title: Overlapping genetic susceptibility variants between three autoimmune disorders: rheumatoid arthritis, type 1 diabetes and coeliac disease.
abstract: BACKGROUND
  Genome wide association studies, replicated by numerous well powered validation studies, have revealed a large number of loci likely to play a role in susceptibility to many multifactorial diseases. It is now well established that some of these loci are shared between diseases with similar aetiology. For example, a number of autoimmune diseases have been associated with variants in the PTPN22, TNFAIP3 and CTLA4 genes. Here we have attempted to define overlapping genetic variants between rheumatoid arthritis (RA), type 1 diabetes (T1D) and coeliac disease (CeD).
  
  
  METHODS
  We selected eight SNPs previously identified as being associated with CeD and six T1D-associated SNPs for validation in a sample of 3,962 RA patients and 3,531 controls. Genotyping was performed using the Sequenom MassArray platform and comparison of genotype and allele frequencies between cases and controls was undertaken. A trend test P-value < 0.004 was regarded as significant.
  
  
  RESULTS
  We found statistically significant evidence for association of the TAGAP locus with RA (P = 5.0 × 10-4). A marker at one other locus, C1QTNF6, previously associated with T1D, showed nominal association with RA in the current study but did not remain statistically significant at the corrected threshold.
  
  
  CONCLUSIONS
  In exploring the overlap between T1D, CeD and RA, there is strong evidence that variation within the TAGAP gene is associated with all three autoimmune diseases. Interestingly a number of loci appear to be specific to one of the three diseases currently studied suggesting that they may play a role in determining the particular autoimmune phenotype at presentation.
authors.affiliation: Arthritis Research UK, Epidemiology Unit, Stopford Building, Oxford Road, The University of Manchester, Manchester M13 9PT, UK. steve.eyre@manchester.ac.uk
authors.forename: Stephen
authors.initials: S
authors.lastname: Eyre
authors.forename: Anne
authors.initials: A
authors.lastname: Hinks
authors.forename: John
authors.initials: J
authors.lastname: Bowes
authors.forename: Edward
authors.initials: E
authors.lastname: Flynn
authors.forename: Paul
authors.initials: P
authors.lastname: Martin
authors.forename: Anthony G
authors.initials: AG
authors.lastname: Wilson
authors.forename: Ann W
authors.initials: AW
authors.lastname: Morgan
authors.forename: Paul
authors.initials: P
authors.lastname: Emery
authors.forename: Sophia
authors.initials: S
authors.lastname: Steer
authors.forename: Lynne J
authors.initials: LJ
authors.lastname: Hocking
authors.forename: David M
authors.initials: DM
authors.lastname: Reid
authors.forename: Pille
authors.initials: P
authors.lastname: Harrison
authors.forename: Paul
authors.initials: P
authors.lastname: Wordsworth
authors.forename: Wendy
authors.initials: W
authors.lastname: Thomson
authors.forename: Jane
authors.initials: J
authors.lastname: Worthington
authors.forename: Anne
authors.initials: A
authors.lastname: Barton
mesh_terms: D000328:Adult; D001172:Arthritis, Rheumatoid / Q000235:genetics*; D002446:Celiac Disease / Q000235:genetics*; D003922:Diabetes Mellitus, Type 1 / Q000235:genetics*; D005260:Female; D020690:GTPase-Activating Proteins / Q000235:genetics*; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D020411:Oligonucleotide Array Sequence Analysis; D020641:Polymorphism, Single Nucleotide
chemical_list: D020690:GTPase-Activating Proteins; C557017:TAGAP protein, human