No polymorphism in the tissue transglutaminase gene detected in coeliac disease patients.
BACKGROUND
The autoantigen for the anti-endomysial antibody (AEA) found in coeliac disease has recently been reported to be the enzyme tissue transglutaminase (tTG). Polymorphisms in the gene for tTG would result in different enzymic isoforms being expressed. Certain isoforms may interact with gliadin to create antigenic neoepitopes, which could then generate an immune response in genetically predisposed individuals possessing major histocompatibility complex (MHC) class II DQ2.


METHODS
We have sequenced the coding region of tTG in coeliac patients and normal controls. Total RNA was extracted from mucosal biopsies from eight AEA-positive histologically proven coeliac disease patients and four control patients with a histologically normal duodenum and a negative AEA. The 2-kb coding region of tTG was amplified in overlapping fragments by reverse transcription polymerase chain reaction (PCR), using five sets of PCR primers. Each overlapping PCR fragment was sequenced using the fmol DNA sequencing system.


RESULTS
tTG transcripts were detected in all samples. There was no difference in the coding sequence of tTG between the four control and eight coeliac patients, even though we observed differences in sequence between our study and the original published sequence. These differences have also been reported in sequences published subsequent to the original description.


CONCLUSIONS
Polymorphisms in the tTG gene have not been observed in coeliac disease patients and therefore cannot explain the creation of neoepitopes.
Aldersley
M A
MA
Molecular Medicine Unit and Division of Medicine, St James's University Hospital, Leeds, UK.
Hamlin
P J
PJ
Jones
P F
PF
Markham
A F
AF
Robinson
P A
PA
Howdle
P D
PD
D000595:Amino Acid Sequence; D001323:Autoantibodies / Q000032:analysis; D002446:Celiac Disease / Q000235:genetics* / Q000276:immunology; D000939:Epitopes / Q000235:genetics; D019204:GTP-Binding Proteins / Q000235:genetics*; D006801:Humans; D007413:Intestinal Mucosa / Q000201:enzymology*; D007527:Isoenzymes / Q000235:genetics; D008969:Molecular Sequence Data; D018485:Muscle Fibers, Skeletal / Q000276:immunology; D011110:Polymorphism, Genetic; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D011503:Transglutaminases / Q000235:genetics*
D001323:Autoantibodies; D000939:Epitopes; D007527:Isoenzymes; D012333:RNA, Messenger; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins