Browsing by keyword "*Models, Genetic"
Now showing items 1-5 of 5
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Design and delivery of antisense oligonucleotides to block microRNA function in cultured Drosophila and human cellsMicroRNAs (miRNAs), approximately 22-nt RNAs that mediate post-transcriptional regulation of mRNAs in animals and plants, are a diverse class of regulatory genes whose specific biological functions are largely unknown. Here we detail a protocol to design and introduce into cultured Drosophila and human cells sequence-specific antisense oligonucleotides (ASOs) that block the function of individual miRNAs. Coupled with recent studies that catalog the miRNAs expressed in diverse cultured cells, our method offers a rapid (<1 >week) approach to validate miRNA targets and to study the cellular functions of individual human and Drosophila miRNAs. ASO-based inactivation of miRNAs is faster and simpler than comparable genetic or 'sponge'-based approaches, for which extensive recombinant DNA manipulation is required. We present our ASO design principles and an optimized transfection protocol in which transfection efficiency of Drosophila Schneider 2 cells can approach 100%. Our 3'-cholesterol-modified ASOs have enhanced potency, allowing miRNA inhibition for at least 7 d from a single transfection.
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Is coronary artery disease a multifactorial inherited disorder with a sex-influenced traitThe genetic linkage of coronary artery disease is well-established. However, the transmission of this disease is not clearly defined. Although the Mendelian autosomal dominant pattern has been seen in familial hypercholesterolemia and mutant MEF2A induced familiar myocardial infarction, and a multifactorial genetic model has been proposed for non-familial CAD, the gender difference in this disease is not well explained. We hypothesized that CAD is a multifactorial inherited disorder with a sex-influenced trait, which shows an autosomal dominant pattern in men and autosomal recessive transmission in women. This hypothesis is supported by the facts including an age-dependent higher prevalence in men, the autosomal locations of CAD associated genes, the gender difference seen even in familiar CAD, and the potential gene-gene interactions between CAD associated genes on autosomal chromosomes and those found on the X chromosome. Further investigation of genetic components will provide not only the critical information about the etiology of CAD, but also help to clarify the confusion in the use of exogenous female hormones in the prevention and/or the treatment of the disease.
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Nucleosome dynamics as modular systems that integrate DNA damage and repairBy some estimates, a eukaryotic cell must repair up to 10,000 DNA lesions per cell cycle to counteract endogenous sources of DNA damage. Exposure to environmental toxins, UV sources, or other radiations only increases this enormous number. Failure to repair such lesions can lead to a deleterious mutation rate, genomic instability, or cell death. The timely and efficient repair of eukaryotic DNA damage is further complicated by the realization that DNA lesions must be detected and repaired in the context of chromatin with its complex organization within the nucleus. Numerous studies have shown that chromatin packaging can inhibit nearly all repair pathways, and recent work has defined specific mechanisms that facilitate DNA repair within the chromatin context. In this review, we provide a broad overview of chromatin regulatory mechanisms, mainly at the nucleosomal level, and then focus on recent work that elucidates the role of chromatin structure in regulating the timely and efficient repair of DNA double-strand breaks (DSBs).
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Segment self-repulsion is the major driving force of influenza genome packagingThe genome of influenza A virus consists of eight separate RNA segments, which are selectively packaged into virions prior to virus budding. The microscopic mechanism of highly selective packaging involves molecular interactions between packaging signals in the genome segments and remains poorly understood. We propose that the condition of proper packaging can be formulated as a large gap between RNA-RNA interaction energies in the viable virion with eight unique segments and in improperly packed assemblages lacking the complete genome. We then demonstrate that selective packaging of eight unique segments into an infective influenza virion can be achieved by self-repulsion of identical segments at the virion assembly stage, rather than by previously hypothesized intricate molecular recognition of particular segments. Using Monte Carlo simulations to maximize the energy gap, without any other assumptions, we generated model eight-segment virions, which all display specific packaging, strong self-repulsion of the segments, and reassortment patterns similar to natural influenza. The model provides a biophysical foundation of influenza genome packaging and reassortment and serves as an important step towards robust sequence-driven prediction of reassortment patterns of the influenza virus.
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Shifts in targeting of class switch recombination sites in mice that lack mu switch region tandem repeats or Msh2The mechanisms that target class switch recombination (CSR) to antibody gene switch (S) regions are unknown. Analyses of switch site locations in wild-type mice and in mice that lack the Smu tandem repeats show shifts indicating that a 4-5-kb DNA domain (bounded upstream by the Imu promoter) is accessible for switching independent of Smu sequences. This CSR-accessible domain is reminiscent of the promoter-defined domains that target somatic hypermutation. Within the 4-5-kb CSR domain, the targeting of S site locations also depends on the Msh2 mismatch repair protein because Msh2-deficient mice show an increased focus of sites to the Smu tandem repeat region. We propose that Msh2 affects S site location because sequences with few activation-induced cytidine deaminase targets generate mostly switch DNA cleavages that require Msh2-directed processing to allow CSR joining.
