3.6—Barnase in GM crops will not cause kidney damage


Barnase in GM crops will not cause kidney damage

See Genetic Roulette’s False Claims at Bottom of Page

Analysis of Peer-Reviewed Research:

The Barnase story told by Jeffrey Smith is a perfect example of the pseudo-scientific deception that is typical of Genetic Roulette. Barnase kills cells when it is produced in the cell or injected into the cell.  That is why the developer used Barnase—to kill certain cells.  Tests show Barnase is not present in grain from plants that contain the gene so we would never be exposed to any significant or even measurable amount of Barnase (note that we are careful here not to say zero because it is possible that infinitesimal amounts that are below what science can measure might be present).  There is no evidence that Barnase is toxic when administered in food or feed.  In fact, grain products containing Barnase have been studied in animals where they caused no ill effect—which Smith neglects to tell the reader. The fact that these products have been consumed around the world by millions and millions of animals and humans with no ill effect does suggest that the products are safe.

  1. When kidneys were perfused with solutions containing large amounts of Barnase, toxic effects were noted. As stated in Genetic Roulette, there is little doubt that if Barnase is produced in a cell or organ, or if it is injected or perfused (that is, forcing a large amount of fluid containing Barnase though the organ), it is toxic and potentially lethal (Ilinskaya and others 1997, Prior and others 1996).  In point of fact that is why the developers used the Barnase gene to create plants that produce male-sterile pollen.  It is important to note that when Barnase is produced inside cells, abnormalities and cell death are observed.  One interesting potential application of Barnase is using it to kill cancer cells.
  2. No measurable amounts of Barnase can be found in seeds from plants containing the Barnase-encoding gene. The developers presented data that demonstrated that Barnase was expressed only in the intended tissue and was not present in leaves or seeds; in particular, it was undetectable in the seed that is the part of the plant that is consumed by humans and animals (FDA 1996).  These tests showed that the genes were not transcribed into RNA messages, and that proteins resembling Barnase were not present.  This should come as no surprise since, as mentioned above, cells that produce Barnase cease to exist. Smith speculates that Barnase is likely to be produced in other tissues when the evidence clearly shows that it is not produced in any measurable amount.  It has also been shown that Barnase has no similarity to known toxins or allergens, is digested in gastric juice, and is inactivated at low pH values such as those found in the stomach.  Finally, the developer noted that Barnase is present in all plants and is a normally-occurring dietary component (FDA 1996, Hérouet and others 2005)
  3. It is misleading, incorrect, and maybe even dishonest to compare the results of organ perfusion with consumption of corn containing the Barnase gene. Genetic Roulette, and the so-called expert scientists like David Schubert that it cites, claim that Barnase could be toxic to kidneys and other cells if we consumed grains containing the Barnase gene.  They base this claim on experiments found in two papers that studied the effect of injecting or perfusing solutions containing large amounts of Barnase to isolated rat organs and cells (Ilinskaya and others 1997, Prior and others 1996).  There is not a single study that shows that Barnase is toxic if it is fed to an animal.  Many proteins are toxic when they are injected and yet they are safe to eat.  Barnase is very similar to digestive enzymes (called RNAases) that are secreted into our digestive canal by the pancreas (Carver and Walker 1995) where they do no harm because they are not reabsorbed by the body, and neither is Barnase. This is because our body breaks down proteins into small fragments and amino acids (the basic building block of proteins) before they are absorbed, and Barnase is a protein. Animals and humans do not absorb significant quantities of whole proteins.
  4. The arguments presented about Barnase-containing crops are representative of the deliberate distortion of facts and logic that are common in Genetic Roulette. The published scientific evidence says that animals and humans will not be exposed to Barnase by eating food derived from these transgenic crops.  There are also no studies that show Barnase is toxic to eat—virtually all known proteins are non-toxic (Delaney and others 2008, Hérouet and others 2005). The only toxic effects of Barnase are observed when large quantities are injected into kidneys.  Somehow Smith concludes Barnase may cause kidney damage and will be harmful. Regulators in the European Union, Canada, the United States and many other countries looked at the data and approved the products containing Barnase for human and animal consumption.  Why would they do this if there were doubt about safety?

References:

Carver J, and Walker WA (1995). The role of nucleotides in human nutrition. The Journal of Nutritional Biochemistry 6: 58-72. Information on RNA in food and its digestion.
Delaney B, Astwood JD, Cunny H, Conn RE, Herouet-Guicheney C, Macintosh S, Meyer LS, Privalle L, Gao Y, Mattsson J, Levine M; ILSI International Food Biotechnology Committee Task Force on Protein Safety (2008). Evaluation of protein safety in the context of agricultural biotechnology. Food and Chemical Toxicology 46 Suppl 2:S71-97. Epub 2008 Feb 2.
FDA (1996). Biotechnology Consultation Note to the File BNF No. 000031.  March 15, 1996. www.cfsan.fda.gov/~rdb/bnfm031.html accessed Jan 7 2009. “The corn line containing transformation event MS3 and its progeny are not materially different in composition, safety, and other relevant parameters from conventional corn varieties.”
Hérouet C, Esdaile DJ  Mallyon BA  Debruyne E, Schulz A, Currier T, Hendrickx K, van der Klis R-J and Rouan D  (2005). Safety evaluation of the phosphinothricin acetyltransferase proteins encoded by the pat and bar sequences that confer tolerance to glufosinate-ammonium herbicide in transgenic plants. Regulatory Toxicology and Pharmacology 41:134–149.
Ilinskaya O and Vamvakas S (1997). Nephrotic effect of bacterial ribonucleases in theisolated and perfused rat kidney. Toxicology, 120:55-63.
Prior T, Kunwar S and Pastan I (1996). Studies on the activity of barnase toxins invitro and in vivo. Biocong Chem, 7:23-9.

Genetic Roulette Falsely Claims: Pollen-sterilizing Barnase in GM crops may cause kidney damage

  1. Corn and canola are engineered to produce a pollen-sterilizing toxin called Barnase
  2. Barnase is toxic to human cells and causes kidney damage in rats
  3. Although the GM plants were designed to produce the toxin in a non-food portion of the plant, some of the toxin is likely produced in all parts of the plant.

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