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Biomedical subjects

F Skovby

Publications and source records attributed to F Skovby.

At least 55 records · Page 3Linked to original sources
PubMed1997

Investigation of deletions at 7q11.23 in 44 patients referred for Williams-Beuren syndrome, using FISH and four DNA polymorphisms.

Williams syndrome (WS) is associated with a submicroscopic deletion of the elastin gene (ELN) at 7q11.23. The deletion encompasses closely linked DNA markers. We have investigated 44 patients referred for possible WS using fluorescence in situ hybridization (FISH) analysis with a P1 clone containing an insert from the ELN, as well as performing genotype analysis of patients and parents with four DNA polymorphisms. Twenty-four patients were found to have deletions, 19 of whom were found clinically to have typical WS. The facial features were especially characteristic. None of the patients without detectable deletions was reported to have typical WS features, although one had supravalvular aortic stenosis, hypercalcemia, and mental retardation. No evidence was found in this material for variability of the size of the deletion. Our study supports the usefulness of analysis of ELN deletion in WS patients, both for confirmation of diagnosis and for genetic counselling.

Adolescent↗
PubMed1997

Quantification, by solid-phase minisequencing, of the telomeric and centromeric copies of the survival motor neuron gene in families with spinal muscular atrophy.

In an analysis of 30 families affected by spinal muscular atrophy (SMA) we have used the solid-phase minisequencing method to determine the ratio between the number of telomeric and centromeric copies of the survival motor neuron gene (SMN and cBCD541 respectively) on normal and SMA chromosomes. This has enabled us to establish haplotypes with regard to SMN and cBCD541, and estimate their frequencies, on both types of chromosomes. Six predominant haplotypes were identified, three for normal chromosomes and three for SMA chromosomes, characterized by having 0, 1, or 2 copies, respectively, of cBCD541. We found evidence for the presence of patients homozygous for a deletion of SMN and with only one copy of cBCD541, but found none deleted for all copies of this gene. Several asymptomatic carriers of SMA with only a single copy of SMN and no copy of cBCD541 were identified. We could not confirm the hypothesis that the presence of more copies of cBCD541 is correlated to a less severe course of the disease. The frequencies of haplotypes characterized by having 0, 1, or 2 copies, respectively, of cBCD541 were found to differ significantly between normal and SMA chromosomes. This distribution can be explained by an underrepresentation of the haplotype completely lacking SMN genes, which is expected to cause early embryonic death in homozygotes. This first report of a direct haplotype analysis of SMN and cBCD541 should help clarify the role of cBCD541 in the pathogenesis of SMA.

Centromere↗
PubMed1997

Parental mosaicism and autosomal dominant mutations causing structural abnormalities of collagen I are frequent in families with osteogenesis imperfecta type III/IV.

Protein-chemical and molecular studies were conducted on all osteogenesis imperfecta (OI) type III/IV patients referred to our hospital during the last 15 y. Of a total of 16 OI type III/IV patients studied, 15 patients were heterozygous for a mutation in one of the two genes coding for collagen I, COL1A1 or COL1A2. Cultured fibroblasts from these 15 patients produced both normal and abnormal collagen I molecules, pointing to a dominant-negative effect of the mutation. Nine mutations had not been described previously. Parental mosaicism was demonstrated in three families. In the 16th child the causative mutation was not found. In conclusion, OI type III/IV in most patients of Western European ancestry is caused by dominant mutations in the genes for collagen I, and recurrence of OI is caused in most cases by parental gonadal mosaicism.

Adolescent↗
PubMed1996

[A follow-up study of carriers of cystic fibrosis].

The aim of the present study was to assess the long-term impact of carrier screening for cystic fibrosis. The impact of being identified as a carrier for cystic fibrosis was assessed through three questionnaires measuring the emotional responses, changes in reproductive attitudes and decisions, retention of the result, and sharing of the information about the result with relatives. The questionnaires were sent to 160 women identified as carriers between 1990 and 1992 and to 200 randomly selected women with a negative result. Carriers became surprised, anxious and worried upon receipt of their result. However, this response disappeared once the partners had been tested and found negative. No sign of residual anxiety was found among carriers who answered the third questionnaire in November 1994. Carriers freely shared the information about their result with relatives, friends, and general practitioners. Few carriers changed their reproductive plans or attitudes to abortion of a foetus with CF due to the result. No decline in fertility or change in reproductive pattern were observed among carriers after testing. The imperfect sensitivity of the carrier test caused some misunderstanding in the retention of the result. This may reflect inadequacies in the information and counselling. Psychological factors are also believed to contribute to the misunderstanding of the result. The information should be improved to avoid false reassurance.

Carrier State↗
PubMed1996

First-trimester prenatal diagnosis of Crouzon syndrome.

Crouzon syndrome, one of the best known of many craniofacial syndromes, is an autosomal dominant disorder characterized by craniosynostosis, prominent eyes, and midfacial hypoplasia due to abnormal development and premature fusion of the skull. Recently mutations in the fibroblast growth factor receptor 2 gene (FGFR2) were found to cause Crouzon. We have identified the recurrent mutation C342Y in two unrelated patients with Crouzon syndrome. One patient (A) belongs to a family in which Crouzon could be followed in three generations, while the other patient (B) represents a sporadic case. The identification of the disease-causing mutation allowed first-trimester prenatal diagnosis as requested by both patients in their subsequent pregnancies. A chorionic villus biopsy was performed in the 11th gestational week of patient A's pregnancy. DNA isolated from the biopsy revealed a fetus heterozygous for the C342Y mutation, i.e., having Crouzon syndrome. The pregnancy was terminated and the molecular diagnosis was confirmed later by analysis of fetal and placental tissue. Patient B had a missed abortion before the scheduled chorionic villus biopsy was performed. Mutation analysis of the aborted fetal tissue did not show the C342Y mutation.

Base Sequence↗
PubMed1996

Genetic counselling and prenatal diagnosis of osteogenesis imperfecta caused by paternal mosaicism.

In a family with recurrent osteogenesis imperfecta (OI) caused by paternal mosaicism, prenatal diagnosis was made using restriction enzyme analysis for a mutation in COL1A2. Parental mosaicism is important to consider in genetic counselling for OI. Prenatal diagnosis of OI is available currently by means of collagen or gene analyses in the first trimester or by ultrasonography in the second trimester.

Chorionic Villi Sampling↗
PubMed1996

Deletion of a Gly-Pro-Pro repeat in the pro alpha2(I) chain of procollagen I in a family with dominant osteogenesis imperfecta type IV.

We have investigated one member of a family with dominant osteogenesis imperfecta type IV through three generations. In protein-chemical studies of cultured fibroblasts derived from the proband, collagen I was overmodified, with normal processing of procollagen I, normal thermal stability, and a cyanogen bromide peptide map that suggested a C-terminal location of the structural abnormality in the collagen triple helix. Sequencing of the gene encoding the alpha2(I) chain of collagen I (COL1A2) indicated a nine base-pair deletion of nucleotides 3418-3426. When a polymerase chain reaction product containing the nucleotides in question was electrophoresed in a 12% polyacrylamide gel, two bands with a difference in size of nine base pairs could be shown. Sequencing of the molecular weight band confirmed the deletion of the nine base pairs involving codons 1003-1006 of COL1A2. The deletion introduced a SfiI restriction site that was used for confirmation of the deletion in genomic DNA from the proband. The deletion resulted in the removal of three amino acids (Gly-Pro-Pro), but this did not disrupt the Gly-X-Y sequence of the collagen triple helix, as is often the case in the more common glycine substitutions. We discuss the ways in which this deletion could result in osteogenesis imperfecta.

Adult↗
PubMed1996

Variable clinical expression in a family with OI type IV due to deletion of three base pairs in COL1A1.

We have studied a family with autosomal dominant osteogenesis imperfecta (OI) type IV. Electrophoresis of collagen produced by cultured fibroblasts revealed a slower migrating population of collagen I. Cyanogen bromide peptide mapping localised the structural defect to the area of the alpha 1(1)CB3 peptide. Subsequent sequencing revealed a deletion of nucleotides 1964-1966 in exon 27 of COL1A1. By means of restriction enzyme analysis, the deletion could be detected in all affected family members. This in-frame deletion resulted in the removal of alanine-438 and Glu437Asp substitution in the pro alpha 1(I) collagen chain. Clinical variation was considerable among affected family members. The most consistent clinical features were reduced height and extraosseous manifestations of OI.

Cells, Cultured↗
PubMed1996

Psychological and social impact of carrier screening for cystic fibrosis among pregnant woman--a pilot study.

The aim of the current study was to assess the psychological and social impact of delta F508 carrier screening for cystic fibrosis among pregnant women. The impact of carrier screening was assessed in terms of anxiety, perception of health, reproductive decisions, retention of results, and sharing of information with relatives by two self-administered questionnaires sent to 160 women with a positive and 200 women with a negative test result. While no attempt was made to make women accept or decline testing, 22-28% of those tested found it difficult to reject the test when offered. Women with a positive test result became more anxious than did women with a negative result. However, their perception of future health did not change. Most carriers shared the information about their result with relatives and friends. Carriers had the best retention of pretest information and test result, although a third of the carriers believed that they could not have a child with cystic fibrosis when the partner's test for delta F508 and five other mutations were negative. Most women with a negative test result did not remember their result correctly a year after testing. Few women with a positive result changed their reproductive plans because of the result of the test.

Attitude to Health↗
PubMed1996

Gly802Asp substitution in the pro alpha 2(I) collagen chain in a family with recurrent osteogenesis imperfecta due to paternal mosaicism.

A proband with osteogenesis imperfecta (OI) type III/IV was born to clinically normal parents, who subsequently had two pregnancies terminated because of OI in the fetuses. Cultured fibroblasts from the proband, one fetus and the father produced abnormal collagen I. Cyanogen bromide mapping localised the defect to the region of the alpha 1(I)CB7 peptide. Sequencing revealed a G to A transition at nucleotide 2814 in COL1A2 in the proband, the fetus, and the father, which resulted in a Gly802Asp substitution in the pro alpha 2(I) collagen chain. About 25% of the paternal alleles from fibroblasts and leucocytes and 40% of paternal alleles from spermatocytes carried the mutation consistent with somatic and germinal mosaicism. For genetic counselling, parental mosaicism must be considered in all sporadic cases of OI.

Aspartic Acid↗
PubMed1996

Psychological impact of carrier screening for cystic fibrosis among pregnant women.

The aim of the present study was to assess the impact of being identified carrier of cystic fibrosis. The impact was assessed in terms of retention of the result, sharing of the information about the result with relatives, non-relatives and GPs, changes in reproductive plans, and regrets about having been tested Three unsupervised questionnaires were sent to 160 women identified as carriers between 1990 and 1992 in June 1992, October 1993, and November 1994. Carriers freely shared the information about their result with relatives, friends, and GPs. The inconclusiveness of the test gave rise to some confusion. This may reflect inadequacies in the information and counselling given to carriers, but psychological factors are also believed to be responsible. Thus, false reassurance may be a problem in a carrier screening with a test that detect only a proportion of carriers. Few carriers considered changing their reproductive plans due to the result of the test. A few women identified as carrier regretted having had the test.

Cystic Fibrosis↗
PubMed1996

Mutation spectrum in patients with Wiskott-Aldrich syndrome and X-linked thrombocytopenia: identification of twelve different mutations in the WASP gene.

Twelve different mutations in the WASP gene were found in twelve unrelated families with Wiskott-Aldrich syndrome (WAS) or X-linked thrombocytopenia (XLT). Four frameshift, one splice, one nonsense mutation, and one 18-base-pair deletion were detected in seven patients with WAS. Only missense mutations were found in five patients diagnosed as having XLT. One of the nucleotide substitutions in exon 2 (codon 86) results in an Arg to Cys replacement. Two other nucleotide substitutions in this codon, R86L and R86H, have been reported previously, both giving rise to typical WAS symptoms, indicating a mutational hot spot in this codon. The finding of mutations in the WASP gene in both WAS and XLT gives further evidence of these syndromes being allelic. The relatively small size of the WASP gene facilitates the detection of mutations and a reliable diagnosis of both carriers and affected fetuses in families with WAS or XLT.

Base Sequence↗
PubMed1995

Cerebellar hypoplasia in children with the carbohydrate-deficient glycoprotein syndrome.

We describe seven children with the carbohydrate-deficient glycoprotein syndrome, an autosomal recessive inborn error of protein glycosylation characterised by failure to thrive, neurological dysfunction and a unique pattern of physical abnormalities. Neuro-radiological investigations revealed cerebellar hypoplasia in all seven children. Two children also developed supratentorial atrophy following episodes of neurological deterioration.

Carbohydrate Metabolism, Inborn Errors↗
PubMed1995

Abnormal synthesis of dolichol-linked oligosaccharides in carbohydrate-deficient glycoprotein syndrome.

Carbohydrate-deficient glycoprotein syndrome (CDGS) is a rare metabolic disorder presenting in infancy with severe neurologic involvement and variable multisystemic abnormalities. Diagnosis relies upon the detection of abnormal serum glycoprotein isoforms on isoelectric focusing (IEF) gels. Carbohydrate structural analyses were performed on the N-linked oligosaccharides of serum alpha 1-antitrypsin (alpha-1AT) from two Danish children with classical type I CDGS. Following preparative gel electrophoresis of alpha-1AT isoforms, oligosaccharide charge and monosaccharide composition analyses revealed increased glycosylation heterogeneity in CDGS compared with normal alpha-1AT. CDGS alpha-1AT isoforms bore N-glycans co-migrating with monosialylated standards, while normal alpha-1AT oligosaccharides co-migrated with both mono- and disialylated standards. While the monosaccharide contents of normal alpha-1AT isoforms were relatively uniform, those of CDGS alpha-1AT isoforms varied widely, and many were relatively mannose enriched. The mannose-rich oligosaccharides of CDGS alpha-1AT were not typical oligomannose structures since they were not released by endo-beta-N-acetylglucosaminidase H (endo H) digestion. Metabolic labelling of CDGS fibroblasts with [3H]mannose showed lower than normal intracellular total mannose, free mannose and phosphorylated mannose species, as well as diminished [3H]mannose incorporation into dolichol-linked and protein-linked oligosaccharides. In addition, the glycans liberated from CDGS dolichol-linked oligosaccharides were significantly truncated compared with those from normal fibroblasts. These data suggest that our type I CDGS patients produce abnormal N-linked oligosaccharides due to impaired biosynthesis of dolichol-oligosaccharide precursors.

Congenital Disorders of Glycosylation↗
PubMed1995

A novel variant of lysosomal acid lipase (Leu336-->Pro) associated with acid lipase deficiency and cholesterol ester storage disease.

Cholesterol ester storage disease (CESD) is associated with premature atherosclerosis, hepatomegaly, elevated LDL cholesterol levels, and in most cases, low HDL cholesterol levels. Previous studies have shown a G-->A mutation at the 3' splice junction of exon 8 (E8SJM) of the gene encoding lysosomal acid lipase (LAL) in two kindreds with CESD. In a Canadian-Norwegian kindred with this disease, we show this mutation in conjunction with an as yet unknown T-->C transition in exon 10 predicting a Leu336-->Pro (L336P) replacement and an A-->C transversion in exon 2 predicting a T-6P replacement in the prepeptide. Identification of the L336P rather than the T-6P replacement as the second defect underlying CESD in our patient is deduced from three lines of evidence. First, the E8SJM allele is located in cis with the mutation predicting the T-6P-encoding allele but in trans with the L336P-encoding allele; second, the L336P but not the T-6P replacement cosegregates with low LAL activity in the family; third, the T-6P replacement was found in 6 of 28 alleles from subjects with normal lysosomal acid lipase activity, suggesting that this variant represents a frequent nonfunctional polymorphism. Since the residual LAL activity is higher and the clinical phenotype based on plasma lipid values and severity of hepatosplenomegaly is milder in this case than in a previously studied case who was homozygous for the E8SJM allele, we conclude that the L336P variant appears to be associated with a phenotypically mild form of CESD.

Adult↗
PubMed1995

Severe insulin-resistant diabetes mellitus in patients with congenital muscle fiber type disproportion myopathy.

Congenital muscle fiber type disproportion myopathy (CFTDM) is a chronic, nonprogressive muscle disorder characterized by universal muscle hypotrophy and growth retardation. Histomorphometric examination of muscle shows a preponderance of smaller than normal type 1 fibers and overall fiber size heterogeneity. Concomitant endocrine dysfunctions have not been described. We report the findings of altered insulin secretion and insulin action in two brothers affected with CFTDM and glucose intolerance as well as in their nonconsanguineous glucose-tolerant parents. Results are compared with those of six normoglycemic control subjects. All study participants underwent an oral glucose tolerance test to estimate insulin secretion. The oldest boy and his parents volunteered for studies of whole-body insulin sensitivity consisting of a 4-h euglycemic hyperinsulinemic clamp in combination with indirect calorimetry. Insulin receptor function and glycogen synthase (GS) activity and expression were examined in biopsies of vastus lateralis muscle. Despite a 45-90-fold increase in both fasting and postprandial serum insulin levels, both CFTDM patients had diabetes mellitus. Clamp studies revealed that the oldest boy had severe insulin resistance of both liver and peripheral tissues. The impaired insulin-stimulated glucose disposal to peripheral tissues was primarily due to reduced nonoxidative glucose metabolism. These changes were paralleled by reduced basal values of muscle GS total activity, allosterical activation of GS by glucose-6-phosphate, GS protein, and GS mRNA. The father expressed a lesser degree of insulin resistance, and studies of muscle insulin receptor function showed a severe impairment of receptor kinase activity. In conclusion, CFTDM is a novel form of severe hyperinsulinemia and insulin resistance. Whether insulin resistance is causally related to the muscle disorder awaits to be clarified.

Adolescent↗