The tau gene locus and frontotemporal dementia

Frontotemporal lobar degeneration (FTLD) has become an increasingly recognised form of dementia. It has been demonstrated that a proportion of cases of FTLD result from mutations in the tau gene on chromosome 17. A pathological hallmark in the brains from patients with tau mutations is an accumulation of insoluble tau within neurons and glia that is considered neurotoxic. However, there are reports of families with FTLD linked to the tau locus on chromosome 17 in which no mutations have been found, and these families lack any accumulation of insoluble tau. Recently, two new tau mutations have been described that also appear to cause disease in the absence of any tau accumulation. The role of the tau locus and tau accumulation in contributing to the neurodegenerative process in chromosome-17-linked families without mutations and in families with tau mutations without insoluble tau is discussed.