A family based study shows no association between rheumatoid arthritis and the PADI4 gene in a white French population

Abstract

BACKGROUND: Autoantibodies to citrullinated proteins (ACPA) are considered a specific marker for rheumatoid arthritis. Peptidylarginine deiminase (PAD) is the enzyme that converts arginyl into citrullyl residues; different isoforms of the enzyme are expressed in mammals. It has been suggested that the PADI4 gene may contribute to genetic susceptibility to rheumatoid arthritis, but conflicting results have been obtained in different populations. OBJECTIVE: To test the hypothesis that the PADI4 gene may confer susceptibility to rheumatoid arthritis in a white French population, using powerful and highly reliable family based association tests. METHODS: DNA samples were analysed from 100 families where one member was affected by rheumatoid arthritis and both parents were available for sampling. Five single nucleotide polymorphisms, located within the PADI4 gene and in its close proximity, were genotyped by restriction fragment length polymorphism, and haplotypes were constructed. The analysis involved use of the transmission disequilibrium test and genotype relative risk. ACPA were detected by ELISA on cyclic citrullinated peptides and on human deiminated fibrinogen. RESULTS: No single SNP or haplotype was associated with the disease, or was preferentially transmitted. No association was found when patients were partitioned according to ACPA positivity. CONCLUSIONS: No PADI4 haplotype is associated with rheumatoid arthritis in a white French population. The role of genes encoding the other PAD isoforms, or modulating tissue expression or enzyme activity, remains to be elucidated

Synovial intracellular citrullinated proteins colocalizing with peptidyl arginine deiminase as pathophysiologically relevant antigenic determinants of rheumatoid arthritis–specific humoral autoimmunity

“…However, the association between functional haplotypes of PADI4 and RA remains controversial (40,(51)(52)(53). Furthermore, in contrast to PAD-2, the PAD-4 protein was extensively distributed throughout RA synovium, did not colocalize selectively with intracellular citrullinated proteins, and was also found in OA synovium (54).…”

Haplotypes of PADI4 susceptible to rheumatoid arthritis are also associated with ulcerative colitis in the Japanese population

“…With regard to haplotypes of PADI4 (GenBank accession number: NT_030584), three single nucleotide polymorphisms (SNPs), padi4_92, padi4_96, and padi4_102, were selected and analyzed, as reported by Caponi et al (19). Subsequently, haplotypes were determined to be based on combinations of their three SNPs (10), as shown in Tables 2 and 3, because SNPs in PADI4 lie in a strong linkage disequilibrium block.…”

“…The three SNPs, padi4_92, padi4_96, and padi4_102, were detected by the polymerase chain 5'-AGGGTTTCGGCAGCTGTGCC-3' for padi4_102 (19), and 1 U Taq DNA polymerase (Invitrogen Co., Carlsbad, CA). The amplification protocol comprised initial denaturation at 94°C for 5 min, followed by 35 cycles of denaturation at 94°C for 30 sec, annealing at 60°C for padi4_92, at 52°C for padi4_96, and at 68°C for padi4_102 for 30 sec, extension at 72°C for 30 sec, and final extension at 72°C for 5 min.…”

“…The amplification protocol comprised initial denaturation at 94°C for 5 min, followed by 35 cycles of denaturation at 94°C for 30 sec, annealing at 60°C for padi4_92, at 52°C for padi4_96, and at 68°C for padi4_102 for 30 sec, extension at 72°C for 30 sec, and final extension at 72°C for 5 min. The 192-base pair (bp) PCR products for padi4_92, 316-bp PCR products for padi4_96, and 400-bp PCR products for padi4_102 were digested at 37°C overnight by restriction enzymes, Msp I (Takara Bio, Shiga, Japan), Hae III (Toyobo, Osaka, Japan), and Rsa I (Toyobo), respectively (19). The digests were subjected Czin 10 to electrophoresis on a 6% polyacrylamide gel (Nacalai Tesque, Kyoto, Japan) for padi4_92, or on a 2% agarose gel (Nacalai Tesque) for padi4_96 and padi4_102, then stained with ethidium bromide (Nacalai Tesque) and visualized with UV transilluminator (Alpha Innotech, San Leandro, CA).…”

Non-HLA genes modulate the risk of rheumatoid arthritis associated with HLA-DRB1 in a susceptible North American Native population

“…[15][16][17] Examples are a PTPN22-R620W polymorphism which is strongly associated with RA and other autoimmune diseases in Caucasian populations, but is absent in Orientals, and an association with PADI4 SNP found in Japanese populations which is not detected in most Caucasian populations, despite the presence of these gene polymorphisms. [15][16][17][18][19][20] Our own studies of the Cree/Ojibway population in Central Canada have suggested a 2-3% prevalence rate of diagnosed RA, and a 60-70% frequency of SE alleles in the background population. 7,8,21 We sought to determine additional non-HLA genes that may contribute to the high frequency of RA detected in this population.…”