Scientists have wrestled to understand why Huntington's disease, which is caused by a single gene mutation, can produce such variable symptoms. An authoritative review by a group of leading experts summarizes the progress relating cell loss in the striatum and cerebral cortex to symptom profile in Huntington's disease, suggesting a possible direction for developing targeted therapies. The article is published in the latest issue of the Journal of Huntington's Disease.
Huntington's disease (HD) is an inherited progressive neurological disorder for which there is presently no cure. It is caused by a dominant mutation in the HD gene leading to expression of mutant huntingtin (HTT) protein. Expression of mutant HTT causes subtle changes in cellular functions, which ultimately results in jerking, uncontrollable movements, progressive psychiatric difficulties, and loss of mental abilities.
Although it is caused by a single gene, there are major variations in the symptoms of HD. The pattern of symptoms shown by each individual during the course of the disease can differ considerably and present as varying degrees of movement disturbances, cognitive decline, and mood and behavioral changes. Disease duration is typically between ten and twenty years.
Recent investigations have focused on what the presence of the defective gene does to various structures in the brain and understanding the relationship between changes in the brain and the variability in symptom profiles in Huntington's disease.
Analyses of post-mortem human HD tissue suggest that the variation in clinical symptoms in HD is strongly associated with the variable pattern of neurodegeneration in two major regions of the brain, the striatum and the cerebral cortex. The neurodegeneration of the striatum generally follows an ordered and topographical distribution, but comparison of post-mortem human HD tissue and in vivo neuroimaging techniques reveal that the disease produces a striking bilateral atrophy of the striatum, which in these recent studies has been found to be highly variable.
"What is especially interesting is that recent findings suggest that the pattern of striatal cell death shows regional differences between cases in the functionally and neurochemically distinct striosomal and matrix compartments of the striatum which correspond with symptom variation," says author Richard L.M. Faull, MB, ChB, PhD, DSc, Director of the Centre for Brain Research, University of Auckland, New Zealand.