Research produces dramatic results in laboratory studies involving fatal myelin disease that strikes children
A team led by Case Western Reserve University medical researchers has developed a potential treatment method for Pelizaeus-Merzbacher disease (PMD), a fatal neurological disorder that produces severe movement, motor and cognitive dysfunction in children. It results from genetic mutations that prevent the body from properly making myelin, the protective insulation around nerve cells.
Using mouse models, the researchers identified and validated a new treatment target-a toxic protein resulting from the genetic mutation. Next, they successfully used a family of drugs known as ASOs (antisense oligonucleotides) to target the ribonucleic acid (RNA) strands that created the abnormal protein to stop its production. This treatment reduced PMD’s hallmark symptoms and extended lifespan, establishing the clinical potential of this approach.
By demonstrating effective delivery of the ASOs to myelin-producing cells in the nervous system, researchers raised the prospect for using this method to treat other myelin disorders that result from dysfunction within these cells, including multiple sclerosis (MS).
Their research was published online July 1 in the journal Nature.
“The pre-clinical results were profound. PMD mouse models that typically die within a few weeks of birth were able to live a full lifespan after treatment,” said Paul Tesar, principal investigator on the research, a professor in the Department of Genetics and Genome Sciences at the School of Medicine and the Dr. Donald and Ruth Weber Goodman Professor of Innovative Therapeutics. “Our results open the door for the development of the first treatment for PMD as well as a new therapeutic approach for other myelin disorders.”
Study co-authors include an interdisciplinary team of researchers from the medical school, Ionis Pharmaceuticals Inc., a Carlsbad, California-based pioneer developer of RNA-targeted therapies, and Cleveland Clinic. First author Matthew Elitt worked in Tesar’s lab as a Case Western Reserve medical and graduate student.
PMD attacks the young
PMD is a rare, genetic condition involving the brain and spinal cord that primarily affects boys. Symptoms can appear in early infancy and begin with jerky eye movements and abnormal head movements. Over time, children develop severe muscle weakness and stiffness, cognitive dysfunction, difficulty walking and fail to reach developmental milestones such as speaking. The disease cuts short life-expectancy, and people with the most severe cases die in childhood.
The disease results from errors in a gene called proteolipid protein 1 (PLP1). Normally, this gene produces proteolipid protein (PLP) a major component of myelin, which wraps and insulates nerve fibers to allow proper transmission of electrical signals in the nervous system. But a faulty PLP1 gene produces toxic proteins that kill myelin producing cells and prevent myelin from developing and functioning properly-resulting in the severe neurological dysfunction in PMD patients.
PMD impacts a few thousand people around the world. So far, no therapy has lessened symptoms or extended lifespans.
For nearly a decade, Tesar and his team have worked to better understand and develop new therapies for myelin disorders. They have had a series of successes, and their myelin-regenerating drugs for MS are now in commercial development.
In the current laboratory work, the researchers found that suppressing mutant PLP1 and its toxic protein restored myelin-producing cells, produced functioning myelin, reduced disease symptoms and extended lifespans.
After validating that PLP1 was their therapeutic target, the researchers pursued pre-clinical treatment options. They knew mutations in the PLP1 gene produced faulty RNA strands that, in turn, created the toxic PLP protein.
Additional team members included Lilianne Barbar, Elizabeth Shick, Yuka Maeno-Hikichi, Mayur Madhavan, Kevin Allan, Baraa Nawash, Artur Gevorgyan, Stevephen Hung, Zachary Nevin, Hannah Olsen, Daniela Schlatzer, David LePage, Weihong Jiang and Ronald Conlon from Case Western Reserve University School of Medicine; Berit Powers, Hien Zhao, Adam Swayze and Frank Rigo from Ionis Pharmaceuticals; and Midori Hitomi from Cleveland Clinic.
This research was supported by grants from the National Institutes of Health, New York Stem Cell Foundation and European Leukodystrophy Association. Philanthropic support was provided by the Geller, Goodman, Fakhouri, Long, Matreyak, Peterson and Weidenthal families and the CWRU Research Institute for Children’s Health.