Huntington’s Disease: Gene Editing Shows Promise in Mouse Studies

Cas9 clipping the Huntington's repeatsMy father was a folk song collector, and I grew up listening to the music of Woody Guthrie. On July 14th, folk music enthusiasts will be celebrating the 105th anniversary of Guthrie’s birth in his hometown of Okemah, OK. Besides being renowned for writing “This Land is Your Land” and other folk classics, Guthrie has another more tragic claim to fame: he provided the world with a glimpse at the devastation caused by a rare, inherited neurological disorder called Huntington’s disease.

When Guthrie died from complications of Huntington’s a half-century ago, the disease was untreatable. Sadly, it still is. But years of basic science advances, combined with the promise of innovative gene editing systems such as CRISPR/Cas9, are providing renewed hope that we will someday be able to treat or even cure Huntington’s disease, along with many other inherited disorders.

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Creative Minds: Can Diseased Cells Help to Make Their Own Drugs?

Matthew Disney

Matthew Disney

Matthew Disney grew up in a large family in Baltimore in the 1980s. While his mother worked nights, Disney and his younger brother often tagged along with their father in these pre-Internet days on calls to fix the microfilm machines used to view important records at hospitals, banks, and other places of business. Watching his father take apart the machines made Disney want to work with his hands one day. Seeing his father work tirelessly for the sake of his family also made him want to help others.

Disney found a profession that satisfied both requirements when he fell in love with chemistry as an undergraduate at the University of Maryland, College Park. Now a chemistry professor at The Scripps Research Institute, Jupiter, FL, Disney is applying his hands and brains to develop a treatment strategy that aims to control the progression of a long list of devastating disorders that includes Huntington’s disease, amyotrophic lateral sclerosis (ALS), and various forms of muscular dystrophy.

The 30 or so health conditions on Disney’s list have something in common. They are caused by genetic glitches in which repetitive DNA letters (CAGCAGCAG, for example) in transcribed regions of the genome cause some of the body’s cells and tissues to produce unwieldy messenger RNA molecules that interfere with normal cellular activities, either by binding other intracellular components or serving as templates for the production of toxic proteins.

The diseases on Disney’s list also have often been considered “undruggable,” in part because the compounds capable of disabling the lengthy, disease-causing RNA molecules are generally too large to cross cell membranes. Disney has found an ingenious way around that problem [1]. Instead of delivering the finished drug, he delivers smaller building blocks. He then uses the cell and its own machinery, including the very aberrant RNA molecules he aims to target, as his drug factory to produce those larger compounds.

Disney has received an NIH Director’s 2015 Pioneer Award to develop this innovative drug-delivery strategy further. He will apply his investigational approach initially to treat a common form of muscular dystrophy, first using human cells in culture and then in animal models. Once he gets that working well, he’ll move on to other conditions including ALS.

What’s appealing about Disney’s approach is that it makes it possible to treat disease-affected cells without affecting healthy cells. That’s because his drugs can only be assembled into their active forms in cells after they are templated by those aberrant RNA molecules.

Interestingly, Disney never intended to study human diseases. His lab was set up to study the structure and function of RNA molecules and their interactions with other small molecules. In the process, he stumbled across a small molecule that targets an RNA implicated in a rare form of muscular dystrophy. His niece also has a rare incurable disease, and Disney saw a chance to make a difference for others like her. It’s a healthy reminder that the pursuit of basic scientific questions often can lead to new and unexpectedly important medical discoveries that have the potential to touch the lives of many.

Reference:

[1] A toxic RNA catalyzes the in cellulo synthesis of its own inhibitor. Rzuczek SG, Park H, Disney MD. Angew Chem Int Ed Engl. 2014 Oct 6;53(41):10956-10959.

Links:

Disney Lab (The Scripps Research Institute, Jupiter, FL)

Disney NIH Project Information (NIH RePORTER)

NIH Director’s Pioneer Award Program

NIH Support: Common Fund; National Institute of Neurological Disorders and Stroke

Cool Videos: Coordinated Chaos in the Cell’s Cytosol

CellDance

When Amy Gladfelter arrived at the University of Basel in Switzerland to pursue post-doctoral work in 2001, she remembers that her research interests were still a little up in the air. As she settled into the new lab, Gladfelter remembers watching movies that others had made of the filamentous fungus Ashbya gossypii and wondering how on earth its myriad nuclei could share the same cytoplasm and do different things. Now, more than a decade later, this cell biologist finds herself at Dartmouth College, Hanover, N.H., where she is leading a lab that is making its own thought-provoking movies and pushing the envelope in an effort to answer this and many other scientific questions.

As you’ll learn by watching this video, Gladfelter’s work has implications far beyond the world of fungi because the filamentous proteins called septins, which act to define territory within Ashbya cells, are very similar to certain proteins found in human cells. While such proteins are normally very flexible, they can morph into toxic, solid states in certain human disorders, including Alzheimer’s disease and Huntington’s disease. Besides illustrating the value of Ashbya for uncovering clues to neurodegenerative disorders, this video delivers a broader message about the importance of all kinds of model organisms for efforts to understand our own biology.

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Yeast Reveals New Drug Target for Parkinson’s

Untreated yeast shows clumps of brightly colored spots, while treated yeast are more even in their color.

Caption: Left, yeast sick with too much α-synuclein, a protein that is implicated in Parkinson’s disease. Right, the same yeast cells after a dose of NAB, which seems to reverse the toxic effects of α-synuclein.
Credit: Daniel Tardiff, Whitehead Institute

Many progressive neurodegenerative disorders like Alzheimer’s, Huntington’s, and Parkinson’s disease, are characterized by abnormal clumps of proteins that clog up the cell and disrupt normal cellular functions. But it’s difficult to study these complex disease processes directly in the brain—so NIH-funded researchers, led by a team at the Whitehead Institute for Biomedical Research, Cambridge, MA, have turned to yeast for help.

Now, it may sound odd to study a brain disease in yeast, a microorganism long used in baking and brewing. After all, the brain is made up of billions of cells of many different types, while yeast grows as a single cell. But because the processes of protein production are generally conserved from yeast to humans, we can use this infinitely simpler organism to figure out what the proteins clumps are doing and test various drug candidates to halt the damage.

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Making This A Land for You and Me

Photo of Woody Guthrie and Led Belly walking down a dirt road

Photo from liner notes of the Folkways CD

Today is International Rare Disease Day. In honor of the occasion, I’d like to pay tribute to a few real-life heroes whose struggles have forever changed the landscape of rare disease research.

Folk singer Woody Guthrie is best known for his song, “This Land Is Your Land.” Written more than 70 years ago, “This Land” has taken its place among our nation’s great anthems, setting forth a vision of inclusiveness that has inspired generations of Americans to “sing along.” But the last couple of verses are often omitted. Here’s a version of one of them:

As I was walkin’I saw a sign there
And that sign said
no trespassin’
But on the other side … it didn’t say nothin’!
Now that side was made for you and me!

These verses brought into the foreground those whom society had marginalized. “This Land” reminded us of their existence, challenged us to live up to our ideals—and include all people in our best vision of ourselves.

Woody performing one version of “This Land”:

Even as he was singing about inclusiveness, Woody Guthrie was starting a long battle against a disease that increasingly cast him outside mainstream society: Huntington’s disease. In most cases—and as was indeed the case for Woody—symptoms of Huntington’s disease do not appear until adulthood. Gradually, this rare, inherited neurological disorder seizes control of its sufferer’s body, mind—and even voice. In 1965, 13 years after he was diagnosed, Woody fell mute. He had long since lost his ability to play guitar. Two years later, he died at the age of 55.

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