Cell genomicsMar 26, 2026

Balancing unwanted and intended effects to improve CRISPR-Cas9 gene knockout tools

CRISPR Gene Editing Weekly Brief ↗PubMed ↗DOI ↗

Updated Jun 27, 2026

Abstract

Essence

A CRISPR guide-selection framework balances off-target exclusion with on-target activity for compact knockout libraries.

Evidence

This genome-wide library design and validation resource presents the human Jacquere and mouse Julianna CRISPR-Cas9 knockout libraries for large-scale functional screens.

Caveat

The abstract describes library construction and validation, not performance across all downstream screen readouts or biological contexts.

Simplified

The continued development of high-dimensional CRISPR screen readouts, such as single-cell RNA sequencing and high-content imaging, necessitates compact libraries to enable functional interrogation at genome scale. Improved genome annotations cause library deprecation over time, further motivating an updated genome-wide design effort. Additionally, while on-target efficacy and off-target avoidance are often optimized in isolation, we lack a robust framework for simultaneously weighing and balancing these competing priorities. Here, we present a selection strategy that identifies guides with sufficient off-target activity to justify omission from the library, thus avoiding the unnecessary exclusion of active guides, allowing the inclusion of those with maximal on-target activity. We create, validate, and make available to the community the Jacquere library for knockout screens of the human genome, as well as its mouse counterpart, Julianna, to facilitate gene function discovery at scale.