This is the first mutation described in the short, antiparallel beta-sheet domain of the prion protein. This report highlights the importance of genetic analysis of patients with atypical dementia even in the absence of a family history.

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Aim: To assess the role of genetic factors, other than the CAG repeat length, on the development of Huntington’s disease (HD) in an isolated Caucasian population in the south-west of Western Australia. Methods: 114 patients with symptomatic HD according to the Unified HD Rating Scale research criteria were examined along with 51 control patients. The length of the CAG repeat sequence in the IT15 gene and the adjacent CCG and Δ2642 polymorphisms were determined by polymerase chain reaction along with common genotypes of the angiotensin-converting enzyme (ACE) and apolipoprotein E (APOE) genes. Results: The CAG expansion was associated with age of onset and the development of neurological dysfunction. We found no effect of the expanded CCG allele on age of onset, neurological dysfunction or the size of the CAG expansion. We observed a twofold increase in the Δ2642 polymorphism and the risk of developing symptomatic HD which was not significant (OR 2.06; 95% CI 0.60–7.07). The presence of an APOE Ε4 allele was associated with an increased risk of HD which was not significant either (OR 1.04–1.73; 95% CI 0.10–10.68). ACE genotypes showed no association with risk factors for the disease. Conclusion: In our study of a geographically isolated Caucasian HD population in the south-west of Western Australia we have not observed that the expanded CCG allele, the Δ2642 polymorphism, the APOE Ε4 allele and ACE genotypes are associated with an increased risk for the development of symptomatic HD.

Glutamate has been implicated in the pathogenesis of Alzheimer's disease (AD). Controversial data exists regarding changes in the N-methyl-D-aspartate (NMDA) receptor complex in AD. We wished to elucidate the hypothesis that the NMDA receptor system is involved in the pathogenesis of AD using a gene expression approach targeting the mRNA of the universal subtype of the NMDA receptor NR1. This was performed using in situ hybridization and antisense 35S-labelled oligonucleotides on brain tissue collected at post-mortem. Relative mRNA expression was measured in standardised optical density units (OD units) using videodensitometry without knowledge of the diagnosis. The study population consisted of AD (n = 6) and neurodegenerative non-Alzheimer controls (non-AD, n = 14). Gene expression was measured in the frontal lobe, superior temporal gyrus and three areas within the hippocampus. We have observed no significant differences in the relative mRNA expression of the NR1 subtype of glutamate receptor in the following regions: frontal lobe AD = 60.7 +/- 14.1 OD units mRNA (x +/- 1SE) vs 52.6 +/- 1 in non-AD (Mann-Whitney test, p = 0.477); the superior temporal gyrus: AD = 53.3 +/- 13.9 vs 38.2 +/- 7 (p = 0.37); the CA1 region: AD = 37.8 +/- 7.75 vs 81.5 +/- 25.7 (p = 0.66); subiculum AD = 46.7 +/- 11.0 vs 105 +/- 43.3 (p = 0.82); parahippocampal gyrus AD = 36.6 +/- 9.3 vs 81.7 +/- 40.6 (p = 0.90). There were trends to a reduction in NR1 mRNA in the hippocampus and increased NR1 within the frontal and superficial temporal gyrus which were not significant. There was variation within and between all patients with and without AD in the magnitude of NR1 expression in all anatomical regions studied. The findings suggest heterogeneity in the involvement of the post-synaptic glutamatergic system in AD.

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.