Ann-Christine Syvänen

Association of Genetic Risk Variants With Expression of Proximal Genes Identifies Novel Susceptibility Genes for Cardiovascular Disease

Background—Population-based genome-wide association studies have identified several single nucleotide polymorphisms (SNPs) associated with cardiovascular disease or its risk factors. Genes in close proximity to these risk-SNPs are often thought to be pathogenetically important based on their location alone. However, the actual connections between SNPs and disease mechanisms remain largely unknown. Methods and Results—To identify novel susceptibility genes, we investigated how 166 SNPs previously found to be associated with increased cardiovascular risk and/or predisposing metabolic traits relate to the expression of nearby genes. Gene expression in 577 samples of aorta, liver, mammary artery, and carotid atherosclerotic plaque was measured using expression arrays. For 47 SNPs, the expression levels of proximal genes (located within 200 kb) were affected (P<0.005). More than 20 of these genes had not previously been identified as candidate genes for cardiovascular or related metabolic traits. SNP-associated gene effects were tissue-specific and the tissue specificity was phenotype-dependent. Conclusions—This study demonstrates several instances of association between risk-SNPs and genes immediately adjacent to them. It also demonstrates instances in which the associated gene is not the immediately proximal and obvious candidate gene for disease. This shows the necessity of careful studies of genetic marker data as a first step toward application of genome-wide association studies findings in a clinical setting.

Isolation and immunologic properties of a heterogenous antigen with the characteristics of the heavy chain of human plasma kininogen

Kininogen antigen was purified from human plasma fraction IV by ion exchange chromatography, gel filtration and affinity chromatography with antibody specific immunoadsorbents. The immunologically pure glycoprotein had a mol. wt of approximately 60,000 and only one polypeptide chain by SDS-PAGE. An extensive charge heterogeneity by isoelectric focusing and gel filtration on polyacrylamide agarose could only in part depend on a comparatively high sialic acid content, but may be caused by differences in the carbohydrate structures sustained by lectin-binding heterogeneity on Con A-Sepharose. This antigen shares a dominating determinant with native plasma kininogens shown by complete patterns of identity in immunochemical analyses and with the monospecific antisera developed in rabbits against the heterogeneous components. The similar size, amino acid composition, low histidine content, lack of N-terminal amino acid and antigenic homogeneity fit all the so far known characteristics of the human kininogen heavy chain. Notably the antigenic determinant is resistant to degradation by activated kallikrein. This antigen with unimpaired immunologic activity may be a useful tool for preparation of antiserum for immunochemical determination of human plasma kininogen.

Conformation and sequence dependent antigenic determinants in human low molecular weight kininogen

Conformation and sequence-dependent antigenic determinants were investigated using a kinin-free low molecular weight kininogen isolated from Cohns plasma fraction IV. This antigen contains the determinants of the apparently intact heavy chain common to the high molecular weight and low molecular weight kininogens. Straightforward reduction and carboxymethylation destroyed the immunoreactivity of this molecule. Antiserum prepared against the reduced protein recognized both reduced and unreduced antigen showing the presence of both types of antigenic determinant. The corresponding antibodies were separated using immunoadsorbent columns. As shown by the higher avidity of the antibodies, the conformation-dependent determinants dominate the antigenic structure.

Identification in human plasma of low Mr protein fragments with antigenic determinants of kininogen

Identification in human plasma of low Mr protein fragments with antigenic determinants of kininogen

Kininogen molecular heterogeneity by affinity chromatography on concanavalin A and Ricinus communis lectins

Kininogen molecular heterogeneity by affinity chromatography on concanavalin A and Ricinus communis lectins

Studies on the Antigenic Determinants of Human Low Molecular Weight Kininogen

The antigenic reactivity of proteins is located in restricted parts of the molecule forming the antigenic determinants that react with the binding sites of the antibody molecule.1 Low molecular weight (LMr) and high molecular weight (HMr) kininogens are immunologically related molecules with common antigenic determinants in the heavy chain of both proteins. 2–4 We have further characterized the nature of these determinants using a kinin-free LMr kininogen isolated from Cohns plasma fraction IV (He antigen). 5,6 shown recently7 the determinant structure of kininogen reside in the polypeptide backbone of the molecule and is not influenced by the partial removal of carbohydrates. This antigen has a heterogeneous light chain which can be isolated after reduction and carboxymethylation. An antiserum produced against the native HC antigen recognizes all native forms of kininogen in human plasma.

Kininogen in factor VIII-deficient plasma (haemophilia A)

The HMr and LMr molecular forms of kininogen were found to occur in normal distribution in plasma from a patient with severe haemophilia A. Present findings indicate that lack of Factor VIII does not influence, the normal content and distribution of immunoreactive kininogens determined by single radial immunodiffusion and radioimmunoassay. The partially purified HMr and LMr kininogens were antigenically identical with the kininogens in normal human plasma determined using the monospecific antisera raised in rabbits against purified kininogen antigens. Low kallikrein activity on H-D-Pro-Phe-Arg-pNA in the haemophilic plasma was apparently due to preparative procedures. This concept is supported by the normal binding ratio of trypsin to pure α2-macroglobulin isolated from the haemophilic plasma.