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A Munnich

Publications and source records attributed to A Munnich.

At least 433 records · Page 24Linked to original sources
PubMed1992

X-linked hydrocephalus: clinical heterogeneity at a single gene locus.

X-linked hydrocephalus-stenosis of the aqueduct of Sylvius sequence (H-SAS, MIM number 30007) is a rare genetic disorder characterized by hydrocephalus, macrocephaly, adducted thumbs, spasticity, agenesis of corpus callosum and mental retardation. We confirm here the localisation of the mutant gene on Xq (Xq 2.8) by linkage analysis in a 5-generation pedigree (maximum lod score of Z = 4.57 at theta = 0.04 with probe St14 at locus DXS52) and emphasise the phenotypic variability of the disease. Ventricular dilatation in affected males was either severe and diagnosed antenatally or moderate and consistent with a long survival with little or no macrocephaly. Since other X-linked syndromes of mental retardation with spasticity and flexion deformities of the thumbs have previously been shown to map to the Xq 2.8 region as well (e.g. MASA syndrome and spastic paraplegia), the present results raise the question of whether H-SAS syndrome, MASA syndrome and spastic paraplegia with mental retardation might represent different phenotypic expression of various mutations at the same locus.

Adult↗
PubMed1992

Clinical and genetic heterogeneity of Charcot-Marie-Tooth disease.

The autosomal dominant forms of hereditary motor and sensory neuropathies include the hypertrophic form (CMT1) and the neuronal form of Charcot-Marie-Tooth disease (CMT2). While at least two distinct loci have been shown to be linked to the CMT1 phenotype (CMT1A and CMT1B, on chromosomes 17 and 1, respectively), whether the CMT2 phenotype results from mutations allelic to either of the CMT1 genes remains unknown. Studying one CMT1 and two CMT2 pedigrees, we were able to exclude the CMT2 disease locus from the region of chromosome 17 (Z = -2.80 at theta = 0.05 for D17S58) where the CMT1A gene maps (Z = +3.67 at theta = 0.00). Similarly, negative lod score values were obtained in CMT2 for the region of chromosome 1 where the CMT1B gene has been located (Z = -3.09 at theta = 0.05 for D1S61). The present study therefore provides evidence for genetic heterogeneity between the hypertrophic and the neuronal forms of Charcot-Marie-Tooth disease and demonstrates that the CMT2 gene is not allelic to either of the CMT1 genes mapped to date.

Charcot-Marie-Tooth Disease↗
PubMed1992

3-Methylglutaconic aciduria associated with Pearson syndrome and respiratory chain defects.

3-Methylglutaconic aciduria was detected in four patients with Pearson syndrome, a multitissue disorder with hematologic abnormalities, lactic acidosis resulting from defective oxidative phosphorylation, and deletions in the mitochondrial genome. 3-Methylglutaconic acid may be an additional useful marker for Pearson syndrome and may be a more specific marker than other organic acids identified in this disorder.

Acidosis, Lactic↗
PubMed1992

Alpha-ketoglutarate dehydrogenase deficiency presenting as congenital lactic acidosis.

We report an inborn error of the tricarboxylic acid cycle, alpha-ketoglutarate dehydrogenase deficiency, in three siblings with hypotonia, metabolic acidosis, and hyperlactatemia immediately after birth. Neurologic deterioration resulted in death at about 30 months of age. We propose low molar ratios of ketone bodies in plasma of neonates with congenital lactic acidosis as an indication of dysfunction of the tricarboxylic acid cycle.

Acidosis, Lactic↗
PubMed1992

Deficiency in complex II of the respiratory chain, presenting as a leukodystrophy in two sisters with Leigh syndrome.

We report 2 sisters with a degenerative neurological disorder presenting clinically as a leukodystrophy. CT scan and MRI demonstrated small symmetrical foci of necrosis in the substentia nigra and in the basal ganglia typical of Leigh syndrome and diffuse cerebral white matter abnormalities. In these patients a deficiency in complex II of the respiratory chain was demonstrated in isolated mitochondria from muscle, as well as in fibroblasts and lymphocytes.

Brain↗
PubMed1992

The gene for hereditary multiple exostoses does not map to the Langer-Giedion region (8q23-q24).

Hereditary multiple exostoses is a dominantly inherited skeletal disorder which alters enchondral bone during growth and is characterised by exostoses of the juxta-epiphyseal regions. Using polymorphic DNA probes, we have been able to exclude the disease gene from close proximity to the 8q24.1 region where a dominant syndrome with multiple exostoses, the trichorhinophalangeal syndrome type II (TRP II, Langer-Giedion syndrome, MIM 15025), has been previously localised (pairwise linkage Z = -8.96 at theta = 0 with probe L48 at locus D8S51). Multipoint linkage analysis using probes L48, L24, and L1 consistently excluded the HME gene from a large area of the distal long arm of chromosome 8, spanning the smallest region of overlap assigned to the TRP II gene. These studies support the clinical view that HME and TRP II are distinct entities.

Chromosomes, Human, Pair 8↗
PubMed1992

[Phenotypic expression of 12 mutations of the phenylalanine hydroxylase gene].

BACKGROUND: Several mutations in the human phenylalanine hydroxylase (PAH) gene have been described and it may be interesting to tentatively correlate mutant genotypes and clinical phenotypes of phenylketonuria (PKU). METHODS: Twelve mutations were searched for using classical techniques of molecular biology in a total of 126 patients. 3 phenotypes were arbitrarily defined: typical PKU, atypical PKU or Mediterranean form, and persistent mild hyperphenylalaninemia. The patients were classified according to the residual in vivo PAH activity. RESULTS: Mutations were found in 64 patients. One mutation was found in each of the 2 alleles in 20 children. Only one mutation could be identified in the other 44. Only 45 children could be assigned to a phenotype. Mutations leading to total loss of PAH activity were associated with typical PKU (in homozygotes or compound heterozygotes). Mutations leading to residual PAH activity were associated in homozygotes with atypical PKU; they were also associated in compounded heterozygotes with atypical PKU, irrespective of the fact that the other allele suppressed enzyme activity or was unknown. A mutation which changed the affinity of PAH for phenylalanine was associated with mild hyperphenylalaninemia. CONCLUSION: The clinical heterogeneity of PKU can be correlated with identified mutations of the human PAH gene. Molecular studies do not help to predict either the phenotype or the long-term outcome. However, description of the biochemical changes combined with identification of the mutation should lead to a better understanding of consequences of mutation for PAH activity.

Child↗
PubMed1992

Site specific screening for point mutations in ornithine transcarbamylase deficiency.

Ornithine transcarbamylase (OTC) deficiency is a frequent X linked disorder of the urea cycle which is responsible for lethal neonatal hyperammonaemia in males and for various clinical symptoms in heterozygous females. In order to improve the efficiency of our screening for mutant genotypes, we focused on molecular domains of functional or structural importance in the OTC gene, namely the carbamyl phosphate binding domain (encoded by the third exon) and the MspI restriction sites (CCGG) of the coding sequence (located in exons 2 and 7 respectively), as they contain mutation hot spots (CpG doublets). Using this procedure, we were able to identify three new mutant genotypes in OTC deficient children including one nonsense mutation (E 87 K, G 50 ter, G 162 R). Since genetic counselling for OTC deficiency is frequently difficult, molecular screening directed towards specific sites of the coding sequence could allow rapid detection of mutant genotypes and help solve diagnostic problems, especially when carrier status cannot be clarified easily.

Amino Acid Metabolism, Inborn Errors↗
PubMed1992

[Molecular genetics and prenatal diagnosis].

Recombinant DNA techniques have provided new insight into genetic and prenatal diagnosis during the last 10 years. Human gene mapping data are increasing exponentially due to molecular biology advances. Most analyses are possible from chorionic villi biopsy specimens as early as the 10th week of fetal life. When the gene is known and cloned, the diagnosis is regularly made by using the polymerase chain reaction technique; when the gene is unknown but mapped, the restriction fragment length polymorphism technique is used. However, these methods for prenatal assessment require a reliable diagnosis of index case disease and a preliminary familial DNA study.

Female↗
PubMed1992

[Enzymatic activities of the mitochondrial respiratory chain in child cardiomyopathies. 34 cases prospectively studied by endomyocardial biopsy].

The arguments in favour of mitochondrial pathology of certain childhood cardiomyopathies (multi tissue involvement, lactic acidosis, histochemical abnormalities of skeletal muscle) are indirect and may be absent in isolated cardiomyopathy. The authors therefore set up a prospective study of enzyme activity of the mitochondrial respiratory chain directly by endomyocardial biopsy. Fifty children aged 2 months to 16 years were included. Thirty four had cardiomyopathy which was dilated and hypokinetic with thin walls in 21 cases, restrictive in 2 cases, and hypertrophic in 11 cases; the remaining 16 children had either normal hearts (13 catheterised for other reasons) or myocardial hypertrophy due to pulmonary or aortic stenosis (3 cases). Both ventricles were evaluated in 3 cases; macro-surgical biopsies were obtained in 6 cases and skeletal muscle biopsy was obtained in 9 cases. The results indicate the method to be reliable with no difference between the micro and macro biopsies. The absolute values of enzyme activity were too variable to serve as quantitative parameters but some ratios of activity were remarkably stable and allowed a qualitative assessment which was all the more accurate when identical values were obtained in the myocardium, skeletal muscle and liver. The mitochondrial respiration was independent of ventricular pressures and of the type (right or left) of ventricle. Enzyme activity was nearly always normal in dilated cardiomyopathy (20/21) which suggests that it was unaffected by dilatation of the heart and by abnormal myocardial contractility. The results could be normal in myocardial hypertrophy and in valvular stenosis and in over half the cases of hypertrophic cardiomyopathy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Maternally inherited duplication of the mitochondrial genome in a syndrome of proximal tubulopathy, diabetes mellitus, and cerebellar ataxia.

Two sisters in the first year of life presented with a proximal tubulopathy of unknown etiology. They subsequently developed a pluritissular disorder including diabetes mellitus, skin abnormalities, mitochondrial myopathy with ragged-red fibers, and cerebellar ataxia. Their mother had ptosis, ophthalmoplegia, and muscle weakness. Analysis of the mitochondrial respiratory chain showed a complex III deficiency in both skeletal muscle and lymphocytes of the second girl. Southern blot analysis provided evidence for a heteroplasmic partial duplication of the mtDNA (26 kb), involving one full-length and one partly deleted mitochondrial genome and with one single abnormal junction between the genes for ATPase 6 and cytochrome b. Using PCR amplification of lymphocyte DNA, we were able to detect minute amounts of duplicated molecules in the mother, which provided evidence for maternal inheritance of the partial duplication. While maternal transmission of point mutations have been reported in Leber disease, retinitis pigmentosa, and MERRF disease, this observation is, to our knowledge, the first example of a maternally inherited duplication of the mitochondrial genome in man.

Adenosine Triphosphatases↗
PubMed1992

[Leber's optic neuropathy: new diagnostic prospects].

The diagnosis of Leber's hereditary optic neuropathy, essentially based on a family history of a similar illness, becomes difficult in sporadic cases. In this disease, mitochondrial DNA mutations have been recently discovered and detected by digestion with restriction enzyme after amplification by the Polymerase Chain Reaction. We present two patients in whom these molecular biological techniques confirmed the diagnosis of Leber's hereditary optic neuropathy in the absence of a convincing family history. These new molecular biological methods, providing a precious diagnostic test, would certainly play a greater part in genetic counselling and would probably be a prerequisite for the development of new forms of therapy.

Adult↗
PubMed1991

A 3-base pair in-frame deletion of the phenylalanine hydroxylase gene results in a kinetic variant of phenylketonuria.

Phenylketonuria (PKU) is an autosomal recessive disease due to deficiency of a hepatic enzyme, phenylalanine hydroxylase (PAH). The absence of PAH activity results in typical PKU while persistence of a residual enzyme activity gives rise to variant forms of the disease. We report here a 3-base pair in-frame deletion of the PAH gene (delta 194) in a mild variant, with markedly reduced affinity of the enzyme for phenylalanine (Km = 160 nM), and we provide functional evidence for responsibility of the deletion in the mutant phenotype. Since the deletion was located in the third exon of the gene, which presents no homology with other hydroxylases, we suggest that exon 3 is involved in the specificity of the enzyme for phenylalanine. Finally, since none of the 98 PKU patients tested were found to carry this particular deletion, our study suggests that this molecular event probably occurred recently on the background of a haplotype 2 gene in Portugal.

Base Composition↗