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« Gene Editing »

“Gene-editing” or “genome-editing” describes a range of new techniques to alter the genetic material of plants, animals, and microbes, such as bacteria. The most common of these techniques currently used in experiments is called CRISPR. The techniques raise many of the same risk questions as earlier techniques of genetic engineering, and raise the same environmental, social, economic and ethical concerns.

The new techniques can make it easier and faster to genetically engineer (genetically modify) a wider range of organisms, for more purposes. They are powerful research tools that are being used to better understand gene function and, in particular, to genetically modify mice and other research animals to study human diseases. They are also being used to promise new GM foods. The biotechnology industry argues that gene editing should not be classified as genetic modification, and should not be regulated or labelled.

Updates

Research undertaken by experts at the US Food and Drug Administration found errors in the genome of cows genetically engineered to not grow horns. The cows have for some years been held up as a positive example of the application of new gene editing techniques but the gene-editing has resulted in major unintended effects:

  • Read the paper Template plasmid integration in germline genome-edited cattle, Alexis L. Norris et al, July 2019: « We analyzed publicly available whole genome sequencing data from cattle which were germline genome-edited to introduce polledness. Our analysis discovered the unintended heterozygous integration of the plasmid and a second copy of the repair template sequence, at the target site. Our finding underscores the importance of employing screening methods suited to reliably detect the unintended integration of plasmids and multiple template copies. »
  • « No matter how « precise » the initial gene-editing event is in terms of location, undesirable outcomes can occur at the intended site stemming from the DNA repair processes that follow the cutting of the DNA by the editing tool. The findings described in the paper by the US FDA scientists are yet another illustration that looking only for off-target effects from a gene-editing procedure is not enough to identify the full spectrum of undesirable outcomes, which can occur even at the intended gene-editing site. » – from Gene-edited hornless cattle: Flaws in the genome overlooked, GMWatch, August 9, 2019.
  • « …the new FDA finding demonstrates is that the Recombinetics gene-edited cattle do contain DNA unnatural to cattle, despite the claims of their developers to the contrary. Thus FDA does have the authority to regulate. » – from FDA Finds Unexpected Antibiotic Resistance Genes in ‘Gene-Edited’ Dehorned Cattle by Jonathan Latham, PhD & Allison Wilson, PhD, Independent Science News, August 12, 2019.
  • Background on the company Recombinetics from Testbiotech.

Background

“Gene editing” or “genome editing” refers to the modification of the genome at a specific, targeted location. Using enzymes that act as molecular scissors to cut DNA along with natural DNA repair mechanisms of cells, the genome can be modified by adding, deleting or altering parts of the DNA sequence. This can be distinguished from approaches that introduce new genetic material into unspecified locations within the genome, though most genome editing techniques still use familiar genetic engineering tools such as the use of recombinant DNA (a combination of DNA elements from multiple sources) and also involve transformation of plant cells (uptake of the DNA by a cell).

As seen with previous genetic engineering (genetic modification or GM) techniques, the disruption of the genome via genetic engineering can have long-distance effects on the balance of global expression of genes.

Claims that these technologies are safer than other GM techniques are unproven. Each gene editing technique each bring their own set of risks and uncertainties. Whilst many of these are the same as with older genetic engineering techniques, there are also serious additional concerns. There is a strong scientific case for classifying all these techniques as genetic engineering (genetic modification or GM) and regulating their use with as much rigour as previous and current GM techniques.

Is gene editing precise?

The term “editing” is misleading because it implies a level of precision that is not currently, and may never be possible. It suggests the ability to rewrite the genetic code and to simply cut and paste DNA but, in reality, the results are still determined by processes in the organism that we neither fully understand nor control.

It is commonly said that gene editing is capable of creating precise, accurate and specific alterations to DNA but this is technically inaccurate. Gene editing can more efficiently target sites in the genome but the enzymes used in gene editing have been shown to cut DNA in the wrong spots and create off-target mutations. After a cut is made, the cell’s DNA repair mechanisms are in control of what happens next for the organism. The results are alterations – such as deletions, insertions, and rearrangements – at the intended site, but also at unintended, off-target sites.

Precise edits, even if possible, do not necessarily yield precise outcomes. Even a simple genetic “tweak” can have wide-ranging effects on an organism’s genome.

Unexpected effects

Any attempt to engineer genomes with such invasive methods can cause unexpected and unpredictable effects.

Unexpected large deletions or rearrangements of DNA can take place at the intended editing site or elsewhere, and can disrupt the function of non-target genes. Unwanted changes may slip by undetected. Even the intended alteration can inadvertently alter other important genes, causing changes in chemistry or protein production that can be important for food and environmental safety. Gene editing may also have unintended impacts on an organism’s ability to express or suppress other genes. The orchestration of gene function in an organism is part of a complex regulatory network that is poorly understood.

Regulation

The biotechnology industry argues that gene editing should not be classified as genetic modification and that the products should therefore be exempt from regulation.

In July 2018, the European Court of Justice ruled that « gene edited » organisms (obtained by directed mutagenesis techniques) are genetically modified organisms (GMOs) and therefore subject to existing GMO regulations.

Canada assesses the risks of genetically engineered organisms under regulations for « Novel Foods” and “Plants with Novel Traits”. Most, but not necessarily all, gene edited products will be covered by these regulations because the Canadian government regulates products if they have a “novel” trait, regardless of the process used to make them.

The U.S. government is not conducting risk assessments before gene edited products are approved. European regulations for genetically modified organisms cover gene editing.

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