Background Genetic variants in complement genes have been associated with a wide range of human disease states, but well-powered genetic association studies of complement activation have not been... Show moreBackground Genetic variants in complement genes have been associated with a wide range of human disease states, but well-powered genetic association studies of complement activation have not been performed in large multiethnic cohorts. Methods We performed medical records?based genome-wide and phenome-wide association studies for plasma C3 and C4 levels among participants of the Electronic Medical Records and Genomics (eMERGE) network. Results In a GWAS for C3 levels in 3949 individuals, we detected two genome-wide significant loci: chr.1q31.3 (CFH locus; rs3753396-A; ?=0.20; 95% CI, 0.14 to 0.25; P=1.52x10(-11)) and chr.19p13.3 (C3 locus; rs11569470-G; ?=0.19; 95% CI, 0.13 to 0.24; P=1.29x10(-8)). These two loci explained approximately 2% of variance in C3 levels. GWAS for C4 levels involved 3998 individuals and revealed a genome-wide significant locus at chr.6p21.32 (C4 locus; rs3135353-C; ?=0.40; 95% CI, 0.34 to 0.45; P=4.58x10(-35)). This locus explained approximately 13% of variance in C4 levels. The multiallelic copy number variant analysis defined two structural genomic C4 variants with large effect on blood C4 levels: C4-BS (?=?0.36; 95% CI, ?0.42 to ?0.30; P=2.98x10(-22)) and C4-AL-BS (?=0.25; 95% CI, 0.21 to 0.29; P=8.11x10(-23)). Overall, C4 levels were strongly correlated with copy numbers of C4A and C4B genes. In comprehensive phenome-wide association studies involving 102,138 eMERGE participants, we cataloged a full spectrum of autoimmune, cardiometabolic, and kidney diseases genetically related to systemic complement activation. Conclusions We discovered genetic determinants of plasma C3 and C4 levels using eMERGE genomic data linked to electronic medical records. Genetic variants regulating C3 and C4 levels have large effects and multiple clinical correlations across the spectrum of complement-related diseases in humans.Significance Statement The complement pathway represents one of the critical arms of the innate immune system. We combined genome-wide and phenome-wide association studies using medical records data for C3 and C4 levels to discover common genetic variants controlling systemic complement activation. Three genome-wide significant loci had large effects on complement levels. These loci encode three critical complement genes: CFH, C3, and C4. We performed detailed functional annotations of the significant loci, including multiallelic copy number variant analysis of the C4 locus to define two structural genomic variants with large effects on C4 levels. Blood C4 levels were strongly correlated with the copy number of C4A and C4B genes. Lastly, using genome-wide genetic correlations and electronic health records?based phenome-wide association studies in 102,138 participants, we catalogued a spectrum of human diseases genetically related to systemic complement activation, including inflammatory, autoimmune, cardiometabolic, and kidney diseases. Show less
Bronson, P.G.; Komorowski, L.K.; Ramsay, P.P.; May, S.L.; Noble, J.; Lane, J.A.; ... ; Barcellos, L.F. 2010
Objective. Genetic susceptibility to systemic lupus erythematosus (SLE) is well established, with the HLA class II DRB1 and DQB1 loci demonstrating the strongest association. However, HLA may also... Show moreObjective. Genetic susceptibility to systemic lupus erythematosus (SLE) is well established, with the HLA class II DRB1 and DQB1 loci demonstrating the strongest association. However, HLA may also influence SLE through novel biologic mechanisms in addition to genetic transmission of risk alleles. Evidence for increased maternal-offspring HLA class II compatibility in SLE and differences in maternal versus paternal transmission rates (parent-of-origin effects) and nontransmission rates (noninherited maternal antigen [NIMA] effects) in other autoimmune diseases have been reported. Thus, we investigated maternal-offspring HLA compatibility, parent-of-origin effects, and NIMA effects at DRB1 in SLE. Methods. The cohort comprised 707 SLE families and 188 independent healthy maternal-offspring pairs (total of 2,497 individuals). Family-based association tests were conducted to compare transmitted versus nontransmitted alleles (transmission disequilibrium test) and both maternally versus paternally transmitted (parent-of-origin) and nontransmitted alleles (using the chi-square test of heterogeneity). Analyses were stratified according to the sex of the offspring. Maternally affected offspring DRB1 compatibility in SLE families was compared with paternally affected offspring compatibility and with independent control maternal-offspring pairs (using Fisher's test) and was restricted to male and nulligravid female offspring with SLE. Results. As expected, DRB1 was associated with SLE (P < 1 x 10(-4)). However, mothers of children with SLE had similar transmission and nontransmission frequencies for DRB1 alleles when compared with fathers, including those for the known SLE risk alleles HLA-DRB1*0301, *1501, and *0801. No association between maternal-offspring compatibility and SLE was observed. Conclusion. Maternal-offspring HLA compatibility, parent-of-origin effects, and NIMA effects at DRB1 are unlikely to play a role in SLE. Show less
