Preeclampsia does not share common risk alleles in 9p21 with coronary artery disease and type 2 diabetes.

INTRODUCTION: Preeclampsia is a common and partially genetic pregnancy complication characterized by hypertension and proteinuria. Association with cardiovascular disease and type 2 diabetes has been reported in 9p21 by several genome-wide association studies. It has been hypothesized that cardiometabolic diseases may share common etiology with preeclampsia. MATERIALS AND METHODS: We tested association with the 9p21 region to preeclampsia in the Finnish population by genotyping 23 tagging single nucleotide polymorphisms (SNPs) in 15 extended preeclampsia families and in a nationwide cohort consisting of 281 cases and 349 matched controls. Replication was conducted in additional datasets. RESULTS: Four SNPs (rs7044859, rs496892, rs564398 and rs7865618) showed nominal association (p ≤ 0.024 uncorrected) with preeclampsia in the case-control cohort. To increase power, we genotyped two SNPs in additional 388 cases and 341 controls from the Finnish Genetics of Preeclampsia Consortium (FINNPEC) cohort. Partial replication was also attempted in a UK cohort (237 cases and 199 controls) and in 74 preeclamptic families from Australia/New Zealand. We were unable to replicate the initial association in the extended Finnish dataset or in the two international cohorts. CONCLUSIONS: Our study did not find evidence for the involvement of the 9p21 region in the risk of preeclampsia. Key Message Chromosome 9p21 is not associated with preeclampsia.

An obesity-related FTO variant and the risk of preeclampsia in a Finnish study population.

Previous studies have demonstrated a common variant of the obesity and fat mass-related FTO gene, rs9939609, to be associated with obesity, type 2 diabetes, and elevated blood pressure. We investigated whether the FTO SNP rs9939609 is associated with the risk of preeclampsia (PE) in a Finnish study population. 485 women with prior PE and 449 women who had given birth after a normotensive pregnancy were genotyped (TaqMan) for the SNP rs9939609. The prevalences of genotypes AA, AT, and TT were 15%, 53%, and 32%, respectively, among the PE cases, and 16%, 47%, and 37%, respectively, among the controls (P = 0.199). We found no evidence of an association between the FTO SNP rs9939609 and PE. However, our cases were dominated by severe, early-onset PE. Thus, we are unable to exclude an association with the milder, later-onset form of the disease in which the role of maternal metabolic predisposition could be more significant.

Association of the rs1424954 polymorphism of the ACVR2A gene with the risk of pre-eclampsia is not replicated in a Finnish study population.

BACKGROUND: Pre-eclampsia/eclampsia is a common vascular pregnancy disorder associated with high maternal and infant mortality and morbidity worldwide. The role of Activin A and more recently type 2 Activin A receptor (ACVR2A) in the pathogenesis of pre-eclampsia has been the subject of genetic and biochemical research with controversial results. FINDINGS: We genotyped a candidate pre-eclampsia-associated single nucleotide polymorphism rs1424954 in ACVR2A in three independent study populations of Finnish pre-eclamptic (total N = 485) and non-pre-eclamptic (total N = 449) women using pre-designed TaqMan allele discrimination assay and polymerase chain reaction. The possible association of the alleles and genotypes of interest with pre-eclampsia was evaluated using the chi-square test and logistic regression analysis. We found no association of rs1424954 to pre-eclampsia in Finnish patients. CONCLUSIONS: rs1424954 was not associated to pre-eclampsia in the Finnish study population. We hypothesise that while the gene associates to pre-eclampsia worldwide, the causative polymorphism in ACVR2A may be unique in genetically differing populations. Further research is needed to characterise the haplotype structure of ACVR2A in order for the causative genetic variant to be identified.

Non-synonymous sequence variants within the oxygen-dependent degradation domain of the HIF1A gene are not associated with pre-eclampsia in the Finnish population.

BACKGROUND: Reduced placental perfusion predisposes to the maternal syndrome pre-eclampsia characterized by systemically reduced perfusion. Considerable data support the role of angiogenic factors in the development of the maternal syndrome. Hypoxia-inducible factor (HIF-1) mediates the cellular responses to hypoxia e.g. by promoting angiogenesis. METHODS: Here we studied whether two single nucleotide sequence variants, c.1744 C>T that changes residue 582 of HIF-1alpha from proline to serine (P582S) and c.1762 G>A that changes residue 588 of HIF-1alpha from alanine to threonine (A588T) in the exon 12 of the HIF1A gene, are associated with pre-eclampsia. We studied 108 women with pre-eclampsia in their first pregnancy, and 101 controls with normotensive pregnancies. Pre-eclampsia was defined as a blood pressure level of at least 140/90 mmHg in a woman who was normotensive before 20 weeks of gestation, and proteinuria at least of 0.3 g per 24-hour urine collection. The patients and controls were genotyped for variations in the exon 12 of HIF1A gene by sequencing RESULTS: The frequencies of the c.1744 C>T and c.1762G>A sequence variants were not significantly different between women with pre-eclamptic first pregnancies and women with normotensive pregnancies. In addition, two synonymous variants (c.1740G>A and c.1800A>T) were detected at comparable levels in the two groups. All variants were identified in the heterozygous form. CONCLUSION: The sequence variants in the exon 12 of the HIF1A gene were not associated with pre-eclampsia in the Finnish population.

Evaluation of STOX1 as a preeclampsia candidate gene in a population-wide sample.

Preeclampsia is a common, pregnancy-specific vascular disorder characterised by hypertension and proteinuria. A recent report suggested association of the STOX1 gene on chromosome 10q22.1 with preeclampsia in the Dutch population. Here, we present a comprehensive assessment of STOX1 as a candidate gene for preeclampsia in the Finnish population by re-examining our previous genetic linkage analysis results for both chromosome 10 and paralogous loci, by genotyping representative markers in a nationwide data set, and by studying STOX1 expression in placentas from preeclamptic and uncomplicated pregnancies. In conclusion, we are unable to validate STOX1 as a common preeclampsia susceptibility gene.

Differential mobilization of newly synthesized cholesterol and biosynthetic sterol precursors from cells.

Previous work demonstrates that the biosynthetic precursor of cholesterol, desmosterol, is released from cells and that its efflux to high density lipoprotein or phosphatidylcholine vesicles is greater than that of newly synthesized cholesterol (Johnson, W. J., Fischer, R. T., Phillips, M. C., and Rothblat, G. H. (1995) J. Biol. Chem. 270, 25037-25046). Here we report that the release of individual precursor sterols varies with the efflux of newly synthesized zymosterol being greater than that of lathosterol and both exceeding that of newly synthesized cholesterol when using either methyl-beta-cyclodextrin or complete serum as acceptors. The transfer of newly synthesized lathosterol to methyl-beta-cyclodextrin was inhibited by actin polymerization but not by Golgi disassembly whereas that of newly synthesized cholesterol was inhibited by both conditions. Newly synthesized lathosterol associated with cellular detergent-resistant membranes more rapidly than newly synthesized cholesterol. Upon efflux to serum, newly synthesized cholesterol precursors associated with both high and low density lipoproteins. Stimulation of the formation of direct endoplasmic reticulum-plasma membrane contacts was accompanied by enhanced efflux of newly synthesized lathosterol but not of newly synthesized cholesterol to serum acceptors. The data indicate that the efflux of cholesterol precursors differs not only from that of cholesterol but also from each other, with the more polar zymosterol being more avidly effluxed. Moreover, the results suggest that the intracellular routing of cholesterol precursors differs from that of newly synthesized cholesterol and implicates a potential role for the actin cytoskeleton and endoplasmic reticulum-plasma membrane contacts in the efflux of lathosterol.

Chicken avidin-related proteins show altered biotin-binding and physico-chemical properties as compared with avidin.

Chicken avidin and bacterial streptavidin are proteins familiar from their use in various (strept)avidin-biotin technological applications. Avidin binds the vitamin biotin with the highest affinity known for non-covalent interactions found in nature. The gene encoding avidin (AVD) has homologues in chicken, named avidin-related genes (AVRs). In the present study we used the AVR genes to produce recombinant AVR proteins (AVRs 1, 2, 3, 4/5, 6 and 7) in insect cell cultures and characterized their biotin-binding affinity and biochemical properties. Amino acid sequence analysis and molecular modelling were also used to predict and explain the properties of the AVRs. We found that the AVR proteins are very similar to avidin, both structurally and functionally. Despite the numerous amino acid substitutions in the subunit interface regions, the AVRs form extremely stable tetramers similar to those of avidin. Differences were found in some physico-chemical properties of the AVRs as compared with avidin, including lowered pI, increased glycosylation and, most notably, reversible biotin binding for two AVRs (AVR1 and AVR2). Molecular modelling showed how the replacement Lys(111)-->isoleucine in AVR2 alters the shape of the biotin-binding pocket and thus results in reversible binding. Both modelling and biochemical analyses showed that disulphide bonds can form and link monomers in AVR4/5, a property not found in avidin. These, together with the other properties of the AVRs described in the present paper, may offer advantages over avidin and streptavidin, making the AVRs applicable for improved avidin-biotin technological applications.

ORP2, a homolog of oxysterol binding protein, regulates cellular cholesterol metabolism.

Oxysterol binding protein (OSBP) related proteins (ORPs) constitute a family that has at least 12 members in humans. In the present study we characterize one of the novel OSBP homologs, ORP2, which we show to be expressed ubiquitously in mammalian tissues. The ORP2 cDNA encodes a deduced 55 kDa protein that lacks a pleckstrin homology (PH) domain, a feature found in the other family members. Sucrose gradient centrifugation analysis of Chinese hamster ovary (CHO) cell post-nuclear supernatant demonstrated that ORP2 is distributed in soluble and membrane-bound fractions. Immunofluorescence microscopy of the endogenous and overexpressed ORP2 in CHO cells suggested that the membrane-bound fraction of the protein localizes to the Golgi apparatus. Stably transfected CHO cells that overexpress ORP2 showed an increase in [14C]cholesterol efflux to serum, apolipoprotein A-I (apoA-I), and phosphatidyl choline vesicles. The proportion of cellular [14C]cholesterol that is esterified and the ACAT activity measured as [14C]oleyl-CoA conversion into cholesteryl [14C]oleate by the cellular membranes, were markedly decreased in the ORP2 expressing cells. Transient high level overexpression of ORP2 interfered with the clearance of a secretory pathway protein marker from the Golgi complex. The results implicate ORP2 as a novel regulator of cellular sterol homeostasis and intracellular membrane trafficking.

Cloning and characterization of Scavidin, a fusion protein for the targeted delivery of biotinylated molecules.

We have constructed a novel fusion protein "Scavidin" consisting of the macrophage scavenger receptor class A and avidin. The Scavidin fusion protein is transported to plasma membranes where the avidin portion of the fusion protein binds biotin with high affinity and forms the basis for the targeted delivery of biotinylated molecules. Subcellular fractionation analysis, immunostaining, and electron microscopy demonstrated endosomal localization of the fusion protein. According to pulse-labeling and cross-linking studies Scavidin is found as monomers (55 kDa), dimers, and multimers, of which the 220-kDa form was the most abundant. The biotin binding capacity and active endocytosis of the biotinylated ligands were demonstrated in rat malignant glioma. Local Scavidin gene transfer to target tissues could have general utility as a universal tool to deliver biotinylated molecules at systemic low concentrations for therapeutic and imaging purposes, whereby high local concentration is achieved.

Dynamic association of human insulin receptor with lipid rafts in cells lacking caveolae.

Cholesterol-sphingolipid rich plasma membrane domains, known as rafts, have emerged as important regulators of signal transduction. The adipocyte insulin receptor (IR) is localized to and signals via caveolae that are formed by polymerization of caveolins. Caveolin binds to IR and stimulates signalling. We report that, in liver-derived cells lacking caveolae, autophosphorylation of the endogenous IR is dependent on raft lipids, being compromised by acute cyclodextrin-mediated cholesterol depletion or by antibody clustering of glycosphingolipids. Moreover, we provide evidence that IR becomes recruited to detergent-resistant domains upon ligand binding and that clustering of GM2 ganglioside inhibits IR signalling apparently by excluding the ligand-bound IR from these domains. Our results indicate that, in cells derived from liver, an important insulin target tissue, caveolae are not required for insulin signalling. Rather, the dynamic recruitment of the ligand-bound IR into rafts may serve to regulate interactions in the initiation of the IR signalling cascade.