Polymorphisms in the tau gene in sporadic frontotemporal dementia and other neurodegenerative disorders.

The tau gene on chromosome 17 is fundamental in the pathogenesis of a number of neurodegenerative disorders. Mutations in tau are found in familial frontotemporal dementia (FTD) and the A0/A0 genotype associated with progressive supranuclear palsy (PSP). This study investigates the hypothesis that polymorphisms in the tau gene are associated with sporadic FTD. Western Australian populations of patients with sporadic frontotemporal dementia, PSP, Alzheimer's disease (AD), Huntington's disease (HD) and normal controls were studied. A new method was developed using fluorescently labelled probes to determine polymorphisms in the GT repeat region of intron 9. The A0/A0 genotype was found in 95% of PSP patients (n=20), 58.3% of FTD patients (n=48), 60.8% of AD patients (n=52), 75% of HD patients (n=40), and 75% of normal controls (n=40). None of these differences in genotype frequency were found to be significant by the Fisher exact test (P > 0.05). There were no significant differences in the frequencies of A0/A3 and A0/A1 haplotypes. We have not observed a significant increase in the A0/A0 genotype frequency in sporadic frontotemporal dementia suggesting that this polymorphism is unlikely to be related to the development of this condition. Furthermore, we have observed an increase in the A0/A0 genotype in PSP which did not reach statistical significance, suggesting that there may be population differences in the role of genetic factors in conferring risks to neurodegenerative disorders. Our work does not exclude that tau may interact with other genetic factors.