On the issue of transmissibility of Alzheimer disease: A critical review

Results from recent experiments with rodents imply that Alzheimer disease might be inducible by seeding Aβ peptides into recipient animals. In respect to this new experimental data, public health aspects as well as epidemiological data have to be reevaluated. In this article, the available experimental and epidemiological data are reviewed.     

Automated band mapping in electrophoretic gel images using background information

Some popular methods for polymorphism and mutation discovery involve ascertainment of novel bands by the examination of electrophoretic gel images. Although existing strategies for mapping bands work well for specific applications, such as DNA sequencing, these strategies are not well suited for novel band detection. Here, we describe a general strategy for band mapping that uses background banding patterns to facilitate lane calling and size calibration. We have implemented this strategy in GelBuddy, a user-friendly Java-based program for PC and Macintosh computers, which includes several utilities to assist discovery of mutations and polymorphisms. We demonstrate the use of GelBuddy in applications based on single-base mismatch cleavage of heteroduplexed PCR products. Use of software designed to facilitate novel band detection can significantly shorten the time needed for image analysis and data entry in a high-throughput setting. Furthermore, the interactive strategy implemented in GelBuddy has been successfully applied to DNA fingerprinting applications, such as AFLP. GelBuddy promises to make electrophoretic gel analysis a viable alternative to DNA resequencing for discovery of mutations and polymorphisms.     

Ascertainment Bias Causes False Signal of Anticipation in Genetic Prion Disease

Anticipation is the phenomenon whereby age of onset in genetic disease decreases in successive generations. Three independent reports have claimed anticipation in Creutzfeldt-Jakob disease (CJD) caused by the c.598G>A mutation in PRNP encoding a p.Glu200Lys (E200K) substitution in the prion protein. If confirmed, this finding would carry clear implications for genetic counseling. We analyzed pedigrees with this mutation from four prion centers worldwide (n = 217 individuals with the mutation) to analyze age of onset and death in affected and censored individuals. We show through simulation that selective ascertainment of individuals whose onset falls within the historical window since the mutation’s 1989 discovery is sufficient to create robust false signals both of anticipation and of heritability of age of onset. In our data set, the number of years of anticipation observed depends upon how strictly the data are limited by the ascertainment window. Among individuals whose disease was directly observed at a study center, a 28-year difference between parent and child age of onset is observed (p = 0.002), but including individuals ascertained retrospectively through family history reduces this figure to 7 years (p = 0.005). Applying survival analysis to the most thoroughly ascertained subset of data eliminates the signal of anticipation. Moreover, even non-CJD deaths exhibit 16 years anticipation (p = 0.002), indicating that ascertainment bias can entirely explain observed anticipation. We suggest that reports of anticipation in genetic prion disease are driven entirely by ascertainment bias. Guidelines for future studies claiming statistical evidence for anticipation are suggested.     

High-throughput discovery of rare human nucleotide polymorphisms by Ecotilling

Human individuals differ from one another at only ~0.1% of nucleotide positions, but these single nucleotide differences account for most heritable phenotypic variation. Large-scale efforts to discover and genotype human variation have been limited to common polymorphisms. However, these efforts overlook rare nucleotide changes that may contribute to phenotypic diversity and genetic disorders, including cancer. Thus, there is an increasing need for high-throughput methods to robustly detect rare nucleotide differences. Toward this end, we have adapted the mismatch discovery method known as Ecotilling for the discovery of human single nucleotide polymorphisms. To increase throughput and reduce costs, we developed a universal primer strategy and implemented algorithms for automated band detection. Ecotilling was validated by screening 90 human DNA samples for nucleotide changes in 5 gene targets and by comparing results to public resequencing data. To increase throughput for discovery of rare alleles, we pooled samples 8-fold and found Ecotilling to be efficient relative to resequencing, with a false negative rate of 5% and a false discovery rate of 4%. We identified 28 new rare alleles, including some that are predicted to damage protein function. The detection of rare damaging mutations has implications for models of human disease.     

Molecular basis of Cd+2 stress response in Candida tropicalis

Applied Microbiology and Biotechnology - This study examines the bioremediation potential and cadmium-induced cellular response on a molecular level in Candida tropicalis 3Aer. Spectroscopic...     

Anchorless 23–230 PrPC Interactomics for Elucidation of PrPC Protective Role

Accumulation of conformationally altered cellular proteins (i.e., prion protein) is the common feature of prions and other neurodegenerative diseases. Previous studies demonstrated that the lack of terminal sequence of cellular prion protein (PrP^C), necessary for the addition of glycosylphosphatidylinositol lipid anchor, leads to a protease-resistant conformation that resembles scrapie-associated isoform of prion protein. Moreover, mice overexpressing the truncated form of PrP^C showed late-onset, amyloid deposition, and the presence of a short protease-resistant PrP fragment in the brain similar to those found in Gerstmann–Sträussler–Scheinker disease patients. Therefore, the physiopathological function of truncated_/anchorless 23–230 PrP^C (Δ23–230 PrP^C) has come into focus of attention. The present study aims at revealing the physiopathological function of the anchorless PrP^C form by identifying its interacting proteins. The truncated_/anchorless Δ23–230 PrP^C along with its interacting proteins was affinity purified using STrEP-Tactin chromatography, in-gel digested, and identified by quadrupole time-of-flight tandem mass spectrometry analysis in prion protein-deficient murine hippocampus (HpL3-4) neuronal cell line. Twenty-three proteins appeared to interact with anchorless Δ23–230 PrP^C in HpL3-4 cells. Out of the 23 proteins, one novel protein, pyruvate kinase isozymes M1/M2 (PKM2), exhibited a potential interaction with the anchorless Δ23–230 form of PrP^C. Both reverse co-immunoprecipitation and confocal laser-scanning microscopic analysis confirmed an interaction of PKM2 with the anchorless Δ23–230 form of PrP^C. Furthermore, we provide the first evidence for co-localization of PKM2 and PrP^C as well as PrP^C-dependent PKM2 expression regulation. In addition, given the involvement of PrP^C in the regulation of apoptosis, we exposed HpL3-4 cells to staurosporine (STS)-mediated apoptotic stress. In response to STS-mediated apoptotic stress, HpL3-4 cells transiently expressing 23–230-truncated PrP^C were markedly less viable, were more prone to apoptosis and exhibited significantly higher PKM2 expressional regulation as compared with HpL3-4 cells transiently expressing full-length PrP^C (1–253 PrP^C). The enhanced STS-induced apoptosis was shown by increased caspase-3 cleavage. Together, our data suggest that the misbalance or over expression of anchorless Δ23–230 form of PrP^C in association with the expressional regulation of interacting proteins could render cells more prone to cellular insults-stress response, formation of aggregates and may ultimately be linked to the cell death.     

Prion Peptide Uptake in Microglial Cells – The Effect of Naturally Occurring Autoantibodies against Prion Protein

In prion disease, a profound microglial activation that precedes neurodegeneration has been observed in the CNS. It is still not fully elucidated whether microglial activation has beneficial effects in terms of prion clearance or whether microglial cells have a mainly detrimental function through the release of pro-inflammatory cytokines. To date, no disease-modifying therapy exists. Several immunization attempts have been performed as one therapeutic approach. Recently, naturally occurring autoantibodies against the prion protein (nAbs-PrP) have been detected. These autoantibodies are able to break down fibrils of the most commonly used mutant prion variant PrP106-126 A117V and prevent PrP106-126 A117V-induced toxicity in primary neurons. In this study, we examined the phagocytosis of the prion peptide PrP106-126 A117V by primary microglial cells and the effect of nAbs-PrP on microglia. nAbs-PrP considerably enhanced the uptake of PrP106-126 A117V without inducing an inflammatory response in microglial cells. PrP106-126 A117V uptake was at least partially mediated through scavenger receptors. Phagocytosis of PrP106-126 A117V with nAbs-PrP was inhibited by wortmannin, a potent phosphatidylinositol 3-kinase inhibitor, indicating a separate uptake mechanism for nAbs-PrP mediated phagocytosis. These data suggest the possible mechanisms of action of nAbs-PrP in prion disease.     

Methane Yields and Digestion Dynamics of Press Fluids from Mechanically Dehydrated Maize Silages Using Different Types of Digesters

The mechanical dehydration of ensiled agricultural crops results in two major products: a fibrous press cake and a press fluid containing mainly easily digestible constituents. This study is aimed at the investigation on methane yields and digestion dynamics of the press fluids from maize silages using different types of digesters. Methane yields investigated in batch experiments account for 390?C506?l_N CH₄/kg?volatile solids (VS) with a degree of degradation of the organic matter in the fluid of more than 90%. The investigation of digestion dynamics in a continuously working stirrer tank digester at different levels of retention time and volume load suggests that a stable fermentation of press fluids can only be achieved with retention times of more than 20?days and with volume loads below 2?g VS/l/day. In a continuously working fixed bed digester a steady fermentation could be achieved at a retention time of 8?days and a volume load of 3?g VS/l/day.     

Investigating the Association of ApoE Genotypes with Blood-Brain Barrier Dysfunction Measured by Cerebrospinal Fluid-Serum Albumin Ratio in a Cohort of Patients with Different Types of Dementia

Background

Since more than a decade ApoE is known to be a strong risk factor for Alzheimer''s disease (AD); however, molecular pathways mediating this risk are still unclear. In recent years it has been hypothesized that ApoE might play a role in the disintegration of blood-brain barrier (BBB). In the present study we addressed the question if ApoE genotypes might be associated with BBB function measured by albumin ratio (Q_Alb) in a large cohort of patients with different types of dementia.

Methods

Five hundred twenty (520) patients with Creutzfeldt-Jakob disease (CJD, n = 350), Alzheimer''s disease (n = 71) and cerebral small vessel disease (n = 99) were assessed for their ApoE genotype. BBB function was measured in all patients using Q_Alb and was compared between ApoE genotypes. Dominant and additive genetic models were assumed in order to investigate the potential effect of ApoE on BBB function.

Results

We observed no systematic differences in Q_Alb between ApoE genotypes within the present study. Increased Q_Alb levels were shown for those without E3 allele in the subgroup of CJD patients when assuming a dominant genetic model (p = 0.035). This could not be confirmed for patients with other forms of dementia (p = 0.234).

Discussion

Although there was some evidence for a protective effect of E3 alleles in CJD patients, this study does not support the hypothesis of a systematic role of ApoE genotypes in BBB function in individuals with a diagnosis of dementia. Thus, changes in BBB function do not seem to contribute to the increased risk of cognitive decline associated with certain ApoE genotypes. The interpretation of the results of this study must take into account that BBB function was only assessed by measuring Q_Alb which has been shown to be a good marker for overall BBB integrity but might not reflect all qualities of the barrier.