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An aggregate of protein in nerve cells can cause ALS

People with ALS, can have a genetic mutation causing the protein SOD1 to aggregate in motor neurons of the brain and spinal cord. Research has found that SOD1 injected into mice nerve cells, spreads rapidly and leads to ALS.

ALS, Amyotrophic lateral sclerosis, is a disorder which causes death of motor neurons in the brain and spinal cord controlling muscles. This leads to progressive paralysis and death, often due to carbon dioxide narcosis — a condition of abnormally elevated carbon dioxide (CO2) levels in the blood.

"The occurrence of SOD1 aggregates in nerve cells of ALS patients has been known for a while. But it has been unclear what role these aggregates play in progression of the disease in humans who carry hereditary traits for ALS.

"We have now shown that SOD1 aggregates start a domino effect that rapidly spreads the disease up through the spinal cord in mice — and suspect this could be the case in humans as well."

Thomas Brännström PhD, Professor of Pathology, Umeå University, Umeå, Sweden and one of the article authors.

The work is described in the Journal of Clinical Investigation.

Researchers at the Departments of Medical Biosciences, Pharmacology and Clinical Neuroscience at Umeå University, experimented to see if SOD1 aggregates accumulating inside nerve cells drives ALS disease, or if it is a harmless side-effect.

They identified two different kinds of SOD1 aggregates in mice. Both caused an increased spread of SOD1 when a small amount was injected into mouse spinal cords. Aggregates progressed along the entire spinal cord leading to rapid and fatal outcomes.

"The results show that the aggregation of SOD1 plays a critical role in ALS progression - an hypothesis upon which Umeå researchers have long based their work. More research is needed, but our aim is to develop interventions that prevent or stop the fatal course of the disease in carriers of hereditary ALS."

Stefan Marklund PhD, Professor, Clinical Chemistry, Umeå University, Umeå, Sweden.

Amyotrophic lateral sclerosis (ALS) is an adult-onset degeneration of motor neurons that is commonly caused by mutations in the gene encoding superoxide dismutase 1 (SOD1). Both patients and Tg mice expressing mutant human SOD1 (hSOD1) develop aggregates of unknown importance. In Tg mice, 2 different strains of hSOD1 aggregates (denoted A and B) can arise; however, the role of these aggregates in disease pathogenesis has not been fully characterized. Here, minute amounts of strain A and B hSOD1 aggregate seeds that were prepared by centrifugation through a density cushion were inoculated into lumbar spinal cords of 100-day-old mice carrying a human SOD1 Tg. Mice seeded with A or B aggregates developed premature signs of ALS and became terminally ill after approximately 100 days, which is 200 days earlier than for mice that had not been inoculated or were given a control preparation. Concomitantly, exponentially growing strain A and B hSOD1 aggregations propagated rostrally throughout the spinal cord and brainstem. The phenotypes provoked by the A and B strains differed regarding progression rates, distribution, end-stage aggregate levels, and histopathology. Together, our data indicate that the aggregate strains are prions that transmit a templated, spreading aggregation of hSOD1, resulting in a fatal ALS-like disease.

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May 9, 2016   Fetal Timeline   Maternal Timeline   News   News Archive   

Aggregated SOD1 protein can be seen as green dots in the cell fluid of a motor neuron
located in the spinal cord of an ALS patient. The red part is the nerve cell nucleus.
Image Credit: Peter Andersen, Umeå University, Umeå, Sweden





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