A new study that will be published in the January, 2012 issue of Cell Reports reveals that a team of international researchers has detected the gene that causes the rare childhood neurological disorder PKD/IC, or “paroxysmal kinesigenic dyskinesia with infantile convulsions.” The disease causes epilepsy in babies and movement disorders in older children.

The large, international team involved clinics from Tokyo, New York, London and Istanbul and was led by scientists at the University of California, San Francisco. The study could help to improve the diagnosis of PKD/IC and may also help to explain other movement disorders, such as Parkinson’s disease.

The researchers identified a mysterious gene in the brain called PRRT2. No knowledge exists about the function or ability of this gene, which bears little resemblance to anything else in the human genome.

Louis Ptacek, MD, research leader and John C. Coleman Distinguished Professor of Neurology at UCSF as well as a Howard Hughes Medical Institute Investigator declared:

“This is both exciting and a little
bit scary.”

The discovery of this gene that causes PKD/IC will aid researchers in gaining more understanding in terms of how the disease works, and provides doctors with a potential new approach of positively diagnosing the disease by searching for genetic mutations in the gene. It may also potentially help in explaining other movement disorders, such as Parkinson’s disease.

Ptacek commented:

“Understanding the underlying biology of this disease is absolutely going to help us understand movement disorders in general.”

About the Disease

PKD/IC is a rare disorder in infants with epileptic seizures, affecting approximately 1 in every 100,000 children in the U.S. according to Ptacek’s estimation. It commonly disappears within a year or two but often reemerges later in childhood as a movement disorder, which is characterized by sudden, startling, involuntary jerks when the children start moving. In some children just the thought of moving will cause them to jerk involuntarily. The disease is classified as “idiopathic”, which, as Ptacek said, is basically just another way of saying we don’t really understand it.

MRI scans in PKD/IC patients will look completely normal, with no visible injuries, tumors or other obvious signs accounting for the jerky movements. This is often common in cases of movement disorders, yet working with patients in the clinic led to the belief that the disease may be caused by a genetic cause.

During the past few years, Ptacek and his team collected data and developed a large cohort of patients, whose families have a history of the disease. He explained: “Sometimes we trace the family tree, and lo and behold, there is a history of it.”

Ptacek and his team conducted the new study on a cohort of 103 of such families, which included one or more members with the disease. During genetic testing of the families, the researchers identified mutations in the PRRT2 gene that is present in the brain and spinal cord. The mutation causes the proteins that the PRRT2 gene encodes to shorten or to completely disappear from the individual’s brain and spinal cord.

According to the researchers, the neurological symptoms may be caused due to a loss of neuronal regulation, meaning that when the genetic mutations cause the gene products to disappear, the nerve cells, which normally appear in those locations, may become overly excited, firing signals too frequently or strongly, which leads to the involuntary movements.

Written by Petra Rattue