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Biomedical subjects

Michael Christiansen

Publications and source records attributed to Michael Christiansen.

At least 37 records · Page 2Linked to original sources
PubMed2005

Mutations in the HERG K+-ion channel: a novel link between long QT syndrome and sudden infant death syndrome.

In a 7-week-old infant who experienced sudden infant death syndrome (SIDS), a novel missense mutation was identified in KCNH2, causing a lysine-to-glutamic acid amino acid substitution at position 101 (K101E). KCNH2 codes for the HERG ion channel and mutations in the gene are associated with congenital long-QT syndrome (LQTS), and in the family of this case of SIDS, the mutation was associated with Torsades de pointes tachycardia, making SIDS the most likely outcome of congenital LQTS.

DNA-Binding Proteins↗
PubMed2005

High-throughput single-strand conformation polymorphism analysis on a microfabricated capillary array electrophoresis device.

A high-density 384-lane microfabricated capillary array electrophoresis device is evaluated for high-throughput single-strand conformation polymorphism (SSCP) analysis. A delayed back bias direct electrokinetic injection scheme is used to provide better than 10-bp resolution with an 8.0-cm effective separation length. Separation of a HaeIII digest of PhiX174 yielded theoretical plate numbers of 4.0 x 10(6). Using 5% PDMA containing 10% glycerol and 15% urea, 21 single-nucleotide polymorphisms (SNPs) from HFE, MYL2, MYL3, and MYH7 genes associated with hereditary hemochromatosis (HHC) and hereditary hypertrophic cardiomyopathy (HCM) are discriminated at two running temperatures (25 degrees C and 40 degrees C), providing 100% sensitivity. The data in this study demonstrate that the 384-lane microCAE device provides the resolution and detection sensitivity required for SSCP analysis, showing its potential for ultrahigh-throughput mutation detection.

Cardiomyopathies↗
PubMed2005

The level of ADAM12-S in maternal serum is an early first-trimester marker of fetal trisomy 18.

BACKGROUND: ADAM12-S is a pregnancy-associated insulin-like growth factor binding protein-3 (IGFBP-3) and IGFBP-5 protease present in human gestational serum. Recently, maternal serum levels of ADAM12-S were found to be markedly reduced during the first trimester of pregnancies with a Down syndrome (DS) fetus. On the basis of this finding, it was suggested that ADAM12-S might be a useful maternal serum marker of fetal chromosomal disease. OBJECTIVE: Retrospective examination of the use of ADAM12-S as a marker for fetal trisomy 18. METHOD: Serum samples were obtained from ten women during the first semester of their pregnancies with fetuses that had trisomy 18. An ELISA was used to determine the levels of ADAM12 in maternal serum. Results were compared to ADAM12-S levels, previously measured in the serum of 170 women carrying normal pregnancies during the first trimester. RESULTS: In all cases, the ADAM12-S concentration in maternal serum samples was lower in trisomy 18 pregnancies than in normal pregnancies, with a median multiple of the median (MoM) of 0.28 (p < 0.001) CONCLUSION: A reduced concentration of ADAM12-S in maternal serum is a promising marker for foetal trisomy 18, as well as for DS.

ADAM Proteins↗
PubMed2005

Weight adjustment of serum markers in early first-trimester prenatal screening for Down syndrome.

OBJECTIVE: To assess whether existing weight correction formulas for PAPP-A and free-beta-hCG developed for weeks 11 to 14 can be applied to pregnancies in weeks 8 to 10. METHODS: Development of formulas based on limited data sets of 8- to 10-week pregnancies and comparison with existing formulas. Calculation of median MoMs adjusted with different formulas for weight correction. RESULTS: Weight correction formulas for the gestational age of 11 to 14 weeks were not appropriate in the 8- to 10-week gestational age interval for PAPP-A, whereas existing weight correction formulas could be applied to free-beta-hCG, independent of gestational age interval. CONCLUSION: If PAPP-A is used in different gestational age intervals, weight corrections should be developed for the interval.

Body Weight↗
PubMed2005

Mutations in the genes KCND2 and KCND3 encoding the ion channels Kv4.2 and Kv4.3, conducting the cardiac fast transient outward current (ITO,f), are not a frequent cause of long QT syndrome.

BACKGROUND: Long QT syndrome (LQTS) is a hereditary cardiac arrhythmogenic disorder characterized by prolongation of the QT interval in the electrocardiogram, torsades de pointes arrhythmia, and syncopes and sudden death. LQTS is caused by mutations in ion channel genes. However, only in half of the families is it possible to identify mutations in one of the seven known LQTS genes, why further genetic heterogeneity is expected. The genes KCND2 and KCND3, encoding the alpha-subunits of the voltage-gated potassium channels Kv4.2 and Kv4.3 conducting the fast transient outward current (I(TO,f)) of the cardiac action potential (AP) in the myocardium, have been associated with prolongation of AP duration and QT prolongation in murine models. METHODS: KCND2 and KCND3 were examined for mutations using single-strand conformation polymorphism (SSCP) analysis in 43 unrelated LQTS patients, where mutations in the coding regions of known LQTS genes had been excluded. RESULTS: Seven single nucleotide polymorphismsm (SNPs) were found, two exonic SNPs in KCND2 and three exonic and two intronic in KCND3. None of the five exonic SNPs had coding effect. All seven SNPs are considered normal variants. CONCLUSION: The data suggest that mutations in KCND2 and KCND3 are not a frequent cause of long QT syndrome.

Action Potentials↗
PubMed2005

(alpha)B-crystallin in cerebrospinal fluid of patients with multiple sclerosis.

BACKGROUND: (alpha)B-crystallin is a chaperone protein and a potential myelin antigen to human T cells in Multiple Sclerosis (MS). In this study we investigate the existence of (alpha)B-crystallin in the cerebrospinal fluid (CSF) of patients with clinical symptoms of MS and control individuals without these symptoms, using a newly developed (alpha)B-crystallin specific chicken antibody. METHODS: A chicken anti-(alpha)B-crystallin was raised against recombinant (alpha)B-crystallin, characterized and used in a semi-quantitative Western blot analysis of CSF from 16 MS patients and 16 neurological patients without MS. RESULTS: Western blot analysis revealed the presence of high molecular weight (alpha)B-crystallin in CSF. Possibly posttranslationally modified aggregates of (alpha)B-crystallin were found in human astroglioma U373 cells. CSF (alpha)B-crystallin was seen in the CSF in 100% of MS patients and 88% of neurological controls without MS. CONCLUSION: (alpha)B-crystallin is present in the CSF in patients with MS and other neurological controls. Furthermore, (alpha)B-crystallin in CSF and human astroglioma cell line U373 is found in aggregates.

Adult↗
PubMed2005

Tetranectin in cerebrospinal fluid: biochemical characterisation and evidence of intrathecal synthesis or selective uptake into CSF.

BACKGROUND: Tetranectin (TN) is a 67 kDa glycoprotein thought to play a prominent role in the regulation of proteolytic processes via its binding to plasminogen and indirect activation of plasminogen. The TN concentration in serum is approximately 10 mg/l and is reduced in patients with several cancers. The TN concentration in the normal CSF has not been examined. METHODS: The TN concentration in the serum and CSF of 47 normal subjects without neurological disorders was established using a polyclonal sandwich ELISA. RESULTS: The median TN concentration (quartile range) was 10.8 mg/l (9.0-12.1) in serum and 0.43 mg/l (0.3-0.53) in CSF. The TN index median (quartile range), defined as (TN CSF concentration/TN serum concentration)/(Albumin CSF concentration/Albumin serum concentration), was found to be 5.5 (4.7-7.6), suggesting intrathecal synthesis or selective uptake of TN in CNS. Immunohistochemistry showed TN immunoreactivity in neurons and dendrites, but no staining in glial cells in the cerebrum and cerebellum. In plexus choroideus, the ependymal cells exhibited strong immunoreactivity. TN in serum and CSF were immunochemically identical and of similar size. CONCLUSION: TN is present in normal brain and CSF, and the TN index is very high, but further studies are necessary to decide whether TN is synthesised in the CNS or selectively transported over the blood-brain barrier.

Cerebrospinal Fluid↗
PubMed2005

Functional assessment of compound mutations in the KCNQ1 and KCNH2 genes associated with long QT syndrome.

BACKGROUND: Long QT syndrome (LQTS) is a cardiovascular disorder characterized by prolonged QTc time, syncope, or sudden death caused by torsades de pointes and ventricular fibrillation. We investigated the clinical and electrophysiologic phenotype of individual mutations and the compound mutations in a family in which different genotypes could be found. OBJECTIVES: The purpose of this study was to determine the impact of genotype-based diagnostic assessment in LQTS. METHODS: We used cascade screening and functional analyses to investigate the phenotype in a family with LQTS. The contributions of the compound mutations in the KCNQ1 and KCNH2 genes (KCNQ1 R591H, KCNH2 R328C) were analyzed by heterologous expression in Xenopus laevis oocytes using two-electrode voltage clamp and by confocal imaging. RESULTS: KCNH2 R328C did not show any functional phenotype whereas KCNQ1 R591H resulted in severe reduction of current. Neither wild-type nor mutant channels affected each other functionally in coexpression experiments. Therefore, a direct interaction between KCNQ1 and KCNH2 was ruled out under these conditions. CONCLUSION: Assessment of novel mutational findings in LQTS should include accurate genetic and functional analysis. Notably, appropriate studies are needed if two or more mutations in different genes are present in one proband. Our findings prompt reconsideration of the impact of compound mutations in LQTS families and reinforce the need for thorough functional evaluation of novel ion channel mutations before assignment of pathogenic status.

Alleles↗
PubMed2005

One third of Danish hypertrophic cardiomyopathy patients with MYH7 mutations have mutations [corrected] in MYH7 rod region.

Familial hypertrophic cardiomyopathy (FHC) is, in most cases, a disease of the sarcomere, caused by a mutation in one of 10 known sarcomere disease genes. More than 266 mutations have been identified since 1989. The FHC disease gene first characterized MYH7, encodes the cardiac beta-myosin heavy chain, and contains more than 115 of these mutations. However, in most studies, only the region encoding the globular head and the hinge region of the mature cardiac beta-myosin heavy chain have been investigated. Furthermore, most studies carries out screening for mutations in the most prevalent disease genes, and discontinues screening when an apparent disease-associated mutation has been identified. The aim of the present study was to screen for mutations in the rod region of the MYH7 gene in all probands of the cohort, regardless of the known genetic status of the proband. Three disease-causing mutations were identified in the rod region in four probands using capillary electrophoresis single-strand conformation polymorphism as a screening method. All mutations were novel: N1327K, R1712W, and E1753K. Two of the probands had already been shown to carry other FHC-associated mutations. In conclusion, we show that in the Danish cohort we find one third of all MYH7 mutations in the rod-encoding region and we find that two of the patients carrying these mutations also carry mutations in other FHC disease genes stressing the need for a complete screening of all known disease genes in FHC-patients.

Amino Acid Substitution↗
PubMed2005

Reduction of the disintegrin and metalloprotease ADAM12 in preeclampsia.

OBJECTIVES: The secreted form of ADAM12 is a metalloprotease that may be involved in placental and fetal growth. We examined whether the concentration of ADAM12 in first-trimester maternal serum could be used as a marker for preeclampsia. METHODS: We developed a semiautomated, time-resolved, immunofluorometric assay for the quantification of ADAM12 in serum. The assay detected ADAM12 in a range of 78-1248 microg/L. Serum samples derived from women in the first trimester of a normal pregnancy (n = 324) and from women who later developed preeclampsia during pregnancy (n = 160) were obtained from the First Trimester Copenhagen Study. ADAM12 levels were assayed in these serum samples. Serum levels of ADAM12 were converted to multiples of the median (MoM) after log-linear regression of concentration versus gestational age. RESULTS: Serum ADAM12 levels in women who developed preeclampsia during pregnancy had a mean log MoM of -0.066, which was significantly lower than the mean log MoM of -0.001 for ADAM12 levels observed in serum samples from women with normal pregnancy (P = .008). The mean log MoM was even lower in serum derived from preeclamptic women whose infant's weight at birth was less than 2,500 g (n = 27, mean log MoM of -0.120, P = .053). CONCLUSION: The maternal serum levels of ADAM12 are significantly lower during the first trimester in women who later develop preeclampsia during pregnancy when compared with levels in women with normal pregnancies. Because the secreted form of ADAM12 cleaves insulin-like growth factor binding protein (IGFBP)-3 and IGFBP-5, the IGF axis may play a role in preeclampsia. ADAM12 may be a useful early marker for preeclampsia. LEVEL OF EVIDENCE: II-2.

Adult↗
PubMed2004

Pregnancy-associated plasma protein A and its endogenous inhibitor, the proform of eosinophil major basic protein (proMBP), are related to complex stenosis morphology in patients with stable angina pectoris.

BACKGROUND: The metalloproteinase pregnancy-associated plasma protein-A (PAPP-A) has been implicated in coronary plaque disruption. Its endogenous inhibitor, the proform of eosinophil major basic protein (proMBP), may also play a role in this process. Atheromatous plaque disruption often presents as complex angiographic lesions. We sought to assess whether PAPP-A, proMBP, and PAPP-A/ProMBP ratio are markers of angiographic plaque complexity in patients with chronic stable angina. METHODS AND RESULTS: We studied 396 stable angina patients (age 63+/-10 years, 230 men) of whom 289 had angiographically documented coronary artery disease (> or =75% stenosis). All coronary stenoses > or =30% diameter reduction (n =531 in 322 patients) were assessed and classified as complex (n =228) or smooth (n =303) by previously validated criteria. PAPP-A, proMBP, and C-reactive protein (hs-CRP) serum levels were measured by ELISA. Patients with complex coronary stenoses had a significantly (P<0.001) higher PAPP-A/proMBP ratio (3.1+/-1.2 versus 2.7+/-0.8x10(-3)) and PAPP-A levels (5.9+/-1.6 versus 5.1+/-1.4 mIU/L) than those without. On univariate analysis, male gender (P<0.001), age (P<0.001), previous history of myocardial infarction (P=0.013), reduced ejection fraction (P<0.001), severe coronary artery disease (P<0.001), aspirin treatment (P<0.001), PAPP-A levels (P<0.001), and PAPP-A/proMBP ratio (P<0.001) were correlated with the number of complex stenoses. Multiple regression analysis showed that male gender, age, severe coronary artery disease, and PAPP-A/proMBP ratio were independent predictors of the number of angiographically complex stenoses. CONCLUSIONS: In patients with stable angina, PAPP-A and PAPP-A/proMBP ratio are associated with angiographic plaque complexity.

Aged↗
PubMed2004

Inhibition of proteolysis by the proform of eosinophil major basic protein (proMBP) requires covalent binding to its target proteinase.

By proteolytic cleavage of insulin-like growth factor binding proteins, the metalloproteinase pregnancy-associated plasma protein-A (PAPP-A) is able to control the biological activity of insulin-like growth factors. PAPP-A circulates in pregnancy as a proteolytically inactive complex, disulfide bound to the proform of eosinophil major basic protein (proMBP). We here demonstrate that co-transfection of mammalian cells with PAPP-A and proMBP cDNA results in the formation of a covalent PAPP-A/proMBP complex in which PAPP-A is inhibited. Formation of the complex also occurs when PAPP-A and proMBP synthesized separately are incubated. Complex formation was monitored by Western blotting, and by using an immunoassay specific for the complex. Using mutagenesis, we further demonstrate that the complex forms in a specific manner and depends on the presence of two proMBP cysteine residues. Mutated proMBP, in which Cys-51 and -169 are replaced by serine, is unable to form the covalent complex with PAPP-A. Of particular interest, such mutated proMBP further lacks the ability to inhibit PAPP-A. For the first time, this conclusively demonstrates that proMBP is a proteinase inhibitor. We further conclude that proMBP inhibits PAPP-A in an unusual manner, not paralleled by other proteinase inhibitors of our knowledge, which requires proMBP to be covalently bound to PAPP-A by disulfide bonds. ProMBP binding to PAPP-A most likely either abrogates substrate access to the active site of PAPP-A or induces a conformational change in the structure of PAPP-A, as we, by further mutagenesis, were able to exclude that the inhibitory mechanism of proMBP is based on a cysteine switch-like mechanism.

Amino Acid Substitution↗
PubMed2004

Does KCNE5 play a role in long QT syndrome?

BACKGROUND: Long QT syndrome [LQTS] is a congenital cardiac disease characterised by prolonged QTC-time, syncopes and sudden cardiac death. LQTS is caused by mutations in genes coding for ion channels involved in the action potential. KCNE5 codes for a novel beta-subunit of the ion channel conducting the delayed rectifier repolarizing current IKs. As KCNE5 is expressed in the human heart and suppresses the IKs current in heterologous systems, it is a candidate gene that may be mutated in LQTS families where no causative mutations in known LQTS associated genes have been found. We examined whether this was the case. METHODS: Genomic DNA from LQTS patients [n=88] and normal controls [n=90] was screened for mutations in KCNE5 by endonuclease-enhanced single strand conformation polymorphism analysis [EE-SSCP], and DNA sequencing of aberrant conformers. Mutations in other LQTS associated ion channels were excluded by SSCP. RESULTS: No mutations were found in the coding region of the KCNE5 gene in LQTS patients. One polymorphism, a T-to-C transition at nucleotide 97, causing an amino acid polymorphism P33S, was present in 16 persons, nine heterozygotes and seven homozygotes. The T-allele frequency was 0.13 in LQTS patients and 0.10 in controls.

Action Potentials↗
PubMed2004

T wave morphology analysis distinguishes between KvLQT1 and HERG mutations in long QT syndrome.

OBJECTIVES: The aim of this study was to develop an objective method to distinguish between HERG and KvLQT1 genotypes on the surface ECG. BACKGROUND: The two most prevalent genes affected in long QT syndrome (LQTS) are KvLQT1 (KCNQ1) and HERG (KCNH2), which are mutated in >90% of patients with a reported LQTS genotype. It is known that T waves have lower amplitude and more notches in HERG patients than T waves in KvLQT1 patients, but this semiquantitative method lacks the discriminative power to be used in a clinical setting. We developed a simple mathematical method that allowed us to quantify T wave shape in LQTS mutations for clinical use. METHODS: ECGs from 24 HERG patients, 13 KvLQT1 LQTS patients, and 13 healthy relatives were examined. The repolarizing integral (RI) was constructed from the T wave. The resulting RI is sigmoid and was modeled using the Hill equation as (RI(t) = V(max)*[t(n)/[K(m)(n) + t(n)]]). V(max) is equivalent to the total T wave area, K(m) is the time when 50% of the T wave area is reached, and n is a measure of the slope of the sigmoid RI. RESULTS: The RI correlated nearly perfectly to the fitted sigmoid, r = 0.99. In lead V(2), V(max) was larger in KvLQT1 (0.148 +/- 0.021) (mean +/- SE) compared to HERG (0.080 +/- 0.012) and controls (0.067 +/- 0.021). The Hill coefficient n of the RI discriminated perfectly between HERG (2.00 +/- 0.11) and KvLQT1 (4.11 +/- 0.15). CONCLUSIONS: RI allows distinguishing between HERG and KvLQT1 mutations based solely on the T wave morphology in the present LQTS population.

Adolescent↗
PubMed2004

Genetic and phenotypic characterization of mutations in myosin-binding protein C (MYBPC3) in 81 families with familial hypertrophic cardiomyopathy: total or partial haploinsufficiency.

Mutations in the MYBPC3 gene, encoding the sarcomere protein myosin-binding protein C, are among the most frequent causes of autosomal dominant familial hypertrophic cardiomyopathy (FHC). We studied the frequency, type, and pathogenetic mechanism of MYBPC3 mutations in an unselected cohort of 81 FHC families, consecutively enrolled at a tertiary referral center. Nine mutations, six of which were novel, were found in 10 (12.3%) of the families using single-strand conformation polymorphism and DNA sequencing. A frameshift mutation in exon 2 clearly suggests that haploinsufficiency is a pathogenetic mechanism in FHC. In addition, splice site mutations in exon 6 and intron 31, a deletion in exon 13, and a nonsense mutation in exon 25, all lead to premature termination codons, most likely causing loss of function and haploinsufficiency. Furthermore, there were two missense mutations (D228N and A833 T) and one in-frame deletion (DeltaLys813). A considerable intrafamilial variation in phenotypic expression of MYBPC3-based FHC was noted, and we suggest that mutations influencing stability of mRNA could play a role in the variable penetrance and expressivity of the disease, perhaps via partial haploinsuffciency.

Adult↗
PubMed2004

Apolipoprotein E genotype and cognitive dysfunction after noncardiac surgery.

BACKGROUND: Apolipoprotein E is important in recovery after neuronal damage. The epsilon4 allele of the apolipoprotein E gene has been shown as a risk factor for Alzheimer disease, poor outcome after cerebral injury, and accelerated cognitive decline with normal aging. The authors hypothesized that patients with the epsilon4 allele would have an increased risk of postoperative cognitive dysfunction (POCD) after noncardiac surgery. METHODS: In a multicenter study, a total of 976 patients aged 40 yr and older undergoing noncardiac surgery were tested preoperatively and 1 week and 3 months after surgery with a neuropsychological test battery comprising seven subtests. POCD was defined as a decline in test performance of more than 2 SD from the expected. Apolipoprotein E genotypes were determined by blood sample analysis at a central laboratory. Multivariate logistic regression analysis with POCD as the dependent variable assessed presence of the epsilon4 allele (yes/no) and other possible risk factors. RESULTS: The epsilon4 allele was found in 272 patients. One week after surgery, the incidence of POCD was 11.7% in patients with the epsilon4 allele and 9.9% in patients without the epsilon4 allele (P = 0.41). Three months later, POCD was found in 10.3% of patients with the epsilon4 allele and in 8.4% of patients without the epsilon4 allele (P = 0.40). Multivariate logistic regression analysis did not identify the epsilon4 allele as a risk factor at 1 week (P = 0.33) or 3 months (P = 0.57). CONCLUSIONS: The authors were unable to show a significant association between apolipoprotein E genotype and POCD, but statistical power was limited because of a lower incidence of POCD than expected.

Adult↗
PubMed2004

Cell surface adhesion of pregnancy-associated plasma protein-A is mediated by four clusters of basic residues located in its third and fourth CCP module.

The metalloproteinase pregnancy-associated plasma protein-A (PAPP-A) cleaves a subset of insulin-like growth factor binding proteins (IGFBP), which inhibit the activities of insulin-like growth factor (IGF). Through this proteolytic activity, PAPP-A is believed to regulate IGF bioavailability in several biological systems, including the human reproductive system and the cardiovascular system. PAPP-A adheres to mammalian cells by interactions with glycosaminoglycan (GAG), thus targeting the proteolytic activity of PAPP-A to the cell surface. Based on site-directed mutagenesis, we here delineate the PAPP-A GAG-binding site in the C-terminal modules CCP3 and CCP4. Using heparin affinity chromatography, commonly employed in such studies, we define three clusters of arginines and lysines of CCP3, which are important for the interaction of PAPP-A with heparin. In a model of PAPP-A CCP3-CCP4, basic residues of these sequence clusters form a contiguous patch located on one side of the structure. Binding to the unknown, natural cell surface receptor of PAPP-A, assessed by flow cytometry, also depends on residues of these three basic clusters. However, single or double residue substitutions generally have a modest effect on PAPP-A heparin binding assessed by chromatography, but cell surface adhesion was critically reduced by several of these substitutions, emphasizing the relevance of analysis by flow cytometry. The contributions of positively charged residues located in CCP4 were all minor when analyzed by heparin affinity chromatography. However, the mutation of CCP4 residues Arg1459 and Lys1460 to Ala almost abrogated cell surface adhesion. Furthermore, when acidic residues of the homologous proteinase PAPP-A2 (Asp1547, Glu1555 and Glu1567) were introduced into the corresponding positions in the sequence of PAPP-A, located in each of the three basic clusters of CCP3, binding to heparin was strongly impaired and cell surface binding was abrogated. This explains, at least in part, why PAPP-A2 lacks the ability of cell surface adhesion, and further emphasizes the role of the basic clusters defined in PAPP-A.

Amino Acid Sequence↗