Characterization of human presenilin 1 transgenic rats: increased sensitivity to apoptosis in primary neuronal cultures.

Mutations in the gene for presenilin 1 are causative for the majority of cases of early onset familial Alzheimer's disease. Yet, the physiological function of presenilin 1 and the pathological mechanisms of the mutations leading to Alzheimer's disease are still unknown. To analyse potential pathological effects of presenilin 1 over-expression, we have generated transgenic rats which express high levels of human presenilin 1 protein in the brain. The over-expression of presenilin 1 leads to saturation of its normal processing and to the appearance of full-length protein in the transgenic rat brain. The transgenic protein is expressed throughout the brain and is predominantly found in neuronal cells. Cultured primary cortical neurons derived from these transgenic rats are significantly more sensitive than non-transgenic controls to apoptosis induced by standard culture conditions and to apoptosis induced by trophic factor withdrawal. Furthermore, the observed apoptosis is directly correlated with the expression of the transgenic protein. The results further emphasize the role of presenilin 1 in apoptotic cell death in native neuronal cultures.

Proteolytical processing of mutated human amyloid precursor protein in transgenic mice.

The evidence that betaA4 is central to the pathology of Alzheimer's disease (AD) came from the identification of several missense mutations in the amyloid precursor protein (APP) gene co-segregating with familial AD (FAD). In an attempt to study the proteolytical processing of mutated human APP in vivo, we have created transgenic mice expressing the human APP695 isoform with four FAD-linked mutations. Expression of the transgene was controlled by the promoter of the HMG-CR gene. Human APP is expressed in the brain of transgenic mice as shown by Western blot and immunohistology. The proteolytic processing of human APP in the transgenic mice leads to the generation of C-terminal APP fragments as well as to the release of betaA4. Despite substantial amounts of betaA4 detected in the brain of the transgenic mice, neither signs of Alzheimer's disease-related pathology nor related behavioural deficits could be demonstrated.

A 700-bp fragment of the human antithrombin III promoter is sufficient to confer high, tissue-specific expression on human apolipoprotein A-II in transgenic mice.

The human antithrombin III-encoding gene (hAT-III) promoter (phAT-III) was used to generate transgenic mice producing a human hepatic apolipoprotein, apolipoprotein A-II (hApoA-II). Integration of the transgene into the mouse genome resulted in the efficient production of hApoA-II in plasma, reaching up to 0.40 g/l in two transgenic lines. The human ApoA-II mRNA was detected at high levels, both in the liver and in the kidney of transgenic mice. The rat AT-III gene shows the same expression pattern. In contrast, as previously described, the same promoter permitted the expression of the SV40 large T antigen only in the liver of transgenic mice. In view of the extra-hepatic distribution of the ApoA-II mRNA, a preliminary characterization of the hAT-III proximal promoter (phAT-III), driving the expression of the transgene, was realized. Using DNase I footprinting analysis with liver nuclear extracts, four protected regions (I-IV) were identified in the first 175 bp of the 5' region of hAT-III. Electrophoretic mobility shift assays performed with liver and kidney nuclear extracts indicate that region III (nucleotides (nt) -67 to -90) interacts with the liver-enriched HNF4 nuclear factor. Furthermore, our data suggest that region I (nt -123 to -138) interacts with the liver-enriched HNF3 transcription factor family, both in liver and kidney. Taken together, these results demonstrate that phAT-III is a useful tool to create transgenic mice producing high plasma levels of a human apolipoprotein due to expression of the transgene in liver and kidney.(ABSTRACT TRUNCATED AT 250 WORDS)