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Huntington's spreads like 'fire in the brain.' Scientists say they've found the spark

A MARTÍNEZ, HOST:

Diseases such as Alzheimer's and Parkinson's spread through the brain like a forest fire, so researchers have been trying to figure out how the fire starts. NPR's Jon Hamilton reports on a study that may provide an answer.

JON HAMILTON, BYLINE: The study looked at Huntington's disease, a rare inherited disorder. Randal Halfmann of the Stowers Institute in Kansas City says Huntington's has symptoms that overlap those of diseases like Alzheimer's and Parkinson's.

RANDAL HALFMANN: These individuals begin to lose control of their body movements. They have mental impediments over time, and eventually they die.

HAMILTON: Like other neurodegenerative diseases, Huntington's occurs when certain proteins in one area of the brain begin to form toxic clumps. Then, Halfmann says, the process starts spreading.

HALFMANN: As the disease progresses, you're effectively watching sort of a forest fire, right? And you're trying to figure out what started it. What does a match look like?

HAMILTON: A match about to be lit. To find out, Halfmann's team knew they had to zoom in on the process.

HALFMANN: So you have to go closer and closer and closer to such an extent that you're looking at a single match.

HAMILTON: To do that, Halfmann says his team developed a tool that allowed them to conduct a series of experiments inside individual cells.

HALFMANN: And so basically, we use cells as the test tubes.

HAMILTON: In Huntington's disease, the segment of a protein that becomes abnormal is called polyQ. So the team began creating and testing lots of different versions of polyQ inside living cells. Halfmann says the approach worked. The team found the match that seems to ignite Huntington's disease.

HALFMANN: In the end, what starts this little forest fire in the brain or in a neuron is a single molecule of polyQ.

HAMILTON: And once the team had identified that molecule, they were able to find a way to prevent it from spreading - at least in the lab. The trick was to flood the cell with proteins that, in effect, snuffed out the flame. Halfmann says the next step will be to develop a drug that can do something similar in people.

HALFMANN: Ultimately, it only matters if we actually create a therapy, right? You know, otherwise, it's just academics.

HAMILTON: The study, which appears in the journal eLife, could help researchers studying other diseases, including Alzheimer's, Parkinson's and ALS, or Lou Gehrig's disease.

Corinne Lasmezas is a professor at the Wertheim UF Scripps Institute in Jupiter, Fla. Lasmezas, who was not connected with the study, says it makes sense to approach these diseases as forest fires in the brain.

CORINNE LASMEZAS: You could use this metaphor, absolutely. You have to go back when the fire starts so that it doesn't propagate in the entire forest.

HAMILTON: The Alzheimer's field appears to be learning that lesson. Early drugs targeted only the large amyloid plaques found in the brains of people with the disease. But these drugs didn't help patients, perhaps because the plaques they remove are just the charred remains of a forest that has already burned. Lasmezas says the latest drugs still remove large clumps of amyloid...

LASMEZAS: But they also recognize the ones that are smaller and that are more toxic, and this is why they block more efficiently the neuronal toxicity.

HAMILTON: The process that kills brain cells. Lasmezas says these smaller clumps are closer to the event that touches off Alzheimer's in the first place. She believes scientists are finally closing in on strategies that will slow or halt many of the diseases that ravage the brain.

LASMEZAS: For a long time, we didn't know much about the mechanism of neurodegenerative diseases. And within the last, let's say, 15 years, there's been literally an explosion of knowledge.

HAMILTON: One that will result not only in a better understanding of these diseases, but in drugs to treat them.

Jon Hamilton, NPR News.

(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.

NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.

Jon Hamilton is a correspondent for NPR's Science Desk. Currently he focuses on neuroscience and health risks.