Alpha-gliadin genes from the A, B, and D genomes of wheat contain different sets of celiac disease epitopes

Herpen, Teun WJM van and Goryunova, Svetlana V and Schoot, Johanna van der and Mitreva, Makedonka and Salentijn, Elma and Vorst, Oscar (2006) Alpha-gliadin genes from the A, B, and D genomes of wheat contain different sets of celiac disease epitopes. BMC Genomics. pp. 1-13.

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Background: Bread wheat (Triticum aestivum) is an important staple food. However, wheat gluten
proteins cause celiac disease (CD) in 0.5 to 1% of the general population. Among these proteins,
the α-gliadins contain several peptides that are associated to the disease.
Results: We obtained 230 distinct α-gliadin gene sequences from severaldiploid wheat species
representing the ancestral A, B, and D genomes of the hexaploid bread wheat. The large majority
of these sequences (87%) contained an internal stop codon. All α-gliadin sequences could be
distinguished according to the genome of origin on the basis of sequence similarity, of the average
length of the polyglutamine repeats, and of the differences in the presence of four peptides that
have been identified as T cell stimulatory epitopes in CD patients through binding to HLA-DQ2/8.
By sequence similarity, α-gliadins from the public database of hexaploid T. aestivum could be
assigned directly to chromosome 6A, 6B, or 6D. T. monococcum (A genome) sequences, as well as
those from chromosome 6A of bread wheat, almost invariably contained epitope glia-α9 and glia-
α20, but never the intact epitopes glia-α and glia-α2. A number of sequences from T. speltoides, as
well as a number of sequences fromchromosome 6B of bread wheat, did not contain any of the
four T cell epitopes screened for. The sequences from T. tauschii (D genome), as well as those from
chromosome 6D of bread wheat, were found to contain all of these T cell epitopes in variable combinations per gene. The differences in epitope composition resulted mainly from point
mutations. These substitutions appeared to be genome specific.
Conclusion: Our analysis shows that α-gliadin sequences from the three genomes of bread wheat
form distinct groups. The four known T cell stimulatory epitopes are distributed non-randomly
across the sequences, indicating that the three genomes contribute differently to epitope content.
A systematic analysis of all known epitopes in gliadins and glutenins will lead to better understanding
of the differences in toxicity among wheat varieties. On the basis of such insight, breeding strategies
can be designed to generate less toxic varieties of wheat which may be tolerated by at least part of
the CD patient population.

Item Type: Article
Subjects: Medical and Health Sciences > Basic medicine
Divisions: Faculty of Medical Science
Depositing User: Mirjana Kocaleva
Date Deposited: 29 Nov 2012 14:21
Last Modified: 29 Nov 2012 14:21

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