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  • 1
    Publication Date: 2016-04-28
    Description: The bacterial CRISPR/Cas9 system allows sequence-specific gene editing in many organisms and holds promise as a tool to generate models of human diseases, for example, in human pluripotent stem cells. CRISPR/Cas9 introduces targeted double-stranded breaks (DSBs) with high efficiency, which are typically repaired by non-homologous end-joining (NHEJ) resulting in nonspecific insertions, deletions or other mutations (indels). DSBs may also be repaired by homology-directed repair (HDR) using a DNA repair template, such as an introduced single-stranded oligo DNA nucleotide (ssODN), allowing knock-in of specific mutations. Although CRISPR/Cas9 is used extensively to engineer gene knockouts through NHEJ, editing by HDR remains inefficient and can be corrupted by additional indels, preventing its widespread use for modelling genetic disorders through introducing disease-associated mutations. Furthermore, targeted mutational knock-in at single alleles to model diseases caused by heterozygous mutations has not been reported. Here we describe a CRISPR/Cas9-based genome-editing framework that allows selective introduction of mono- and bi-allelic sequence changes with high efficiency and accuracy. We show that HDR accuracy is increased dramatically by incorporating silent CRISPR/Cas-blocking mutations along with pathogenic mutations, and establish a method termed 'CORRECT' for scarless genome editing. By characterizing and exploiting a stereotyped inverse relationship between a mutation's incorporation rate and its distance to the DSB, we achieve predictable control of zygosity. Homozygous introduction requires a guide RNA targeting close to the intended mutation, whereas heterozygous introduction can be accomplished by distance-dependent suboptimal mutation incorporation or by use of mixed repair templates. Using this approach, we generated human induced pluripotent stem cells with heterozygous and homozygous dominant early onset Alzheimer's disease-causing mutations in amyloid precursor protein (APP(Swe)) and presenilin 1 (PSEN1(M146V)) and derived cortical neurons, which displayed genotype-dependent disease-associated phenotypes. Our findings enable efficient introduction of specific sequence changes with CRISPR/Cas9, facilitating study of human disease.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Paquet, Dominik -- Kwart, Dylan -- Chen, Antonia -- Sproul, Andrew -- Jacob, Samson -- Teo, Shaun -- Olsen, Kimberly Moore -- Gregg, Andrew -- Noggle, Scott -- Tessier-Lavigne, Marc -- 8 UL1 TR000043/TR/NCATS NIH HHS/ -- T32GM007739/GM/NIGMS NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2016 May 5;533(7601):125-9. doi: 10.1038/nature17664. Epub 2016 Apr 27.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory of Brain Development and Repair, The Rockefeller University, 1230 York Avenue, New York, New York 10065, USA. ; The New York Stem Cell Foundation Research Institute, New York, New York 10032, USA. ; Weill Cornell Graduate School of Medical Sciences, The Rockefeller University and Sloan-Kettering Institute Tri-institutional MD-PhD Program, 1300 York Avenue, New York, New York 10065, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/27120160" target="_blank"〉PubMed〈/a〉
    Keywords: Adolescent ; Age of Onset ; Alleles ; Alzheimer Disease/genetics ; Amyloid beta-Protein Precursor/genetics/secretion ; Animals ; Base Sequence ; CRISPR-Cas Systems/*genetics ; DNA Breaks, Double-Stranded ; DNA Cleavage ; DNA Repair/genetics ; Female ; Genes, Dominant/genetics ; Genetic Association Studies ; Genetic Engineering/*methods ; *Heterozygote ; *Homozygote ; Humans ; Induced Pluripotent Stem Cells/metabolism ; Male ; Mice ; Mutagenesis/*genetics ; Mutation/*genetics ; Presenilins/genetics ; RNA, Guide/genetics ; Sequence Homology ; Substrate Specificity ; Templates, Genetic
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2013-08-09
    Description: LINE-1 retrotransposons are abundant repetitive elements of viral origin, which in normal cells are kept quiescent through epigenetic mechanisms. Activation of LINE-1 occurs frequently in cancer and can enable LINE-1 mobilization but also has retrotransposition-independent consequences. We previously reported that in cancer, aberrantly active LINE-1 promoters can drive transcription of flanking unique sequences giving rise to LINE-1 chimeric transcripts (LCTs). Here, we show that one such LCT, LCT13, is a large transcript (〉300 kb) running antisense to the metastasis-suppressor gene TFPI-2 . We have modelled antisense RNA expression at TFPI-2 in transgenic mouse embryonic stem (ES) cells and demonstrate that antisense RNA induces silencing and deposition of repressive histone modifications implying a causal link. Consistent with this, LCT13 expression in breast and colon cancer cell lines is associated with silencing and repressive chromatin at TFPI-2 . Furthermore, we detected LCT13 transcripts in 56% of colorectal tumours exhibiting reduced TFPI-2 expression. Our findings implicate activation of LINE-1 elements in subsequent epigenetic remodelling of surrounding genes, thus hinting a novel retrotransposition-independent role for LINE-1 elements in malignancy.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4161-4171 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Accurate measurements of the minority carrier- and lattice scattering-diffusion constant and mobility in float zone silicon have been determined using photoconductance decay. For the more lightly doped specimens our results indicate slightly higher mobility than published majority carrier values. This is attributed to purer samples which allow a more accurate measurement of the lattice scattering mobility. In the dopant range 1015–1017 cm−3 the results for both electrons and holes are, within experimental error, equal to the majority carrier values. Unlike other methods this technique is a very direct measurement of the diffusion constant as only the thickness and decay time of the wafer need to be determined. The method is estimated to have a one standard deviation uncertainty of 2%–4% which is comparable to the best accuracy previously obtained for majority carrier measurements.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6783-6795 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article provides a theoretical investigation of recombination at grain boundaries in both bulk and p-n junction regions of silicon solar cells. Previous models of grain boundaries and grain boundary properties are reviewed. A two dimensional numerical model of grain boundary recombination is presented. This numerical model is compared to existing analytical models of grain boundary recombination within both bulk and p-n junction regions of silicon solar cells. This analysis shows that, under some conditions, existing models poorly predict the recombination current at grain boundaries. Within bulk regions of a device, the effective surface recombination velocity at grain boundaries is overestimated in cases where the region around the grain boundary is not fully depleted of majority carriers. For vertical grain boundaries (columnar grains), existing models are shown to underestimate the recombination current within p-n junction depletion regions. This current has an ideality factor of about 1.8. An improved analytical model for grain boundary recombination within the p-n junction depletion region is presented. This model considers the effect of the grain boundary charge on the electric field within the p-n junction depletion region. The grain boundary charge reduces the p-n junction electric field, at the grain boundary, enhancing recombination in this region. This model is in agreement with the numerical results over a wide range of grain boundary recombination rates. In extreme cases, however, the region of enhanced, high ideality factor recombination can extend well outside the p-n junction depletion region. This leads to a breakdown of analytical models for both bulk and p-n junction recombination, necessitating the use of the numerical model. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2851-2854 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A dimensionless solution is presented for the surface recombination component τs of the effective lifetime τeff of the fundamental mode of excess carrier decay in semiconductors. The case of different surface recombination velocities S1 and S2 is analyzed. As the problem is solved in terms of dimensionless variables, the solution obtained is a general one. A normalized surface lifetime τ *s is plotted as a function of normalized surface recombination velocities S*1 and S*2. This allows rapid calculation and visualization of the influence of surface recombination on τs, for all possible cases of recombination parameters. That is, for any value of S1, S2, W (the width of a sample), and D (the diffusion constant) a solution for the surface lifetime τs can be found from the one graphical solution. It is a useful tool for rapidly interpreting the effect of surface recombination in transient lifetime measurement experiments. For the cases where S=S1=S2, or where S1 or S2 is zero, this approach is an elegant tool for investigating useful approximations for τs.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 1214-1225 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A considerable improvement in the accuracy of the measurement of the intrinsic carrier concentration in silicon near room temperature has recently been reported. This was achieved by the accurate analysis of minority-carrier current flow in specially fabricated p-n junction devices. In this paper this technique has been extended to measurements down to 77 K. A further improvement of the technique has been the simultaneous measurement of the minority-carrier electron mobility utilizing open-circuit voltage decay measurements.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 846-854 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A recent review has suggested that the commonly cited value of 1.45×1010 cm−3 for the silicon intrinsic carrier concentration at 300 K is inconsistent with the best experimental data. An alternate value of 1.08×1010 cm−3 was proposed. From measurements of the current-voltage characteristics of p-n junction diodes, this paper reports a new and more accurate determination of this parameter over the 275–375 K temperature range which supports such lower values. The one-standard-deviation uncertainty in the measurement of the intrinsic carrier concentration is estimated to lie in the 3%–4% range, about three times smaller than previous measurements at these temperatures. Additionally, this technique provides information on the minority carrier electron diffusivity in silicon.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 5473-5481 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An improved method is described for extracting material parameters from an experimental electron-beam-induced current (EBIC) contrast profile across a vertical grain boundary by directly fitting an analytical expression. This allows the least-squares values of the grain boundary recombination velocity and the diffusion length in each grain to be determined without the need for the reduction of the experimental profile to a few integral parameters, as is required in a previously reported method. Greater accuracy of the extracted values is expected since none of the information contained in the experimental contrast data is discarded and a less extensive spatial range of measured data is required than in the commonly used method. Different models of the carrier generation volume are used in the fitting and the effect of the choice of generation model on extracted values is investigated. In common with other EBIC approaches, this method is insensitive to changes in the diffusion length when the collection efficiency is high and diffusion lengths may not be reliably established in those cases. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 255-257 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A recent review suggests that the commonly cited value of 1.45×1010 cm−3 for the silicon intrinsic carrier concentration at 300 K is inconsistent with the best experimental and theoretical results. An alternative value of 1.08×1010 cm−3 was suggested. A new experimental measurement of 1.01×1010 cm−3 is reported with an estimated one standard deviation uncertainty of only 3%. This appears to be the most accurate experimental determination of this parameter at any temperature.
    Type of Medium: Electronic Resource
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  • 10
    Publication Date: 2000-02-15
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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