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Enabling large-scale genome editing at repetitive elements by reducing DNA nicking.

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Dead-Cas9 base editors (dBEs) enable large-scale genome editing of repetitive elements in mammalian cells. This new technology overcomes cell death barriers, allowing precise mutations at thousands of loci.

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Area of Science:

  • Genetics
  • Molecular Biology
  • Biotechnology

Background:

  • Genome editing technologies are crucial for biological research and therapeutic development.
  • Editing repetitive genomic elements presents significant challenges due to potential toxicity and off-target effects.
  • Existing base editors face limitations in scalability and survival rates for large-scale editing.

Purpose of the Study:

  • To develop and validate novel dead-Cas9 base editor (dBE) variants for efficient editing of repetitive elements in mammalian genomes.
  • To overcome cell death associated with DNA breaks during large-scale genome engineering.
  • To significantly increase the number of editable loci per cell.

Main Methods:

  • Utilized a set of dead-Cas9 base editor (dBE) variants.
  • Employed guide RNAs (gRNAs) targeting repetitive elements with varying copy numbers (32 to 161,000 per cell).
  • Assessed cell survival and mutation efficiency in 293T cells and human induced pluripotent stem cells (hiPSCs).

Main Results:

  • dBEs enabled survival after large-scale base editing, overcoming toxicity barriers.
  • Achieved targeted mutations at up to ~13,200 loci in 293T cells and ~12,200 loci in hiPSCs.
  • Demonstrated a three-orders-of-magnitude increase in editable loci compared to previous methods.

Conclusions:

  • The developed dBEs significantly extend the capabilities of genome editing, particularly for repetitive elements.
  • This approach overcomes critical barriers to cell survival, enabling unprecedented scale in genome engineering.
  • dBEs offer a powerful tool for future research and therapeutic applications involving large-scale genomic modifications.