Mutations in the endothelin-receptor B gene in Hirschsprung disease in Sweden.
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Amino Acid Substitution↗
Biomedical subjects
M Anvret
Publications and source records attributed to M Anvret.
CTG-repeat length in distal and proximal leg muscles of symptomatic and non-symptomatic patients with myotonic dystrophy: relation to muscle strength and degree of histopathological abnormalities.
Myotonic dystrophy (DM) is an autosomal dominant, multisystemic disorder with a variable phenotypic expression including muscle weakness and myotonia. The muscle wasting is most marked in distal limbs and in facial and neck muscles, although proximal limb muscles become affected as the disease progresses. The CTG-trinucleotide-repeat expansion associated with myotonic dystrophy is usually larger in muscle tissue than in leukocytes. It is unclear whether the repeat length itself bears any relation to the differences in the degree of weakness and atrophy between different muscles. We therefore analysed CTG-repeat lengths in blood and in proximal (m. vastus lateralis) and distal (m. tibialis anterior) muscles of patients with DM (n = 4) and non-symptomatic carriers of the mutant DM allele (n = 2) using conventional Southern blot hybridization. Muscle strength and histopathological abnormalities were evaluated for each muscle. In patients with clinical symptoms, the degree of paresis and morphological abnormalities was markedly more pronounced in m. tibialis anterior than in m. vastus lateralis. In these individuals, the CTG-repeat length was larger in muscles than in leukocytes, whereas in the two non-symptomatic carriers no difference could be detected. Furthermore, there was no clear difference in the repeat length between the two muscles in any of the patients. In conclusion, the selective muscular weakness and atrophy in DM do not seem to be related to differences in CTG-repeat length between different muscles.
Adult↗
Autosomal dominant myopathy with proximal weakness and early respiratory muscle involvement maps to chromosome 2q.
Two Swedish families with autosomal dominant myopathy, who also had proximal weakness, early respiratory failure, and characteristic cytoplasmic bodies in the affected muscle biopsies, were screened for linkage by means of the human genome screening set (Cooperative Human Linkage Center Human Screening Set/Weber version 6). Most chromosome regions were completely excluded by linkage analysis (LOD score <-2). Linkage to the chromosomal region 2q24-q31 was established. A maximum combined two-point LOD score of 4.87 at a recombination fraction of 0 was obtained with marker D2S1245. Haplotype analysis indicated that the gene responsible for the disease is likely to be located in the 17-cM region between markers D2S2384 and D2S364. The affected individuals from these two families share an identical haplotype, which suggests a common origin.
Chromosomes, Human, Pair 2↗
Simultaneous analysis of expression of the three myotonic dystrophy locus genes in adult skeletal muscle samples: the CTG expansion correlates inversely with DMPK and 59 expression levels, but not DMAHP levels.
The causative mutation in the majority of cases of myotonic dystrophy has been shown to be the expansion of a CTG trinucleotide repeat, but the mechanism(s) by which this repeat leads to the very complex symptomatology in this disorder remains controversial. We have developed a highly sensitive and quantifiable assay, based on competitive RT-PCR, to test the hypothesis that the expansion disrupts the expression of the genes in its immediate vicinity, DMPK, 59 and DMAHP. In order to avoid cell culture-induced artifacts we performed these experiments using adult skeletal muscle biopsy samples and analysed total cytoplasmic poly(A)+mRNA levels for each gene simultaneously, as this is more physiologically relevant than allele-specific levels. There was considerable overlap between the expression levels of the three genes in myotonic dystrophy patient samples and samples from control individuals. However, in the myotonic dystrophy samples we detected a strong inverse correlation between the repeat size and the levels of expression of DMPK and 59. This is the first report of a possible effect of the CTG expansion on gene 59. Our results indicate that whilst a simple dosage model of gene expression in the presence of the mutation is unlikely to be sufficient in itself to explain the complex molecular pathology in this disease, the repeat expansion may be a significant modifier of the expression of these two genes.
Adult↗
The trophoblastic epithelial barrier is not infected in full-term placentae of human immunodeficiency virus-seropositive mothers undergoing antiretroviral therapy.
To study the mechanism of the placental barrier function, we examined 10 matched samples of term placentae, cord blood, and maternal blood obtained at delivery from human immunodeficiency virus (HIV)-infected mothers with children diagnosed as HIV negative in Sweden. All placentae were histologically normal, and immunochemistry for HIV type 1 p24 and gp120 antigens was negative. Highly purified trophoblasts (93 to 99% purity) were negative for HIV DNA and RNA, indicating that the trophoblasts were uninfected. Although HIV DNA was detected in placenta-derived T lymphocytes and monocytes, microsatellite analysis showed that these cells were a mixture of maternal and fetal cells. Our study indicates that the placental barrier, i.e., the trophoblastic layer, is not HIV infected and, consequently, HIV infection of the fetus is likely to occur through other routes, such as breaks in the placental barrier.
Anti-HIV Agents↗
A heterozygous frameshift mutation in the endothelin-3 (EDN-3) gene in isolated Hirschsprung's disease.
Hirschsprung's disease, affecting one in 5000 live newborns, is the most common cause of neonatal intestinal obstruction. The obstruction or, later in life, constipation arises from the lack of enteric ganglia in the hindgut, thus resulting in poor coordination of peristalsis. Mutations in Hirschsprung patients have so far been reported in five genes associated in two different receptor-ligand systems, RET-GDNF/NTN and EDNRB-EDN-3, and an additional gene with yet unknown precise function, SOX10. We report the results of single-stranded conformation polymorphism screening of the endothelin-3 gene in a Swedish population-based material of 66 sporadic and nine familial Hirschsprung's disease cases. We have found a novel heterozygous mutation in exon 2, c.262insG, in a patient with sporadic short segment Hirschsprung's disease without any Waardenburg features. This frameshift results in a premature stop two codons further on. Because this stop is introduced 5' of the biologically active protein, this mutation can hence be predicted to result in haplo-insufficiency.
Amino Acid Sequence↗
A novel missense mutation Ile538Val in the fibroblast growth factor receptor 3 in hypochondroplasia. Mutations in brief no. 122. Online.
Hypochondroplasia and achondroplasia are skeletal dysplasias, characterized by autosomal dominant inheritance and disproportionate short stature, which occurs mainly due to growth failure of the extremities. Both dysplasias have been mapped to fibroblast growth factor receptor 3 (FGFR3) gene. For hypochondroplasia, two point mutations, both responsible for the Asn540Lys substitution in the region coding the tyrosine kinase domain have been reported. Here we report an A to G transition at position 1651, predicting an Ile538Val substitution in the FGFR3, in hypochondroplasia. The substitution is found in a swedish family with three affected members. The criteria for hypochondroplasia were disproportionate short stature and radiological evidence of shortened long bones and decrease or absence of normal increase in interpedicular distances of the lumbar column. The mutation was detected by direct sequencing and restriction enzyme Tai I digestion. The base change was not found in the FGFR3 genes of unaffected members of the family nor in seventy-five unrelated unaffected individuals, suggesting that it was not a polymorphism. The Ile538Val substitution is a conservative amino acid change (a hydrophobic amino acid incorporated for another hydrophobic amino acid). Nevertheless, it is located in the stretch of nine amino acids, which is highly conserved among all the human fibroblast growth factor receptors. Considering the location of this substitution and the segregation with the phenotype in this family, we propose that it is a causative mutation of hypochondroplasia. It is difficult to establish whether the Ile538Val substitution is rare in hypochondroplasia patients or whether the individuals, who have a moderate degree of short stature, rarely seek medical help for the short stature and consequently are rarely diagnosed as affected by hypochondroplasia.
Achondroplasia↗
Phenotypic variation in a family with mutations in two Hirschsprung-related genes (RET and endothelin receptor B).
Hirschsprung disease is a congenital malformation affecting 1 in 5000 live births. The absence of parasympathetic neuronal ganglia (Meissner, Auerbach) in the hindgut results in poor coordination of peristaltic movement, and a varying degree of constipation. Four different genes have been implicated in the pathogenesis of Hirschsprung disease: the RET tyrosine kinase receptor gene; one of its ligands, the glial cell line-derived neurotrophic factor (GDNF) gene; the endothelin receptor B (EDNRB) gene; and its ligand, endothelin-3 (EDN3). Recently, combinations of mutations in two of these genes (RET and GDNF) have been reported in Hirschsprung patients. We report a family with missense mutations in both the RET gene (R982C) and the EDNRB gene (G57S). In this family, three out of five members have the two mutations, but only one, a boy, has the Hirschsprung disease phenotype. This illustrates the complexity of the molecular background of Hirschsprung disease.
DNA Restriction Enzymes↗
Welander hereditary distal myopathy, a molecular genetic comparison to hereditary myopathies with inclusion bodies.
Welander distal myopathy (WDM) is an autosomal dominant disorder with late onset predominantly affecting distal extensor muscles of the hands and the feet. The disorder is considered as the most common of the distal myopathies but is almost only seen in Sweden and some parts of Finland. The finding of rimmed vacuoles in muscle biopsies from patients with moderate and severe symptoms constitutes one similarity with hereditary inclusion body myopathy (HIBM) sparing the quadriceps as described by Argov and Yarom [Argov Z, Yarom R. J Neurol Sci 1984;64:33-43]. The question has been raised whether some of the different forms of distal myopathy might be allelic. In previous reports the gene defects for HIBM and autosomal recessive hereditary distal myopathy with rimmed vacuoles (DMRV) have been mapped to chromosome 9pl-q1. The Finnish tibial muscular dystrophy (TMD) that displays similar histopathological findings has recently been linked to chromosome 2q. We have investigated the regions of interest with dispersed microsatellite markers in four well-described pedigrees, and this study now excludes the regions on chromosome 9pl-q1 and 2q from linkage to WDM both by haplotype analysis and linkage analysis with the MLINK program. WDM, showing morphological similarities with HIBM, is clearly separated from the disorders mapped to chromosomes 9 and 2 on clinical and genetical grounds.
Adult↗
Welander distal myopathy--an overview.
Welander distal myopathy has an autosomal dominant inheritance and a late onset. The onset of symptoms is in the hands and gradually distal muscles of the lower extremities are involved. The most-affected muscles are the long extensors of the hands and feet. CK-values are normal or slightly elevated. There is never any cardiac involvement in Welander distal myopathy. Neurophysiological findings are of both myopathic and neuropathic character. Histopathological findings in muscle biopsies are mainly of myopathic type and include rimmed vacuoles which correspond to autophagic vacuoles on the ultrastructural level. Tubulo-filamentous inclusions with a diameter of 16-21 nm, i.e. of the same type as found in patients with Inclusion Body Myositis, are found in the sarcoplasm and in myofibre nuclei. A neurogenic component in Welander distal myopathy has been suggested, on the grounds of a sensory dysfunction, neuropathic findings on neurophysiology and muscle biopsy and a decrease of A-delta nerve fibres on sural nerve biopsy. Genetic analysis has excluded linkage to other defined distal myopathies and hereditary Inclusion Body Myopathy loci.
Adult↗
A Huntington disease-like neurodegenerative disorder maps to chromosome 20p.
Huntington disease (HD) is an autosomal dominant neurodegenerative disorder characterized by motor disturbance, cognitive loss, and psychiatric manifestations. The disease is associated with a CAG trinucleotide-repeat expansion in the Huntington gene (IT15) on chromosome 4p16.3. One family with a history of HD was referred to us initially for predictive testing using linkage analysis. However, the chromosome 4p region was completely excluded by polymorphic markers, and later no CAG-repeat expansion in the HD gene was detected. To map the disease trait segregating in this family, whole-genome screening with highly polymorphic dinucleotide-, trinucleotide-, and tetranucleotide-repeat DNA markers was performed. A positive LOD score of 3.01 was obtained for the marker D20S482 on chromosome 20p, by two-point LOD-score analysis with the MLINK program. Haplotype analysis indicated that the gene responsible for the disease is likely located in a 2.7-cM region between the markers D20S193 and D20S895. Candidate genes from the mapping region were screened for mutations.
Adult↗
Failure to achieve gene conversion with chimeric circular oligonucleotides: potentially misleading PCR artifacts observed.
Recently, a novel strategy for nucleotide exchange of target DNA using chimeric RNA/DNA oligonucleotides (CO) was reported. The CO can easily be transfected into cells, remain stable within the cells, and migrate to the nucleus. We have in this study used 42 similar constructs for targeting six different human and canine loci. A variety of cationic lipids, electroporation, and microinjection were used for transfection of the CO into lymphoblastoids, Huh7, HT 1080, and Jurkat cell lines, and canine primary fibroblasts and hepatocytes. However, no nucleotide exchange was detected in any of the targeted loci. Using PCR followed by restriction enzyme analysis, nucleotide exchange in approximately 2%-10% of the PCR products was observed during the first 3 days after transfection with CO-vWF-28S2 designed for repairing a mutation in the von Willebrand gene. Surprisingly, the observed exchange reverted after culturing the cells for a longer period of time (14 days). Furthermore, a positive indication of gene conversion (5%) was also obtained using an allele-specific PCR method for analysis of the PAI-1 gene. However, cloning of the PCR products revealed no nucleotide exchange. In our view, the most likely explanation is that the initial false positive result originates from a PCR artifact created by the CO itself. Our results imply that an independent method, that is, Southern blotting, must be used to verify an observed nucleotide exchange.
Animals↗
Low frequency of RET mutations in Hirschsprung disease in Sweden.
Hirschsprung disease is a congenital malformation, where absence of intramural ganglia in the hindgut results in a defect in the coordination of peristaltic movement. This leads to ileus in the newborn or, more often, constipation in children and adults. The disease affects one in 5000 live births. Siblings of affected cases are at an increased risk (4%) of developing the disease. Among cases. males are affected more often than females. The first major susceptibility gene for Hirschsprung disease is the RET proto-oncogene on 10q11.2. Germline RET mutations in Hirschsprung disease are mainly inactivating, and have been reported to account for up to 20 and 50% of sporadic and familial cases, respectively. We have screened Swedish population-based samples from 62 sporadic cases and seven familial cases of Hirschsprung disease with single strand conformation polymorphism (SSCP), and found five mutations.
DNA Mutational Analysis↗
Chromosome mapping of Rett syndrome: a likely candidate region on the telomere of Xq.
Rett syndrome (RS) is a disease of neurological development. First reported 30 years ago in 1966, its biological and genetic basis remains obscure. RS is commonly thought of as an X linked dominant disorder lethal to hemizygous males. The few familial cases would arise through mosaicism or because of occasional females failing to manifest the disorder through skewed X inactivation in relevant cell types. We have one family where the mother and daughter are affected with RS, and which can be explained according to this hypothesis. If the alternative proposal of Thomas (1996) is correct, that the lack of males affected by such disorders is the result of a high male to female ratio of germline mutations rather than of gestational lethality, then the RS gene should be located on the grandpaternal chromosome. Genomic screening with markers covering the whole X chromosome has been performed. Studies using multiple informative markers indicate that the RS locus is likely to be located close to one of the X chromosome telomeres. Further investigations in eight additional families suggest the most likely region for the RS gene to be is the distal part of Xq (Xq28).
Chromosome Mapping↗
Larger CAG expansions in skeletal muscle compared with lymphocytes in Kennedy disease but not in Huntington disease.
The size of CAG repeats was compared in lymphocytes and skeletal muscle from nine patients with Huntington disease (HD) and two patients with Kennedy disease (KD). In HD, the number of CAG repeats did not differ between lymphocytes and skeletal muscle. In the two KD patients, however, the CAG expansion was larger in muscle than in lymphocytes. The difference in trinucleotide expansion between lymphocytes and muscle cells is not a universal phenomenon in trinucleotide repeat disorders, but seems to occur in disorders primarily affecting the neuromuscular system.
Aged↗
Reactions to predictive testing in Huntington disease: case reports of coping with a new genetic status.
A predictive testing program for Huntington disease has been available in Stockholm, Sweden since October 1990. Psychosocial assessments were performed throughout the testing program to evaluate the impact of the risk situation itself and the effect of predictive testing, and to identify those individuals who were most vulnerable to severe stress and anxiety reactions. All subjects underwent neurological, neuropsychological, and psychiatric examinations. Individuals undergoing predictive testing were assessed twice by a genetic counsellor before receiving their results, and at 10 days (gene carriers only) and then 2, 6, 12, and 24 months after receiving the results. The process of coping with the test results and the psychological adjustment to knowledge about new genetic status have been shown to vary considerably. In this report, we describe the results obtained from two gene carriers and two noncarriers. The four persons chosen represent different ways of coping with the outcome of the test and of integrating knowledge about their genetic status into everyday life. These cases illustrate common themes and recurrent problems often surfacing during the counselling and testing process. The longitudinal evaluations provide information about the impact, adaptation, and long-term effects of living with a new genetic status.
Adaptation, Psychological↗
[Preimplantation genetic diagnosis. An alternative to traditional prenatal diagnosis].
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Biopsy↗
Characterization and regulation of the nonerythroid porphobilinogen deaminase promoter.
The non-erythroid porphobilinogen deaminase (E.C. 4.3.1.8) promoter was investigated according to sequence changes and transcriptional activity. The minimal promoter sequence required for maximal transcription, was localized by deletion mapping to -243 to -115 relative to the translational start site. A negative transcriptional element was found between -55 and +1, indicating a repression mechanism. A new polymorphism was identified, at position -235 within the minimal promoter, both in acute intermittent porphyria patients and healthy control subjects. The polymorphic variants did not affect expression of cloned promoter fragments under the conditions used.
Humans↗