To develop effective therapeutic modalities, it is important to have a thorough understanding of the clinico-pathophysiological characteristics of MCNS patients showing relapse.

Systemic lupus erythematosus (SLE) is one of the common autoimmune diseases, with complex genetic components. Here, we report on a case-control association study of 178 SLE patients and 899 control subjects, using genome-wide gene-based single nucleotide polymorphism (SNP) markers. An SNP, rs3130342, in a 5' flanking region of the TNXB gene revealed a significant association with SLE [P = 0.000000930, odds ratio (OR) 3.11, with 95% confidence interval (95%CI) of 1.89-5.28] in a Japanese population. This association was replicated independently with 203 cases and 294 controls (P = 0.0440, OR 1.52, with 95%CI of 1.01-2.78). Although a copy number variation (CNV) of the C4 gene adjacent to the TNXB gene was reported to be associated with SLE, our analysis on this CNV revealed that the association of CNV of the C4 gene was weaker than the SNP in the TNXB gene and likely to reflect the linkage disequilibrium between C4 CNV and this particular SNP. Stratified analysis also revealed that the association of SNP rs3130342 with SLE was independent of the HLA-DRB1*1501 allele that has been shown to be associated with SLE. Our findings strongly imply that the TNXB gene is a candidate gene susceptible to SLE in the Japanese population.

Immunoglobulin A (IgA) nephropathy is the most common form of primary glomerulonephritis worldwide. The pathogenesis of IgA nephropathy is unknown, but it is certain that some genetic factors are involved in susceptibility to the disease. Employing a large-scale, case-control association study using genebased single-nucleotide polymorphism (SNP) markers, we previously reported four candidate genes. We report here an additional significant association between IgA nephropathy and an SNP located in the gene encoding immunoglobulin l-binding protein 2 (IGHMBP2) at chromosome 11q13.2-q13.4. The association (v 2 =17.1, p=0.00003; odds ratio of 1.85 with 95% confidence interval of 1.39-2.50 in a dominant association model) was found using DNA from 465 affected individuals and 634 controls. The SNP (G34448A) caused an amino acid substitution from glutamine to lysine (E928K). As the gene product is involved in immunoglobulin-class switching and patients with the A allele revealed higher serum levels of IgA (p=0.048), the amino acid change might influence a class switch to increase serum IgA levels, resulting in a higher risk of IgA nephropathy.