Evidence for malaria selection of a CR1 haplotype in Sardinia.

Department of Biochemistry and Molecular Medicine, Rowe Program in Human Genetics, University of California, Davis, CA 95616, USA.
Genes and immunity (Impact Factor: 3.79). 05/2011; 12(7):582-8. DOI: 10.1038/gene.2011.33
Source: PubMed

ABSTRACT Complement receptor 1 (CR1) levels have been associated with malarial susceptibility and/or severity of the disease in different population groups, and CR1 is a receptor for Plasmodium falciparum. In this study, multiple CR1 single-nucleotide polymorphisms (SNPs) showed strong evidence of population differentiation between Sardinian and other European ethnic groups. Cross population algorithms comparing haplotype structure and differences in haplotype and allele frequency distribution provided additional support for natural selection of CR1 in Sardinia. The predominant Sardinian CR1 haplotype included SNPs that are associated with decreased CR1 levels in Europeans and other population groups. Previous studies have shown that the SNPs within the dominant Sardinian haplotype have a significantly higher frequency in a malaria endemic compared with non-endemic regions in India. Together with the historical evidence of the prevalence of malaria in Sardinia, these data support the role of malaria leading to positive selection of this CR1 haplotype in Sardinia.

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    ABSTRACT: Identifying the genes that influence levels of pro-inflammatory molecules can help to elucidate the mechanisms underlying this process. We first conducted a two-stage genome-wide association scan (GWAS) for the key inflammatory biomarkers Interleukin-6 (IL-6), the general measure of inflammation erythrocyte sedimentation rate (ESR), monocyte chemotactic protein-1 (MCP-1), and high-sensitivity C-reactive protein (hsCRP) in a large cohort of individuals from the founder population of Sardinia. By analysing 731,213 autosomal or X chromosome SNPs and an additional ∼1.9 million imputed variants in 4,694 individuals, we identified several SNPs associated with the selected quantitative trait loci (QTLs) and replicated all the top signals in an independent sample of 1,392 individuals from the same population. Next, to increase power to detect and resolve associations, we further genotyped the whole cohort (6,145 individuals) for 293,875 variants included on the ImmunoChip and MetaboChip custom arrays. Overall, our combined approach led to the identification of 9 genome-wide significant novel independent signals-5 of which were identified only with the custom arrays-and provided confirmatory evidence for an additional 7. Novel signals include: for IL-6, in the ABO gene (rs657152, p = 2.13×10(-29)); for ESR, at the HBB (rs4910472, p = 2.31×10(-11)) and UCN119B/SPPL3 (rs11829037, p = 8.91×10(-10)) loci; for MCP-1, near its receptor CCR2 (rs17141006, p = 7.53×10(-13)) and in CADM3 (rs3026968, p = 7.63×10(-13)); for hsCRP, within the CRP gene (rs3093077, p = 5.73×10(-21)), near DARC (rs3845624, p = 1.43×10(-10)), UNC119B/SPPL3 (rs11829037, p = 1.50×10(-14)), and ICOSLG/AIRE (rs113459440, p = 1.54×10(-08)) loci. Confirmatory evidence was found for IL-6 in the IL-6R gene (rs4129267); for ESR at CR1 (rs12567990) and TMEM57 (rs10903129); for MCP-1 at DARC (rs12075); and for hsCRP at CRP (rs1205), HNF1A (rs225918), and APOC-I (rs4420638). Our results improve the current knowledge of genetic variants underlying inflammation and provide novel clues for the understanding of the molecular mechanisms regulating this complex process.
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