Markus Dettenhofer

Bio: Markus Dettenhofer is an academic researcher from Central European Institute of Technology. The author has contributed to research in topics: Viral replication & Mutant. The author has an hindex of 15, co-authored 23 publications receiving 1800 citations. Previous affiliations of Markus Dettenhofer include Harvard University & Johns Hopkins University.

Altered Histone Acetylation Is Associated with Age-Dependent Memory Impairment in Mice

Abstract: As the human life span increases, the number of people suffering from cognitive decline is rising dramatically. The mechanisms underlying age-associated memory impairment are, however, not understood. Here we show that memory disturbances in the aging brain of the mouse are associated with altered hippocampal chromatin plasticity. During learning, aged mice display a specific deregulation of histone H4 lysine 12 (H4K12) acetylation and fail to initiate a hippocampal gene expression program associated with memory consolidation. Restoration of physiological H4K12 acetylation reinstates the expression of learning-induced genes and leads to the recovery of cognitive abilities. Our data suggest that deregulated H4K12 acetylation may represent an early biomarker of an impaired genome-environment interaction in the aging mouse brain.

Highly Purified Human Immunodeficiency Virus Type 1 Reveals a Virtual Absence of Vif in Virions

Abstract: The vif gene of human immunodeficiency virus type 1 (HIV-1) is essential for the productive infection of primary blood-derived lymphocytes, macrophages, and certain human T-cell lines. It has been shown that Vif is associated with HIV-1 virions purified by sucrose density-equilibrium gradient analysis. However, the specificity of Vif incorporation into virions has not been determined. Moreover, recent studies have demonstrated that standard HIV-1 particle preparations created with sucrose density-equilibrium gradients are contaminated with cell-derived microvesicles. Here we demonstrate, as previously reported, that Vif cosediments with HIV-1 particles in sucrose density-equilibrium gradient analysis. However, we also found that, when Vif was expressed in the absence of all other HIV-1-encoded gene products and then isolated by sucrose density-equilibrium gradient centrifugation from extracellular supernatants, its sedimentation pattern was largely unaltered, suggesting that Vif can be secreted from cells. Using a newly developed OptiPrep velocity gradient method, we were able to physically separate most of the extracellular Vif from the HIV-1 virions without disrupting the infectivity of the virus. By titrating serial dilutions of purified Vif and Gag against the viral peak fraction in the OptiPrep gradient, we demonstrate that <1.0 Vif molecule per virion was present. This study shows that Vif is not significantly present in HIV-1 virions, a finding which is consistent with the idea that Vif functions predominantly in the virus-producing cells during virus assembly. The OptiPrep velocity gradient technique described here could be an easy and rapid way to purify HIV and other enveloped viruses from microvesicles and/or cell debris.

Association of human immunodeficiency virus type 1 Vif with RNA and its role in reverse transcription.

Abstract: The vif gene of human immunodeficiency virus type 1 (HIV-1) is essential for viral replication, although the functional target of Vif remains elusive. HIV-1 vif mutant virions derived from nonpermissive H9 cells displayed no significant differences in the amount, ratio, or integrity of their protein composition relative to an isogenic wild-type virion. The amounts of the virion-associated viral genomic RNA and tRNA3Lys were additionally present at normal levels in vif mutant virions. We demonstrate that Vif associates with RNA in vitro as well as with viral genomic RNA in virus-infected cells. A functionally conserved lentivirus Vif motif was found in the double-stranded RNA binding domain of Xenopus laevis, Xlrbpa. The natural intravirion reverse transcriptase products were markedly reduced in vif mutant virions. Moreover, purified vif mutant genomic RNA-primer tRNA complexes displayed severe defects in the initiation of reverse transcription with recombinant reverse transcriptase. These data point to a novel role for Vif in the regulation of efficient reverse transcription through modulation of the virion nucleic acid components.

Evaluation of Novel Human Immunodeficiency Virus Type 1 Gag DNA Vaccines for Protein Expression in Mammalian Cells and Induction of Immune Responses

Abstract: There is increasing evidence that CD8+ cytotoxic T lymphocytes (CTL) may play an important role in controlling human immunodeficiency virus type 1 (HIV-1) infection. Containment of primary HIV-1 infection in infected individuals correlates with the emergence of virus-specific CTL responses (3, 12, 22). In chronically infected individuals, a high-frequency CTL response against HIV-1 is also correlated with low viral load and slow disease progression (19, 20). An HIV-1-specific CTL response has also been demonstrated in certain highly exposed seronegative individuals (2, 13, 28). Broad, cross-clade CTL responses recognizing conserved epitopes in HIV-1 Gag have been detected in HIV-1-infected individuals (7, 18). It is therefore reasonable to hypothesize that induction of an effective CTL response against conserved internal virion proteins of HIV-1 such as Gag is essential for the development of a safe and effective HIV-1 vaccine. In order to generate an efficient major histocompatibility complex (MHC) class I-restricted cellular immune response to a vaccine, viral proteins must be synthesized endogenously. Efficient production of CTL responses requires endogenous antigen synthesis, usually achieved by using a live, attenuated virus or recombinant virus vectors. Concerns about using a live, attenuated virus vaccine for HIV-1 include potential pathogenic replication and disease development over a longer period of time as well as potential adverse effects of integrated viral DNA. Using recombinant virus-based vectors, it is difficult to achieve repeated boosting because of the strong immune response generated against the viral proteins of the virus vector. Certain virus vectors, such as vaccinia virus, may also inhibit class I MHC-restricted CTL responses (32). Recently, a new approach (DNA vaccination) has been used to express antigens in vivo for the generation of both humoral and cellular immune responses (6). Several groups have used the DNA vaccination approach against HIV-1 (10, 17, 21, 34). Unfortunately, expression of HIV-1 Gag, Pol, and Env proteins by DNA vectors has been hampered by the presence of multiple inhibitory sequences (INS) in the structural genes encoding Gag, Pol, and Env proteins of HIV-1. This makes expression of the structural HIV-1 proteins dependent on the viral regulatory protein Rev, which is responsible for the nuclear export and efficient expression of unspliced HIV-1 mRNAs (5, 8, 23, 24). Rev binds specifically to an RNA site within HIV-1 mRNA named RRE. In the absence of functional Rev/RRE, mRNAs containing INS are either retained in the nucleus or degraded rapidly; therefore, little protein can be expressed from these mRNAs. Furthermore, even with Rev and RRE, expression of HIV-1 Gag, Pol, or Env is very low in certain murine cell lines (10, 33), limiting our ability to study the DNA vaccine-induced immune response against Gag or Pol using a mouse model. It has been reported that type D retroviruses contain a cis-acting posttranscriptional control element (CTE) that can replace the Rev and RRE regulation of HIV-1 (4, 36). When a CTE is inserted into an HIV-1 Rev−/RRE− clone, replication of the CTE-containing clone can approach that of the wild-type HIV-1 clone in cell lines (4, 36). The CTEs of different type D retroviruses are approximately 200 nucleotides in length and form extensive RNA stem-loop structures. They contain binding sites for cellular factors that contain nuclear export signals (9). CTEs function in a wide spectrum of cell types and species (31) and have been identified in both type D simian retroviruses (4, 36) and murine intracisternal-A particles (31). A current hypothesis about the function of INS is that they are binding sites for cellular factors that contribute to mRNA instability (1). Recently, it has been demonstrated that substitutions of AT-rich regions in HIV-1 gag, mostly in third-site positions, without changing the amino acid sequence of the produced Gag protein can result in efficient expression of Gag in a Rev- and RRE-independent fashion (29, 30). In the present study, we have constructed a series of HIV-1 Gag DNA expression vectors and compared the influence of the constitutive transport element (CTE) or of silent-site mutations within HIV-1 gag on Gag expression in a variety of cells of human, simian, and mouse origin. We found that silent-site mutations in HIV-1 gag allowed efficient Gag expression in a species-independent fashion and induced both humoral and CTL responses after naked DNA vaccination in mice. On the other hand, CTE only increased Gag expression moderately in monkey-derived COS cells and negligibly in HeLa (human) or several mouse cell lines. A DNA vaccine containing wild-type gag coding sequence plus CTE did not induce any detectable humoral or CTL response in mice. In contrast, mutated gag not containing INS induced detectable humoral and CTL responses. We have also achieved stable expression of HIV-1 Gag protein in mouse p815 cells and shown that these cells can be used as CTL target cells. Reagents described in this study should facilitate the development and evaluation of HIV-1 DNA vaccine strategies against conserved viral Gag protein in animal models.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

“Bioinformatics” 특집을 내면서

Abstract: BIOE 402. Medical Technology Assessment. 2 or 3 hours. Bioentrepreneur course. Assessment of medical technology in the context of commercialization. Objectives, competition, market share, funding, pricing, manufacturing, growth, and intellectual property; many issues unique to biomedical products. Course Information: 2 undergraduate hours. 3 graduate hours. Prerequisite(s): Junior standing or above and consent of the instructor.

Galaxy: a comprehensive approach for supporting accessible, reproducible, and transparent computational research in the life sciences

Abstract: Increased reliance on computational approaches in the life sciences has revealed grave concerns about how accessible and reproducible computation-reliant results truly are. Galaxy http://usegalaxy.org, an open web-based platform for genomic research, addresses these problems. Galaxy automatically tracks and manages data provenance and provides support for capturing the context and intent of computational methods. Galaxy Pages are interactive, web-based documents that provide users with a medium to communicate a complete computational analysis.

Neuroscience 細胞死：最近の知見

Abstract: 中枢神経系疾患の治療は正常細胞（ニューロン）の機能維持を目的とするが，脳血管障害のように機能障害の原因が細胞の死滅に基づくことは多い．一方，脳腫瘍の治療においては薬物療法や放射線療法といった腫瘍細胞の死滅を目標とするものが大きな位置を占める．いずれの場合にも，細胞死の機序を理解することは各種病態や治療法の理解のうえで重要である．現在のところ最も研究の進んでいる細胞死の型はアポトーシスである．そのなかで重要な位置を占めるミトコンドリアにおける反応および抗アポトーシス因子について概要を紹介する．