Wetenschap - 31 januari 2019

Wheat with safe gluten: an end to special diets for coeliac patients?

tekst:
Albert Sikkema

Coeliac patients have to eat gluten-free food but these products often taste worse and are less healthy. PhD candidate Aurélie Jouanin realized that CRISPR-Cas could let you modify the gluten genes in wheat to make the plant produce gluten that is safe for people with this disease.

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Around one to two per cent of all Dutch people have coeliac disease. Products with gluten, which is found in wheat, barley and rye, give them intestinal inflammation. The only remedy for patients is a gluten-free diet but that is tricky as gluten is used in products such as chocolate, meat and liquorice too. Gluten adds structure to food products. The gluten-free products are also less healthy, says René Smulders, Jouanin’s co-supervisor. They lack fibre and the products contain additives such as starch, emulsifying agents, gum and lots of salt to compensate for the lack of gluten.

That is why Jouanin investigated whether she could breed safe wheat. Scientists have not yet managed to produce a wheat variety with safe gluten using traditional plant breeding methods. ‘We know which molecules in gluten proteins trigger the immune response but the problem is that loads of wheat genes produce gluten proteins,’ says Smulders. ‘We know from previous research that more than one hundred genes are involved at six different loci in the genome.’

Mutagenesis
Researchers have tried using traditional mutagenesis, in which the DNA is altered by gamma radiation, to switch off the genes in question to create a gluten-free variant. Smulders ‘They have not succeeded yet. It’s an imprecise method. The plants without the piece of chromosome containing a series of gluten genes also lack other genes. That may affect their ability to grow. And you also need to successfully eliminate all the gluten genes in the plant. The traditional approach won’t ever be able to produce a gluten-free variety.’

The new technique CRISPR-Cas offered a solution. Jouanin was able to use this technique to obtain wheat plants in which several of the hundred wheat genes concerned were modified. Smulders: ‘CRISPR-Cas does not switch off the entire gene, only the part that is immunogenic. You get wheat with safe gluten rather than gluten-free wheat. As a result, this wheat still has the benefits of gluten in terms of health and food structure.’

Cuts
Jouanin used CRISPR-Cas to make precise cuts in gluten genes. When the wheat plant repairs the cuts, it sometimes makes errors that modify the gene slightly. Jouanin then identified the plants with such errors and determined whether the offspring’s seeds still produced gluten. This let her find wheat plants that produced both less gluten and less of the gluten that is not safe for coeliac patients. ‘We are still a long way off completely safe wheat. You don’t get there in one go,’ says Smulders.

In her thesis, the French PhD candidate makes the case for a more flexible approach to the application of CRISPR-Cas in plant breeding. ‘She has an illustration in her PhD thesis,’ says Smulders. ‘One scan shows a modification of the gluten proteins in the genome using CRISPR-Cas, while the image next to it shows exactly the same modification using classical mutagenesis with gamma radiation. We know that the genome is also modified in other places by the classical method but not by CRISPR-Cas. And yet it is CRISPR-Cas that is subject to strict safety regulations. The EU really needs to change its rules.’

The EU really needs to change its rules on CRISPR-Cas

The CRISPR-Cas wheat has a lot of advantages for coeliac patients compared with the current gluten-free products, according to Smulders. ‘But at present those benefits are ignored in the risk assessment. That hurts patients and discourages innovation.’

Aurélie Jouanin received her doctorate on 28 January. Her supervisor was Richard Visser, professor of Plant Breeding.


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