CRISPR Gene Editing Causes Unintended DNA Damage

This genetic study published in Nature Biotechnology revealed that CRISPR-Cas9 gene editing — widely promoted as a precise 'molecular scissors' technology — causes significant unintended DNA damage at and around the target site. The researchers found large deletions, complex rearrangements, and insertions extending thousands of base pairs from the intended edit site.

Using whole-genome sequencing (rather than the short-range PCR methods typically used to verify CRISPR edits), the study detected extensive on-target mutagenesis that had been missed by standard quality control methods. These unintended mutations could alter the expression of nearby genes or create novel proteins with unknown effects.

The findings have major implications for CRISPR-edited food crops and animals entering the food supply, particularly because many regulatory agencies have exempted CRISPR-edited organisms from GMO regulations on the basis that the edits are precise and predictable.

Key Findings

• •CRISPR-Cas9 caused large deletions of up to several thousand base pairs at target sites.
• •Complex DNA rearrangements and insertions were found near intended edit sites.
• •Standard short-range PCR quality checks failed to detect the majority of unintended mutations.
• •Whole-genome sequencing revealed a much higher rate of mutagenesis than previously reported.
• •The findings undermine the regulatory basis for exempting CRISPR-edited organisms from GMO oversight.

Methodology

Mouse embryonic stem cells and human differentiated cells were edited using CRISPR-Cas9 targeting specific genes. Genomic DNA from edited cells was analyzed using both standard short-range PCR (the typical verification method) and long-range PCR followed by whole-genome sequencing. Mutations were cataloged by type, size, and distance from the target site.

Why This Matters for Families

CRISPR-edited foods are being introduced into the food supply without GMO labeling because regulators consider them 'precise.' This study shows they are not. Families concerned about genetic modification in food should be aware that gene-edited foods may soon be unlabeled in grocery stores, making organic certification the only reliable way to avoid them.