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UCSD researchers spot gene marker for Alzheimer’s disease

Thomas Fudge
Data analyst Riccardo Calandrelli and UCSD bioengineering professor Sheng Zhong are shown in their lab where they examined a gene marker for Alzheimer's Disease. Apr. 1, 2022

The study examined 15 years of blood testing and observation of hundreds of people over age 65. It tracked the development of Alzheimer’s over time, in people who were symptomatic and asymptomatic.

The researchers, led by UC San Diego bioengineer Sheng Zhong, said their work finds a clear connection between an overactive gene and the development of Alzheimer's disease.

Zhong said finding a gene marker for Alzheimer’s means we can better predict the disease and, possibly, find a path to a cure.


“To either ameliorate the development of the disease or even reverse the development of the disease. Those are the tests that we are currently doing,” he said.

The scientists said they were surprised by the findings of the study, because the gene and serine, the nutrient it produces, play an important role in brain development.

“It’s like an overshoot of the good guys,” Zhong added. “The good stuff seems to mark an unfortunate disease outcome.”

The overactive gene goes by the acronym PHGDH (phosphoglycerate dehydrogenase). So far, the study has proven a strong correlation between Alzheimer’s and the gene. Research assistant and data analyst Riccardo Calandrelli said they spotted an abundance of PHGDH in blood tests of people whose behavior scored high on what’s called the dementia rating scale.


“We observed that, when this index was getting worse — when the cognitive deficiency was higher — the PHDGH level in these individuals was higher. So we could link both the physiology and the behavior,” Calandrelli said.

Alz photos.png
Courtesy of UC San Diego.
Dark patches on the righthand image show the overactivity of the gene PHDGH in the brain of a person with Alzheimer's in this undated photo.

While researchers have proven a correlation, they have not proven cause and effect. But they think that is what’s happening.

“Our hypothesis,” Zhong said, “is that a pronounced oversupply of serine makes neurons too active, for too long a time, and thus become toxic.”

That, in turn, can cause the conditions that lead to Alzheimer’s.

There is no cure for this disease of the brain, and the UCSD researchers have not discovered one. But Zhong said there are ongoing experiments on mice and on human brain cells (grown in the lab) that could lead to a way to tone down the overactive gene and the overproduction of serine.

Some businesses sell serine as a dietary supplement to increase brain function. Based on what he’s learned about serine, Zhong says for those who may suffer Alzheimer’s, those supplements may be just what they don’t need.