Although CRISPR knockout screening has provided a powerful and precise solution to identify and validate novel drug targets, and to elucidate unknown drug mechanisms, there are some biological studies for which CRISPR knockout screens are not applicable. CRISPRa (and CRISPRi) screening opens up many new possibilities.

What is CRISPRa?

CRISPR activation (CRISPRa) screening provides the capacity to study gain of gene function which allows us to broaden the range of possible applications. They can power our customers’ discovery and drug development programs by offering the highest quality and highest confidence in their screening results

In combination with CRISPRi, our CRISPRa screen can reveal ‘switch’ like genes that display opposing effects when activated or inhibited in the presence of the drug of interest, bringing the prospect of unambiguous target discovery closer.

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Horizon's CRISPRa Screening Tools


  • Study gain-of-function effects on a genome-wide scale
  • Explore drug-gene interactions by studying gain-of-function phenotypes
  • Validate loss-of-function effects with a reverse-function orthologous tool
  • Combine with CRISPRi screening for network analysis
CRISPRa screening platform

Our CRISPRa screening platforms are based on Horizon’s highly sophisticated CRISPR KO screening platform, which has been used in over 200 screens to date.

  • Pooled lentiviral approach
  • Cell line(s) from a pre-optimised cell line list or cell line evaluation prior to the screen
  • Human whole-genome CRISPRa library or custom designed sub library
  • Custom screen design
  • Next-generation sequencing + bioinformatics analysis + hit nominations
  • Timeline 12-24 weeks
  • A list of genes of which inhibition/activation alters response to the compound of interest
  • A final report containing experimental design, all raw & analysed data and conclusions of the study
Learn more about our CRISPR platforms and screening

Explore our platforms by watching our recorded webinar on CRISPRi & CRISPRa screening:

Whole-genome CRISPRa resistance screens in melanoma cells

Proof of concept studies to identify resistance factors against a BRAF kinase inhibitor Vemurafenib (PLX-4032) in A375 melanoma cells that carry a BRAF V600E mutation.

  • Whole-genome CRISPRi or CRISPRa sgRNA libraries
  • Pooled-based approach: lentivirus transduction of the library into cells followed by selection
  • Treatment with Vemurafenib
  • Cell pellet collection and sample preparation
  • NGS and data analysis using an adapted MAGeCK workflow


  • Highlighted hits have been previously identified and validated by CRISPRa screening (Konermann et al., 2014)
  • Top hit EGFR was enriched by over 16,000-fold
  • CRISPRa screening platform was more sensitive than previously published platforms
  • Multiple novel hits were also identified

Download the complete application note:

CRISPRa screening app note

Get expert advice and help for your next CRISPR screening project:

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