Huntingtons Disease Research

Huntington’s disease research, including genetics and gene therapy, can provide valuable clues to the possible treatment, delay of disease progression, and causes of neuron death due to Huntington’s disease.

Gene Therapy for Huntington’s

Genetics plays an important role in Huntington’s disease research. Gene therapy is a source of hope for many Huntington’s disease researchers. Gene therapy is the insertion of genes into an individual’s cells to treat a disease. Gene therapy is most commonly used for hereditary diseases. It attempts to supplement a defective mutant gene with one of a number of alternative functional forms of the same gene. Although gene therapy technology is still in its infancy, it has been successful with some hereditary diseases.

New Advances in RNAi Therapy: Laboratory studies in mice have been evaluating the efficacy of using a virus to transport genetic instructions to the brain’s cells to produce an RNA interference molecule. Researchers at University of Iowa have discovered that treated mice show a forty percent reduction in the huntingtin protein. Should RNAi therapy prove effective in additional testing it could lead to a method of significantly slowing the progression of Huntington’s disease, or heading it off before symptoms develop.

Restoring Brain Function in Huntington’s Disease

The most appealing method for restoring brain function in Huntington’s disease is the replacement of dying neurons with healthy neuronal tissue. Both animal and human pilot studies have attempted this procedure using embryonal stem cells. The research has shown that transplanted cells not only survive, but also grow and establish connections with other resident neurons. This results in beneficial effects for the animals and humans. Using human embryonal cells is controversial and raises a number of ethical questions. Huntington’s disease researchers will likely need to develop other sources of neuronal cells to help patients restore brain function.

Delaying Progression in Huntington’s Disease

It is well known in Huntington’s disease research that the mutant huntingtin protein forms clumps in the neurons of people with Huntington’s disease. Research suggests that these clumps may activate caspases. Caspases are a group of enzymes that can sever other proteins, leading to neuronal cell death. Medications that can inhibit these caspases are available. In animal models, these medications were not shown to cure the disease, but they were shown to delay the progression of the disease.

Huntington’s Disease Research and Causes of Neuron Death

Huntington’s disease research suggests that normal huntingtin plays an important role in providing dendrites with essential nutrients such as brain derived neurotrophic factor (BDNF). Dendrites are slender, branched areas of neurons that receive electrical stimulations from other neurons. Huntington’s disease research indicates that the mutant form of huntingtin may interfere with the transport of BDNF and similar factors within neurons. Without BDNF, the neurons die.

Animal models in Huntington’s disease research have provided researchers with important clues to how the mutation in the huntingtin gene causes neuron cells to die. The Huntington’s disease research indicates that the mutant form of the huntingtin protein has the ability to bind to a number of proteins in the cells that normal huntingtin ignores. Researchers believe this may interfere with normal cell function and cause the neurons to die early. By treating the cells to reactivate the proteins that have been interfered with, Huntington’s disease researchers have found beneficial effects in animal models.

Huntington’s disease research also indicates that mutant huntingtin binds and promotes the activity of NMDA receptors-proteins involved in calcium ion transport and the communication between neurons. The NMDA receptors are receptors for glutamate, and they play a very important role in several types of learning and memory. When these receptors are overstimulated, it causes a calcium ion overload, which results in the death of the cells.

Along the same lines, Huntington’s disease research also suggests that mutant huntingtin may interfere with the normal function of mitochondria. The mitochondria are specialized structures in the cell that produce energy by altering their ability to handle calcium ions. This Huntington’s disease research suggests the use of calcium ion blockers could prove beneficial for treatment of HD.

Resources

Bezprozvanny, I., Hayden, M.R. (2004, August). Deranged neuronal calcium signaling and Huntington’s disease. Biochemical and Biophysical Research Communications 322 (2004), 1310-1317.

Bossy-Wetzel, E., Schwarzenbacher, R., Lipton, S.A. (2004, July). Molecular pathways to neurodegeneration. Nature Medicine 10 (Supplement), S2-9.

Gardian, G., Vecsei, L. (2004, July). Huntington’s disease: Pathomechanism and therapeutic perspectives. Journal of Neural Transmission 111 (2004), 1485-1494.

Ross, C.A. (2004, July 9). Huntington’s disease: New paths to pathogenesis. Cell 118 (1), 4-7.

University of Iowa. (2005, April 5). UI researchers improve Huntington’s disease symptoms in mice. UI News Release.

Vila, M., Przedborski, S. (2003, May). Targeting programmed cell death in neurodegenerative diseases. Nature Reviews: Neuroscience 4 (5), 365-375.