H. A. Kretzschmar

Frontotemporal dementia (FTD) is a clinical syndrome with a heterogeneous molecular basis. The neuropathology associated with most FTD is characterized by abnormal cellular aggregates of either transactive response DNA-binding protein with Mr 43 kDa (TDP-43) or tau protein. However, we recently described a subgroup of FTD patients, representing around 10%, with an unusual clinical phenotype and pathology characterized by frontotemporal lobar degeneration with neuronal inclusions composed of an unidentified ubiquitinated protein (atypical FTLD-U; aFTLD-U). All cases were sporadic and had early-onset FTD with severe progressive behavioural and personality changes in the absence of aphasia or significant motor features. Mutations in the fused in sarcoma (FUS) gene have recently been identified as a cause of familial amyotrophic lateral sclerosis, with these cases reported to have abnormal cellular accumulations of FUS protein. Because of the recognized clinical, genetic and pathological overlap between FTD and amyotrophic lateral sclerosis, we investigated whether FUS might also be the pathological protein in aFTLD-U. In all our aFTLD-U cases (n = 15), FUS immunohistochemistry labelled all the neuronal inclusions and also demonstrated previously unrecognized glial pathology. Immunoblot analysis of protein extracted from post-mortem aFTLD-U brain tissue demonstrated increased levels of insoluble FUS. No mutations in the FUS gene were identified in any of our patients. These findings suggest that FUS is the pathological protein in a significant subgroup of sporadic FTD and reinforce the concept that FTD and amyotrophic lateral sclerosis are closely related conditions.

Scrapie is a slow degenerative encephalopathy of animals caused by unusual infectious particles termed prions. A cDNA encoding the only apparent component of the prion, a protein designated PrP 27-30, has recently been cloned and sequenced. By measuring mRNA levels using in situ hybridization with the PrP cDNA, the authors found that prion proteins are synthesized almost exclusively within neurons. The levels of PrP mRNA varied among different types of neurons, but did not change during scrapie infection. A cDNA encoding glial fibrillary acidic protein (GFAP) was a positive control; GFAP mRNA was confined to astrocytes. Our finding of PrP mRNA in neurons may explain the degeneration and vacuolation that occurs in these cells during scrapie infection.

BACKGROUND: An international study of the epidemiologic characteristics of Creutzfeldt-Jakob disease (CJD) was established in 1993 and included national registries in France, Germany, Italy, the Netherlands, Slovakia, and the United Kingdom. In 1997, the study was extended to Australia, Austria, Canada, Spain, and Switzerland. METHODS: Data were pooled from all participating countries for the years 1993 to 2002 and included deaths from definite or probable CJD of all etiologic subtypes. RESULTS: Four thousand four hundred forty-one cases were available for analysis and included 3,720 cases of sporadic CJD, 455 genetic cases, 138 iatrogenic cases, and 128 variant cases. The overall annual mortality rate between 1999 and 2002 was 1.67 per million for all cases and 1.39 per million for sporadic CJD. Mortality rates were similar in all countries. There was heterogeneity in the distribution of cases by etiologic subtype with an excess of genetic cases in Italy and Slovakia, of iatrogenic cases in France and the UK, and of variant CJD in the UK. CONCLUSIONS: This study has established overall epidemiologic characteristics for Creutzfeldt-Jakob disease (CJD) of all types in a multinational population-based study. Intercountry comparisons did not suggest any relative change in the characteristics of sporadic CJD in the United Kingdom, and the evidence in this study does not suggest the occurrence of a novel form of human bovine spongiform encephalopathy infection other than variant CJD. However, this remains a possibility, and countries currently unaffected by variant CJD may yet have cases.

BACKGROUND: Diagnosis of Creutzfeldt-Jakob disease (CJD) is made according to the typical clinical picture and can be supported by a positive 14-3-3 CSF immunoblot. Promising results for the diagnostic sensitivity and specificity of tau-protein measurement in CSF already have been described in a smaller group of patients. Both tests in a larger group of patients with the differential diagnosis of CJD were evaluated. METHODS: CSF of 297 patients under the differential diagnosis of CJD (109 definite, 55 probable, 39 possible; 85 others, 1 iatrogenic, 8 genetic), 23 nondemented control subjects, and 15 non-CJD patients with positive 14-3-3 immunoblots were analyzed. The 14-3-3 immunoblot bands were semiquantitatively rated as strong, medium, and weak. Tau-protein was analyzed using a commercially available ELISA. In addition, patients were neuropathologically classified according to prion protein type and polymorphism at codon 129. RESULTS: A diagnostic sensitivity of 94%, a diagnostic specificity of 90%, and a positive predictive value of 92% were achieved for tau-protein at a cut-off of 1,300 pg/mL. These results are comparable with those of the 14-3-3 immunoblot. For patients with type II prion protein and methionine/valine or valine/valine polymorphism at codon 129, tau-protein has a higher diagnostic sensitivity than 14-3-3 protein. Tau-protein levels were significantly higher in patients with higher-rated 14-3-3 immunoblot bands. CONCLUSION: The differential diagnostic significance of the 14-3-3 immunoblot is similar to that of the tau-protein ELISA. The advantage of the tau-protein ELISA is that it is easy to use in routine laboratories. Patients with a negative 14-3-3 immunoblot already have measurable tau-protein levels. This increases information on 14-3-3-negative patients with CJD and especially on patients with other diseases.