Is Huntington's disease a tauopathy?

Tauopathies are a subclass of neurodegenerative diseases typified by the deposition of abnormal microtubule-associated tau protein within the cerebral tissue. Alzheimer's disease, progressive supranuclear palsy, chronic traumatic encephalopathy and some fronto-temporal dementias are examples of the extended family of tauopathies. In the last decades, intermittent reports of cerebral tau pathology in individuals afflicted with Huntington's disease-an autosomal dominant neurodegenerative disorder that manifests by severe motor, cognitive and psychiatric problems in adulthood-have also begun to surface. These observations remained anecdotal until recently when a series of publications brought forward compelling evidence that this monogenic disorder may, too, be a tauopathy. Collectively, these studies reported that: (i) patients with Huntington's disease present aggregated tau inclusions within various structures of the brain; (ii) tau haplotype influences the cognitive function of Huntington's disease patients; and (iii) that the genetic product of the disease, the mutant huntingtin protein, could alter tau splicing, phosphorylation, oligomerization and subcellular localization. Here, we review the past and current evidence in favour of the postulate that Huntington's disease is a new member of the family of tauopathies.