CRISPR Rice

Risks of unintended changes

Experimental evidence shows that New Genetic Engineering processes unintentionally cause genetic changes linked to novel hazard potential. Although there are only a small number of research projects on this topic, studies on rice, rapeseed, wheat and fish, amongst others, show that both the intended and unintended changes induced by the genetic scissors have a novel and specific risk potential.

An example: scientists in China altered the genome of rice using CRISPR/Cas gene scissors to induce smaller growth in the plants, but also produce higher yield. The focus of these particular experiments was, however, not on the intended altered characteristics of the rice plants, but on the unintended changes in the genome caused by the gene scissors. The investigation showed that the intervention into the rice genome was by no means precise.

So-called off-target effects were found in DNA regions that were very similar to the actual target sequence. This is because the genetic scissors can confuse these off-target regions with the target sequence and unintentionally cut at these sites. The scientists used PCR methods to specifically check for such off-target regions in the CRISPR rice. These investigations revealed off-target changes in some of the plants. There are even more precise analyses (so-called whole genome sequencing methods) available to check the whole genome for off-target effects. This, however, involves a more technically complex process and takes longer than the conventional PCR analysis. In the case of CRISPR rice, only PCR analyses were carried out.

When the target sequence was examined in various CRISPR rice plants, different changes were found. Basically, most of the modifications mediate the desired effect, i.e. the target gene is knocked out. However, it can also happen that the DNA change causes the formation of new, undesirable gene products. In one rice variety, the target sequence was altered in such a way that a novel, truncated protein was unintentionally formed. Large, unintended restructuring of the target region was also found, as has already been described several times in human and animal cells.

In addition, there is further source of error relating to unintentional genetic changes: before the genetic scissors can cut, they must first be introduced into thecells. In the case of plants, this is often done using older genetic engineering methods and with auxiliaries, such as genes from soil bacteria. As a result, the process causes additional genes to be unintentionally inserted into the plant genome. Such DNA fragments were also found in the CRISPR rice.

This example shows: If genetic engineering methods are used in plants important for agriculture, all resulting organisms must be thoroughly examined for their risks.

 

Publication year: 
2021