CRISPR/Cas9-mediated knock-in of an optimized TetO repeat for live cell imaging of endogenous loci

Nucleic Acids Res. 2018 Sep 28;46(17):e100. doi: 10.1093/nar/gky501.

Abstract

Nuclear organization has an important role in determining genome function; however, it is not clear how spatiotemporal organization of the genome relates to functionality. To elucidate this relationship, a method for tracking any locus of interest is desirable. Recently clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) or transcription activator-like effectors were adapted for imaging endogenous loci; however, they are mostly limited to visualization of repetitive regions. Here, we report an efficient and scalable method named SHACKTeR (Short Homology and CRISPR/Cas9-mediated Knock-in of a TetO Repeat) for live cell imaging of specific chromosomal regions without the need for a pre-existing repetitive sequence. SHACKTeR requires only two modifications to the genome: CRISPR/Cas9-mediated knock-in of an optimized TetO repeat and its visualization by TetR-EGFP expression. Our simplified knock-in protocol, utilizing short homology arms integrated by polymerase chain reaction, was successful at labeling 10 different loci in HCT116 cells. We also showed the feasibility of knock-in into lamina-associated, heterochromatin regions, demonstrating that these regions prefer non-homologous end joining for knock-in. Using SHACKTeR, we were able to observe DNA replication at a specific locus by long-term live cell imaging. We anticipate the general applicability and scalability of our method will enhance causative analyses between gene function and compartmentalization in a high-throughput manner.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Bacterial Proteins / genetics*
  • CRISPR-Cas Systems* / genetics
  • Carrier Proteins / genetics*
  • Clustered Regularly Interspaced Short Palindromic Repeats / genetics
  • DNA End-Joining Repair / genetics
  • DNA Repeat Expansion / genetics
  • Gene Knock-In Techniques / methods*
  • HCT116 Cells
  • HEK293 Cells
  • Humans
  • In Situ Hybridization, Fluorescence / methods*
  • K562 Cells
  • Organisms, Genetically Modified
  • Sequence Homology, Nucleic Acid
  • Single Molecule Imaging / methods*

Substances

  • Bacterial Proteins
  • Carrier Proteins
  • Tet O resistance protein, Bacteria