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Optimization of AsCas12a for combinatorial genetic screens in human cells.

Nature biotechnology | 2021

Cas12a RNA-guided endonucleases are promising tools for multiplexed genetic perturbations because they can process multiple guide RNAs expressed as a single transcript, and subsequently cleave target DNA. However, their widespread adoption has lagged behind Cas9-based strategies due to low activity and the lack of a well-validated pooled screening toolkit. In the present study, we describe the optimization of enhanced Cas12a from Acidaminococcus (enAsCas12a) for pooled, combinatorial genetic screens in human cells. By assaying the activity of thousands of guides, we refine on-target design rules and develop a comprehensive set of off-target rules to predict and exclude promiscuous guides. We also identify 38 direct repeat variants that can substitute for the wild-type sequence. We validate our optimized AsCas12a toolkit by screening for synthetic lethalities in OVCAR8 and A375 cancer cells, discovering an interaction between MARCH5 and WSB2. Finally, we show that enAsCas12a delivers similar performance to Cas9 in genome-wide dropout screens but at greatly reduced library size, which will facilitate screens in challenging models.

Pubmed ID: 32661438 RIS Download

Research resources used in this publication

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Antibodies used in this publication

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Associated grants

  • Agency: NHLBI NIH HHS, United States
    Id: P01 HL142494
  • Agency: NCI NIH HHS, United States
    Id: R00 CA218870
  • Agency: NIAID NIH HHS, United States
    Id: U19 AI133524

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This is a list of tools and resources that we have found mentioned in this publication.


HEK293T (tool)

RRID:CVCL_0063

Cell line HEK293T is a Transformed cell line with a species of origin Homo sapiens (Human)

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A-549 (tool)

RRID:CVCL_0023

Cell line A-549 is a Cancer cell line with a species of origin Homo sapiens (Human)

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HT-29 (tool)

RRID:CVCL_0320

Cell line HT-29 is a Cancer cell line with a species of origin Homo sapiens (Human)

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A-375 (tool)

RRID:CVCL_0132

Cell line A-375 is a Cancer cell line with a species of origin Homo sapiens (Human)

View all literature mentions

OVCAR-8 (tool)

RRID:CVCL_1629

Cell line OVCAR-8 is a Cancer cell line with a species of origin Homo sapiens (Human)

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