Genetic association study of common variants in TGFB1 and IL-6 with developmental dysplasia of the hip in Han Chinese population

Developmental dysplasia of the hip (DDH) is a congenital or developmental deformation or misalignment of the hip joint that is affected by environmental and genetic factors. Recently, polymorphisms in both TGFB1 and IL-6 have been identified as being significantly associated with hip osteoarthritis in Caucasians. In this study, we conducted a case-control study involving 4,206 Han Chinese individuals to investigate the effects of TGFB1 and IL-6 on the disease status and severity of DDH. A total of 32 single-nucleotide polymorphisms (SNPs) were selected to ensure coverage of the two genetic loci. We found SNP rs1800470 in TGFB1 (OR = 1.255, P = 0.0004) and rs1800796 (OR = 0.84, P = 0.0228) in IL-6 to be significantly associated with DDH in this cohort. Further haplotype-based analysis replicated this significant result. Another SNP in IL-6, rs1800796, showed a marginally significant association with DDH. As a non-synonymous SNP, rs1800470 alters the amino acid sequence of the polypeptide encoded by TGFB1; however, bioinformatics analyses revealed that this SNP has limited functional significance. No significant results were obtained in an association study focusing on the severity of DDH and epistasis analysis. Our findings support an important role for TGFB1 in the risk of DDH. Further research is needed to validate the weak association between rs1800796 in IL-6 and DDH.