Objective: To investigate the possible association of a single nucleotide polymorphism (SNP) at position 9250 in exon 7 of osteopontin gene (OPN gene 9250) with lupus nephritis (LN) in southern Chinese patients.

Methods: Altogether 109 patients with LN (12 males and 97 females) diagnosed according to the American College of Rheumatology criteria (revised in 1982) for systemic lupus erythematosus (SLE) and 180 healthy ethnically matched controls (34 males and 146 females), all Han people living in South China, were enrolled in this study with informed consent. Blood samples from all subjects were collected in EDTA tube for genomic DNA extraction according to the standard isolation procedures. OPN gene 9250 polymorphism was typed by PCR-restriction fragment length polymorphism (PCR-RFLP).

Results: All the genotype frequencies of OPN gene 9250 were in Hardy-Weinberg equilibrium. Compared with the controls, LN patients showed significantly lower frequency of TT genotype of OPN gene 9250 (70% vs 51%, P<0.05) and significantly higher frequency of TC genotype (29.4% vs 45%, P<0.05). There were significant differences in OPN gene 9250 allele and phenotype frequencies between LN patients and the controls (P<0.05). Compared with the female controls, the frequency of TT genotype of OPN gene 9250 was significantly lower in female LN patients (68.5% vs 54%, P<0.05), and there was a significant difference in OPN gene 9250 allele frequency between them (P<0.05).

Conclusion: OPN gene 9250 polymorphism appears to be associated with the susceptibility to LN in southern Chinese Han population.