Genetic Variability of RXRB, PPARA, and PPARG in Wegener's Granulomatosis

A major genomic region involved in Wegener's granulomatosis includes the gene for retinoid receptor beta (RXRB) which forms heterodimers with peroxisome proliferator-activated receptors (PPARs). It is unclear whether this association directly arises from the RXRB allele(s) or via a linked variation. In order to reveal any hitherto unknown and potentially disease-relevant variation of the RXRB gene, we have genotyped four tagging SNPs of this genomic region and have directly sequenced selected WG patients and controls representing disease-associated haplotypes. Additionally, we have genotyped 2 SNPs each in the genes for PPARα and PPARγ (PPARA and PPARG). Hence, we confirmed the strong association of the RXRB locus with WG but could not reveal any novel variation in RXRB. None of the PPARA and PPARG SNPs showed association with WG. Moreover, no epistatic effect was seen between RXRB and PPARA/PPARG alleles. These results do not support an etiopathological role of PPAR in WG. Analyses of further genes functionally linked to RXRB may provide additional data useful to evaluate the RXRB association found in WG.