By Ricki Lewis, PhD

When you hear hoof beats, think horses, not zebras.” So goes the mantra of first-year medical students. If a common disease is a horse and a rare disease a zebra, then giant axonal neuropathy (GAN), with only 50 or so recognized cases worldwide, is surely a unicorn.

Five years ago this week, nine-year-old Hannah Sames of Rexford, New York, who lives near me, received a diagnosis of GAN, a disease much like amyotrophic lateral sclerosis. And this month, thanks in part to the herculean fundraising efforts of Hannah’s Hope Fund (HHF), the cover and lead article of the Journal of Clinical Investigation reveals most of the story behind the devastating inherited disease, with repercussions that will reach far beyond the tiny GAN community.

If all goes well at the next Recombinant DNA Advisory Committee meeting at the NIH, a phase 1 clinical trial may be underway before year’s end to evaluate gene therapy for GAN. “A fire started burning deep in my core exactly five years ago when Hannah was diagnosed. We will not rest until we have a successful treatment for our kids. They are rare, but they are no longer neglected,” says Lori Sames, Hannah’s mom and executive director of HHF.

Charming Hannah

On March 5, 2004, when Lori and her husband Matt first glimpsed their newborn daughter’s kinky reddish fuzz, they were both delighted and puzzled. Madison, five, and Reagan, two, have stick-straight hair, as do Lori and Matt. When the birthing goop dried, Hannah’s cap of tight curls sprang to life.

For many months, the little girl seemed okay. She smiled, sat, crawled and hauled herself upright on schedule. But her footsteps were halting, hesitant. Hannah slowly grew clumsy, the strength ebbing from her legs. Lori made the usual rounds of specialists assuring her all was well, but already, filaments of protein were distending the long axons of the motor neurons running down Hannah’s legs, blocking messages to her muscles.

By Hannah’s third birthday, Lori and Matt suspected something was seriously wrong. Both of Hannah’s arches now bowed, and she tottered. More doctors gave false reassurances, hardly hiding their diagnosis of Lori as a helicopter mom. Then Lori’s sister showed cell phone video of Hannah walking to a physical therapist friend, who thought Hannah’s gait was like that of a child with muscular dystrophy. Six months of neurological tests followed; all results were normal.

Identifying a Unicorn

That’s what happens with a disease so rare that few physicians have seen it or even heard of it. They can’t recognize a unicorn, don’t know what to test for. But finally an astute pediatric neurologist gave Matt and Lori an answer, and it didn’t come from an exome sequence or a sophisticated scan. “He took out a huge textbook and showed us a photo of a skinny little boy with kinky hair, a high forehead and braces that went just below the knee– he looked exactly like Hannah. And he had GAN,” Lori recalls. Three days of tests at a children’s hospital in New York City confirmed the diagnosis.

Meeting with a genetic counselor was devastating. Lori recites what they learned: “Matt and I are each carriers of GAN, and we passed the disease to Hannah. Each of our two other daughters has a two in three chance of being a carrier. GAN is a rare ‘orphan genetic disorder’ for which there is no cure, no treatment, no clinical trial and no ongoing research.”

“So you are telling us this is a death sentence?” Lori recalls asking the genetic counselor.

“Yes.”

The disease would progress slowly, the counselor said. Hannah’s legs would continue to weaken. By first grade she’d likely need a walker in addition to her ankle supports, and soon after, a wheelchair. She might lose her sight and hearing, and eventually be bedridden.

Hannah’s Hope Fund

hhfMatt and Lori walked around like zombies for a few days. And then they founded Hannah’s Hope Fund. Their basement became a war room where they used their business backgrounds to assemble the first ever research conference for GAN. As Lori taught herself molecular biology, she became convinced that gene therapy was a logical approach, but at the same time recognized the value of learning anything about GAN. They were lucky to find Jude Samulski, director of the Gene Therapy Center at the University of North Carolina at Chapel Hill, and he recommended a young investigator, Steven Gray, to lead the team. It’ll be the first gene therapy delivered to the spinal cord. A clinical trial is incredibly expensive, and HHF’s fundraising efforts are amazing– they’ve earned $1 million in just the past eight months. They’re just one of many not-for-profits in the rare disease community who have taken the helm of funding research.

Reproduced with permission from the American Society for Clinical Investigation; J. Clin. Invest. 2013; 123(5)In parallel to the gene therapy efforts, HHF supports research into the nature of the cellular glitch behind GAN, in the labs of Robert Goldman and Puneet Opal at Northwestern University, Jean-Pierre Julien at Université Laval in Quebec, Pascale Bomont at the INSERM neurological institute in Montpelier, France and others. The group reports on a remarkable set of experiments in May’s JCI that probe the out-of-control parts of the cell’s inner skeleton, the intermediate filaments (IFs).

GAN is the perfect disease to investigate IFs because it’s caused by a single gene and has a large, measurable effect. Other conditions may affect IFs secondarily or reflect input from several genes or environmental exposures.

At fault in GAN is a protein called gigaxonin that normally interacts with the IFs. Most kids with GAN have abnormal forms of the protein; Hannah is highly unusual in that she lacks it entirely.

Continue reading this story at DNA Science Blog.

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