Huntington's Disease & the Use of Technology

Huntington's disease (HD) is an inherited neurological disorder that causes gradual loss of muscle control and progressive dementia, among other symptoms. Symptoms typically first become apparent in the late 30s or early 40s, although the age of onset can vary significantly and in some patients occurs at a much younger age. Unfortunately, scientists have yet to find a cure; modern technology has, however, enhanced our understanding of--and ability to diagnose--the disease.

Diagnosis

• Although HD was first described by Dr. George Huntington in 1872, the mutation responsible for the disorder wasn't identified until 1993. HD is caused by a genetic abnormality in the Huntingtin gene on chromosome 4; if one of your parents had HD, there's usually a 50 percent chance that you will also. One to 3 percent of patients with HD have no family history of the disorder. Labs can test DNA from a blood sample to determine whether you have the defective gene--a technique made possible by modern advances in technology. Choosing to be tested for HD is a difficult, life-changing decision, however, and many people who are at risk prefer not to be tested for the gene.

Presymptomatic Testing

• Testing for HD provides information that can help with other decisions. Some people who find they've inherited the mutant version of the gene can opt for adoption or assisted-reproduction to ensure their children don't end up with the same problem. On the other hand, if genetic testing reveals that you didn't inherit HD, you're spared the painful burden of anxiety. Consequently, while genetic testing in children of patients of HD can't prevent or cure the disorder, it can help people who are at risk make some important choices.

Mouse Models

• One technological advance that's contributed greatly to the study of HD was the development of a mouse model of the disease in 1996. By genetically engineering a mouse whose genome incorporated a fragment of the human Huntingtin gene, scientists were able to produce mice that exhibit some of the symptoms and in whom new treatments can be tested.

RNAi

• Perhaps one of the more promising areas of research in HD is RNA interference or RNAi. Basically, RNAi is a mechanism in cells whereby small RNAs that do not code for protein bind to messenger RNAs (transcripts of active genes), silencing the gene or reducing the amount of protein produced by the gene. RNAi offers scientists a way to "switch off" a defective gene by introducing small interfering RNAs (siRNAs) into cells. Medical researchers could potentially use this approach to switch off the defective copy of the Huntingtin gene in HD. There are a number of obstacles researchers must overcome, however, in order to make this technique practical for use in humans.

Stem Cells

• Stem cell technology is another recent innovation that could find an application in the treatment of HD. Stem cells are undifferentiated cells that can give rise to any tissue type in the body. It's possible that stem cell technology might offer doctors the ability to replace dead brain cells in patients with HD, although as with RNAi there are a number of challenges researchers must surmount before stem cell therapy for HD becomes viable.