‘Gene Scissors’ cause chaotic disturbance in plant genome

Recent publications show that the application of gene scissors in plants is associated with a much higher risk of in-depth genomic disturbances than previously thought. Large areas of the genome can be involved.

Chromothripsis-like effects play a decisive role in this context. Chromothripsis refers to a phenomenon in which several hundred genetic changes can occur simultaneously in a 'catastrophic' event. Many sections of the genetic material can be swapped, twisted, recombined or even lost if this occurs. It was already known that these effects can be triggered by the use of CRISPR/Cas gene scissors in mammalian (and human) cells. Now, for the first time, chromothripsis-like effects have also been demonstrated in plants following the use of CRISPR/Cas gene scissors.

The exact mechanisms of chromothripsis are not yet fully understood. However, it is known that the simultaneous break of both strands of the genetic material can be a trigger for these chaotic effects. When both strands of DNA are cut, as is typically the case with the CRISPR/Cas gene scissors, the chromosomes lose contact with the ends that were separated in this process. If the repair of the break in the chromosomes fails, the separated end can be lost, or restructured and also incorporated elsewhere.

The use of gene scissors significantly increases the frequency of chromothripsis occurring. In addition, there is an increased probability that specific protected sites in the genome can be affected. The potential undesirable consequences include a wide range of risks such as disruption of plant health, altered interactions of the plants with the environment and undesirable changes in plant composition.

The results now available shed new light on the alleged precision of the gene scissors: New Genetic Engineering (New GE) can be used to target specific sites in the genome in order to knock out gene functions. However, the consequences of these 'cuts' into the genome are not predictable and cannot
be controlled. Unintended genetic changes can affect large sections of chromosomes. Plants obtained from New GE procedures cannot therefore be considered 'safe', and risks must be thoroughly examined.