team that previously made history by completing the first human genome. Their work was published in the journal Cell.
Marmosets are especially useful for studying brain diseases because they are primates — meaning they are more closely related to humans than animals like mice — and they naturally develop age-related memory loss similar to what happens in humans with Alzheimer's. Their small size also makes them easier to work with than larger primates like macaques.
Using their new complete genome, the researchers examined DNA from 230 marmosets. They found differences in many genes already linked to Alzheimer's disease in humans, as well as genes important for the immune system. The team identified 76 genes connected to Alzheimer's, Parkinson's, and other neurodegenerative diseases, giving scientists high-quality references to study these conditions more accurately than ever before.
"We see variation in these marmosets in the same genes that we do in humans, further reinforcing the idea that the marmoset is a good model for studying Alzheimer's disease in humans," Hebbar said. "Now, we have this really complete, high-quality resource that people can take advantage of."
The research could eventually help scientists develop better treatments for Alzheimer's and other diseases that affect millions of people worldwide. Because the marmoset genome is now complete, researchers everywhere have a powerful new tool for understanding what goes wrong in the human brain as it ages.