In a significant scientific breakthrough, researchers have successfully reversed memory and learning deficits in a mouse model of Down syndrome (DS) by targeting the body’s response to cellular stress. The findings, published in Science on November 14, 2019, offer new hope for improving cognitive function in individuals with DS — the most common genetic cause of intellectual disability.What Is The Research About?A team led by researchers at UC San Francisco and Baylor College of Medicine found that in the brains of DS-model mice, learning impairments were linked to disrupted protein production in the hippocampus — a key brain region responsible for learning and memory. But by using specific drugs that modulate the body’s stress response, they were able to restore protein synthesis and significantly improve cognitive performance.Traditionally, DS research has focused on how an extra copy of chromosome 21 affects gene expression. However, this study took a different route. The scientists zeroed in on "proteostasis," the process by which cells maintain a healthy balance of protein production and regulation. They discovered that in DS mice, the integrated stress response (ISR) — a natural protective mechanism that reduces protein production during cellular stress — was unusually active in hippocampal cells. This reduction in protein synthesis, while generally protective, was impairing the brain’s ability to form long-term memories.“The cell is always checking in on its own health,” said Dr. Peter Walter, professor of biochemistry at UCSF and co-senior author of the study. “When something’s off, like an extra chromosome, it can trigger a stress response that shuts down protein production — and that’s detrimental for cognitive function.”Using three different methods, including a drug called ISRIB, the researchers suppressed this stress response and observed dramatic improvements in learning and memory among DS mice. The animals performed significantly better in two behavioural tests and showed enhanced synaptic activity in the brain, suggesting real physiological change.To strengthen their findings, the team examined brain tissue from people with DS. They found that the ISR was similarly activated in those with the extra chromosome — reinforcing the link between the stress response and DS symptoms.Interestingly, they identified a specific enzyme, PKR, as the main culprit behind this stress activation. By blocking PKR, either genetically or pharmacologically, the team was able to prevent the decline in protein production and restore cognitive function in mice.Although these results are preliminary and require further investigation in human models, the study marks a promising first step toward developing treatments for DS. “We started with a situation that looked hopeless,” Walter said. “Nobody thought anything could be done. But we may have struck gold.”The study was supported by the NIH and the Howard Hughes Medical Institute. While some of the researchers have industry ties related to the drug ISRIB, they report no additional conflicts of interest.This research signals a paradigm shift — from solely genetic approaches to exploring how cellular stress management could hold the key to treating cognitive disorders like Down syndrome.