A mechanism that may help explain Parkinson's and other neurological disorders.

Brain disorder suggests common mechanism may underlie many neurodegenerative diseases
A Mayo Clinic-led international consortium has found a mechanism that may help explain Parkinson's and other neurological disorders.
Studying just eight families worldwide, the international team of researchers have discovered a genetic defect that results in profound depression and parkinsonism in a disorder known as Perry syndrome. Although this syndrome is exceedingly rare, the mechanism implicated in it may help explain the origins of a variety of neurodegenerative disorders, such as Parkinson's and amyotrophic lateral sclerosis diseases, and even common depression and sleep disorders that are also hallmarks of the disorder, the researchers say.

In the study, to be published in the February issue of Nature Genetics (online January 11), the researchers report that people with Perry syndrome have mutations in a subunit of the dynactin complex (DCTN1; p150glued), which is essential to the movement of molecular "cargo" inside brain cells, or neurons. In this case, the mutations meant that the cargo was being driven on a "train" that essentially had faulty brakes. And because Perry syndrome resembles many other neurodegenerative diseases, the findings suggest breakdowns along the cell's interior transportation grid may be a common mechanism underlying neurodegeneration.

"Understanding why distinct neurons are selectively vulnerable to neurodegeneration in different brain disorders is one of the greatest puzzles in neuroscience," says the study's lead investigator, Matthew J. Farrer, Ph.D., a professor of neuroscience at Mayo Clinic. "These findings suggest that trafficking of specific cargoes inside brain cells may be a general problem in a variety of neurodegenerative diseases, depression, and other disorders."

"It points us to a unified theory of what is going wrong in many of them," says the study's senior author, Zbigniew K. Wszolek, M.D., professor of neurology at Mayo Clinic.

Molecules, vesicles and organelles within a cell are constantly carried via a network of crisscrossing microtubules that act like the tracks of an elaborate railroad system. Because, for the most part, neurons do not regenerate or divide as do other cells in the body, trafficking cargo efficiently over the lifetime of a neuron is fundamentally important, says Dr. Farrer.

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What are neurological disorders?
Neurological disorders are diseases of the central and peripheral nervous system. In other words, the brain, spinal cord, cranial nerves, peripheral nerves, nerve roots, autonomic nervous system, neuromuscular junction, and muscles. These disorders include epilepsy, Alzheimer disease and other dementias, cerebrovascular diseases including stroke, migraine and other headache disorders, multiple sclerosis, Parkinson's disease, neuroinfections, brain tumours, traumatic disorders of the nervous system such as brain trauma, and neurological disorders as a result of malnutrition.

Mental disorders, on the other hand, are "psychiatric illnesses" or diseases which appear primarily as abnormalities of thought, feeling or behaviour, producing either distress or impairment of function.

Hundreds of million of people worldwide are affected by neurological disorders: For example, 50 million people have epilepsy; 62 million are affected by cerebrovascular disease; 326 million people suffer from migraine; 24 million are affected by Alzheimer disease and other dementias globally.