Original Article

Genes and Immunity (2009) 10, 517–524; doi:10.1038/gene.2009.33; published online 14 May 2009

Evaluation of C1q genomic region in minority racial groups of lupus

B Namjou1, C Gray-McGuire1, A L Sestak1, G S Gilkeson2, C O Jacob3, J T Merrill1, J A James1,7, E K Wakeland4, Q-Z Li4, C D Langefeld5, J Divers5, J Ziegler5, K L Moser1, J A Kelly1, K M Kaufman1,6 and J B Harley1,6,7

  1. 1Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
  2. 2Department of Medicine, Division of Rheumatology, Medical University of South Carolina, Charleston, SC, USA
  3. 3Department of Medicine, University of Southern California, Los Angeles, CA, USA
  4. 4Department of Immunology, University of Texas at Southwest Medical Center, Dallas, TX, USA
  5. 5Department of Biostatistical Sciences, Wake Forest University Health Sciences, Medical Center Blvd., Winston-Salem, NC, USA
  6. 6US Department of Veterans Affairs Medical Center, Oklahoma City, OK, USA
  7. 7University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA

Correspondence: Dr JB Harley, Oklahoma Medical Research Foundation, 825 NE 13th Street, Oklahoma City, OK 73104, USA. E-mail: john-harley@omrf.org

Received 23 December 2008; Revised 30 March 2009; Accepted 30 March 2009; Published online 14 May 2009.

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Abstract

Complement cascade plasma proteins play a complex role in the etiopathogenesis of systemic lupus erythematosus (SLE). Hereditary C1q deficiency has been strongly related to SLE; however, there are very few published SLE studies that evaluate the polymorphisms of genes encoding for C1q (A, B and C). In this study, we evaluated 17 single nucleotide polymorphisms (SNPs) across 37kb of C1QA, C1QB and C1QC in a lupus cohort of individuals of the African-American and Hispanic origin. In a case-only analysis, a significant association at multiple SNPs in the C1QA gene was detected in African Americans with kidney nephritis (best P=4.91 × 10−6). In addition, C1QA was associated with SLE in African Americans with a lack of nephritis and accompanying photosensitivity when compared with that in normal controls (P=6.80 × 10−6). A similar trend was observed in the Hispanic subjects (P=0.003). Quantitative analysis showed that some SNPs in C1q genes might be correlated with C3 complement levels in an additive model among African Americans (best P=0.0001). The C1QA gene is associated with subphenotypes of lupus in the African-American and Hispanic subjects. Further studies with higher SNP densities in this region and other complement components are necessary to elucidate the complex genetics and phenotypic interactions between complement components and SLE.

Keywords:

C1Q, SLE, genetics

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