Huntington's disease: pathomechanism and therapeutic perspectives

Huntington's disease is an autosomal dominantly inherited progressive neurodegenerative disorder. The mutant gene has been localised to chromosome 4p16.3. The gene product Huntingtin is widely distributed in both neurones and extraneuronal tissues. The mutation in Huntington's disease involves the expansion of a trinucleotide (CAG) repeat encoding glutamine. The etiology of Huntington's disease is yet unknown but increasing evidence suggests important role of altered gene transcription, mitochondrial dysfunction and excitotoxicity. The expanded polyglutamine stretch leads to a conformational change and abnormal protein-protein interactions. Mutant Huntingtin can bind to transcription factors, resulting in reduced levels of acetylated histones. One consequence of this appears to be a decreased expression of genes which may play critical roles in neuronal survival. To date, a number of palliative therapies have been demonstrated to be effective in reducing the motor features, and particularly the chorea, but no treatment is at hand for the other symptoms of Huntington's disease. However, these treatments produce very limited symptomatic benefit. In the absence of disease-modifying treatment, the other avenue is the neural transplantation.However, recent advances in understanding have furnished new hope that a therapeutic strategy may one day be possible.