Variation in FCN1 affects biosynthesis of ficolin-1 and is associated with outcome of systemic inflammation.

Ficolin-1 is a recognition molecule of the lectin complement pathway. The ficolin-1 gene FCN1 is polymorphic, but the functional and clinical consequences are unknown.The concentration of ficolin-1 in plasma and FCN1 polymorphisms in positions -1981 (rs2989727), -791 (rs28909068), -542 (rs10120023), -271 (rs28909976), -144 (rs10117466) and +7918 (rs1071583) were determined in 100 healthy individuals. FCN1 expression by isolated monocytes and granulocytes and ficolin-1 levels in monocyte culture supernatants were assessed in 21 FCN1-genotyped individuals. FCN1 polymorphisms were determined in a cohort of 251 patients with systemic inflammation. High ficolin-1 plasma levels were significantly associated with the minor alleles in position -542 and -144. These alleles were also significantly associated with high FCN1 mRNA expression. The level of ficolin-1 in culture supernatants was significantly higher in individuals homozygous for the minor alleles at positions -542 and -144. Homozygosity for these alleles was significantly associated with fatal outcome in patients with systemic inflammation. None of the other investigated polymorphisms were associated with FCN1 and ficolin-1 expression, concentration or disease outcome. Functional polymorphic sites in the promoter region of FCN1 regulate both the expression and synthesis of ficolin-1 and are associated with outcome in severe inflammation.

The impact of FCN2 polymorphisms and haplotypes on the Ficolin-2 serum levels.

Ficolin-2 (L-ficolin), derived from the FCN2 gene, is an innate immunity pattern recognition molecule found in human serum in which inter-individual variation in serum appears to be under genetic control. To validate and extend this finding, we developed a sandwich ELISA for detection of human Ficolin-2 in serum samples and identified FCN2 genotypes with a Taq Man-based minor groove binder assay and by sequencing. Serum samples were applied to gel-permeation chromatography and fractions were analysed by an ELISA, SDS-PAGE and subsequently Western blotting. In 214 Danish blood donors, the median Ficolin-2 serum concentration was determined to 5.4 microg/ml (range: 1.0-12.2 microg/ml). An ELISA, SDS-PAGE and Western blot analysis of gel-permeation chromatography fractions showed that Ficolin-2 comprises a mixture of covalently and non-covalently linked Ficolin-2 oligomers independent of the individual genotypes. The variation in serum concentration was associated with three polymorphisms in the promoter and one polymorphism in the structural part of the FCN2 gene. Further analysis indicated that two particular alleles on the same haplotype determined a low Ficolin-2 concentration. Our results show that inter-individual variation of Ficolin-2 concentration is associated with polymorphisms in the promoter and the structural part of the FCN2 gene.

Association between an interleukin-13 promoter polymorphism and atopy.

Several studies indicate genetic involvement of Th2 cytokines in allergic diseases. Interleukin (IL)-13 has been mapped to the cytokine cluster on chromosome 5q31-33, which has been associated with atopic conditions. Recently, an association was reported between the T allele in a promoter polymorphism in the IL-13 gene (C to T exchange) at position -1055 and allergic asthma in a population study in the Netherlands. This observation was apparently confirmed in a case-control study using probands and spouses from a Dutch asthma family study, but the polymorphism in that study was reported to occur at position -1111. In the present study, we established that this polymorphism is located at position -1024 relative to the ATG translation initiation codon, and investigated whether it confers a genetic predisposition to atopic conditions and the Th1 condition multiple sclerosis (MS) in Caucasian subjects. We confirmed the association between the IL-13 -1024TT genoype and inhalation allergy (P = 2.4E-02). By combining the data from the three studies, we demonstrated a strong association (P = 1.09E-05) between the IL-13 -1024 marker and inhalation allergy. Furthermore, we showed for the first time that this association also exists in atopic dermatitis (P = 2.0E-02). No association with MS was found.