Biomedical subjects

S Liechti-Gallati

Publications and source records attributed to S Liechti-Gallati.

At least 37 records · Page 2Linked to original sources

PubMed1997

Mutations in the MTM1 gene implicated in X-linked myotubular myopathy. ENMC International Consortium on Myotubular Myopathy. European Neuro-Muscular Center.

X-linked recessive myotubular myopathy (XLMTM) is characterized by severe hypotonia and generalized muscle weakness, with impaired maturation of muscle fibres. The gene responsible, MTM1, was identified recently by positional cloning, and encodes a protein (myotubularin) with a tyrosine phosphatase domain (PTP). Myotubularin is highly conserved through evolution and defines a new family of putative tyrosine phosphatases in man. We report the identification of MTM1 mutations in 55 of 85 independent patients screened by single-strand conformation polymorphism for all the coding sequence. Large deletions were observed in only three patients. Five point mutations were found in multiple unrelated patients, accounting for 27% of the observed mutations. The possibility of detecting mutations and determining carrier status in a disease with a high proportion of sporadic cases is of importance for genetic counselling. More than half of XLMTM mutations are expected to inactivate the putative enzymatic activity of myotubularin, either by truncation or by missense mutations affecting the predicted PTP domain. Additional mutations are missenses clustered in two regions of the protein. Most of these affect amino acids conserved in the homologous yeast and Caenorhabditis elegans proteins, thus indicating the presence of other functional domains.

Alternative Splicing↗

PubMed1996

A 900-kb cosmid contig and 10 new transcripts within the candidate region for myotubular myopathy (MTM1).

The X-linked myotubular myopathy locus (MTM1) has been assigned to the Xq28 region by linkage analysis. By observation of an interstitial deletion in a female patient, the candidate region could be further reduced to a region of 600 kb flanked by the markers DXS304 and DXS497. We describe here cosmid contigs covering a region of 900 kb, including the entire MTM1 candidate region. Cosmids from the region were used to construct an enriched cDNA library from this area. Filter grids carrying this library were then screened by hybridization with whole cosmid clones, with CpG island-containing fragments from linking clones located in the area, and with total exon trap products of cosmid clones from the candidate region. In this analysis, 10 new transcripts were identified and localized precisely within the map. Genes in this area are candidates for MTM1 and a number of other diseases localized by genetic linkage studies to the chromosomal band Xq28.

Adult↗

PubMed1996

Ornithine transcarbamylase deficiency: characterization of gene mutations and polymorphisms.

We identified three new and three known mutations in male patients with OTC deficiency using PCR amplification of all the individual exons, including the adjacent intron sequences, followed by direct sequencing of the amplimers. Two mutations were found in males presenting with neonatal fatal hyperammonemia and no detectable enzyme activity in their livers. The H302Y mutation found in one patient affects the putative binding site for ornithine. The second patient had an R141X mutation, which is one of the few recurrent mutations in the OTC gene. Four different missense mutations were identified in male patients with late onset of the disease and residual OTC activities between 14% and 35%. The mutations are Y176C and P220A and the known mutations K88N and T343K, respectively. Four of the patients' mothers were identified as carriers. In two cases, the mutations had occurred spontaneously. In addition, the frequency of four polymorphisms of the OTC gene was studied. The K46R polymorphism in exon 2 and the Q27OR polymorphism in exon 8 were found in 36% and 4% of screened alleles, respectively. Two questionable polymorphisms in exon 4, F101L and L111P, were not present in any of the screened alleles.

Ammonia↗

PubMed1996

Identification of four novel splice site mutations in the ornithine transcarbamylase gene.

Ornithine transcarbamylase (OTC) deficiency, the most common inborn error of the urea cycle, shows X-linked inheritance with frequent new mutations. Using polymerase chain reaction (PCR) amplification of the individual exons including adjacent intron sequences followed by direct sequencing of the amplimers we identified four new mutations affecting donor splice sites of introns 2, 5, 6, and 8. The mutation at the first position of intron 2 was a G to A exchange associated with acute neonatal hyperammonemia in a male patient at the age of 5 months. A G to C substitution in intron 5 was detected in a boy who developed 2 days after birth hypotonia, and respiratory distress, followed by severe hyperammonemia and terminal coma. The intron 6 mutation, a G to T substitution, was detected in a girl presenting with first episodes of vomiting and agitation at the age of 2 months. The mutation in intron 8, also a G to T transition, caused fatal hyperammonemia and early death at the age of 15 days in a male patient. We present four donor splice site mutations resulting in severe neonatal or very early onset of the disease in three boys and in one female patient. As the GT dinucleotide of the 5' donor splice site is invariant and required for correct splicing the described mutations may lead to improperly spliced mRNAs and aberrant gene products.

Amino Acid Metabolism, Inborn Errors↗

PubMed1996

Detection of a new polymorphism in the plasma-membrane Ca2+ ATPase isoform-3 gene and its exclusion as a candidate for X-linked myotubular myopathy (MTM1).

The severe neonatal centronuclear/myotubular myopathy (XLMTM) is an X-linked disorder characterized by generalized muscle weakness, hypotonia and serious respiratory insufficiency. The gene for this disease has been assigned to the long arm of chromosome X in the Xq28 band. Ca2+ ATPase isoform-3 (ATP2B3) has also been mapped to the human Xq28 region. Moreover, it is expressed in fetal but not in adult muscle, suggesting the developmental regulation of gene transcription. These findings render the ATP2B3 gene as an interesting candidate gene for XLMTM. Four families and 7 unrelated XLMTM patients have been analysed by using cDNA and genomic probes of ATP2B3. No large deletions or duplications have been found but a new EcoRI polymorphism has been identified. In addition, the DNA of an XLMTM male deletion patient has been hybridized with the ATP2B3 gene sequences. Our results therefore support the exclusion of ATP2B3 as the causal disease gene of XLMTM. The isolation of the MTM1 gene has recently been reported by another group. However, our approach has led to the detection of a new polymorphism that is an informative marker for linkage and mutation studies in other Xq28-mapped neurological or neuromuscular disorders.

Adult↗

PubMed1996

X-linked myotubular myopathy: refinement of the critical gene region.

X-linked recessive myotubular myopathy (XLMTM) is a severe neonatal neuro-muscular disease characterized by muscle weakness, hypotonia, and respiratory problems. The locus for the XLMTM gene (MTM1) has previously been mapped to Xq28 between the markers DXS304 and DXS497 by linkage analyses and by determining the breakpoints of deletion patients. We report linkage analysis data or 20 XLMTM families who were tested using the DNA markers DXS1113, DXS304, DXS455, DXS1684, DXS305 and DXS52 and present two families showing recombination between MTM1 and either DXS304, DXS334 or DXS305. We found each of the families to be informative for at least three markers. Based on these findings we excluded 30 women from being carriers, the carrier status of 17 obligate carrier mothers could be confirmed and eight mothers and sisters were identified as to be at high risk of carrying a MTM1 mutation. By combining recently published data with the results of our recombinant families, we suggest that the MTM1 locus maps between DXS334 and DXS497 narrowing the region of interest from 600 kb to an estimated < 500 kb interval. This additional refinement in the localization of MTM1 means a further step towards the isolation of the gene in the near future, and allows more reliable and efficient carrier detection and prenatal diagnosis.

Chromosome Mapping↗

PubMed1996

Differential expression of Na+,H(+)-antiporter mRNA in biliary epithelial cells and in hepatocytes.

BACKGROUND/AIMS: Amiloride inhibitable Na+,H(+)-exchange has recently been identified and characterized in rat biliary epithelial cells where its activity at low intracellular pH is significantly higher than in hepatocytes. METHODS: Northern blot and reverse transcription-polymerase chain reaction were used to study the expression of the different Na+,H(+)-antiporter isoforms in isolated biliary epithelial cells and hepatocytes. RESULTS: The present study demonstrates for the first time the expression of Na+,H(+)-antiporter isoform 1 mRNA in rat biliary epithelial cells. Moreover, steady-state levels of this message were several-fold higher in biliary epithelial cells than in hepatocytes. In addition, the expression of Na+,H(+)-antiporter isoform 2 in bile duct epithelial cell but not hepatocytes could be demonstrated by reverse transcription-polymerase chain reaction. CONCLUSIONS: The higher expression of Na+,H(+)-antiporter isoform 1 mRNA may indicate a higher rate of synthesis and therefore a higher Na+,H(+)-exchange activity in biliary epithelial cells than in hepatocytes and is entirely compatible with the results of the previous functional studies.

Animals↗

PubMed1996

Combined 3-methylglutaconic and 3-hydroxy-3-methylglutaric aciduria with endocardial fibroelastosis and dilatative cardiomyopathy in male and female siblings with partial deficiency of complex II/III in fibroblasts.

We report on 2 children, brother and sister, who presented with cardiomyopathy and muscular hypotonia at the age of B months. They both excreted significant amounts of 3-hydroxy-3-methylglutaric acid (3-HMG) and 3-methylglutaconic acid (3-MGC) but no 3-methylglutaric acid (3-MG). Enzyme analysis in fibroblasts revealed normal activities of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) lyase and of 3-methylglutaconyl hydratase and other enzymes of 3-HMG metabolism. Loading tests with leucine did not affect the excretion of 3-HMG and 3-MGC. The girl died as a result of her cardiomyopathy, while the boy recovered and was treated with cardiac supportive therapy. He showed a steady improvement during his clinical course with biochemical normalization of the urinary excretion of 3-HMG, concomitant with marked improvement in the hypertrophic cardiomyopathy. In cultured fibroblasts from both patients a reduced activity of complex II/III of the respiratory chain was measured which may be the cause of this new type of 3-HMG uria. Analysis of mitochondrial DNA heart muscle, liver and fibroblast culture of the patient did not reveal any major mitochondrial DNA rearrangements (deletion, duplication) or any point mutation that had been described in association with mitochondrial cardiomyopathy.

Cardiomyopathy, Dilated↗

PubMed1996

Efficient and reliable PCR-based detection of the ABO blood group alleles: genotyping on stamps and other biological evidence samples.

PCR-based ABO genotyping was established using restriction enzyme digestion followed by horizontal polyacrylamide gel electrophoresis and silver staining. The method described here is fast, with results obtained within hours, not days, it obviates the need for radioisotopes and can be performed with 1-2 ng of extracted genomic DNA. ABO blood group determination was successful in various types of biological materials of forensic interest such as bloodstains, vaginal swabs, cigarette butts, and hair roots. Moreover, after preincubation in distilled water, DNA (2-8 ng) was extracted from 12 up to 10-years-old stamps and was correctly typed at the ABO locus. The results presented here indicate that the PCR-based ABO genotyping is a fast, sensitive, reliable, and economic method providing blood group determination in DNA from a variety of different types of specimens. It can provide determination from specimens of limited amount and/or with partially degraded DNA as well. Therefore, it is very useful for first-step suspect screening as well as in forensic research for the analysis of biological evidence.

ABO Blood-Group System↗

PubMed1995

Ornithine transcarbamylase deficiency: new sites with increased probability of mutation.

Ornithine transcarbamylase (OTC) deficiency, the most common inborn error of the urea cycle, shows an X-linked inheritance with frequent new mutations. Investigations of patients with OTC deficiency have indicated an overproportionate share of mutations at CpG dinucleotides. These statistics may, however, be biased because of the easy detection of CpG mutations by screening for TaqI and MspI restriction sites. In the present study, we investigated 30 patients, with diagnosed OTC deficiency, for new sites with an increased probability of mutation by complete DNA sequence analysis of all ten exons of the OTC gene. In six patients, two codons in exons 2 and 5, respectively, contained novel recurrent mutations, all of them affecting CpG dinucleotides. They included C to T and G to A transitions in codon 40, changing an arginine to cysteine and histidine, respectively, and a C to T transition in codon 178 causing the substitution of threonine by methionine. The first two mutations were characterized by a mild clinical course with high risk of sudden death in late childhood or early adulthood, whereas the third mutation showed a more severe phenotypic expression. In addition to these novel mutations, we identified four patients with the known R277W mutation, making it the most common point mutation of the OTC gene.

Adolescent↗

PubMed1995

The age at onset of chronic Pseudomonas aeruginosa colonization in cystic fibrosis--prognostic significance.

To evaluate the prognostic significance of the age at onset of chronic Pseudomonas aeruginosa colonization (OPCP) with respect to pulmonary disease progression in patients with cystic fibrosis (CF), a retrospective long-term analysis using annual chest radiographs was performed on 54 CF patients. Thirty-seven patients (68%) were chronically colonized before the age of 12 years (group 1), 17 patients (32%) thereafter (group 2). These two groups did not significantly differ in terms of mean duration of follow up (16.2 +/- 5.9 years), sex, CF genotypes, colonization with other respiratory pathogens, supportive medical treatment and death rate during the study period. Chest radiographs were evaluated according to the Chrispin-Norman score, increasing scores representing increasing severity of respiratory disease. In both groups, progression of score means was not accelerated of score means was not accelerated up to 6 years after OCPC (Scores at OCPC set 0; mean score +/- SEM 6 years prior to OCPC -5.6 +/- 2.0; 10 years after OCPC +3.6 +/- 0.7 points). Patients chronically colonized prior to age 12 years (group 1) scored significantly higher between age 2 and 11 years (maximum difference at age 8 years [mean +/- SEM]: 9.4 +/- 0.7 vs. 4.3 +/- 1.3 points; P = 0.002) as compared to group 2. After age 11 years, mean scores were similar in both groups, since in group 2 scores increased rapidly after age 8 years. We conclude that OCPC did not cause an immediate acceleration of CF lung disease judged by serial chest radiographs. Rapid progression in group 2 (OCPC after age 12 years) was independent of OCPC since it occurred earlier. These data indicate that OCPC may be a marker rather than the cause of respiratory disease progression.

Adolescent↗

PubMed1995

Cystic fibrosis mutations and immotile cilia syndrome.

The immotile cilia syndrome (ICS) presents with autosomal recessive inheritance and is a chronic respiratory disease supposed to be caused by different genetic determinants. The hypothesis that cystic fibrosis (CF) heterozygotes may have a predisposition to develop bronchial or respiratory diseases other than CF prompted us to look for CF mutations in patients with ICS. Five patients, as well as the parents and two healthy brothers of one patient were tested for 12 CF mutations, for the polymorphic GATT repeat in intron 6a and for the CF gene flanking markers XV-2c, KM19, MP6d-9, J3.11. None of the 12 mutations at the CF locus have been detected in the ICS patients and no linkage was found between ICS and the polymorphic markers. Thus, based on our data, ICS and CF seem to be two different clinical entities.

Adult↗

PubMed1995

Chronic metabolic alkalosis: not uncommon in young children with severe cystic fibrosis.

The acid-base balance of 199 patients with cystic fibrosis, seen from 1987 through 1992 at the Bern Outpatient Clinic, were evaluated. Simple metabolic alkalosis was demonstrated in 16 and mixed metabolic alkalosis and respiratory acidosis in 9 patients. When compared with 10 patients with simple respiratory acidosis and 16 with normal hydrogen ion balance, those with simple metabolic alkalosis were significantly younger. The need for pancreatic enzymes was significantly higher and the relative underweight significantly more severe in patients with either simple or mixed metabolic alkalosis and respiratory acidosis. The results indicate the rather common occurrence of chronic metabolic alkalosis in cystic fibrosis. It is observed in young patients, in patients who need high doses of pancreatic enzymes and in the those with poor nutritional status.

Acidosis, Respiratory↗

PubMed1995

Sex determination of forensic samples by simultaneous PCR amplification of alpha-satellite DNA from both the X and Y chromosomes.

Simultaneous amplification of the alphoid repeated sequences clustered in the centromeric regions of both the human X and Y chromosome was performed. Modification and improvement of the polymerase chain reaction conditions resulted in detectable amplification products from less than 1 ng of genomic DNA template. Sex determination was successful in various types of biological materials of forensic interest as bloodstains, vaginal swabs, cigarette butts, bones, and hair roots. The authors suggest that the coamplification of both X- and Y-sequences in a unique reaction mixture is a fast, human specific, sensitive and reliable method providing internal reaction control and sex determination in DNA from a variety of different types of specimens as well as from specimens of limited amount, thus, being very useful in forensic research for the analysis of biological evidence.

Adult↗

PubMed1994

Clonality and X-inactivation patterns in hematopoietic cell populations detected by the highly informative M27 beta DNA probe.

About 80% to 90% of females are informative for X-inactivation/methylation analysis with the probe M27 beta, which would therefore seem attractive in assessing clonality in hematologic cell populations. Eighteen acute lymphoid or myeloid leukemias, three chronic lymphocytic leukemias, and three chronic myelogenous leukemias as well as 12 malignant non-Hodgkin's lymphomas mostly showed extremely skewed clonal X inactivation (median allelic cleavage ratio [ACR] of unmethylated/inactive M27 beta alleles was 50, range 1 to 100) or hypermethylation of both alleles. Two lymphomas showed random M27 beta X inactivation but clonal antigen-receptor gene rearrangements. In normal peripheral blood leukocytes from 105 healthy females aged 2 to 96 years, the median ACR was 2 (range 1 to 100). Thus, it was significantly lower than in the leukemias (P = .0001, Mann-Whitney test), but extremely skewed patterns (ACR > 10.8, ie, > 80th percentile) were seen not only in the leukemias but also in 21/105 samples (20%) of normal leukocytes, and significantly more frequent in a population of elderly women (aged 75 to 96 years) compared with healthy children (aged 2 to 8 years) and younger women (aged 20 to 58 years) (P = .00125; chi 2 test). We conclude that in a population of cells derived from the hematopoietic system where clonality is uncertain, skewed M27 beta patterns are not reliable indicators for the presence of a clonal neoplastic disorder. The basis for severe X-inactivation skewing is unclear at present, but this finding raises interesting questions regarding the composition of the hematopoietic stem cell pool.

Acute Disease↗

PubMed1994

On the origin of deletions and point mutations in Duchenne muscular dystrophy: most deletions arise in oogenesis and most point mutations result from events in spermatogenesis.

We present the results of a study of the rate and origin of mutations in Duchenne muscular dystrophy (DMD). Depending on the type of mutation (deletion/duplication or point mutation) present in the patient, there are widely varying ratios of male to female mutation rates. In deletions, the male mutation rate is only 30% of the female one. In non-deletional/non-duplicational mutations (presumably containing a high proportion of point mutations) the male mutation rate is at least 2.2 as high as the female one and probably much higher. Allowing for the presence of autosomal recessive phenocopies we find that k in non-deletional/non-duplicational mutations is 40.3. These findings mean that the vast majority of deletions arise in oogenesis, while most point mutations stem from spermatogenesis. Previous investigations have shown that in other diseases and genes, most notably haemophilia B and A, but also the ZFY and ZFX genes, the male mutation rate for point mutations tends to be higher than the female one. Our results can be seen as a confirmation of this for the special case of DMD. The influence on risk figures is considerable. As an example, the risk of the mother of an isolated case of DMD without an apparent structural anomaly of the gene of being a carrier increases from 67% to at least 76%. Given the estimate of 40.3 for k, allowing for the presence of autosomal recessive phenocopies mentioned above, it increases even further to 98%. However, as confidence intervals are still large, more data are needed to improve the estimates. Germinal mosaicism in this context is discussed.

Fathers↗

PubMed1994

Protease-antiprotease imbalance in the lungs of children with cystic fibrosis.

Cystic fibrosis (CF) is characterized in the lung by chronic purulent bronchitis culminating in pulmonary insufficiency. There is evidence to suggest that neutrophil elastase (NE) released by neutrophils on the respiratory epithelial surface plays a major role in the pathogenesis of this lung disease. This study sought to determine the age of onset of the chronic neutrophil-dominated inflammation in CF and the consequences to the NE-anti-NE screen on the respiratory epithelial surface of the CF lung. NE and anti-NE defensive molecules were evaluated in respiratory epithelial lining fluid (ELF) in 27 children with stable CF (1 to 18 yr of age). Despite normal antigenic concentrations of alpha 1-antitrypsin (alpha 1AT) and secretory leukoprotease inhibitor (SLPI), 25 of 27 children with CF had neutrophil-dominated inflammation (> 500 neutrophils/microliters ELF). Active NE was found in ELF in 20 of 27 children, including two of four aged 1 yr. Western blot analysis showed the majority of alpha 1AT and SLPI molecules to be complexed and/or degraded. These observations demonstrate that a chronic imbalance of the NE-anti-NE protective screen develops early on the respiratory epithelial surface in persons with CF and is likely well established by 1 yr of age, with resultant potential for lung damage.

Adolescent↗

PubMed1993

[Quadriceps myopathy as dystrophin-associated myopathy].

Duchenne and Becker muscular dystrophy are both caused by a deletion in the dystrophin gene. In the past few years, many reports of atypical myopathies have been published where an association with a deletion within the same gene was found. We report one sporadic and one familial case of myopathy where we were able to demonstrate a deletion of the dystrophin locus using DNA analysis.

Adult↗