Search PubMed⌕ Search

Biomedical subjects

A Munnich

Publications and source records attributed to A Munnich.

At least 181 records · Page 10Linked to original sources
PubMed1999

Facial anomalies in D-2-hydroxyglutaric aciduria.

D-2-hydroxyglutaric aciduria is a rare autosomal recessive organic aciduria with variable clinical expression. The biochemical defect is still unknown, and genetic heterogeneity has been suggested. Here, we report on facial anomalies in two unrelated cases of D-2-hydroxyglutaric aciduria presenting with epileptic encephalopathy. In a review, we found that minor facial anomalies have been mentioned in three patients. A flat face with a broad nasal bridge and external ear anomalies were present in our patients and in reported cases. We suggest giving consideration to D-2-hydroxyglutaric aciduria as a cause of minor facial anomalies in epileptic encephalopathy of unknown origin.

Amino Acid Metabolism, Inborn Errors↗
PubMed1999

Effect of idebenone on cardiomyopathy in Friedreich's ataxia: a preliminary study.

BACKGROUND: Friedreich's ataxia is caused by a deficiency of frataxin, a protein involved in regulation of mitochondrial iron content. We have reported a combined deficiency of a Krebs-cycle enzyme, aconitase, and three mitochondrial respiratory-chain complexes in endomyocardial biopsy samples from patients with this disorder. All four enzymes share iron-sulphur cluster-containing proteins that are damaged by iron overload through generation of oxygen free radicals. We used an in-vitro system to elucidate the mechanism of iron-induced injury and to test the protective effects of various substances. On the basis of these results, we assessed the effect of idebenone (a free-radical scavenger) in three patients with Friedreich's ataxia. METHODS: Heart homogenates from patients with valvular stenosis were tested for respiratory-chain complex II activity, lipoperoxidation, and aconitase activity by spectrophotometric assays, in the presence of reduced iron (Fe2+), oxidised iron (Fe3+), desferrioxamine, ascorbic acid, and idebenone. The Friedreich's ataxia patients (aged 11 years, 19 years, and 21 years) underwent ultrasonographic heart measurements at baseline and after 4-9 months of idebenone (5 mg/kg daily). FINDINGS: Fe2+ (but not Fe3+) decreased complex II activity and increased lipoperoxidation in heart homogenate. Addition of ascorbate or desferrioxamine increased some of the iron-induced adverse effects. Idebenone protected against these effects. In the three patients, left-ventricular mass index decreased from baseline to 4-9 months of idebenone treatment (patient 1, 145 g to 114 g; patient 2, 215 g to 151 g; patient 3, 408 g to 279 g). INTERPRETATION: Our in-vitro data suggest that both iron chelators and antioxidant drugs that may reduce iron are potentially harmful in patients with Friedreich's ataxia. Conversely, our preliminary findings in patients suggest that idebenone protects heart muscle from iron-induced injury.

Adult↗
PubMed1999

Protein truncation test for screening hamartin gene mutations and report of new disease-causing mutations.

Considering the prevalence of truncating mutations in the tuberous sclerosis (TSC) hamartin gene (TSC1), we devised a protein truncation test (PTT) to analyze the full length coding sequence of TSC1. Studying 12 sporadic cases and three familial forms by a combination of PTT and single-strand conformation polymorphism analysis (SSCA), we found 5/15 mutations while PTT alone detected 4/15 truncating mutations, two of which escaped SSCA analysis. SSCA alone picked up one missense mutation and two mutations also detected by PTT. Interestingly, a TSC1 mutation was identified in all three familial forms (3/3) while the rate of mutation detection was lower in sporadic cases (2/12). In conclusion, PTT proves to be a useful technique for the rapid detection of disease-causing mutations in the TSC1 gene.

Amino Acid Sequence↗
PubMed1999

Human genes involved in chromatin remodeling in transcription initiation, and associated diseases: An overview using the GENATLAS database.

Chromatin structure is inextricably linked to transcription regulation and differentiation. It consists of a multicomponent system, and impairments in such complex arrays may elicit dramatic biological effects and diseases. We present an overview of human genes involved in chromatin remodeling, which consist of the histone acetyltransferase/deacetylase system and the SWI/SNF-like complexes containing DNA-dependent ATPase activity. Special attention is given to the functional and physical interactions in which these components are involved, notably as transcriptional coactivators and/or corepressors of a large variety of genes. Linking seemingly distinct pathways allows integration of individual components into complex genetic and molecular processes and assessment of the underlying molecular bases of diseases. This was performed using GENATLAS (http://www.infobiogen.fr/), a gene database which compiles the information relevant to the mapping efforts from the published literature.

Chromatin↗
PubMed1999

The mutant genotype is the main determinant of the metabolic phenotype in phenylalanine hydroxylase deficiency.

Phenylketonuria and mild hyperphenylalaninemias are allelic disorders caused by mutations in the phenylalanine hydroxylase (PAH) gene. Following identification of the disease-causing mutation in 11 PAH-deficient patients, we tested the activity of the mutant gene products in an eukaryotic expression system. Two mutations markedly reduced PAH activity (A259V and L333F), one mutation mildly altered the enzyme activity (E390G), while the majority of mutant genotypes reduced the in vitro expression of PAH activity to 15-30% of controls. Comparing the predicted residual activity derived from expression studies to the clinical phenotypes of our PAH-deficient patients, we found that homozygosity for the L333F and E390G mutations resulted in severe and mild PAH deficiencies, respectively, both in vivo and in vitro, while compound heterozygosity (L333F/E390G) resulted in an intermediate dietary tolerance. Similarly, in vitro expression studies largely predicted dietary tolerance in compound heterozygotes for the A259V/IVS12nt1 (typical PKU), A259V/A403V, G218V/I65T, and G218V/R158Q mutations (mild variants). Taken together, these results support the view that expression studies are useful in predicting residual enzyme activity and that the mutant genotype at the PAH locus is the major determinant of metabolic phenotype in hyperphenylalaninemias.

Alleles↗
PubMed1999

Leber congenital amaurosis.

Leber's congenital amaurosis (LCA) is the earliest and most severe form of all inherited retinal dystrophies responsible for congenital blindness. Genetic heterogeneity of LCA has been suspected since the report by Waardenburg of normal children born to affected parents. In 1995, we localized the first disease causing gene, LCA1, to chromosome 17p13 and confirmed the genetic heterogeneity. In 1996, we ascribed LCA1 to mutations in the photoreceptor-specific guanylate cyclase gene (retGC1). RetGC1 is an essential protein implicated in the phototransduction cascade, especially in the recovery of the dark state after the excitation process of photoreceptor cells by light stimulation. In 1997, mutations in a second gene were reported in LCA, the RPE65 gene, which is the first specific retinal pigment epithelium gene. The protein RPE65 is implicated in the metabolism of vitamin A, the precursor of the photoexcitable retinal pigment (rhodopsin). Finally, a third gene, CRX, implicated in photoreceptor development, has been suspected of causing a few cases of LCA. Taken together, these three genes account for only 27% of LCA cases in our series. The three genes encode proteins that are involved in completely different physiopathologic pathways. Based on these striking differences of physiopathologic processes, we reexamined all clinical physiopathological discrepancies and the results strongly suggested that retGC1 gene mutations are responsible for congenital stationary severe cone-rod dystrophy, while RPE65 gene mutations are responsible for congenital severe but progressive rod-cone dystrophy. It is of tremendous importance to confirm and to refine these genotype-phenotype correlations on a large scale in order to anticipate the final outcome in a blind infant, on the one hand, and to further guide genetic studies in older patients on the other hand.

Animals↗
PubMed1999

Conservation of the Caenorhabditis elegans timing gene clk-1 from yeast to human: a gene required for ubiquinone biosynthesis with potential implications for aging.

Mutations in the Caenorhabditis elegans gene clk-1 have a major effect on slowing development and increasing life span. The Saccharomyces cerevisiae homolog COQ7 encodes a mitochondrial protein involved in ubiquinone biosynthesis and, hence, is required for respiration and gluconeogenesis. In this study, RT-PCR and 5' RACE were used to isolate both human and mouse clk-1/COQ7 homologs. Human CLK-1 was mapped to Chr 16(p12-13.1) by Radiation Hybrid (RH) and fluorescence in situ hybridization (FISH) methods. The number and location of human CLK1 introns were determined, and the location of introns II and IV are the same as in C. elegans. Northern blot analysis showed that three different isoforms of CLK-1 mRNA are present in several tissues and that the isoforms differ in the amount of expression. The functional equivalence of human CLK-1 to the yeast COQ7 homolog was tested by introducing either a single or multicopy plasmid containing human CLK-1 cDNA into yeast coq7 deletion strains and assaying for growth on a nonfermentable carbon source. The human CLK-1 gene was able to functionally complement yeast coq7 deletion mutants. The protein similarities and the conservation of function of the CLK-1/clk-1/COQ7 gene products suggest a potential link between the production of ubiquinone and aging.

Aging↗
PubMed1999

The neurogenic weakness, ataxia and retinitis pigmentosa (NARP) syndrome mtDNA mutation (T8993G) triggers muscle ATPase deficiency and hypocitrullinaemia.

UNLABELLED: Based on the study of three unrelated families, we report what we believe to be the first in vivo evidence of muscle ATPase deficiency in individuals carrying the neurogenic weakness, ataxia and retinitis pigmentosa (NARP) syndrome mtDNA mutation (T8993G). Since plasma citrulline was consistently low in 4/5 patients, we suggest that the NARP mutation caused complex V deficiency in the small intestine as well, thus reducing the availability of mitochondrial ATP required for citrulline synthesis. CONCLUSION: We suggest giving consideration to hypocitrullinaemia as a hallmark of the neurogenic weakness, ataxia and retinitis pigmentosa syndrome mutation and more generally of impaired oxidative phosphorylation in the small intestine in vivo.

Adenosine Triphosphatases↗
PubMed1999

A mitochondrial cytochrome b mutation but no mutations of nuclearly encoded subunits in ubiquinol cytochrome c reductase (complex III) deficiency.

Ubiquinol cytochrome c reductase (complex III) deficiency represents a clinically heterogeneous group of mitochondrial respiratory chain disorders that can theoretically be subject to either a nuclear or a mitochondrial mode of inheritance. In an attempt to elucidate the molecular bases of the disease, we first determined the nucleotide sequence of three unknown subunits (9.5 kDa, 7.2 kDa, 6.4 kDa) by cyberscreening of human expressed sequence tag data bases and sequenced the 11 cDNA subunits encoding complex III in five patients with isolated complex III deficiency. No mutation in the nuclearly encoded complex III subunits was observed, but a mutation in the cd2 helix of the mitochondrial (mt) cytochrome b gene was found to alter the conformation of the bc1 complex in one patient with severe hypertrophic cardiomyopathy. The present study is highly relevant to genetic counseling as the absence of mtDNA mutations in all but one patient in our series strongly supports autosomal rather than maternal inheritance in the majority of patients with complex III deficiency.

Amino Acid Sequence↗
PubMed1999

Age-related macular degeneration in grandparents of patients with Stargardt disease: genetic study.

PURPOSE: To report clinical features and molecular genetic study in three unrelated families in which age-related macular degeneration was observed in grandparents of patients with Stargardt disease. METHODS: A complete ophthalmologic examination including best-corrected visual acuity measurement, fundus examination, and fluorescein angiography was performed on all members of the three families. The entire coding sequence of the ABCR gene was analyzed using a combination of single strand conformation polymorphism and direct sequence analysis of the 50 exons. RESULTS: Compound heterozygous missense mutations were observed in patients with Stargardt disease (Arg212Cys, Argl107Cys, Gly1977Ser, Arg2107His, and le2113Met). Heterozygous missense mutations were observed in the grandparents with age-related macular degeneration (Arg212Cys and Arg1107Cys). CONCLUSIONS: We report phenotype and genotype findings in three unrelated families segregating patients with Stargardt disease and age-related macular degeneration. The hypothesis that the Arg212Cys and Arg1107Cys ABCR gene mutations could be susceptibility factors for age-related macular degeneration is discussed. We speculate that the relatives of patients affected with Stargardt disease who are carriers of heterozygous ABCR gene mutations may have a higher risk of developing age-related macular degeneration.

ATP-Binding Cassette Transporters↗
PubMed1999

Mutations within or upstream of the basic helix-loop-helix domain of the TWIST gene are specific to Saethre-Chotzen syndrome.

Saethre-Chotzen syndrome (ACS III) is an autosomal dominant craniosynostosis syndrome recently ascribed to mutations in the TWIST gene, a basic helix-loop-helix (b-HLH) transcription factor regulating head mesenchyme cell development during cranial neural tube formation in mouse. Studying a series of 22 unrelated ACS III patients, we have found TWIST mutations in 16/22 cases. Interestingly, these mutations consistently involved the b-HLH domain of the protein. Indeed, mutant genotypes included frameshift deletions/insertions, nonsense and missense mutations, either truncating or disrupting the b-HLH motif of the protein. This observation gives additional support to the view that most ACS III cases result from loss-of-function mutations at the TWIST locus. The P250R recurrent FGFR 3 mutation was found in 2/22 cases presenting mild clinical manifestations of the disease but 4/22 cases failed to harbour TWIST or FGFR 3 mutations. Clinical re-examination of patients carrying TWIST mutations failed to reveal correlations between the mutant genotype and severity of the phenotype. Finally, since no TWIST mutations were detected in 40 cases of isolated coronal craniosynostosis, the present study suggests that TWIST mutations are specific to Saethre-Chotzen syndrome.

Acrocephalosyndactylia↗
PubMed1999

Respiratory chain deficiency presenting as recurrent myoglobinuria in childhood.

Myoglobinuria is an abnormal urinary excretion of myoglobin due to an acute destruction of skeletal muscle fibres. Several metabolic diseases are known to account for myoglobinuria including defects of glycolysis and fatty acid oxidation. Here, we report on respiratory chain enzyme deficiency in three unrelated children with recurrent episodes of myoglobinuria and muscle weakness (complex I: one patient, complex IV: two patients). All three patients had generalized hyporeflexia during attacks, a feature which is not commonly reported in other causes of rhabdomyolysis. Studying respiratory chain enzyme activities in cultured skin fibroblasts might help diagnosing this condition, especially when acute rhabdomyolysis precludes skeletal muscle biopsy during and immediately after episodes of myoglobinuria.

Acute Disease↗