Prepared by Angela Ryan
The Right Honorable Michael Meacher, Minister for the Environment
Professor Don Grierson, Plant Molecular Geneticist, Nottingham
A group of scientists (see above) were invited to the DETR by the Right Honorable Michael Meacher. The agenda was set to discuss the special safety concerns raised by the effects of random insertion of DNA vectors and horizontal gene transfer.
Following formal introductions the minister asked the scientists: does GM raise issues beyond conventional breeding practices?
Dr Phil Dale responded first and spoke of how GM was no different from conventional breeding practices except that it is more precise. In conventional breeding, seeds are irradiated to cause mutations at points all along the germ line DNA. Following germination the seedlings undergo analysis and selection protocols which eventually lead to the isolation of varieties that can be used in farming. With GM a specific gene can be inserted in a single copy so that a specific desired trait can be introduced into an organism. The site of insertion is determined using southern blotting and the chromosomal location is also determined using fluorescent in situ hybridization (FISH). The expression pattern of the insert is analysed over many generations to demonstrate that it is completely stable and has become a constitutive part of that organism. GM is much more precise and therefore safer than conventional breeding.
Dr. Mae-Wan Ho disagreed. GM technology is not at all precise. She identified four special safety concerns arising from current transgenic technologies.
Dr Michael Antonio explained the way in which genes work in genomes. Genes do not function in isolation, they work in groups and are highly integrated with one another. They are constantly interacting and are under strict molecular control where genomic position is important. There are regions of active transcription where genes are being transcribed and there are silent regions where no transcription is taking place. A gene vector can land in either region but in order for it to be actively transcribed it must land in a region of active transcription. Random insertion can cause insertion mutagenesis and it is well understood that many viral induced cancers are caused in this way. Insertion may also disrupt the gene regulation and natural groupings of the genes that are functional in the region of insertion. The use of strong promoters and enhancers in the vectors may cause metabolic stress to the transformants. Both these factors may lead to the emergence of novel toxins or allergens and there is no way to predict this at present for we are in the early days of understanding gene function. In convention breeding, the natural order or groupings of the genes is not disturbed. Point mutations may result in changes to the amino acid sequence of the gene products but that does not interfere with the natural groupings of the genes and alleles, which we know to be vital to gene regulation. There are just too many unknowns at present.
The Right Honorable Michael Meacher then made the point that novel toxins and allergens may occur in organisms being produced via conventional breeding as well and perhaps further scientific study should have been done on organisms being produced in this way?
Dr Michael Antonio and Dr Mae-wan Ho both agreed that this is a very valid point.
Dr Phil Dale reasserted his view that although the GM constructs are inserted randomly at first, further analysis via southern blotting and FISH isolates the precise region in the genome and on which chromosome the insert has integrated.
Dr Michael Antonio replied and said that without further gene mapping work it is impossible to understand how the act of insertion is affecting the recipient genomes gene expression. The full extent of gene regulation is yet to be elucidated and the effects of insertion on the recipient genome will be largely unknown until we have gained a better understanding of gene function. Knowing where an insert is on a southern blot and which chromosome it is on, does not constitute knowing where it is in the recipient genome's gene regulation system. He then strongly recommends further research in gene mapping in order to understand this important safety aspect of GM.
Dr Ian Garner stated that it has been known for many years, from the work of Barbara Maclintock, that genomes are fluid and dynamic. GM is doing nothing more beyond what nature has been doing for millions of years.
Dr Andrew Lilly added that the rate of evolution in bacteria is incredibly rapid and that they are constantly changing their gene expression. His colleague, Dr Mark Bailey reasserted that GM is merely utilising an already well established natural system.
Dr Mae-wan Ho agreed that bacteria evolved rapidly and drew attention to a paper by J. de Vries & W. Wackernagel, Mol. Gen.. Genet.. (1998) 257: 606-613 regarding transfer frequency from transgenic plant DNA to soil bacteria. She pointed out that in transgenic potatoes, as little as 18 ng of potato DNA (2.5 x 10 3 genome equivalents, each with one copy of an the Kanamycin-resistant gene npt11) was required to produce one kanamycin-resistant bacterial transformant. She added that GM may greatly accelerate the rate of horizontal gene transfer and enlarge it's scope.
Dr Mark Bailey said he knew about this paper because he reviewed it and he knows the authors personally. He warns we must be careful about misinterpreting this paper. These experiments were conducted under strict laboratory conditions and the plasmids were designed to have homology with the Kanamycin-resistant gene within the transgenic plant DNA. This would not occur normally in the wild in the absence of such specific homology.
Angela Ryan questioned this remark and stated that many gene constructs used in GM do contain, to a greater or lesser degree, plasmid DNA, viral DNA especially viral promoters e.g. CaMV promoter, long terminal repeats (LTRs) and left and right borders, all of which are highly conserved and may in theory find sequence homology in the wider environment.
Dr. Phil Dale remarked that just because it happens in the laboratory does not mean it happens in nature.
Dr Mae-Wan Ho asked whether he could guarantee it will never take place in nature, and added that although these experiments were conducted in the laboratory the system used was actually adapted to natural transformation and therefore could take place in the wild. Furthermore, homology is not neccessary for successful horizontal gene transfer. Many insertions into the genome happen without sequence homology, especially those involved in making transgenic organisms.
The Right Honorable Michael Meacher then asked just how much evidence will be needed before we can be sure that GMOs are safe? And how long will it be until such time, five or maybe ten years?
Dr Mae-wan Ho responded and confirmed that there are many unanswered questions surrounding GMOs and that is imperative that the precautionary principle be applied. An inverse precautionary principle has been at work regarding GMOs to date. She recommended an immediate ban on all commercial plantings of GMO crops and called for a five year moratorium in order to further identify the risks and conduct the necessary experimental research. A full independent inquiry into the future of agriculture and food security for all was also needed.
Dr Ian Garner and Dr Phil Dale said they did not believe a moratorium was necessary.
Steven Tindale then asks about the CaMV promoter and its affects?
Dr Phil Dale said that we eat the CaMV all the time and it is present in many of the vegetables that make up our staple diet. It does not have any harmful effects.
Dr Mae-wan Ho refuted this remark and said that there is a great difference between the CaMV we may eat everyday in vegetables and the CaMV promoter used in GMOs. Viruses are protected in the environment by a protein coat which also confers species specificity. The CaMV cannot enter mammalian cells because it's protein coat is specific to plant cells. The CaMV promoter used in GMOs however, comes in the form of naked viral DNA and naked DNA of any sort is highly infectious. The CaMV promoter is also highly conserved and has been shown to have sequence homology with other viruses. It is closely related to human Hepatitis B virus and also to retroviruses like HIV. It is a very strong promoter, it shouts in a recipient genome to be transcribed and that is why it is so widely used. It may recombine with latent or infecting viruses within the host or beyond and give rise to new super-viruses. The wide use of the CaMV promoter alone carries enough risk to impose an immediate moratorium on GMOs.
The Right Honorable Michael Meacher then asked the scientists for their views on Dr Pusztai's results.
Dr Ian Garner stated that we must be very careful not to take too seriously experimental data that has not been peer reviewed.
Dr Mae-wan Ho refuted this remark and explained that Pusztai's work has been peer reviewed by 20 scientists who confirmed his results as significant.
Dr Phil Dale added that lectins are well-known toxins and therefore the result is not unusual considering this.
Dr Michael Antonio clarified this comment and said that the snowdrop lectin had been specifically selected because it had no toxicity in mammalian cells, it was only toxic to insects. He explained that the transgenic potato contained the snowdrop lectin to confer insect resistance.
Angela Ryan then added that Dr Pusztai's experiments were designed to develop new methods of testing GM food. He had worked for seven years on this and was alarmed by the results he found. The symptoms observed in the rats were consistent with viral infection.
Dr Phil Dale and Dr Ian Garner said they did not believe this.
Dr Mae-wan Ho confirmed that the rats had reduced weight in vital organs, impairment of immunological responsiveness and signs suggestive of viral infection.
Steven Tindale then asked if other feeding experiments have been conducted?
Dr Phil Dale explained that because GM food is completely digested in the gut, feeding experiments had been considered unnecessary, although he wasn't sure what had happened in America. Nobody had died yet from eating GM food and he believes it to be perfectly safe.
Dr Mae-wan Ho confirmed that Dr Pusztai's experiments were the first comprehensive feeding experiments to be conducted. She refuted the claim that GM food is completely digested in the gut and referred to evidence which demonstrates that viral and plasmid DNA fed to mice had been found to resist digestion in the gut. Large fragments passed into the bloodstream and entered white blood cells, spleen and liver cells. It was found attached to mouse DNA, suggesting integration, and when fed to pregnant mice it was found in the nucleus of cells of the foetus and new-born. She warned that if GM foods were having ill-effects on the public we would not know about them as no one is monitoring for such effects. She pointed to the catastrophic thalidomide incident in which 8000 babies with truncated limbs were born before thalidomide was admitted as the harmful agent. Dr Pusztai's work should be repeated and not be dismissed in anyway.
The Right Honorable Michael Meacher confirmed that the Government was taking Dr Pusztai's experiments very seriously and would certainly not dismiss them.
At this point the meeting came to and end and Michael Meacher thanked all the scientists for coming along and giving their time. He said he has come to a better understanding of the complications regarding GMOs now, and that he would welcome further help and advise.
** NOTICE: In accordance with Title 17 U.S.C. Section 107, this material is distributed for research and educational purposes only. **
Last Updated on 5/27/99
By Karen Lutz