The aim of this study was to investigate the possible association in the interleukin-6 (IL-6) gene with Rheumatoid arthritis (RA) in Chinese Han population from Shandong Province. Target regions of IL-6 gene were amplified by polymerase chain reaction (PCR) and genotyped. A logistic regression analysis was performed to detect potential associations in our case-control sample, the odd ratio(OR) and 95% confidence intervals(CIs) were calculated. Furthermore, we systematically tracked all the published studies in the field and performed a meta-analysis for the single nucleotide polymorphisms (SNPs) under study. 256 RA patients and 331 healthy controls were recruited into the case-control study. We found allele frequencies of rs1800795, rs1800797 and rs1474347 in RA patients differ from control subjects (P = 0.016, 0.024, 0.020, respectively). Significant difference was observed in haplotype frequencies of GCCGCT between RA patients and controls (P = 0.0001, OR = 4.066, 95%CI = 1.891 ~ 8.746), while GGCGCT frequencies was found lower in RA than controls (P = 0.006, OR = 0.669, 95%CI = 0.501 ~ 0.894). The results of the meta-analysis showed association polymorphism within the IL-6 promoter with RA. These findings suggest that rare IL-6 gene polymorphisms may associate with RA susceptibility in Han Chinese populations; however further studies are needed to assess the validity of the association of IL-6 with RA.

Background: Tryptophan hydroxylase-2 (TPH2) is the rate-limiting enzyme in the synthetic pathway for brain serotonin and is considered key factor for maintaining normal serotonin transmission in the central neuron system (CNS). Gene-disease association studies have reported a relationship between TPH2 and major depressive disorder (MDD) in different populations, however subsequent studies have produced contradictory results.Objectives: We performed a systematic overview and a meta-analysis with all available data up-to-date.Methods: We scrutinized PubMed, Embase, HuGNet and China National Knowledge Infrastructure (CNKI) and last update was held on October 2011. We also searched the manuscripts and the supplementary documents of the published genome-wide association studies in the field. Effect sizes of independent loci that have been studied in more than 3 articles were synthesized using fixed and random effects models.Results: We found 27 eligible articles that studied a total of 74 single nucleotide polymorphisms (SNPs). Finally, 12 independent loci were included in the meta-analysis. The synthesis of the data shown that two SNPs (rs4570625 and rs17110747) were associated with MDD using fixed effects models. SNP rs4570625 had low heterogeneity and remained significant using the more conservative random effects calculations with a summary OR = 0.83 (95% CI: 0.73-0.96).Conclusion: The current study identified a SNP (rs4570625) with strong epidemiological credibility; however more studies are required to provide robust evidence for other weak associations.