CASAAV: A CRISPR‐Based Platform for Rapid Dissection of Gene Function In Vivo

Nathan J. VanDusen1, Yuxuan Guo1, Weiliang Gu2, William T. Pu3

1 Department of Cardiology, Boston Children's Hospital, Boston, Massachusetts, 2 Department of Pharmacology, School of Pharmacy, Shanghai University of Traditional Chinese Medicine, Shanghai, 3 Harvard Stem Cell Institute, Harvard University, Cambridge, Massachusetts
Publication Name:  Current Protocols in Molecular Biology
Unit Number:  Unit 31.11
DOI:  10.1002/cpmb.46
Online Posting Date:  October, 2017
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In vivo loss‐of‐function studies are currently limited by the need for appropriate conditional knockout alleles. CRISPR/Cas9 is a powerful tool commonly used to induce loss‐of‐function mutations in vitro. However, CRISPR components have been difficult to deploy in vivo. To address this problem, we developed the CASAAV (CRISPR/Cas9/AAV‐based somatic mutagenesis) platform, in which recombinant adeno‐associated virus (AAV) is used to deliver tandem guide RNAs and Cre recombinase to Cre‐dependent Cas9‐P2A‐GFP mice. Because Cre is under the control of a tissue‐specific promoter, this system allows temporally controlled, cell type‐selective knockout of virtually any gene to be obtained within a month using only one mouse line. Here, we focus on gene disruption in cardiomyocytes, but the system could easily be adapted to inactivate genes in other cell types transduced by AAV. © 2017 by John Wiley & Sons, Inc.

Keywords: CRISPR; Adeno‐associated virus; Mouse model; Genetic mosaic; Cardiomyocyte

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Table of Contents

  • Introduction
  • Basic Protocol 1: Target and gRNA Selection
  • Basic Protocol 2: Construction and Delivery of AAV9 Vector
  • Basic Protocol 3: Immunostaining Isolated Cardiomyocytes
  • Commentary
  • Literature Cited
  • Figures
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Basic Protocol 1: Target and gRNA Selection

  • Computer with internet connection

Basic Protocol 2: Construction and Delivery of AAV9 Vector

  • gRNA oligonucleotides (from protocol 1)
  • Annealing buffer (10 mM Tris pH 8.0, 50 mM NaCl, 1 mM EDTA)
  • AAV‐U6gRNA1‐U6gRNA2‐TnT‐Cre vector (Addgene, cat. no. 87682)
  • AarI enzyme and buffer (Thermo Fisher, cat. no. ER1581)
  • SapI enzyme and buffer (NEB, cat. no. R0569L)
  • 6× DNA loading dye (NEB, cat. no. B7024S)
  • Agarose (GeneMate, cat. no. E‐3120‐500)
  • 50× TAE (Boston BioProducts, cat. no. BM250)
  • Ethidium bromide (Sigma‐Aldrich, cat. no. E7637)
  • Gel purification kit (Thermo Fisher Scientific, cat. no. K210012)
  • Chemically competent cells, e.g., MAX Efficiency Stbl2 Competent Cells (ThermoFisher, cat. no. 10268019).Recombination‐resistant bacteria are essential.
  • Quick ligation kit (NEB, cat. no. M2200L)
  • Ampicillin (Thermo Fisher, cat. no. 11593027)
  • LB agar plates with 100 µg/ml Ampicillin (Teknova, cat. no. L1004)
  • LB media (40 g/liter H 2O, Teknova, cat. no. L9115)
  • Miniprep kit (Thermo Fisher Scientific, cat. no. K210011)
  • TnT‐R sequencing primer, AGGGACTTCGGGCACAATCG
  • Midiprep kit (Thermo Fisher Scientific, cat. no. K210014)
  • Isoflurane (Baxter, cat. no. 10019‐360‐40)
  • PCR tubes
  • Thermal cycler
  • 37°C incubator
  • 37°C shaking incubator
  • Gel electrophoresis chamber
  • UV transilluminator (365 nm)
  • 42°C heat block or waterbath
  • Miniprep culture tubes (Corning, cat. no. 352059)
  • Nanodrop spectrophotometer (Thermo Fisher Scientific, cat. no. ND‐1000)
  • Isoflurane anesthesia setup (anesthesia machine, induction chamber, scavenging system).
  • 0.3‐ml syringes (XELINT, cat. no. 26200)
  • Rosa26Cas9‐GFP mice (Jackson Laboratory, cat. no. 026175)
  • Additional reagents and equipment for AAV production and purification (unit 23.16; Wakimoto, et al., ).

Basic Protocol 3: Immunostaining Isolated Cardiomyocytes

  • 1 mg/ml laminin (Corning, cat. no. 354239) in PBS
  • PBS (Thermo Fisher Scientific, cat. no. 10010‐023)
  • AAV‐treated Rosa26Cas9‐GFP mice (from protocol 2)
  • Blebbistatin (EMD Millipore, cat. no. 203390)
  • Dulbecco's modified Eagle's medium (DMEM), high glucose (Gibco, cat. no. 11995‐065)
  • 4% paraformaldehyde (PFA; Electron Microscopy Sciences, cat. no. 15710), diluted in PBS
  • PBST: PBS containing 0.1% Triton X‐100 (Sigma‐Aldrich, cat. no. T9284)
  • Block solution: PBS containing 4% BSA (Sigma‐Aldrich, cat. no. A3912‐1006)
  • Prolong Diamond Antifade Mountant (Thermo Fisher Scientific, cat. no. P36961)
  • Primary antibody
  • Secondary antibody
  • Round coverslips (Fisher Scientific, cat. no. 50‐121‐5159)
  • 24‐well dishes (Corning, cat. no. 3526)
  • Coverglass forceps (Fine Science Tools, cat. no. 11074‐02)
  • 27‐gauge needle (BD Biosciences, cat. no. 305136)
  • 37°C, humidified CO 2 incubator
  • Langendorf perfusion apparatus and materials for collagenase perfusion (O'Connell et al., ).
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Literature Cited

Literature Cited
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  Guo, Y., VanDusen, N. J., Zhang, L., Gu, W., Sethi, I., Guatimosim, S., … Pu, W. T. (2017). Analysis of cardiac myocyte maturation using CASAAV, a platform for rapid dissection of cardiac myocyte gene function in vivo. Circulation Research, 120, 18741888. doi: 10.1161/CIRCRESAHA.116.310283.
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  Prasad, K. M. R., Xu, Y., Yang, Z., Acton, S. T., & French, B. A. (2011). Robust cardiomyocyte‐specific gene expression following systemic injection of AAV: In vivo gene delivery follows a Poisson distribution. Gene Therapy, 18, 43–52. doi: 10.1038/gt.2010.105.
  Prendiville, T. W., Guo, H., Lin, Z., Zhou, P., Stevens, S. M., He, A., … Pu, W. T. (2015). Novel roles of GATA4/6 in the postnatal heart identified through temporally controlled, cardiomyocyte‐specific gene inactivation by adeno‐associated virus delivery of Cre recombinase. PLoS One, 10, e0128105. doi: 10.1371/journal.pone.0128105.
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  Wakimoto, H., Seidman, J. G., Foo, R. S. Y., & Jiang, J. (2016). AAV9 Delivery of shRNA to the Mouse Heart. Current Protocols in Molecular Biology, 115, 23.16.21–23.26.29. doi: 10.1002/cpmb.9.
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