Canadian Researchers Found Cure in Mice for Chorea Huntington
For the first time researchers have been able to cure Huntington Disease (HD) in a mouse. Dr. Michael Hayden of the Child and Family Research Institute's Centre for Molecular Medicine and Therapeutics (CMMT), Vancouver, Canada, and his colleagues have discovered that by preventing the cleavage of the mutant huntingtin protein responsible for Huntington disease in a mouse model, the degenerative symptoms underlying the illness do not appear and the mouse displays normal brain function. He reported about these findings at the International Conference on Neurodegenerative Diseases International Conference on "Neurodegenerative Diseases: Molecular Mechanism in a Functional Genomics Framework" in the Max Delbrück Communications Center (MDC.C) in Berlin, Germany. They have also been published in the journal Cell (June 16, 2006, Vol. 125, 6, 1179-91).
Dr. Hayden, Director and Senior Scientist at the University of British Columbia's CMMT and his team had discovered that the protein huntingtin is cleaved by what he calls "molecular scissors", indicating that cleavage of this protein may be crucial in causing the disease.
The researchers developed a mouse which carries the human gene for Huntington disease and expresses the mutant protein huntingtin. This allowed them to study the progression of the disease, including the cleavage of the mutant protein. They could demonstrate that the deadly cleavage is caused by an enzyme called caspase-6. By blocking this enzyme the cleavage stopped and the mouse did not develop any symptoms of Huntington disease.
Caspases are enzymes which cut proteins at certain sites to make them prone for proteolysis. The activation of caspases leads to the formation of protein-fragments, which in patients with Chorea Huntington is formed in the nucleus of nerve cells. "However, the relationship between the proteolysis of huntingtin and the pathogenesis of Chorea Huntington is unknown", Dr. Hayden pointed out in Berlin.
It remains to be seen if the findings about stopping the deadly process in mouse will lead to the development of a therapy for humans in the future.
Recent findings of Dr. Hayden and his team suggest that the insoluble aggregated proteins in Chorea Huntington and also Alzheimer disease might not be toxic for nerve cells in humans. In addition, mouse models have shown that loss of nerve cells can occur in the absence of detectable aggregates.
Chorea Huntington, first described by the New York physician George Huntington in 1872, is an inherited disease. All persons who carry the gene eventually develop the disease, usually around middle age.
Ten to thirty years after the appearance of the first symptoms, nerve cells of affected individuals gradually die off in those areas of the brain involved in intellect, movement, and emotions, leaving the patient physically and mentally impaired until, ultimately, the patient dies. Researchers assume that these plaques made of the protein huntingtin (htt) are the cause of Chorea Huntington.
The disease is characterized by jerky, uncontrolled movements of body and face and, therefore, is called Chorea (Greek for "dance") Huntington. There is no cure for the disease and it can neither be stopped nor reversed. Researchers estimate that 1 in 10,000 persons is effected. So far 30,000 cases are known in the United States, 10, 000 in Canada, and 8,000 in Germany.
The four-day conference, which started on September 6, is organized by the Max Delbrück Center for Molecular Medicine (MDC), the Charité Universitätsmedizin Berlin, and the University of Bonn (all in Germany). 200 clinicians and researchers from Canada, Europe, Japan, and the USA discuss their latest findings there.
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