Apolipoprotein E4 (1–272) fragment is associated with mitochondrial proteins and affects mitochondrial function in neuronal cells

<p>Abstract</p> <p>Background</p> <p>Apolipoprotein E allele ε4 (apoE4) is a strong risk factor for developing Alzheimer's disease (AD). Secreted apoE has a critical function in redistributing lipids among central nervous system cells to maintain normal lipid homeostasis. In addition, previous reports have shown that apoE4 is cleaved by a protease in neurons to generate apoE4(1–272) fragment, which is associated with neurofibrillary tanglelike structures and mitochondria, causing mitochondrial dysfunction. However, it still remains unclear how the apoE fragment associates with mitochondria and induces mitochondrial dysfunction.</p> <p>Results</p> <p>To clarify the molecular mechanism, we carried out experiments to identify intracellular apoE-binding molecules and their functions in modulating mitochondria function. Here, we found that apoE4 binds to ubiquinol cytochrome <it>c </it>reductase core protein 2 (UQCRC2) and cytochrome C1, both of which are components of mitochondrial respiratory complex III, and cytochrome <it>c </it>oxidase subunit 4 isoform 1 (COX IV 1), which is a component of complex IV, in Neuro-2a cells. Interestingly, these proteins associated with apoE4(1–272) more strongly than intact apoE4(1–299). Further analysis showed that in Neuro-2a cells expressing apoE4(1–272), the enzymatic activities of mitochondrial respiratory complexes III and IV were significantly lower than those in Neuro-2a cells expressing apoE4(1–299).</p> <p>Conclusion</p> <p>ApoE4(1–272) fragment expressed in Neuro2a cells is associated with mitochondrial proteins, UQCRC2 and cytochrome C1, which are component of respiratory complex III, and with COX IV 1, which is a member of complex IV. Overexpression of apoE4(1–272) fragment impairs activities of complex III and IV. These results suggest that the C-terminal-truncated fragment of apoE4 binds to mitochondrial complexes and affects their activities, and thereby leading to neurodegeneration.</p

Beta-amyloid increases the expression level of ATBF1 responsible for death in cultured cortical neurons

Background: Recently, several lines of evidence have shown the aberrant expression of cell-cycle-related proteins and tumor suppressor proteins in vulnerable neurons of the Alzheimer's disease (AD) brain and transgenic mouse models of AD; these proteins are associated with various paradigms of neuronal death. It has been reported that ATBF1 induces cell cycle arrest associated with neuronal differentiation in the developing rat brain, and that gene is one of the candidate tumor suppressor genes for prostate and breast cancers in whose cells overexpressed ATBF1 induces cell cycle arrest. However, the involvement of ATBF1 in AD pathogenesis is as yet unknown. Results: We found that ATBF1 was up-regulated in the brains of 17-month-old Tg2576 mice compared with those of age-matched wild-type mice. Moreover, our in vitro studies showed that Aβ1-42 and DNA-damaging drugs, namely, etoposide and homocysteine, increased the expression ATBF1 level in primary rat cortical neurons, whereas the knockdown of ATBF1 in these neurons protected against neuronal death induced by Aβ1-42, etoposide, and homocysteine, indicating that ATBF1 mediates neuronal death in response to these substances. In addition, we found that ATBF1-mediated neuronal death is dependent on ataxia-telangiectasia mutated (ATM) because the blockage of ATM activity by treatment with ATM inhibitors, caffeine and KU55933, abolished ATBF1 function in neuronal death. Furthermore, Aβ1-42 phosphorylates ATM, and ATBF1 interacts with phosphorylated ATM. Conclusions: To the best of our knowledge, this is the first report that Aβ1-42 and DNA-damaging drugs increased the ATBF1 expression level in primary rat cortical neurons; this increase, in turn, may activate ATM signaling responsible for neuronal death through the binding of ATBF1 to phosphorylated ATM. ATBF1 may therefore be a suitable target for therapeutic intervention of AD

Genome wide screen identifies microsatellite markers associated with acute adverse effects following radiotherapy in cancer patients

<p>Abstract</p> <p>Background</p> <p>The response of normal tissues in cancer patients undergoing radiotherapy varies, possibly due to genetic differences underlying variation in radiosensitivity.</p> <p>Methods</p> <p>Cancer patients (n = 360) were selected retrospectively from the RadGenomics project. Adverse effects within 3 months of radiotherapy completion were graded using the National Cancer Institute Common Toxicity Criteria; high grade group were grade 3 or more (n = 180), low grade group were grade 1 or less (n = 180). Pooled genomic DNA (gDNA) (n = 90 from each group) was screened using 23,244 microsatellites. Markers with different inter-group frequencies (Fisher exact test <it>P </it>< 0.05) were analyzed using the remaining pooled gDNA. Silencing RNA treatment was performed in cultured normal human skin fibroblasts.</p> <p>Results</p> <p>Forty-seven markers had positive association values; including one in the <it>SEMA3A </it>promoter region (P = 1.24 × 10^-5). <it>SEMA3A </it>knockdown enhanced radiation resistance.</p> <p>Conclusions</p> <p>This study identified 47 putative radiosensitivity markers, and suggested a role for <it>SEMA3A </it>in radiosensitivity.</p

CT Image Segmentation Using FEM with Optimized Boundary Condition

The authors propose a CT image segmentation method using structural analysis that is useful for objects with structural dynamic characteristics. Motivation of our research is from the area of genetic activity. In order to reveal the roles of genes, it is necessary to create mutant mice and measure differences among them by scanning their skeletons with an X-ray CT scanner. The CT image needs to be manually segmented into pieces of the bones. It is a very time consuming to manually segment many mutant mouse models in order to reveal the roles of genes. It is desirable to make this segmentation procedure automatic. Although numerous papers in the past have proposed segmentation techniques, no general segmentation method for skeletons of living creatures has been established. Against this background, the authors propose a segmentation method based on the concept of destruction analogy. To realize this concept, structural analysis is performed using the finite element method (FEM), as structurally weak areas can be expected to break under conditions of stress. The contribution of the method is its novelty, as no studies have so far used structural analysis for image segmentation. The method's implementation involves three steps. First, finite elements are created directly from the pixels of a CT image, and then candidates are also selected in areas where segmentation is thought to be appropriate. The second step involves destruction analogy to find a single candidate with high strain chosen as the segmentation target. The boundary conditions for FEM are also set automatically. Then, destruction analogy is implemented by replacing pixels with high strain as background ones, and this process is iterated until object is decomposed into two parts. Here, CT image segmentation is demonstrated using various types of CT imagery

Out-of-Core Distance Transforms

(a) Input CT image of an object (b) Distance field on the inside of the object (c) Distance field on the outside of the object Figure 1: The result of the OoCDT algorithm for an ”Cylinder-Head ” model (size: 850 × 800 × 1059 ≈ 700M cells). Note that the data size of the distance field is about 3GB (4 bytes/cell), which is too large to allocate to the RAM. Our algorithm can compute such large distance fields on common 32-bit computers. This paper presents a method for computing distance fields from large volumetric models. Conventional methods have strict limits in terms of the amount of memory space available, as all volumetric models must be allocated to the random access memory (RAM) to compute distance fields. We resolve this problem through an outof-core strategy. Our algorithm starts by decomposing volumetric models into small regions known as clusters, and distance fields are then computed by Local Distance Transform (LDT) and Inter-Cluster Propagation (ICP). LDT computes the distance transform for each cluster, and since it is independent, other clusters can also be saved to the storage medium. ICP propagates the distance at the boundary of the cluster to neighboring clusters to remove inconsistency in distance fields. In addition, we propose an efficient ordering algorithm based on the propagated distance to reduce LDT and ICP. This paper also demonstrates the results of distance transform from volumetric models with over a billion cells

Efficient Medial Voxel Extraction for Large Volumetric Models

Here we propose a method for medial voxel extraction from large volumetric models based on an out-of-core framework. The method improves upon geodesic-based approaches to enable the handling of large objects. First, distance fields are constructed from input volumes using an out-of-core algorithm. Second, medial voxels are extracted from these distance fields through multi-phase evaluation processes. Trivial medial or non-medial voxels are evaluated by the low-cost pseudo-geodesic distance method first, and the more expensive geodesic distance computation is run last. Using this strategy allows most of the voxels to be extracted in the low-cost process. This paper outlines a number of results regarding the extraction of medial voxels from large volumetric models. Our method also works in parallel, and we demonstrate that computation time becomes even shorter in multi-core environments

Radiation sensitivity determined by the flow of information through intracellular networks

Gordon Research Conference

Experimental determination of individual patient\u27s haplotypes of radiation sensitivity-associated gene

A novel methodology of haplotype determination involving sensitive amplification of single chromosomes was developed. Limited dilution of chromosomes was performed within heated alkaline agarose solution to avoid extensive aggregation during dilution process. Aliquoted and solidified agarose gel pieces were then treated by exogenously provided Phi29 DNA polymerase and random hexamer oligonucleotides, yielding up to 120 000-fold amplification of immobilized chromosomes. The amplified materials were recovered in solution in PCR-ready form by simple heating to melt the gel, making them conveniently available for further applications such as multiple locus genotyping. With this amplification methodology, haplotypes of radiation sensitivity-associated gene were successfully evaluated in individual cancer patients.The 7th International Workshop on Advanced Genomic