Of Mice and Monkeys: Tulane Scientists Research Rare and Fatal Genetic Disease

The Almy family, from left to right – Kales, Ander, Trevor, Katie, and Karis

By Avery Werther

The power was out at 1 a.m. in Clinton, Mississippi, and the machines that help keep 6-year-old Karis Almy alive would only hold their battery charge for so long. Her parents, Katie and Trevor, were frantically checking messages from their power company, which promised that electricity would be back in an hour. They could make it an hour, but an hour turned into five, and the machines began to die one by one – the stat monitor, the bipap, the cough assist, the nebulizer, the feeding pump, the oxygen supply. The waiting game was getting dangerous, and Katie began to wonder if it was time to wake up their other two kids and go to the hospital.

At 5:30 a.m., she went out to look for a place to charge the batteries and get in touch with the power company, but with no success. Fortunately, all three children had early morning dentist appointments, so Katie loaded all the machines into the van and took them to charge there. Some friends later helped the family get a generator to avoid another crisis like this, but sleepless nights and dire emergencies have been part of their life ever since Karis was diagnosed with Krabbe disease at five months old.

“The lysosome is essentially the garbage disposal of the cell,” says Dr. Bruce Bunnell, director of the Tulane Center for Stem Cell Research and Regenerative Medicine. In Krabbe disease, an enzyme that helps break down wastes is missing from the lysosomes, causing wastes to accumulate until the cell is distended. “The garbage disposal gets so backed up that even the house it sits in is no longer usable,” he adds.

This mutation prevents the formation of new myelin, or white matter, the fatty cell sheath that surrounds nerves. Dr. Bunnell likens this to the plastic insulation of an electrical wire. “It helps the electrical impulses flow along the nerve rather than just firing off in random directions,” he explains. Without this insulation, the central and peripheral nervous systems break down, and the muscles are not able to receive signals, causing them to grow weaker over time.

The disease is extremely rare, with only 1 in every 100,000 babies born in the United States affected. As a genetic disease, both parents must be carriers in order to pass it on to a child, and each of their children will have a 25% chance of exhibiting it.

When Karis was born, she seemed perfectly healthy. For several weeks, there was no reason to believe that anything was wrong. “We started noticing that she had some interesting posturing; she would lock out her elbows, and around two months or so she got a little extra fussy, but we attributed that to colic,” says Katie. “And then, at four months of age, she started having difficulty feeding, and it got aggressive to the point that we literally couldn’t keep anything down her. She was projectile vomiting everything.”

After visiting a neurologist, Karis received the worst-case-scenario diagnosis: early onset infantile Krabbe leukodystrophy. She was given six months to live.

Now, more than six years later, Karis continues to fight for each breath. She cannot walk or talk, and she depends on constant care to survive, but she is fully cognizant.

“She’s a little warrior… She has a sense of purpose,” Katie says. “She can’t articulate it, but there have been some life and death moments, and there have been some doctors who have spoken some horrible things over her that she can hear and understand, and there have been several times I’ve just gotten down low and whispered in her ear, ‘You’re not done yet. You don’t stop fighting. And the Lord has a purpose for you. Don’t quit. You don’t quit on your momma right now.’”

Karis receives her first round of medications at six each morning, and then Katie begins the routine of getting her dressed, making sure her lungs are clear, feeding her, emptying her bladder, repositioning her – a routine that must essentially be repeated every few hours throughout the day.

Her teacher comes in the afternoon, using answer cards that Karis can choose with her eye gaze. “Right now, they’re doing currency,” Katie explains. “So she’ll ask her, ‘Is this 2 cents or is this 10 cents? Put your eyes on the right answer.’”

Later, she might watch TV with her brother and sister, 2-year-old Ander and 5-year-old Kales, and when Trevor gets home from his job teaching school, he often reads to her.

“We just finished a book, Bridge to Teribithia,” he says. “And it’s interesting to see, even without words, she’s able to express in her eyes and in her eye contact that she’s very engaged.”

Finally, her nurse comes at night to continue the routine that Katie has kept all day: cough, cath, reposition, repeat.

The key to breaking this routine may lie in a fortuitous discovery made at the Tulane National Primate Research Center; in the mid-90’s, a necropsy on a rhesus monkey revealed that the animal had Krabbe disease. After several years of further study, researchers were able to confirm that Tulane was home to the first and only colony of nonhuman primates carrying a genetic disease. This resource could become invaluable in the quest to find treatments for human Krabbe patients. As Dr. Bunnell says, “We need larger models to test all our therapies in… The one that’s most closely related from a genetic and physiologic standpoint to humans is the monkey model that we have at the Primate Center.”

For now, however, the research at Tulane still relies on testing mice, with the goal of finding a therapy promising enough to proceed to the monkey model. Annie Bowles, a fourth year PhD candidate with the Cell and Molecular Biology Department, conducts studies with “twitcher” mice at the Tulane Medical School. Because there are other institutions working on enzyme replacement therapy, a technique that would essentially cure the disease which still remains elusive, this research is aimed at finding better therapies for patients already living with Krabbe. “In efforts to not compete with something that is going to result in great outcomes anyway, I like to think of it as the next best thing,” Bowles explains.

The few existing treatment options for Krabbe disease are only effective if administered before symptoms appear, but the disease is rarely detected at such an early stage. Thus, Annie’s goal is to find ways to treat patients like Karis, for whom the disease has already progressed so far that they are considered untreatable.

“Once the twitcher mouse is born, I track its date of birth, and – we call it postnatal days – ten days after, they already present with symptoms and signs,” says Bowles. These signs include twitching, hence the name, and hind limbs that clasp together. Once the mice with Krabbe have been identified, Bowles says, “Then I deliver cells, and I want to see, how does it benefit after that?”

The cells in question are adipose-derived stem cells; fat is a promising tissue source, as it is much easier to access than alternatives like bone marrow and is now believed to be comparable in its abilities. These stem cells have the same receptors as immune cells, so Annie’s team primes them in culture to skew them towards a more anti-inflammatory phenotype. In the past, when the cells were injected without priming, the effects on the mice were weaker because the cells took longer to receive signals from their environment and to begin fighting the damage. However, with this new method, says Bowles, “They’re ready to go. They’ve already gotten the signal. They’re ready to counter any inflammatory environment.”

The next step is to collect data. The mice’s feet are painted with food coloring before walking on paper to measure their hind stride length. They are also placed in a motor function testing arena, a glass enclosure where their movements can be observed and recorded. The researchers tally behaviors like rearing and grooming, and video footage is uploaded to closely analyze the average speed and duration of their movements and the angles of their turns. Finally, when the mice die, their lifespan is noted, and the scientists can look at cross sections of their brains and spinal cords to see how the myelin was affected.

The results thus far are encouraging: the mice treated with primed stem cells show an increase in lifespan of up to 25%. The reason for this is that, according to Dr. Bunnel, “The extent of inflammation in most of these patients can dramatically impact the amount of time they live and the severity of the disease.” As for the future of Krabbe treatment, he believes, “We’re going to need combination approaches.”

Annie is optimistic that priming adipose-derived stem cells can be one of those approaches. “We’re showing that there is a method to improve stem cells to better modulate the immune system and be a better therapy,” she says. “At least it’ll sustain some quality of life while there’s a cure out there that still needs to be discovered.”

For the Almy family, this is yet another waiting game.

Katie and Trevor hold out hope for a breakthrough in treatment that will not only improve Karis’s physical health, but also increase her ability to connect with them. “Communication is definitely something I’ve prayed for her since she really started losing it around three years old,” says Katie.

“Beyond the physical needs, which are practical and are challenging in themselves,” wonders Trevor, “how do we meet her on an emotional level?”

This is a question that sometimes the youngest members of the family can answer the best. Kales often crawls into Karis’s bed to fall asleep beside her. Ander likes to zoom his toy cars up and down her arms and legs like a ramp.

During one such playtime, Karis’s hand caught Ander on the neck, and he giggled. Instinctively, Katie took Karis’s hands and helped her tickle him. He began to laugh hysterically, and the effect was contagious. “Not only was Karis in a full smile, I have never seen her try to laugh like I did in that moment,” Katie recalls. “They were sharing so much joy together, and she was truly experiencing what it means to be a big sister.”

It is moments like this that get the Almys through all Karis’s winter bouts of pneumonia, the hospital trips, the spring floods and power outages, the long nights when a nurse cancels her shift. They are, despite these hardships, a happy family, and Karis has been at the heart of that family since before she was born.

‘Karis’ is the Greek word for ‘grace,’ a name her parents chose when they were expecting her – before they had ever heard of Krabbe disease – because they wanted her to one day understand what it means to be saved by God’s grace. Now, her name holds a level of significance that they could never have anticipated.

“We always had the desire to teach Karis about grace,” says Trevor, “but in a very real and profound sense, she is the one who is teaching us about grace.”

Avery Werther is a sophomore at Tulane University studying English.