Loss of progranulin function in frontotemporal lobar degeneration.

Frontotemporal lobar degeneration (FTLD) represents a collection of neurodegenerative diseases of frontal and temporal brain regions. It has long been associated with mutations in microtubule-associated protein tau (MAPT), and more recently with loss-of-function mutations in progranulin (PGRN). Phenotypes of PGRN and MAPT mutation carriers overlap, although disease onset in PGRN carriers is a decade later. Mutations in PGRN might influence susceptibility to a wider range of neurodegenerative diseases including Alzheimer and Parkinson diseases. The recent demonstration that mutations in PGRN result in FTLD provided a novel entrance point to the molecular mechanisms leading to this disorder. The high variability in onset age and age-dependent penetrance suggests that the PGRN pathway is highly susceptible to modulating factors that might be exploited to delay the disease processes.