Mutations in a polycistronic nuclear gene associated with molybdenum cofactor deficiency.

All molybdoenzymes other than nitrogenase require molybdopterin as a metal-binding cofactor. Several genes necessary for the synthesis of the molybdenum cofactor (MoCo) have been characterized in bacteria and plants. The proteins encoded by the Escherichia coli genes moaA and moaC catalyse the first steps in MoCo synthesis. The human homologues of these genes are therefore candidate genes for molybdenum cofactor deficiency, a rare and fatal disease. Using oligonucleotides complementary to a conserved region in the moaA gene, we have isolated a human cDNA derived from liver mRNA. This transcript contains an open reading frame (ORF) encoding the human moaA homologue and a second ORF encoding a human moaC homologue. Mutations can be found in the majority of MoCo-deficient patients that confirm the functional role of both ORFs in the corresponding gene MOCS1 (for 'molybdenum cofactor synthesis-step 1'). Northern-blot analysis detected only full-length transcripts containing both consecutive ORFs in various human tissues. The mRNA structure suggests a translation reinitiation mechanism for the second ORF. These data indicate the existence of a eukaryotic mRNA, which as a single and uniform transcript guides the synthesis of two different enzymatic polypeptides with disease-causing potential.

Worldwide experience in newborn screening for classical congenital adrenal hyperplasia due to 21-hydroxylase deficiency.

The need for a reliable screening test for classical congenital adrenal hyperplasia prompted development of newborn screening programs. Worldwide incidence of classical congenital adrenal hyperplasia in this report was taken from newborn screening programs in France, Italy, Japan, New Zealand, Scotland, and the United States. Two populations in which the occurrence of congenital adrenal hyperplasia among live births has been reported with greater than usual frequency are the Yupik Eskimos of southwestern Alaska (1:282) and the people of La Reunion, France (1:2,141). Aside from these populations, 1,093,310 newborns were screened between 1980 and 1988, of whom 77 had congenital adrenal hyperplasia. Thus, worldwide incidence of this disorder was estimated at 1:14,199 live births for homozygous patients, 1:60 for heterozygous subjects, with a gene frequency of 0.0083. Incidence of congenital adrenal hyperplasia among whites was estimated to be 1:11,909 (41:488,279) for homozygous patients, 1:55 for heterozygous subjects with a gene frequency of 0.0091. Incidence for the salt-wasting form of congenital adrenal hyperplasia was 1:18,850 (58:1,093,310) compared with 1:57,543 (19:1,093,310) for congenital adrenal hyperplasia in the simple virilizing form. Thus, salt-wasting congenital adrenal hyperplasia was three times more common than simple virilizing congenital adrenal hyperplasia. Estimated incidence of congenital adrenal hyperplasia in white populations in Italy and France (1:10,866) was higher than in Scotland (1:17,098), New Zealand (1:14,500). The incidence in an Asian population (Japan) (1:15,800) did not differ significantly from that of the white population. In four of five populations, overall incidence was higher than previously reported, as was the frequency of the salt-wasting form (75% v 50% to 66%), suggesting improved case detection by newborn screening.(ABSTRACT TRUNCATED AT 250 WORDS)

Spherophakia associated with molybdenum cofactor deficiency.

Molybdenum cofactor deficiency is an autosomal recessive disorder characterized by lack of activity of the enzymes sulfite oxidase, aldehyde oxidase, and xanthine dehydrogenase or oxidase. The clinical manifestations are indistinguishable from those of isolated sulfite oxidase deficiency: craniofacial alterations, intractable neonatal convulsions, very severe mental retardation, lens dislocation, and death in the first decade of life. Lens dislocation is found in nearly all patients after neonatal age. In the present case it developed late (at the age of 8 years) and was preceded by bilateral spherophakia. We hypothesize that an abnormal relaxation of the zonular fibers is the cause of spherophakia in this disease; this causes lens dislocation eventually, after days, months, or years.

Outcome of 27 patients with Hurler's syndrome transplanted from either related or unrelated haematopoietic stem cell sources.

Over the last 15 years, we have performed a total of 30 haematopoietic stem cell transplants on 27 children suffering from Hurler's syndrome. These children were of median age 11 months at the time of diagnosis and 25 months at the time of transplantation. The phenotype was severe in 21 cases (78%). The donor was familial in 13 cases: nine genotypically identical, one phenotypically identical father and three HLA-mismatched donors. Unrelated donors were selected in 17 cases: four phenotypically identical and 13 with 1-4 HLA mismatches. The conditioning regimen generally consisted of busulphan 600 mg/m(2) plus cyclophosphamide (Endoxan) 260 mg/kg and cyclosporin with methotrexate for GvHD prophylaxis. Rabbit anti-thymocyte globulin (Thymoglobuline) was given for all unrelated or familial mismatched transplantations. The median nucleated cell dose infused was 6.00 x 10(8) TNC/kg. No bone marrow (apart from one) was T cell depleted. For first transplants, engraftment was observed in 23/27 patients (pts) (85%). Primary graft failure was observed in 4/27 patients (16%), two were retransplanted from an unrelated donor, one with success. Four patients have died. The primary cause of death was infection in three cases (TRM : 11%) and disease progression in one case, after primary graft failure. Of the 23 living patients, two have disease progression after graft failure and 21 (78%) have functional grafts with a favourable long-term outcome after a median follow-up of 4.7 years, having either full or mixed chimaerism. Among surviving patients with functional grafts, 13 (62%) were transplanted from unrelated donors of whom 10 (77 %) had HLA disparities. There was a remarkably low incidence of GvHD. In our experience, haematopoietic stem cell transplantation using an HLA-matched familial donor or an HLA-matched or -mismatched unrelated donor without T cell depletion or irradiation can achieve a favourable outcome in Hurler's syndrome, with improved cognitive function, but with a limited effect on the corneas and skeleton.

[Application of tandem mass spectrometry to neonatal screening of inherited metabolic diseases: focus on present developments]. / La spectrométrie de masse en tandem appliquée au dépistage néonatal des maladies héréditaires du métabolisme: le point sur les utilisations actuelles.

The recent evolution of tandem mass spectrometry allows to diagnose more than twenty inherited metabolic diseases within a single blood spot. Nowadays, it is technically possible to screen newborns for most of fatty acid oxidation, organic acid and amino acid disorders. An important number of prospective pilot studies, using tandem mass spectrometry, have been done worldwide. However, several technical, economical, medical and ethical problems are raised by these applications. This review is intended to focus on this technology and to resume results from the main international studies.

[Sulfite oxidase deficiency presenting as Leigh syndrome]. / Déficit en sulfite oxydase se présentant comme un syndrome de Leigh.

BACKGROUND: An enzyme deficiency can be demonstrated in 15 to 20% of cases of Leigh syndrome. A case of isolated sulphite oxidase deficiency is reported in a girl presenting with Leigh syndrome. CASE REPORT: An 8 month-old girl was admitted suffering from hypotonia and slow increase of head circumference (-1 SD). Examination showed spastic quadriplegia, dyskinesia, axial hypotonia and difficulties in swallowing. The patient had a coarse face, broad nasal bridge, long philtrum and ectopia lentis. Brain CT scan showed bilateral hypodensity of lenticular nuclei and moderate cortical atrophy. Amino acid chromatography showed accumulation of S sulfocysteine and low levels of cysteine. The sulphite test was positive. Sulphite oxidase activity in fibroblasts and liver was undetectable contrasting with a normal activity of xanthine oxidase. Progressive brain damage led to death at 1 year of age. Prenatal diagnosis of sulphite oxidase deficiency was made in two further pregnancies. CONCLUSIONS: The search for sulphite oxidase deficiency must be included in discussing the etiology of Leigh syndrome; the sulphite test is a simple method of screening such cases.

[Neonatal screening of congenital hypothyroidism with TSH measurement in dried blood spots on filter paper. A two years experience (author's transl)]. / Dépistage néonatal de l'hypothyroïdie congenitale par le dosage de la TSH sur tache de sang séché. Expérience de 2 ans dans la région Rhône-Alpes.

Systematic screening for congenital hypothyroidism was started in Lyon in september 1976. This screening was coupled with PKU, using the same dried blood samples on filter paper obtained on the 5th day of life. TSH levels were determined by radioimmunoassay adapted for dried blood samples (Kit Abbott). In 24 months, 56 176 samples were analyzed. The critical level calling for control was successively raised from from 20 to 30, now 40 microUI/ml of serum. A high level of TSH was found in 307 children (0,55%). Pathological deliveries were found in most of these infants (neonatal injury, cesarean, section forceps or ocytocic perfusion, neonatal icterus) and a second or a third measurement showed normal TSH level. Congenital hypothyroidism, was found detected in 18 infants: 12 ectopic gland, 5 athyreosis and 1 dyshormonogenesis. Treatment was begun at a mean age of 38 days (29 to 50 days).

[Neonatal screening for congenital hypothyroidism by measuring TSH in dried blood samples. Two years experience in the method (author's transl)]. / Dépistage néonatal de l'hypothyroïdie congénitale par le dosage de la TSH sur tache de sang séché.

Systematic screening for congenital hypothyroidism was started in Lyon in September 1976. This screening was coupled with PKU screening, using the same dried blood samples in filter paper obtained on the 5 th day of life. TSH levels were determined by radioimmunoassay adapted for dried blood samples (Kit Abbott). In 24 months, 56 176 samples were analyzed. The critical level calling for control was successively raised from 20 to 30 now 40 muUl/ml of serum. A high level of TSH was found in 307 children (0.55 p. 100). Pathological deliveries were found in most of these infants (neonatal injury, cesarean section, forceps or ocytocic perfusion, neonatal icterus) and a second or a third measurement showed normal TSH level. Congenital hypothyroidism, was detected in 18 infants: 12 ectopic gland, 5 athyreosis and 1 dyshormonogenesis. Treatment was begun at a mean age of 38 days (29 to 50 days). Despite a short follow-up the psychomotor development of the infants seems to be normal in all cases but one (one athyreosis with a neonatal injury and a malformative syndrome).

False-positive results in neonatal screening for cystic fibrosis based on a three-stage protocol (IRT/DNA/IRT): Should we adjust IRT cut-off to ethnic origin?

Since 1979, newborn screening for cystic fibrosis (CF) has been possible by measuring immunoreactive tryspinogen (IRT) in blood spots. In France, a programme based on a three-stage strategy (IRT/DNA/IRT) started in 2002. In the Rhône-Alpes area, the positive screening rate (i.e. the proportion of samples sent for genotyping) observed after the first IRT measurement was higher than the expected rate (0.65% versus 0.50%), without a greater CF incidence. We hypothesized that the IRT reference range could differ according to the ethnic origin of the newborns. 35 141 newborns were studied and divided into two groups: European ethnic group 26 324 (75%) and North African ethnic group 8817 (25%). 243 positive newborns were identified: 146 (60%) in the European ethnic group and 97 (40%) in the North African ethnic group. Three CF patients and 11 unaffected heterozygotes were found in the European group, but no mutations were found in the North African group. Mean IRT values and the percentage of IRT values over the cut-off were significantly higher in the North African group than in the European group (mean IRT = 21.17 microg/L and 19.74 microg/L, p < 0.0001; %IRT > cut-off = 1.1% and 0.5%, respectively). For the positive screened newborns, term and IRT mean were comparable, whereas birth weight was higher in the North African ethnic group. These results lead us to conclude that (i) newborns from families of North African origin have higher IRT values and (ii) most of the positive screened newborns in this population could be considered as 'false positives'. These conclusions could explain, in part, the large variations seen in the positive screening rate in the French CF neonatal screening and raise the question whether it is relevant to adapt cut-off to ethnic origin of the newborns.

Molybdenum cofactor deficiency: first prenatal genetic analysis.

Molybdenum cofactor (MoCo) deficiency leads to a combined deficiency of the molybdo-enzymes sulphite oxidase, xanthine dehydrogenase and aldehyde oxidase. No therapy is known for this rare disease, which results in neonatal seizures and other neurological symptoms identical to sulphite oxidase deficiency. It is inherited autosomal-recessively and leads to early childhood death. Prenatal diagnosis has been performed since 1983 by the measurement of sulphite oxidase activity, but no enzymatic carrier diagnosis is possible. The human genes necessary for MoCo biosynthesis have recently been cloned and mutations in the bicistronic MOCS1 gene could be identified in most European patients. In a Danish family we have now performed enzymatic and molecular genetic analysis in parallel after chorionic villus sampling. The sulphite oxidase activity in uncultured CVS material was found to be normal. A MOCS1 splice site mutation, found homozygous in the affected patient, was found in a heterozygous state in cultured chorionic cells. This confirmed that the fetus was not affected, since heterozygous carriers of a MoCo deficiency allele do not display any symptoms.

Studies on the interaction of a thiol-dependent hydrogen peroxide scavenging enzyme and phenylalanine hydroxylase.

Rat liver phenylalanine hydroxylase is irreversibly inactivated by a H2O2-dependent process. Since H2O2 can be produced by autooxidation of the tetrahydropterin cofactor required for the hydroxylation reaction, in vitro assays are usually carried out in the presence of added catalase. On the basis of a dithiothreitol-dependent protecting assay of phenylalanine hydroxylase, carried out in the absence of catalase, we have isolated an enzyme fraction from neonatal rat livers which has similar properties to the known enzyme, glutathione peroxidase. The developmental time course for phenylalanine hydroxylase in rats has been reported to follow two different patterns. Using the dithiothreitol assay, McGee et al. (1972, Biochem. J. 127, 669-674) have found that newborn rats have low phenylalanine hydroxylase activity which increases to adult levels over several months. On the other hand, using catalase-supplemented assays, others have found that newborn rats have nearly adult levels of phenylalanine hydroxylase activity. The protective effect of glutathione peroxidase on phenylalanine hydroxylase suggests that the developmental time course found by McGee et al. may represent the slow developmental time course previously found for glutathione peroxidase. In addition, feeding rats a selenium-deficient diet, which reduces the hepatic activity of the selenium-containing glutathione peroxidase, results in a concomitant irreversible loss of phenylalanine hydroxylase activity, suggesting that glutathione peroxidase may play a vital role in protecting phenylalanine hydroxylase in vivo from peroxide inactivation.

Molybdenum cofactor deficiency in two siblings: diagnostic difficulties.

Two siblings with molybdenum cofactor deficiency are presented. They showed clinical, biochemical and neuroradiological features very similar to those of the few previously described cases. Difficulties in diagnosis are emphasised.

CDG IIx with unusual phenotype.

Congenital disorders of glycosylation (CDG) are a group of genetic diseases characterized by defective protein glycosylation. N-glycosylation defects are divided into two groups (I and II). CDG group II (types IIa to IIe) refers to defects in the Golgi processing of protein-bound glycans. We report a patient with CDG IIx and an unusual phenotype.

A mild form of infantile isolated sulphite oxidase deficiency.

Neonatal sulphite oxidase deficiency is characterised by severe neurologic dysfunction, brain atrophy, dislocation of the lens and increased urinary excretion of sulphite, thiosulphate, taurine and S-sulphocysteine, and by a low plasma cystine. We present clinical, neuroradiological and biochemical data of a patient with late onset symptoms comparing this presentation with the neonatal form and stressing the difficulties of the diagnosis of this disorder.

Genomic structure and mutational spectrum of the bicistronic MOCS1 gene defective in molybdenum cofactor deficiency type A.

Molybdenum cofactor (MoCo) deficiency is a rare and devastating disease resulting in neonatal seizures and other neurological symptoms identical to those of sulphite oxidase deficiency. It is an autosomal recessive disease and no therapy is known. Most patients harbour MOCS1 mutations, which are found in both open reading frames of this unusual gene encoding the first two enzymes required in the MoCo biosynthesis pathway, MOCS1 A and MOCS1 B, in a single transcript. We describe genomic details as a prerequisite for comprehensive mutation analysis. In an initial cohort of 24 MoCo deficiency patients, we identified 13 different mutations on 34 chromosomes, with a mutation detection rate of 70%. Five mutations were observed in more than one patient and together accounted for two thirds of detected mutations. These comprise the most frequent mutation, R319Q, which is restricted to England, two Danish/German mutations (one missense and one splice site mutation), a missense mutation found in England and Germany, and a "Mediterranean" frameshift mutation. All patients with identified mutations are either homozygous or compound heterozygous for mutations in either of the two open reading frames corresponding to MOCS1 A and MOCS1 B, respectively. This observation suggests the existence of more than the two previously described complementation groups in MoCo biosynthesis.

[Familial congenital muscular dystrophy caused by phosphofructokinase deficiency]. / Observation familiale de dystrophie musculaire congénitale par déficit en phosphofructokinase.

Two children, born to related parents, presented since birth a muscular defect rapidly complicated by painful joint stiffness. The oldest child died at 6 months of age, from respiratory complications. The second-14 month old- does not sit without support. The muscle fibres are of unequal calibre and numerous fibres have under-sarcolemmal PAS positive areas contain glycogen, as seen on electron microscopy. In the second patient, the biochemical analysis showed a moderate glycogen accumulation and muscular enzymatic studies demonstrated an isolated and major deficiency in phosphofructokinase activity. Activity was normal in red blood cells and in fibroblasts cultured in vitro. Hence, these cases should be distinguished from formerly reported cases of phosphofructokinase deficiency. This type of P.F.K. deficiency should be looked for in patients with severe congenital muscular dystrophy and early joint involvement.

[Systematic neonatal screening for Duchenne muscular dystrophy]. / Dépistage néonatal systématique de la myopathie de Duchenne de Boulogne (author's transl)]

More than 15% of cases of Duchenne muscular dystrophy (DMD) may be preventable by the neonatal diagnosis of another affected relative. Systematic neonatal screening seems a more efficient way of getting information for genetic counseling. The principle of the test described is the detection of a specific increase of the activity of Creatine-Kinase (CK) in the blood of newborn children with myopathy. Blood may be spotted on paper and posted to a central laboratory. Furthermore this program can be integrated into the systematic screening of phenylketonurie. The specificity and accuracy of the bioluminescent reaction used for the evaluation of CK suggest that this screening reaction is reliable. A systematic neonatal screening program for DMD such as ours in the Rhône-Alpes area (France) will lead to frequent recourse to prenatal diagnosis now possible through sex fetal determination and which would be possible through in utero blood sampling.

Human molybdopterin synthase gene: genomic structure and mutations in molybdenum cofactor deficiency type B.

Biosynthesis of the molybdenum cofactor (MoCo) can be divided into (1) the formation of a precursor and (2) the latter's subsequent conversion, by molybdopterin synthase, into the organic moiety of MoCo. These two steps are reflected by the complementation groups A and B and the two formally distinguished types of MoCo deficiency that have an identical phenotype. Both types of MoCo deficiency result in a pleiotropic loss of all molybdoenzyme activities and cause severe neurological damage. MOCS1 is defective in patients with group A deficiency and has been shown to encode two enzymes for early synthesis via a bicistronic transcript with two consecutive open reading frames (ORFs). MOCS2 encodes the small and large subunits of molybdopterin synthase via a single transcript with two overlapping reading frames. This gene was mapped to 5q and comprises seven exons. The coding sequence and all splice site-junction sequences were screened for mutations, in MoCo-deficient patients in whom a previous search for MOCS1 mutations had been negative. In seven of the eight patients whom we investigated, we identified MOCS2 mutations that, by their nature, are most likely responsible for the deficiency. Three different frameshift mutations were observed, with one of them found on 7 of 14 identified alleles. Furthermore, a start-codon mutation and a missense mutation of a highly conserved amino acid residue were found. The locations of the mutations confirm the functional role of both ORFs. One of the patients with identified MOCS2 mutations had been classified as type B, in complementation studies. These findings support the hypothetical mechanism, for both forms of MoCo deficiency, that formerly had been established by cell-culture experiments.