Extended investigation of tau and mutation screening of other candidate genes on chromosome 17q21 in a Swedish FTDP-17 family.

Frontotemporal dementia and Parkinsonism linked to chromosome 17 (FTDP-17) is an autosomal dominant condition clinically characterized by behavioral, cognitive and motor disturbances. It was recently discovered that the majority of the FTDP-17 families carry missense or 5' splice mutations in the exons coding for the microtubule-binding domains of the tau protein. However, in at least five FTDP-17 families, no such mutations could be identified. In the present study, we aimed at further investigate abnormalities in the tau gene in a Swedish FTDP-17 family, where no mutations in the tau gene previously have been identified. Initially, we searched for larger deletions by Southern blot hybridization. Furthermore, possible abnormal splicing events was investigated by RT-PCR from brain tissue of affected individuals. In addition, we investigated the presence of mutations in other genes in the FTDP-17 candidate region on chromosome 17q21; Gamma-tubulin, Glial Fibrillary Acid Protein (GFAP), Human dual specificity phosphatase tyrosine/serine (VHR), Rap-interacting protein 8 (RPIP8), P35, and the recently identified FTDCG1. In conclusion, no pathological changes in the tau gene were observed, neither was any mutations segregating with the disease detected in the investigated candidate genes. Further investigation of extended intron sequences or promoter regions of the tau gene and additional candidate genes on chromosome 17q21, therefore seems to be necessary in order to identify the additional causes of FTDP-17.