Harvard College

Liu, David R.

Guilinger, John Paul

Pattanayak, Vikram

Vikram Pattanayak

David R Liu

John Paul Guilinger

Engineered nucleases are promising tools for genome manipulation and determining off-target cleavage sites of these enzymes is of great interest. This disclosure provides in vitro selection methods that interrogate 10DNA sequences for their ability to be cleaved by active nucleases, e.g., ZFNs and TALENs. The method revealed hundreds of thousands of DNA sequences that can be cleaved in vitro by two ZFNs, CCR5-224 and VF2468, which target the endogenous human CCR5 and VEGF-A genes, respectively. Analysis of the identified sites in cultured human cells revealed CCR5-224-induced mutagenesis at nine off-target loci. This disclosure provides an energy compensation model of ZFN specificity in which excess binding energy contributes to off-target ZFN cleavage. It was also observed that TALENs can achieve cleavage specificity similar to or higher than that observed in ZFNs.

Evaluation and improvement of nuclease cleavage specificity

Some aspects of this disclosure provide strategies, methods, and reagents for determining nuclease target site preferences and specificity of site-specific endonucleases. Some methods provided herein utilize a novel 'one-cut' strategy for screening a library of concatemers comprising repeat units of candidate nuclease target sites and constant insert regions to identify library members that can been cut by a nuclease of interest via sequencing of an intact target site adjacent and identical to a cut target site. Some aspects of this disclosure provide strategies, methods, and reagents for selecting a site-specific endonuclease based on determining its target site preferences and specificity. Methods and reagents for determining target site preference and specificity are also provided.

Nuclease profiling system

Engineered transcriptional activator-like effectors (TALEs) are versatile tools for genome manipulation with applications in research and clinical contexts. One current drawback of TALEs is their tendency to bind and cleave off-target sequence, which hampers their clinical application and renders applications requiring high-fidelity binding unfeasible. This disclosure provides engineered TALE domains and TALEs comprising such engineered domains, e.g., TALE nucleases (TALENs), TALE transcriptional activators, TALE transcriptional repressors, and TALE epigenetic modification enzymes, with improved specificity and methods for generating and using such TALEs.

Engineered transcription activator-like effector (TALE) domains and uses thereof

Some aspects of this disclosure provide strategies, methods, and reagents for determining nuclease target site preferences and specificity of site-specific endonucleases. Some methods provided herein utilize a novel 'one-cut' strategy for screening a library of concatemers comprising repeat units of candidate nuclease target sites and constant insert regions to identify library members that can been cut by a nuclease of interest via sequencing of an intact target site adjacent and identical to a cut target site.

Methods for identifying a target site of a CAS9 nuclease

Engineered nucleases (e.g., zinc finger nucleases (ZFNs), transcriptional activator-like effector nucleases (TALENs), and others) are promising tools for genome manipulation and determining off-target cleavage sites of these enzymes is of great interest. We developed an in vitro selection method that interrogates 10DNA sequences for their ability to be cleaved by active, dimeric nucleases, e.g., ZFNs and TALENs. The method revealed hundreds of thousands of DNA sequences, some present in the human genome, that can be cleaved in vitro by two ZFNs, CCR5-224 and VF2468, which target the endogenous human CCR5 and VEGF-A genes, respectively. Our findings establish an energy compensation model of ZFN specificity in which excess binding energy contributes to off-target ZFN cleavage and suggest strategies for the improvement of future nuclease design. It was also observed that TALENs can achieve cleavage specificity similar to or higher than that observed in ZFNs.

Engineered nucleases are promising tools for genome manipulation and determining off-target cleavage sites of these enzymes is of great interest. We developed an in vitro selection method that interrogates 10DNA sequences for their ability to be cleaved by nucleases. The method revealed hundreds of thousands of DNA sequences that can be cleaved in vitro by two ZFNs, CCR5-224 and VF2468, which target the endogenous human CCR5 and VEGF-A genes, respectively. Analysis of the identified sites in cultured human cells revealed CCR5-224-induced mutagenesis at nine off-target loci. Similarly, we observed 31 off-target sites cleaved by VF2468 in cultured human cells. Our findings establish an energy compensation model of ZFN specificity in which excess binding energy contributes to off-target ZFN cleavage and suggest strategies for the improvement of future nuclease design. It was also observed that TALENs can achieve cleavage specificity similar to or higher than that observed in ZFNs.

Growing community of inventors

Cambridge, MA, United States of America

Vikram Pattanayak