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N Gregersen

Publications and source records attributed to N Gregersen.

At least 73 records · Page 4Linked to original sources
PubMed1997

Structural organization of the human short-chain acyl-CoA dehydrogenase gene.

Short-chain acyl-CoA dehydrogenase (SCAD) is a homotetrameric mitochondrial flavoenzyme that catalyzes the initial reaction in short-chain fatty acid beta-oxidation. Defects in the SCAD enzyme are associated with failure to thrive, often with neuromuscular dysfunction and elevated urinary excretion of ethylmalonic acid (EMA). To define the genetic basis of SCAD deficiency and ethylmalonic aciduria in patients, we have determined the sequence of the complete coding portion of the human SCAD gene (ACADS) and all of the intron-exon boundaries. The SCAD gene is approximately 13 kb in length and consists of 10 exons. Four polymorphic sites have previously been detected by sequencing of cDNA from fibroblasts of patients excreting elevated amounts of EMA. Three of these polymorphisms (321T/C, 990C/T, 1260G/C) are silent variants, while a 625G/A polymorphism results in an amino acid replacement and has been shown to be associated with ethylmalonic aciduria. From analysis of 18 unrelated Danish families, we show that the four SCAD gene polymorphisms constitute five allelic variants of the SCAD gene, and that the 625A variant together with the less frequent variant form of the three other polymorphisms (321C, 990T, 1260C) constitutes an allelic variant with a frequency of 22% in the general Danish population. Using fluorescence in-situ hybridization, we confirm the localization of the human SCAD gene to the distal part of Chromosome (Chr) 12 and suggest that the SCAD gene is a single-copy gene. The evolutionary relationship between SCAD and five other members of the acyl-CoA dehydrogenase family was investigated by two independent approaches that gave similar phylogenetic trees.

Acyl-CoA Dehydrogenase↗
PubMed1997

A common W556S mutation in the LDL receptor gene of Danish patients with familial hypercholesterolemia encodes a transport-defective protein.

In a group of unrelated Danish patients with familial hypercholesterolemia (FH) we recently reported two common low-density lipoprotein (LDL) receptor mutations, W23X and W66G, accounting for 30% of the cases. In this study, we describe another common LDL receptor mutation, a G to C transition at cDNA position 1730 in exon 12, causing a tryptophan to serine substitution in amino acid position 556 (W556S). In the Danish patients, the W556S mutation was present in 12% of 65 possible mutant alleles. The pathogenicity of the W556S mutation, which is located in one of the five conserved motifs Tyr-Trp-Thr-Asp in the epidermal growth factor homology region, was studied in transfected COS-7 cells expressing normal and mutant LDL receptor cDNAs. Results obtained by immunofluorescence flow cytometry and confocal microscopy, as well as by immunoprecipitation, were compatible with complete retention of the mutant protein in the endoplasmic reticulum. The transport-defective W556S mutation and the W23X and W66G mutations seem to account for about 40% of the LDL receptor defects in Danish families with FH.

Amino Acid Sequence↗
PubMed1997

A sequence variation: 713-8delC in the transforming growth factor-beta 1 gene has higher prevalence in osteoporotic women than in normal women and is associated with very low bone mass in osteoporotic women and increased bone turnover in both osteoporotic and normal women.

Bone mass is partly genetically determined. The genes involved are, however, still largely unknown. Transforming growth factor-beta 1 (TGF-beta 1) is considered a putative regulator of osteoclastic-osteoblastic interaction (coupling). The aim of the present study was therefore to examine whether possible variants of the TGF-beta 1 gene are related to bone mass and osteoporosis. We examined 161 osteoporotic women (at least one low energy spinal fracture) and 131 normal women. We investigated sequence variations in the TGF-beta 1 gene using the single-stranded conformation polymorphism (SSCP) technique combined with DNA sequencing. Seven patients were heterozygous for a cytosine to thymidine base substitution at position 76 in exon 5 (C788-T) (corresponding to position 788 in the TGF-beta 1 cDNA), resulting in a threonine to isoleucine amino acid shift at position 263 in the TGF-beta 1 propeptide (Thr263-Ile). Ten other patients had a one base deletion in the intron sequence 8 bases prior to exon 5 (713-8delC), which could influence splicing. Five normal women exhibited the C788-T sequence variant, and two the 713-8delC. The prevalence of 713-8delC was significantly higher in the osteoporotic group (chi 2 = 4.02, p < 0.05). Osteoporotic patients with the 713-8delC variant had increased levels of bone alkaline phosphatase (p < 0.05). If the osteoporotic patients with a z score of the lumbar spine below -1 were examined separately, we found increased serum levels of bone alkaline phosphatase (p < 0.05), increased urinary excretion of hydroxyproline (p < 0.05), and reduced bone mass of the lumbar spine (p < 0.05) in patients with 713-8delC. No correlation to bone mass was demonstrated in the normal women, but 713-8delC was associated with increased serum levels of bone alkaline phosphatase (p < 0.05). The sequence variation, 713-8delC, in the TGF-beta 1 gene is more frequent in patients with osteoporosis compared to normal controls. The 713-8delC variant seems to be associated with very low bone mass in osteoporotic women with low bone mass and increased bone turnover in both osteoporotic and normal women.

Adult↗
PubMed1997

The molecular basis of medium-chain acyl-CoA dehydrogenase (MCAD) deficiency in compound heterozygous patients: is there correlation between genotype and phenotype?

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is the most commonly recognized defect of mitochondrial beta-oxidation. It is potentially fatal, but shows a wide clinical spectrum. The aim of the present study was to investigate whether any correlation exists between MCAD genotype and disease phenotype. We determined the prevalence of the 14 known and seven previously unknown non-G985 mutations in 52 families with MCAD deficiency not caused by homozygosity for the prevalent G985 mutation. This showed that none of the non-G985 mutations are prevalent, and led to the identification of both disease-causing mutations in 14 families in whom both mutations had not previously been reported. We then evaluated the severity of the mutations identified in these 14 families. Using expression of mutant MCAD in Escherichia coli with or without co-overexpression of the molecular chaperonins GroESL we showed that five of the missense mutations affect the folding and/or stability of the protein, and that the residual enzyme activity of some of them could be modulated to a different extent depending on the amounts of available chaperonins. Thus, some of the missense mutations may result in relatively high levels of residual enzyme activity, whereas the mutations leading to premature stop codons will result in no residual enzyme activity. By correlating the observed types of mutations identified to the clinical/biochemical data in the 14 patients in whom we identified both disease-causing mutations, we show that a genotype/phenotype correlation in MCAD deficiency is not straightforward. Different mutations may contribute with different susceptibilities for disease precipitation, when the patient is subjected to metabolic stress, but other genetic and environmental factors may play an equally important role.

Acyl-CoA Dehydrogenase↗
PubMed1997

Fatty acid oxidation disorders as primary cause of sudden and unexpected death in infants and young children: an investigation performed on cultured fibroblasts from 79 children who died aged between 0-4 years.

BACKGROUND: Disorders of fatty acid metabolism are known to be responsible for cases of sudden and unexpected death in infancy. At least 14 disorders are known at present. 120 cases of sudden infant death syndrome (SIDS) had been examined for a prevalent mutation (G985) causing medium chain acyl CoA dehydrogenase deficiency, which is inherited in an autosomal recessive mode. No over-representation of either homozygous or heterozygous cases was found. AIMS: To investigate a broader spectrum of fatty acid oxidation disorders in a wider range of sudden deaths in infants and young children. METHODS: Seventy nine cases of unexpected death in infants and young children younger than 4 years old were examined for a minimum of nine fatty acid oxidation disorders, using the global [9, 10-3H] myristic acid oxidation assay in cultured fibroblasts from achilles tendon biopsies taken at postmortem examination. RESULTS: Three cases with fatty acid oxidation disorders and two carriers of the G985 mutation were found, all categorized as non-SIDS or borderline SIDS. The global assay used has the advantage of simplicity. CONCLUSIONS: These results indicate that disorders of fatty acid oxidation play a small but significant role in the cause of unexpected death in infants and young children, and that infants and children dying in this way should be regarded as high risk candidates for metabolic diseases.

Acyl-CoA Dehydrogenase↗
PubMed1997

A survey of the newborn populations in Belgium, Germany, Poland, Czech Republic, Hungary, Bulgaria, Spain, Turkey, and Japan for the G985 variant allele with haplotype analysis at the medium chain Acyl-CoA dehydrogenase gene locus: clinical and evolutionary consideration.

Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is an inborn error of fatty acid metabolism. It is one of the most frequent genetic metabolic disorders among Caucasian children. The G985 allele represented 90% of all the variant alleles of the MCAD gene in an extensive series of retrospective studies. To study the distribution of the G985 allele, newborn blood samples from the following countries were tested; 3000 from Germany (1/116). 1000 each from Belgium (1/77). Poland (1/98), Czech Republic (1/240). Hungary (1/168), Bulgaria (1/91), Spain (1/141). Turkey (1/216), and 500 from Japan (none). The frequency is shown in parentheses. The haplotype of G985 alleles in 1 homozygote and 57 heterozygote samples were then analyzed using two intragenic MCAD gene polymorphisms (Iaq1 and GT-repeat). The result indicated that only 1 of the 10 known haplotypes was associated with the G985 mutation, suggesting that G985 was derived originally from a single ancestral source. We made a compilation of the G985 frequencies in these countries and those in nine other European countries studied previously. The G985 distribution was high in the area stretching from Russia to Bulgaria in the east and in all northern countries in western and middle Europe, but low in the southern part of western and middle Europe. The incidence among ethnic Basques appeared to be low. This distribution pattern and the fact that all G985 alleles belong to a single haplotype suggest that G985 mutation occurred later than the delta F508 mutation of the CFTR, possibly in the neolithic or in a later period, and was brought into Europe by IndoEuropean-speaking people. The panEuropean distribution of the G985 allele, including Slavic countries from which patients with MCAD deficiency have rarely been detected, indicates the importance of raising the level of awareness of this disease.

Acyl-CoA Dehydrogenases↗
PubMed1996

Influence of Lewis alpha1-3/4-L-fucosyltransferase (FUT3) gene mutations on enzyme activity, erythrocyte phenotyping, and circulating tumor marker sialyl-Lewis a levels.

Fucosylated glycoproteins carrying alpha1-4 fucose residues are of importance for cell adhesion and as tumor markers. The Lewis gene, FUT3, encodes the only known alpha1-4-fucosyltransferase (FucT), and individuals who are deficient in this enzyme type as Lewis-negative on erythrocytes. We examined the mutational spectrum of the Lewis gene in Denmark and found 6 different mutations. Five, T59G, T202C, C314T, G508A, and T1067A, were frequent, and one, C445A, was only detected in one out of 40 individuals. Allele-specific polymerase chain reaction as well as cloning of FUT3 alleles showed that the 202 and 314 mutations were co-located on the same allele. COS7 cells transfected with an allele having the 202/314 mutations lacked enzyme activity. Polymerase chain reaction-cleavage assays were established for the genotyping of healthy individuals as well as 20 genuine Lewis-negative cancer patients and 10 non-genuine. The latter have Lewis-negative erythrocytes but saliva alpha1-4FucT activity. The genuine Lewis-negative individuals had mutations on both FUT3 alleles. In 66 healthy individuals, a gene dosage effect was detected as FUT3 heterozygous individuals had a lower alpha1-4FucT activity in saliva than did homozygous wild-type individuals. The lower enzyme level in heterozygous individuals resulted in a significantly (p < 0.04) lower level of circulating sialyl-Lewis a structure in serum. This has the clinical impact that cut-off levels in tumor marker assays should be defined on the basis of genotyping. In the group of non-genuine Lewis-negative cancer patients, whose erythrocytes convert from Lewis-positive to Lewis-negative during the disease, FUT3 heterozygosity was significantly (p < 0.05) more common.

ABO Blood-Group System↗
PubMed1996

Structure of the rat gene encoding the multifunctional acyl-CoA-binding protein: conservation of intron 1 sequences in rodents and man. Addendum.

The entire gene encoding the rat acyl-CoA-binding protein (ACBP), and intron 1 of the mouse and human ACBP genes were sequenced and analyzed. A CpG island has been maintained in human ACBP which, in contrast to the rodent ACBP genes, is subject to alternative splicing. Analysis of the rat intron 2 and 3 sequences identified a number of potential alternative splice donor and splice acceptor sites. However, RNase protection analysis revealed no alternatively spliced transcripts in RNA from various rat tissues. Several repetitive elements belonging to the ID, B1 and B2 families are present in introns 2 and 3.

Alternative Splicing↗
PubMed1996

Identification of a novel mutation in exon 13 of the LDL receptor gene causing familial hypercholesterolemia in two Spanish families.

DNA from 30 unrelated Spanish patients with familial hypercholesterolemia (FH) was studied by single-strand conformation polymorphisms (SSCP)/heteroduplex analysis for mutation detection in exon 13 of low density lipoprotein (LDL) receptor gene. Two patients were found to have an abnormal pattern by heteroduplex analysis, and direct sequencing revealed a C to G substitution at nucleotide position 1965, that results in a Phe to Leu change in codon 634, F634L. We have developed a PCR based assay to detect this mutation in family members. We found three additional F634L mutation carriers, and all of them had high cholesterol levels. Haplotype analysis revealed that all F634L mutation carriers had the same allele determined by TaqI -, StuI +, AvaII +, NcoI -, suggesting the presence of a common ancestor. We report a novel mutation located in exon 13 of the LDL receptor gene that causes FH. We also demonstrate the importance of combining SSCP and heteroduplex analysis to improve mutation detection.

Amino Acid Sequence↗
PubMed1996

Allele-specific measurement of low-density lipoprotein receptor transcript levels.

We have developed an assay for allele-specific determination of low-density lipoprotein receptor (LDLR) mRNAs. Transcript levels are measured by reverse transcription (RT), PCR, and electrophoresis on an automatic DNA sequencer using fluorescence-labeled primers and direct quantitation of the allele-specific RT-PCR products. The discrimination between the allelic products is based on the use of DNA polymorphisms located in the coding regions of the gene as markers for the individual alleles. Using this method on LDLR mRNA from heterozygous patients with familial hypercholesterolemia (FH) due to a defective LDLR protein, it is possible to relate the expression of the mutant allele directly to the expressed amounts of the normal allele, thus overcoming the problems of using artificial internal standards in the PCR. To validate the method we have measured (1) the range of normal LDLR allele transcript levels, and (2) the transcript levels in patients heterozygous for different types of mutant LDLR alleles associated with FH. The method is general in principle and can be applied in the allele-specific analysis of transcripts from all genes harbouring DNA polymorphisms in their coding regions.

Alleles↗
PubMed1996

The Trp23-Stop and Trp66-Gly mutations in the LDL receptor gene: common causes of familial hypercholesterolemia in Denmark.

Mutations in the gene for the low density lipoprotein (LDL) receptor cause the autosomal dominant disease familial hypercholesterolemia (FH), the prevalence of which is about 0.2% in most populations. By PCR-SSCP analysis and direct sequencing, we identified the receptor-negative Trp23-Stop LDL receptor mutation (FH Cincinnati-5) in 10 of 63 FH probands and the receptor-defective Trp66-Gly LDL receptor mutation (FH French Canadian-4) in another 10 of the 63 FH probands. These two mutations thus account for 30% of diagnosed FH families in Denmark. Comparison of the mean lipid concentrations (unadjusted and adjusted for age), including serum total cholesterol and LDL-cholesterol, showed no significant differences between the two groups of FH heterozygote probands (cholesterol: 10.7 mmol/l vs. 10.7 mmol/l) and between the probands and 16 and 22 non-proband family members with the Trp23-stop (cholesterol: 10.1 mmol/l) ad Trp66-Gly (cholesterol: 10.7 mmol/l) mutations, respectively.

Adult↗
PubMed1996

Cloning and characterization of human very-long-chain acyl-CoA dehydrogenase cDNA, chromosomal assignment of the gene and identification in four patients of nine different mutations within the VLCAD gene.

Very-long-chain acyl-CoA dehydrogenase (VLCAD) is one of four straight-chain acyl-CoA dehydrogenase (ACD) enzymes, which are all nuclear encoded mitochondrial flavoproteins catalyzing the initial step in fatty acid beta-oxidation. We have used the very fast, Rapid Amplification of cDNA Ends (RACE) based strategy to obtain the sequence of cDNAs encoding human VLCAD from placenta and fibroblasts. Alignment of the predicted amino acid sequence of human VLCAD with those of the other human ACD enzymes revealed extensive sequence homology. Moreover, human VLCAD and human acyl-CoA oxidase showed extensive sequence homology corroborating the notion that these genes are evolutionarily related. Southern blot analysis of genomic DNA from hybrid cell lines was used to localize the VLCAD gene to human chromosome 17p11.2-p11.13105. Using Northern and Western blot analysis to investigate the tissue specific distribution of VLCAD mRNA and protein in several human tissues we showed that VLCAD is most abundant in heart and skeletal muscle. This agrees well with the fact that cardiac and muscle symptoms are characteristic for patients with VLCAD deficiency. Northern blot analysis and sequencing of cloned PCR amplified VLCAD cDNA from four unrelated patients with VLCAD deficiency showed that VLCAD mRNA was undetectable in one patient and that the other three have mutations in both VLCAD alleles. Western blot analysis of patient fibroblasts showed that the identified mutations result in severely reduced amounts of VLCAD protein. None of the patients harbored identical mutations suggesting that the mutational heterogeneity in VLCAD deficiency is large.

Acyl-CoA Dehydrogenase, Long-Chain↗
PubMed1996

Phenotypic characterization of a patient homozygous for the D558N LDL receptor gene mutation.

We describe the clinical, biochemical, and genetic features of a patient with true homozygous familial hypercholesterolemia due to the D558N low-density lipoprotein receptor gene mutation, previously designated FH Cincinnati-4. Functional flow-cytometric analysis of the LDL receptorR protein on upregulated EBV-transformed lymphocytes indicated reduction of the number of receptors on the cell surface by 87% and reduction of receptor activity by 89% compared to control cells. With drugs and a portacaval shunt operation, performed when the patient was 15 years old, serum cholesterol was reduced from about 28 to about 15 mmol/l. He died at the age of 32 of a myocardial infarction. The autopsy showed generalized atherosclerosis, especially in the coronary arteries, which were severely stenosed proximally. A rare finding was a large intracranial xanthoma that apparently had been asymptomatic.

Adult↗
PubMed1996

A G-1-to-A acceptor splice site LDLR mutant allele leads to reduced relative transcript levels in patients with heterozygous familial hypercholesterolemia.

A plethora of different mutations in the gene for the low density receptor (LDLR) are responsible for the autosomal dominant inherited disorder familial hypercholesterolemia (FH). However, only a few splice site mutations have been identified in this gene. We here report a defect presumably affecting the splicing of precursor mRNA, resulting from a novel mutation, a G to A transition at the terminal nucleotide of intron 12, of the LDLR gene detected in three unrelated families with heterozygous FH. This mutation markedly reduced the steady-state transcript level of the mutant LDLR allele as compared to the corresponding normal LDLR allele in heterozygous FH patients as measured by a fluorescence based, allele-specific quantitation technique. In the FH families, the acceptor splice site mutation cosegregates with hypercholesterolemia, and it is associated with onset of ischemic heart disease in the fifth and sixth decade of life.

Adult↗
PubMed1996

Two novel mutations in the LDL receptor gene: common causes of familial hypercholesterolemia in a Spanish population.

In our investigation of the LDL receptor gene in 30 Spanish patients, who were clinically diagnosed as heterozygous FH and were unrelated, we have applied single strand conformation polymorphism (SSCP) analysis and solid-phase sequencing. We identified two novel pathogenic mutations accounting for one third of the FH in this patient sample. Six patients were found to have a G to T substitution at nucleotide position 91 in exon 2 that results in a stop codon, E10X. Four patients were found to have a G deletion at nucleotide 518 in exon 4, causing a translational frameshift and a stop codon, 518delG. We have developed two polymerase chain reaction (PCR) based assays to detect easily these two mutations in all the available family members. We found fourteen E10X mutation carriers and eighteen 518delG mutation carriers. There was no statistically significant difference in mean lipid levels between carriers of these two mutations. Furthermore, haplotype analysis revealed that all E10X mutation carriers had the allele determined by TaqI-, StuI+, AvaII+, NcoI- and all 518delG mutation carriers had the haplotype TaqI-, StuI+, AvaII-, NcoI+. This indicates that both mutations may have been inherited from common ancestors, respectively.

Adolescent↗