To investigate the association of the poly(ADP-ribose) polymerase 1 (PARP-1) gene promoter polymorphism with rheumatoid arthritis (RA) predisposition.
An association study with 213 Spanish RA patients and 242 healthy subjects was carried out to investigate the association of all known PARP-1 gene promoter polymorphisms, i.e., a CA microsatellite repeat, a poly(A)(n), and 3 single point mutations (C410T, C1362T, and G1672A), with disease susceptibility. Additionally, we analyzed the distribution of PARP-1 polymorphisms in 58 Spanish families with 1 or more affected members.
Upon complete genotyping of the panel of 455 samples, strong linkage disequilibrium was observed among the 5 PARP-1 polymorphisms. Only 2 PARP-1 haplotypes were detected: haplotype A (410T-[A](10)-[CA](10-12)-1362C, which includes short PARP-1 CA alleles) and haplotype B (410C-[A](11)-[CA](13-20)-1362T, always paired with long PARP-1 CA variants). Regarding the G1672A variation, although linkage disequilibrium was detected, it did not seem to be part of the conserved haplotypes described. Haplotype B was statistically overrepresented in the RA patient group compared with the healthy subjects (odds ratio 1.42, 95% confidence interval 1.06-1.91, P = 0.019). In addition, a significant dose effect of PARP-1 haplotype carriage on disease predisposition was observed. Of note, within haplotype B, the PARP-1 CA 97-bp allele was found to be the RA-predisposing marker (odds ratio 2.17, 95% confidence interval 1.27-3.72, P = 0.003, corrected P < 0.05).
Our results demonstrate the existence of 2 unique PARP-1 haplotypes in the Spanish population and provide the first evidence that PARP-1 haplotypes play a role in susceptibility to RA.