molybdenum-cofactor and Metal-Metabolism--Inborn-Errors

Molybdenum cofactor (Moco) is synthesized endogenously in humans and is essential for human development. Supplementation of Moco or its precursors has been explored as a therapy to treat Moco-deficient patients but with significant limitations. By using the nematode

Topics: Animals; Caenorhabditis elegans; Coenzymes; Humans; Metal Metabolism, Inborn Errors; Metalloproteins; Molybdenum Cofactors; Pteridines

Topics: Biomarkers; Coenzymes; Cysteine; Diagnosis, Differential; Female; Humans; Infant; Infant, Newborn; Male; Metal Metabolism, Inborn Errors; Metalloproteins; Molybdenum; Molybdenum Cofactors; Oxidoreductases Acting on Sulfur Group Donors; Pteridines; Sulfites; Xanthine

The molybdenum cofactor (Moco) is a 520-Da prosthetic group that is synthesized in all domains of life. In animals, four oxidases (among them sulfite oxidase) use Moco as a prosthetic group. Moco is essential in animals; humans with mutations in genes that encode Moco biosynthetic enzymes display lethal neurological and developmental defects. Moco supplementation seems a logical therapy; however, the instability of Moco has precluded biochemical and cell biological studies of Moco transport and bioavailability. The nematode

Topics: Animals; Bacteria; Biological Transport; Caenorhabditis elegans; Coenzymes; Humans; Metal Metabolism, Inborn Errors; Metalloproteins; Molybdenum Cofactors; Protein Binding; Pteridines

Molybdenum cofactor deficiency (MoCD) is a rare autosomal-recessive disorder that results in the combined deficiency of molybdenum-dependent enzymes. Four different genes are involved in Molybdenum cofactor biosynthesis: MOCS1, MOCS2, MOCS3, and GEPH. The classical form manifests in the neonatal period with severe encephalopathy, including intractable seizures, MRI changes that resemble hypoxic-ischemic injury, microcephaly, and early death. To date, an atypical phenotype with late-onset has been reported in the literature in 13 patients.. We describe a late-onset and a relatively mild phenotype in a patient with MOCS2 homozygous mutation.. Pyramidal and extrapyramidal signs are recognized in those patients, often exacerbated by intercurrent illness. Expressive language is usually compromised. Neurological deterioration is possible even in adulthood, probably due to accumulation of sulfite with time.. Sulfite inhibition of mitochondrial metabolism could be responsible for the ischemic lesions described in patients with MoCD or alternatively could predispose the brain to suffer an ischemic damage through the action of other insults, for instance intercurrent illness. It is possible that sulfite accumulation together with other external triggers, can lead to neurological deterioration even in adulthood. The role of other factors involved in clinical expression should be investigated to establish the reason for phenotypic variability in patients with the same mutation.

Topics: Child; Coenzymes; Female; Homozygote; Humans; Metal Metabolism, Inborn Errors; Metalloproteins; Molybdenum Cofactors; Mutation; Phenotype; Pteridines; Sulfurtransferases

Molybdenum cofactor deficiency is an autosomal recessive inborn error of metabolism, which results from mutations in genes involved in Moco biosynthesis. Moco serves as a cofactor of several enzymes, including sulfite oxidase. MoCD is clinically characterized by intractable seizures and severe, rapidly progressing neurodegeneration leading to death in early childhood in the majority of known cases. Here we report a patient with an unusual late disease onset and mild phenotype, characterized by a lack of seizures, normal early development, a decline triggered by febrile illness and a subsequent dystonic movement disorder. Genetic analysis revealed a homozygous c.1338delG MOCS1 mutation causing a frameshift (p.S442fs) with a premature termination of the MOCS1AB translation product at position 477 lacking the entire MOCS1B domain. Surprisingly, urine analysis detected trace amounts (1% of control) of the Moco degradation product urothione, suggesting a residual Moco synthesis in the patient, which was consistent with the mild clinical presentation. Therefore, we performed bioinformatic analysis of the patient's mutated MOCS1 transcript and found a potential Kozak-sequence downstream of the mutation site providing the possibility of an independent expression of a MOCS1B protein. Following the expression of the patient's MOCS1 cDNA in HEK293 cells we detected two proteins: a truncated MOCS1AB protein and a 22.4 kDa protein representing MOCS1B. Functional studies of both proteins confirmed activity of MOCS1B, but not of the truncated MOCS1AB. This finding demonstrates an unusual mechanism of translation re-initiation in the MOCS1 transcript, which results in trace amounts of functional MOCS1B protein being sufficient to partially protect the patient from the most severe symptoms of MoCD.

Topics: Age of Onset; Carbon-Carbon Lyases; Child; Child, Preschool; Coenzymes; Diet, Protein-Restricted; Frameshift Mutation; Genetic Predisposition to Disease; HEK293 Cells; Humans; Magnetic Resonance Imaging; Male; Metal Metabolism, Inborn Errors; Metalloproteins; Molybdenum Cofactors; Nuclear Proteins; Peptide Fragments; Phenotype; Pteridines

Molybdenum cofactor (MoCo) deficiency is a rare, autosomal-recessive disorder, mainly caused by mutations in MOCS1 (MoCo deficiency type A) or MOCS2 (MoCo deficiency type B) genes; the absence of active MoCo results in a deficiency in all MoCo-dependent enzymes. Patients with MoCo deficiency present with neonatal seizures, feeding difficulties, severe developmental delay, brain atrophy and early childhood death. Although substitution therapy with cyclic pyranopterin monophosphate (cPMP) has been successfully used in both Mocs1 knockout mice and in patients with MoCo deficiency type A, there is currently no Mocs2 knockout mouse and no curative therapy for patients with MoCo deficiency type B. Therefore, we generated and characterized a Mocs2-null mouse model of MoCo deficiency type B. Expression analyses of Mocs2 revealed a ubiquitous expression pattern; however, at the cellular level, specific cells show prominent Mocs2 expression, e.g., neuronal cells in cortex, hippocampus and brainstem. Phenotypic analyses demonstrated that Mocs2 knockout mice failed to thrive and died within 11 days after birth. None of the tested MoCo-dependent enzymes were active in Mocs2-deficient mice, leading to elevated concentrations of purines, such as hypoxanthine and xanthine, and non-detectable levels of uric acid in the serum and urine. Moreover, elevated concentrations of S-sulfocysteine were measured in the serum and urine. Increased levels of xanthine resulted in bladder and kidney stone formation, whereas increased concentrations of toxic sulfite triggered neuronal apoptosis. In conclusion, Mocs2-deficient mice recapitulate the severe phenotype observed in humans and can now serve as a model for preclinical therapeutic approaches for MoCo deficiency type B.

Topics: Animals; Apoptosis; Carbon-Carbon Lyases; Coenzymes; Cysteine; Disease Models, Animal; Gene Expression; Humans; Hypoxanthine; Metal Metabolism, Inborn Errors; Metalloproteins; Mice; Mice, Knockout; Molybdenum Cofactors; Mutation; Nuclear Proteins; Phenotype; Pteridines; Xanthine

Molybdenum cofactor deficiency (MoCD) and Sulfite oxidase deficiency (SOD) are rare autosomal recessive conditions of sulfur-containing amino acid metabolism with overlapping clinical features and emerging therapies. The clinical phenotype is indistinguishable and they can only be differentiated biochemically. MOCS1, MOCS2, MOCS3, and GPRN genes contribute to the synthesis of molybdenum cofactor, and SUOX gene encodes sulfite oxidase. The aim of this study was to elucidate the clinical, radiological, biochemical and molecular findings in patients with SOD and MoCD.. Detailed clinical and radiological assessment of 9 cases referred for neonatal encephalopathy with hypotonia, microcephaly, and epilepsy led to a consideration of disorders of sulfur-containing amino acid metabolism. The diagnosis of six with MoCD and three with SOD was confirmed by biochemical tests, targeted sequencing, and whole exome sequencing where suspicion of disease was lower.. Novel SUOX mutations were detected in 3 SOD cases and a novel MOCS2 mutation in 1 MoCD case. Most patients presented in the first 3 months of life with intractable tonic-clonic seizures, axial hypotonia, limb hypertonia, exaggerated startle response, feeding difficulties, and progressive cystic encephalomalacia on brain imaging. A single patient with MoCD had hypertrophic cardiomyopathy, hitherto unreported with these diseases.. Our results emphasize that intractable neonatal seizures, spasticity, and feeding difficulties can be important early signs for these disorders. Progressive microcephaly, intellectual disability and specific brain imaging findings in the first year were additional diagnostic aids. These clinical cues can be used to minimize delays in diagnosis, especially since promising treatments are emerging for MoCD type A.

Topics: Amino Acid Metabolism, Inborn Errors; Coenzymes; Egypt; Humans; Infant, Newborn; Infant, Newborn, Diseases; Male; Metal Metabolism, Inborn Errors; Metalloproteins; Molybdenum Cofactors; Molybdoferredoxin; Mutation; Phenotype; Pteridines; Sulfite Oxidase

Analysis of α-aminoadipic semialdehyde is an important tool in the diagnosis of antiquitin deficiency (pyridoxine-dependent epilepsy). However continuing use of this test has revealed that elevated urinary excretion of α-aminoadipic semialdehyde is not only found in patients with pyridoxine-dependent epilepsy but is also seen in patients with molybdenum cofactor deficiency and isolated sulphite oxidase deficiency. This should be taken into account when interpreting the laboratory data. Sulphite was shown to inhibit α-aminoadipic semialdehyde dehydrogenase in vitro.

Topics: 2-Aminoadipic Acid; Adolescent; Amino Acid Metabolism, Inborn Errors; Child; Coenzymes; Cysteine; Humans; Infant, Newborn; L-Aminoadipate-Semialdehyde Dehydrogenase; Lysine; Metabolic Networks and Pathways; Metal Metabolism, Inborn Errors; Metalloproteins; Models, Biological; Molybdenum Cofactors; Molybdoferredoxin; Oxidoreductases Acting on Sulfur Group Donors; Pteridines; Sulfite Oxidase; Sulfites

Molybdenum cofactor (Moco) deficiency is a rare neurometabolic disorder, characterized by neurological impairment and refractive seizures, due to toxic accumulation of sulfite in the brain. Earlier it was suggested that in Moco-deficient humans maternal clearance of neurotoxic metabolites prevents prenatal brain damage. However, limited data are available about the time profile in which neurophysiologic deterioration occurs after birth. The amplitude-integrated electroencephalography (aEEG) is a bedside method in neonates to monitor cerebral recovery after hypoxic-ischemic insults, detect epileptic activity, and evaluate antiepileptic drug treatment. We describe a chronological series of changes in aEEG tracings in a neonate with Moco deficiency. He presented with myoclonic spasms and hypertonicity a few hours after birth, however, the aEEG pattern was still normal. Within 2 days, the aEEG rapidly changed into a burst suppression pattern with repetitive seizures. After antiepileptic treatment, the aEEG remained abnormal. In this patient, the normal aEEG pattern at birth may have been due to maternal clearance of sulfite in utero. After birth, accumulation of sulfite causes progressive brain damage, reflected by the progressive depression of the aEEG tracings. This is in agreement with the results from a Moco-deficient mouse model, suggesting that maternal sulfite clearance suppresses prenatal brain damage. To our knowledge, this is the first case report describing the chronological changes in the aEEG pattern in a Moco-deficient patient. Insight into the time profile in which neurologic deterioration in Moco-deficient humans occurs is essential, especially when potential treatment strategies are being evaluated.

Topics: Anticonvulsants; Brain; Brain Waves; Coenzymes; Diffusion Magnetic Resonance Imaging; Electroencephalography; Epilepsy; Humans; Infant, Newborn; Male; Metal Metabolism, Inborn Errors; Metalloproteins; Molybdenum Cofactors; Molybdoferredoxin; Predictive Value of Tests; Pteridines; Sulfites; Time Factors; Treatment Outcome

Topics: Coenzymes; Female; Homocysteine; Humans; Infant, Newborn; Magnetic Resonance Imaging; Metal Metabolism, Inborn Errors; Metalloproteins; Molybdenum Cofactors; Prealbumin; Pteridines; Spectrometry, Mass, Electrospray Ionization; Uric Acid

Topics: Amino Acids; Child, Preschool; Chromatography, High Pressure Liquid; Coenzymes; Humans; Infant, Newborn; Metal Metabolism, Inborn Errors; Metalloproteins; Molybdenum Cofactors; Pteridines; Purines; Sulfates

A patient suffering from a combined deficiency of sulfite oxidase (sulfite dehydrogenase; sulfite:ferricytochrome c oxidoreductase, EC 1.8.2.1) and xanthine dehydrogenase (xanthine:NAD+ oxidoreductase, EC 1.2.1.37) is described. The patient displays severe neurological abnormalities, dislocated ocular lenses, and mental retardation. Urinary excretion of sulfite, thiosulfate, S-sulfocysteine, taurine, hypoxanthine, and xanthine is increased in this individual, while sulfate and urate levels are drastically reduced. The metabolic defect responsible for loss of both enzyme activities appears to be at the level of the molybdenum cofactor common to the two enzymes. Immunological examination of a biopsy sample of liver tissue revealed the presence of the xanthine dehydrogenase protein in near normal amounts. Sulfite oxidase apoprotein was not detected by a variety of immunological techniques. The plasma molybdenum concentration was normal; however, hepatic content of molybdenum and the storage pool of active molybdenum cofactor present in normal livers were below the limits of detection. Fibroblasts cultured from this patient failed to express sulfite oxidase protein or activity, whereas those from the parents and healthy brother of the patient expressed normal levels of this enzyme.

Topics: Child, Preschool; Coenzymes; Female; Fibroblasts; Humans; Immunologic Techniques; Intellectual Disability; Ketone Oxidoreductases; Lens Subluxation; Liver; Metal Metabolism, Inborn Errors; Metalloproteins; Molybdenum; Molybdenum Cofactors; Nervous System Diseases; Oxidoreductases; Oxidoreductases Acting on Sulfur Group Donors; Pteridines; Xanthine Dehydrogenase