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We present the clinical and biochemical data of a patient with infantile isolated sulphite oxidase deficiency with late onset of symptoms. A comparison of the biochemical parameters is made with the neonatal type of this disease and with the data of described patients with the combined defect of sulphite oxidase and xanthine oxidase, due to molybdenum cofactor deficiency. False-negative sulphite dip stick test as a pitfall in the diagnosis of sulphite oxidase deficiency is discussed. [ABSTRACT FROM AUTHOR]

Molybdenum cofactor deficiency (MIM#252150) is a severe autosomal-recessive disorder with a devastating outcome. The cofactor is the product of a complex biosynthetic pathway involving four different genes (MOCS1, MOCS2, MOCS3 and GEPH). This disorder is caused almost exclusively by mutations in the MOCS1 or MOCS2 genes. Mutations affecting this biosynthetic pathway result in a lethal phenotype manifested by progressive neurological damage via the inactivation of the molybdenum cofactor-dependent enzyme, sulphite oxidase. Here we describe a total of ten novel disease-causing mutations in the MOCS1 and MOCS2 genes. Nine out of these ten mutations were classified as pathogenic in nature, since they create a stop codon, affect constitutive splice site positions, or change strictly conserved motifs. The tenth mutation abolishes the stop codon of the MOCS2B gene, thus elongating the corresponding protein. The mutation was expressed in vitro and was found to abolish the binding affinities of the large subunit of molybdopterin synthase (MOCS2B) for both precursor Z and the small subunit of molybdopterin synthase (MOCS2A).

Congenital adrenal hyperplasia (CAH) is primarily caused by 21-hydroxylase deficiency and leads to an accumulation of 17-hydroxyprogesterone and reduced cortisol levels. Newborn screening for CAH is traditionally based on measuring 17-hydroxyprogesterone by different immunoassays. Despite attempts to adjust cutoff levels for birth weight, gestational age, and stress factors, the positive predictive value for CAH screening remains less than 1%. To improve this situation, we developed a method using liquid chromatography-tandem mass spectrometry to measure 17-hydroxyprogesterone, androstenedione, and cortisol simultaneously in blood spots. A total of 1222 leftover blood spots from six different screening programs using different immunoassays (fluorescent immunoassay and ELISA) were reanalyzed in a blinded fashion by liquid chromatography-tandem mass spectrometry. Thirty-one samples were from babies with CAH, 190 had yielded false-positive results by immunoassay, and the remaining 1001 samples were from babies with normal screening results. Steroid profiling allowed for an elimination of 169 (89%) of the false-positive results and for an improvement of the positive predictive value from the reported 0.5 to 4.7%. Although this method is not suitable for mass screening due to the length of the analysis (12 min), it can be used as a second-tier test of blood spots with positive results for CAH by the conventional methods. This would prevent unnecessary blood draws, medical evaluations, and stress to families.

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.

We report twelve novel mutations in patients with isolated sulfite oxidase deficiency. The mutations are in SUOX, the gene that encodes the molybdohemoprotein sulfite oxidase. These include two frameshift mutations, a four-basepair deletion (562del4) and a single-basepair insertion (113insC), both resulting in premature termination. Nonsense mutations predicting Y343X and Q364X substitutions were identified in a homozygous state in three patients, the latter in two sibs. The remaining eight are missense mutations generating single amino acid substitutions. From the position of the substituted residues, seven of these mutations are considered to be causative of the enzyme deficiency: I201L, R211Q, G305S, R309H, K322R, Q339R, and W393R. The eighth, a C>T transition, predicts an R319C substitution, which could affect the binding of the molybdenum cofactor and thus severely reduce sulfite oxidase activity. This mutation, however, is downstream of a frameshift mutation and is therefore not the causative mutation in this individual., (Copyright 2002 Wiley-Liss, Inc.)

Molybdenum cofactor deficiency (MoCoD) is an autosomal recessive, fatal neurological disorder, characterized by the combined deficiency of sulphite oxidase, xanthine dehydrogenase and aldehyde oxidase. We have recently reported an excessive occurrence of this fatal disorder among segments of the Arab population in Northern Israel suggesting that the true incidence of MoCoD is probably underestimated in this highly inbred population. This lethal disease can be diagnosed prenatally by assay of sulphite oxidase activity in chorionic villus samples in pregnancies of couples who have had previously affected children (obligatory carriers). However, to date, there is no biochemical assay for carrier detection among the population at risk. Recently we demonstrated the linkage of a MoCoD gene to an 8-cM region on chromosome 6p21.3 in two consanguineous Israeli-Arab unrelated kindreds. The description of the MOCS1 gene that maps to the same region and which carries multiple mutations in MoCoD type A followed this finding. We describe here one additional kindred of Arab-Israeli origin, which is also linked to the MOCS1 locus, and demonstrate the feasibility of prenatal diagnosis and carrier detection using microsatellite markers in selected families when mutations are unknown. A complete correlation between the biochemical and DNA assays was found in a total of six samples (five chorionic villus and one amniocyte culture sample) obtained from the three MoCoD families.

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.

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.

Molybdenum cofactor deficiency (MoCoD) is a fatal disorder manifesting, shortly after birth, with profound neurological abnormalities, mental retardation, and severe seizures unresponsive to any therapy. The disease is a monogenic, autosomal recessive disorder, and the existence of at least two complementation groups suggests genetic heterogeneity. In humans, MoCoD leads to the combined deficient activities of sulfite oxidase, xanthine dehydrogenase, and aldehyde oxidase. By using homozygosity mapping and two consanguineous affected kindreds of Israeli-Arab origin, including five patients, we demonstrated linkage of a MoCoD gene to an 8-cM region on chromosome 6p21.3, between markers D6S1641 and D6S1672. Linkage analysis generated the highest combined LOD-score value, 3.6, at a recombination fraction of 0, with marker D6S1575. These results now can be used to perform prenatal diagnosis with microsatellite markers. They also provide the only tool for carrier detection of this fatal disorder.

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.

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.

Analysis of uncultured chorionic villus material from a woman at risk of fetus with sulfite oxidase deficiency revealed a deficiency of sulfite oxidase. This was confirmed on termination of the pregnancy.

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.