Prenatal brain disruption in molybdenum cofactor deficiency

Increased ROS levels, antioxidant defense disturbances and bioenergetic disruption induced by thiosulfate administration in the brain of neonatal rats

Sulfite oxidase deficiencies, either caused by deficiency of the apoenzyme or the molybdenum cofactor, and ethylmalonic encephalopathy are inherited disorders that impact sulfur metabolism. These patients present with severe neurodeterioration accompanied by cerebral cortex and cerebellum abnormalities, and high thiosulfate levels in plasma and tissues, including the brain. We aimed to clarify the mechanisms of such abnormalities, so we assessed the ex vivo effects of thiosulfate administration on energetic status and oxidative stress markers in cortical and cerebellar tissues of newborn rats. Thiosulfate (0.5 µmol/g) or PBS (vehicle) was injected into the fourth ventricle of rat pups. Thirty minutes after the injection, animals were euthanized and the brain structures were utilized for the experiments. Our data showed that thiosulfate decreased the reduced glutathione (GSH) concentrations, and superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) activities in the cortical structure. Thiosulfate also increased DCFH oxidation, hydrogen peroxide generation and glutathione reductase activity. In the cerebellum, thiosulfate reduced SOD and glutathione peroxidase activities but increased GST and CAT activities as well as DCFH oxidation. Regarding energy metabolism, thiosulfate specifically decreased complex IV activity in the cortex, whereas it increased cerebellar complex I and creatine kinase activities, indicating bioenergetic disturbances. The results suggest that the accumulation of thiosulfate causing redox disruption and bioenergetic alterations has a prominent role in the pathogenesis of sulfur metabolism deficiencies.

Consensus guidelines for the diagnosis and management of isolated sulfite oxidase deficiency and molybdenum cofactor deficiencies

Sulfite intoxication is the hallmark of four ultrarare disorders that are caused by impaired sulfite oxidase activity due to genetic defects in the synthesis of the molybdenum cofactor or of the apoenzyme sulfite oxidase. Delays on the diagnosis of these disorders are common and have been caused by their unspecific presentation of acute neonatal encephalopathy with high early mortality, followed by the evolution of dystonic cerebral palsy and also by the lack of easily available and reliable diagnostic tests. There is significant variation in survival and in the quality of symptomatic management of affected children. One of the four disorders, molybdenum cofactor deficiency type A (MoCD-A) has recently become amenable to causal treatment with synthetic cPMP (fosdenopterin). The evidence base for the rational use of cPMP is very limited. This prompted the formulation of these clinical guidelines to facilitate diagnosis and support the management of patients. The guidelines were developed by experts in diagnosis and treatment of sulfite intoxication disorders. It reflects expert consensus opinion and evidence from a systematic literature search.

Timing of cerebral damage in molybdenum cofactor deficiency: A meta-analysis of case reports

Purpose

Molybdenum cofactor deficiency (MoCD) classically presents shortly after birth, with neurological symptoms ascribed to postnatal toxicity of accumulating sulphite. Case reports suggest that cerebral damage associated with MoCD may have a prenatal onset.

Methods

A meta-analysis of case reports was performed on individuals with genetically proven MoCD retrieved through a systematic review and in-house search. Cases were categorized as classical or late-onset, based on the time of onset of symptoms. Available cerebral images were scored for the presence of restricted diffusion, pathological signal, subcortical cysts, and atrophy. Estimated onset of each event and the minimal number of events needed to explain the observed imaging abnormalities were deduced by combining age at imaging, type of imaging abnormality, and known natural evolution of the imaging abnormalities.

Results

Of a total of 30 retrieved cases, 21 were classical. Prenatal origin of damage was possible in all classical cases and certain in 11 of 21 (52%). Multiple events were deduced in 5/21 classical cases based on imaging data alone and in 11 of 21 cases when presuming that a postnatal onset of symptoms signifies a recent event. Multiple, but postnatal, events were also described in 3 of 9 late-onset cases.

Conclusion

Prenatal onset of cerebral damage in patients with classical MoCD is more frequently encountered than anticipated. It may have been overlooked by the overwhelming postnatal symptoms erroneously pointing to a single culprit. This insight is important when counseling for prognosis, particularly in the context of considering the timing and anticipated prospects of therapeutic intervention.

Whole-genome sequencing revealed genetic diversity, structure and patterns of selection in Guizhou indigenous chickens

BACKGROUND

The eight phenotypically distinguishable indigenous chicken breeds in Guizhou province of China are great resources for high-quality development of the poultry industry in China. However, their full value and potential have yet to be understood in depth. To illustrate the genetic diversity, the relationship and population structure, and the genetic variation patterns shaped by selection in Guizhou indigenous chickens, we performed a genome-wide analysis of 240 chickens from 8 phenotypically and geographically representative Guizhou chicken breeds and 60 chickens from 2 commercial chicken breeds (one broiler and one layer), together with 10 red jungle fowls (RJF) genomes available from previous studies.

RESULTS

The results obtained in this present study showed that Guizhou chicken breed populations harbored higher genetic diversity as compared to commercial chicken breeds, however unequal polymorphisms were present within Guizhou indigenous chicken breeds. The results from the population structure analysis markedly reflected the breeding history and the geographical distribution of Guizhou indigenous chickens, whereas, some breeds with complex genetic structure were ungrouped into one cluster. In addition, we confirmed mutual introgression within Guizhou indigenous chicken breeds and from commercial chicken breeds. Furthermore, selective sweep analysis revealed candidate genes which were associated with specific and common phenotypic characteristics evolved rapidly after domestication of Guizhou local chicken breeds and economic traits such as egg production performance, growth performance, and body size.

CONCLUSION

Taken together, the results obtained from the comprehensive analysis of the genetic diversity, genetic relationships and population structures in this study showed that Guizhou indigenous chicken breeds harbor great potential for commercial utilization, however effective conservation measures are currently needed. Additionally, the present study drew a genome-wide selection signature draft for eight Guizhou indigenous chicken breeds and two commercial breeds, as well as established a resource that can be exploited in chicken breeding programs to manipulate the genes associated with desired phenotypes. Therefore, this study will provide an essential genetic basis for further research, conservation, and breeding of Guizhou indigenous chickens.

Sulfite Impairs Bioenergetics and Redox Status in Neonatal Rat Brain: Insights into the Early Neuropathophysiology of Isolated Sulfite Oxidase and Molybdenum Cofactor Deficiencies

Isolated sulfite oxidase (ISOD) and molybdenum cofactor (MoCD) deficiencies are genetic diseases biochemically characterized by the toxic accumulation of sulfite in the tissues of patients, including the brain. Neurological dysfunction and brain abnormalities are commonly observed soon after birth, and some patients also have neuropathological alterations in the prenatal period (in utero). Thus, we investigated the effects of sulfite on redox and mitochondrial homeostasis, as well as signaling proteins in the cerebral cortex of rat pups. One-day-old Wistar rats received an intracerebroventricular administration of sulfite (0.5 µmol/g) or vehicle and were euthanized 30 min after injection. Sulfite administration decreased glutathione levels and glutathione S-transferase activity, and increased heme oxygenase-1 content in vivo in the cerebral cortex. Sulfite also reduced the activities of succinate dehydrogenase, creatine kinase, and respiratory chain complexes II and II-III. Furthermore, sulfite increased the cortical content of ERK1/2 and p38. These findings suggest that redox imbalance and bioenergetic impairment induced by sulfite in the brain are pathomechanisms that may contribute to the neuropathology of newborns with ISOD and MoCD. Sulfite disturbs antioxidant defenses, bioenergetics, and signaling pathways in the cerebral cortex of neonatal rats. CII: complex II; CII-III: complex II-III; CK: creatine kinase; GST: glutathione S-transferase; HO-1: heme oxygenase-1; SDH: succinate dehydrogenase; SO32-: sulfite.

Whole exome sequencing identified a homozygous novel mutation in SUOX gene causes extremely rare autosomal recessive isolated sulfite oxidase deficiency

BACKGROUND

Isolated sulfite oxidase deficiency (ISOD) is a rare type of life-threatening neurometabolic disorders characterized by neonatal intractable seizures and severe developmental delay with an autosomal recessive mode of inheritance. Germline mutation in SUOX gene causes ISOD. Till date, only 32 mutations of SUOX gene have been identified and reported to be associated with ISOD.

METHODS

Here, we investigated a 5-days old Chinese female child, presented with intermittent tremor or seizures of limbs, neonatal encephalopathy, subarachnoid cyst and haemorrhage, dysplasia of corpus callosum, neonatal convulsion, hyperlactatemia, severe metabolic acidosis, hyperglycemia, and hyperkalemia.

RESULTS

Whole exome sequencing identified a novel homozygous transition (c.1227G > A) in exon 6 of the SUOX gene in the proband. This novel homozygous variant leads to the formation of a truncated sulfite oxidase (p.Trp409*) of 408 amino acids. This variant causes partial loss of the dimerization domain of sulfite oxidase. Hence, it is a loss-of-function variant. Proband's father and mother is carrying this novel variant in a heterozygous state. This variant was not found in 200 ethnically matched normal healthy control individuals.

CONCLUSIONS

Our study not only expanded the mutational spectrum of SUOX gene associated with ISOD, but also strongly suggested the significance of whole exome sequencing for identifying candidate genes and novel disease-causing variants.

Molybdenum cofactor deficiency: A natural history

Molybdenum cofactor deficiency (MoCD) includes three ultrarare autosomal recessive inborn errors of metabolism (MoCD type A [MoCD-A], MoCD-B, and MoCD-C) that cause sulfite intoxication disorders. This natural history study analyzed retrospective data for 58 living or deceased patients (MoCD-A, n = 41; MoCD-B, n = 17). MoCD genotype, survival, neuroimaging, and medical history were assessed retrospectively. Prospective biomarker data were collected for 21 living MoCD patients. The primary endpoint was survival to 1 year of age in MoCD-A patients. Of the 58 MoCD patients, 49 (MoCD-A, n = 36; MoCD-B, n = 13) had first presenting symptoms by Day 28 (neonatal onset; median: 2 and 4 days, respectively). One-year survival rates were 77.4% (overall), 71.8% (neonatal onset MoCD-A), and 76.9% (neonatal onset MoCD-B); median ages at death were 2.4, 2.4, and 2.2 years, respectively. The most common presenting symptoms in the overall population were seizures (60.3%) and feeding difficulties (53.4%). Sequelae included profound developmental delay, truncal hypotonia, limb hypertonia that evolved to spastic quadriplegia or diplegia, dysmorphic features, and acquired microcephaly. In MoCD-A and MoCD-B, plasma and urinary xanthine and S-sulfocysteine concentrations were high; urate remained below the normal reference range. MOCS1 mutation homozygosity was common. Six novel mutations were identified. MoCD is a severe neurodegenerative disorder that often manifests during the neonatal period with intractable seizures and feeding difficulties, with rapidly progressive significant neurologic disabilities and high 1-year mortality rates. Delineation of MoCD natural history supports evaluations of emerging replacement therapy with cPMP for MoCD-A, which may modify disease course for affected individuals.

Fosdenopterin: a First-in-class Synthetic Cyclic Pyranopterin Monophosphate for the Treatment of Molybdenum Cofactor Deficiency Type A

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Hot Carriers and Photothermal Effects of Monolayer MoOx for Promoting Sulfite Oxidase Mimetic Activity

Local surface plasmon resonance (LSPR)-enhanced catalysis has brought a substantial amount of opportunities across various disciplines such as photocatalysis, photodetection, and photothermal therapeutics. Plasmon-induced photothermal and hot carriers effects have also been utilized to activate the enzyme-like reactions. Compared with natural enzymes, the relatively low catalytic performance of nanozymes severely hampered the potential applications in the field of biomedicine. For these issues mentioned above, herein, we demonstrate a highly efficient sulfite oxidase (SuO_x) mimetic performance of plasmonic monolayer MoO_x (ML-MoO_x) upon LSPR excitation. We also established that the considerable photothermal effect and the injection of hot carriers induced by LSPR are responsible for promoting the SuO_x activity of ML-MoO_x. The high transient local temperature on the surface of ML-MoO_x generated by the photothermal effect facilitates to impact the reaction velocity and feed the SuO_x-like activity, while the generation of hot carriers which are suggested as predominant effects catalyzes the oxidation of sulfite to sulfate through significantly decreasing the activation energy for the SuO_x-like reaction. These investigations present a contribution to the basic understanding of plasmon-enhanced enzyme-like reaction and provided an insight into the optimization of the SuO_x mimetic performance of nanomaterials.

Molybdenum Cofactor Deficiency: Mega Cisterna Magna in Two Consecutive Pregnancies and Review of the Literature

The molybdenum cofactor deficiency is an autosomal recessive disease, characterized by rapidly progressive and severe neurological damage that mimics a hypoxic-ischemic encephalopathy due to the accumulation of toxic metabolites that cause rapid neurodegeneration after the delivery. It is eventually lethal, in a similar way to the rare isolated sulfite oxidase deficiency. This serious pathology usually causes death in the immediate neonatal period in the more severe variants. We report a case of two consecutive pregnancies with enlarged cisterna magna as the only prenatal pathological finding since 26 weeks of gestation (WG) and the subsequent death of the newborns in the first week after birth. After the second pregnancy, we reached the diagnosis of molybdenum cofactor deficiency due to MOCS1 gene mutation. According to the cases reported in the literature, this is the case with the earliest neuroimage prenatal findings.

The peacefulness gene promotes aggression in Drosophila

Natural aggressiveness is commonly observed in all animal species, and is displayed frequently when animals compete for food, territory and mating. Aggression is an innate behaviour, and is influenced by both environmental and genetic factors. However, the genetics of aggression remains largely unclear. In this study, we identify the peacefulness (pfs) gene as a novel player in the control of male-male aggression in Drosophila. Mutations in pfs decreased intermale aggressiveness, but did not affect locomotor activity, olfactory avoidance response and sexual behaviours. pfs encodes for the evolutionarily conserved molybdenum cofactor (MoCo) synthesis 1 protein (Mocs1), which catalyzes the first step in the MoCo biosynthesis pathway. Neuronal-specific knockdown of pfs decreased aggressiveness. By contrast, overexpression of pfs greatly increased aggressiveness. Knocking down Cinnamon (Cin) catalyzing the final step in the MoCo synthesis pathway, caused a pfs-like aggression phenotype. In humans, inhibition of MoCo-dependent enzymes displays anti-aggressive effects. Thus, the control of aggression by Pfs-dependent MoCo pathways may be conserved throughout evolution.

Toxicological and nutritional status of trace elements in hair of women with in vitro fertilization (IVF) pregnancy and their 9-month-old children

The objective of the present study was to assess toxic and nutritional trace element and mineral status in hair of women with IVF pregnancy and their children. Inductively-coupled plasma mass-spectrometry was used to assess hair trace element levels of 50 women with IVF pregnancy and 158 controls with spontaneous pregnancy and their children. Women with IVF pregnancy were characterized by significantly elevated hair As, Hg, Li, K, Na, and reduced Fe, Si, and Zn contents. Children from IVF pregnancy had significantly lower values of hair Cr, Fe, Mg, Sr, and Al content when compared to the control values, whereas hair Hg and Mo levels were higher. Hair trace element levels were associated with pregnancy complications and infertility, but not newborn characteristics. The results suggest the need for preconceptional monitoring and correction of the levels of toxic and essential elements in women in order to improve the course pregnancy and child development.

Neurometabolic Disorders of the Newborn

There is an extensive and diverse set of medical conditions affecting the neonatal brain within the spectrum of neurometabolic disorders. As such, their clinical presentations can be rather nonspecific, and can often mimic acquired entities such as hypoxic-ischemic encephalopathy and sepsis. Similarly, the radiological findings in these entities can also be frequently nonspecific, but a more detailed analysis of imaging findings (especially magnetic resonance imaging) alongside the relevant clinical details can be a rewarding experience, thus enabling a timely and targeted diagnosis. Early diagnosis of an underlying neurometabolic disorder is vital, as some of these entities are potentially treatable, and laboratory and genetic testing can be precisely targeted. Further, their detection helps with counselling families for future pregnancies. We present a review of neurometabolic disorders specific to the newborns with a focus on how neuroimaging findings match their clinical presentation patterns.

Molybdenum cofactor deficiency type A: Prenatal monitoring using MRI

Molybdenum cofactor deficiency type A (MoCD-A) is an inborn error of metabolism presenting early after birth with severe seizures. Recently, experimental substitution treatment with cyclic pyranopterin monophosphate (cPMP) has become available. Because prenatal data is scarce, we report data of prenatal Magnetic Resonance Imaging (MRI) in two cases with MoCD-A demonstrating signs of possible early brain injury. Prenatal MRI can be used for monitoring in MoCD-A to guide decision-making in timing of delivery.

Critical appraisal of genotype assessment in molybdenum cofactor deficiency

INTRODUCTION

Molybdenum cofactor deficiency (MoCD) is an ultra-orphan, life-threatening disease. Substrate substitution therapy has successfully been performed in single cases of MoCD type A and clinical trials are underway for drug registration. We present an innovative approach for classification of genotype severity to test the hypothesis that milder sequence variants in MoCD result in a less severe disease phenotype quantitated by patient survival.

METHODS

All available worldwide published cases with clinical and genetic data were included (n = 40). We stratified the already published disease causing sequence variants as mild or severe with the use of in silico prediction programs, where possible and assessed the possible impact of the variants on the expression of the gene or function of the expressed protein. In a compound heterozygous situation the mildest sequence variant determined the genotype. Subsequently, clinical manifestations and outcomes of both groups were compared.

RESULTS

Patients with a severe genotype showed a median survival of 15 months and had a lower probability of survival compared to patients with mild genotypes who were all alive at last reported follow-up (p = 0.0203, Log-rank test).

DISCUSSION

The severity of the genotype assessed by in silico prediction and further classification explained survival in molybdenum cofactor deficiency and may therefore be considered a confounder for the outcome of therapeutic clinical trials requiring adjustment in the clinical trial design or analysis. These results should further be investigated by future in vitro or in vivo functional studies. Caution should be taken with this approach for the classification of variants in molecular genetic diagnostics or genetic counseling.

Prenatal brain disruption in isolated sulfite oxidase deficiency

Background

Isolated sulfite oxidase deficiency (ISOD) is a very rare autosomal recessive inherited neurometabolic disease. The most striking postnatal neuroimaging finding is multicystic encephalomalacia, which occurs rapidly within days to weeks after birth and mimics severe hypoxic-ischemic encephalopathy. The aim of this study was to describe the prenatal neuroimaging features in a neonate and a fetus diagnosed with ISOD.

Results

We report an 11-day-old female neonate who presented with feeding difficulties, decreased activity, neonatal seizures, and movement disorders within a few days after birth. Brain MRI at 9 days of age showed cystic lesions over the left frontal and temporal areas, diffuse and evident T2 high signal intensity of bilateral cerebral cortex, and increased T2 signal intensity of the globus pallidi. A pronounced low level of plasma cysteine and normal level of plasma uric acid were noted. Mutation analysis of SUOX revealed homozygous c.1200C > G mutations, resulting in an amino acid substitution of tyrosine to a stop codon (Y400X). The diagnosis of ISOD was made. The brain MRI of a prenatally diagnosed ISOD fetus of the second pregnancy of the mother of the index case showed poor gyration and differentiation of cortical layers without formation of cystic lesions at gestational age 21 weeks.

Conclusion

Cystic brain destruction might occur prenatally and neurodevelopment of gyration and differentiation of the cortical layers in the developing brain could be affected by sulfite accumulation early during the second trimester in ISOD patients. This is the first description of the prenatal neurodevelopment of brain disruption in ISOD.

Antenatal manifestations of inborn errors of metabolism: prenatal imaging findings

Prenatal manifestations of inborn errors of metabolism (IEM) are related to severe disorders involving metabolic pathways active in the fetal period and not compensated by maternal or placental metabolism. Some prenatal imaging findings can be suggestive of such conditions-especially in cases of consanguinity and/or recurrence of symptoms-after exclusion of the most frequent nonmetabolic etiologies. Most of these prenatal imaging findings are nonspecific. They include mainly ascites and hydrops fetalis, intrauterine growth restriction (IUGR), central nervous system (CNS) anomalies, echogenic kidneys, epiphyseal stippling, craniosynostosis, and a wide spectrum of dysostoses. These anomalies can be isolated, but in most cases, an IEM is suggested by an association of features. It must be stressed that the diagnosis of an IEM in the prenatal period is based on a close collaboration between specialists in fetal imaging, medicine, genetics, biology, and pathology.

Antenatal manifestations of inborn errors of metabolism: biological diagnosis

Inborn errors of metabolism (IEMs) that present with abnormal imaging findings in the second half of pregnancy are mainly lysosomal storage disorders (LSDs), cholesterol synthesis disorders (CSDs), glycogen storage disorder type IV (GSD IV), peroxisomal disorders, mitochondrial fatty acid oxidation defects (FAODs), organic acidurias, aminoacidopathies, congenital disorders of glycosylation (CDGs), and transaldolase deficiency. Their biological investigation requires fetal material. The supernatant of amniotic fluid (AF) is useful for the analysis of mucopolysaccharides, oligosaccharides, sialic acid, lysosphingolipids and some enzyme activities for LSDs, 7- and 8-dehydrocholesterol, desmosterol and lathosterol for CSDs, acylcarnitines for FAODs, organic acids for organic acidurias, and polyols for transaldolase deficiency. Cultured AF or fetal cells allow the measurement of enzyme activities for most IEMs, whole-cell assays, or metabolite measurements. The cultured cells or tissue samples taken after fetal death can be used for metabolic profiling, enzyme activities, and DNA extraction. Fetal blood can also be helpful. The identification of vacuolated cells orients toward an LSD, and plasma is useful for diagnosing peroxisomal disorders, FAODs, CSDs, some LSDs, and possibly CDGs and aminoacidopathies. We investigated AF of 1700 pregnancies after exclusion of frequent etiologies of nonimmune hydrops fetalis and identified 108 fetuses affected with LSDs (6.3 %), 29 of them with mucopolysaccharidosis type VII (MPS VII), and six with GSD IV (0.3 %). In the AF of 873 pregnancies, investigated because of intrauterine growth restriction and/or abnormal genitalia, we diagnosed 32 fetuses affected with Smith-Lemli-Opitz syndrome (3.7 %).

Neuropädiatrische Differenzialdiagnostik der Mikrozephalie im Kindesalter

Eine Mikrozephalie betrifft 2–3 % der Bevölkerung und geht oftmals mit einer Intelligenzminderung einher. Die zugrunde liegende Reduktion des Gehirnvolumens kann sowohl durch exogene Faktoren als auch durch genetische Ursachen bedingt sein. Problematisch sind sowohl die uneinheitliche Klassifikation als auch die große Heterogenität der hinter dem klinischen Zeichen Mikrozephalie stehenden Erkrankungen. Im vorliegenden Artikel stellen wir unseren Vorschlag für die diagnostische Herangehensweise an ein Kind mit Mikrozephalie aus neuropädiatrischer Sicht vor.

Sulfite Oxidase Activity of Cytochrome c: Role of Hydrogen Peroxide

In humans, sulfite is generated endogenously by the metabolism of sulfur containing amino acids such as methionine and cysteine. Sulfite is also formed from exposure to sulfur dioxide, one of the major environmental pollutants. Sulfite is used as an antioxidant and preservative in dried fruits, vegetables, and beverages such as wine. Sulfite is also used as a stabilizer in many drugs. Sulfite toxicity has been associated with allergic reactions characterized by sulfite sensitivity, asthma, and anaphylactic shock. Sulfite is also toxic to neurons and cardiovascular cells. Recent studies suggest that the cytotoxicity of sulfite is mediated by free radicals; however, molecular mechanisms involved in sulfite toxicity are not fully understood. Cytochrome c (cyt c) is known to participate in mitochondrial respiration and has antioxidant and peroxidase activities. Studies were performed to understand the related mechanism of oxidation of sulfite and radical generation by ferric cytochrome c (Fe³⁺cyt c) in the absence and presence of H₂O₂. Electron paramagnetic resonance (EPR) spin trapping studies using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) were performed with sulfite, Fe³⁺cyt c, and H₂O₂. An EPR spectrum corresponding to the sulfite radical adducts of DMPO (DMPO-SO₃^-) was obtained. The amount of DMPO-SO3- formed from the oxidation of sulfite by the Fe³⁺cyt c increased with sulfite concentration. In addition, the amount of DMPO-SO3- formed by the peroxidase activity of Fe³⁺cyt c also increased with sulfite and H₂O₂ concentration. From these results, we propose a mechanism in which the Fe³⁺cyt c and its peroxidase activity oxidizes sulfite to sulfite radical. Our results suggest that Fe³⁺cyt c could have a novel role in the deleterious effects of sulfite in biological systems due to increased production of sulfite radical. It also shows that the increased production of sulfite radical may be responsible for neurotoxicity and some of the injuries which occur to humans born with molybdenum cofactor and sulfite oxidase deficiencies.

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Cytochrome c oxidizes sulfite to sulfite radical.

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In the presence of H₂O₂, sulfite radical generation from cyt c increases.

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The formation of sulfite radical is sulfite concentration dependent.

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This mechanism of sulfite radical formation may be important in sulfite toxicity.

Efficacy and safety of cyclic pyranopterin monophosphate substitution in severe molybdenum cofactor deficiency type A: a prospective cohort study

BACKGROUND

Molybdenum cofactor deficiency (MoCD) is characterised by early, rapidly progressive postnatal encephalopathy and intractable seizures, leading to severe disability and early death. Previous treatment attempts have been unsuccessful. After a pioneering single treatment we now report the outcome of the complete first cohort of patients receiving substitution treatment with cyclic pyranopterin monophosphate (cPMP), a biosynthetic precursor of the cofactor.

METHODS

In this observational prospective cohort study, newborn babies with clinical and biochemical evidence of MoCD were admitted to a compassionate-use programme at the request of their treating physicians. Intravenous cPMP (80-320 μg/kg per day) was started in neonates diagnosed with MoCD (type A and type B) following a standardised protocol. We prospectively monitored safety and efficacy in all patients exposed to cPMP.

FINDINGS

Between June 6, 2008, and Jan 9, 2013, intravenous cPMP was started in 16 neonates diagnosed with MoCD (11 type A and five type B) and continued in eight type A patients for up to 5 years. We observed no drug-related serious adverse events after more than 6000 doses. The disease biomarkers urinary S-sulphocysteine, xanthine, and urate returned to almost normal concentrations in all type A patients within 2 days, and remained normal for up to 5 years on continued cPMP substitution. Eight patients with type A disease rapidly improved under treatment and convulsions were either completely suppressed or substantially reduced. Three patients treated early remain seizure free and show near-normal long-term development. We detected no biochemical or clinical response in patients with type B disease.

INTERPRETATION

cPMP substitution is the first effective therapy for patients with MoCD type A and has a favourable safety profile. Restoration of molybdenum cofactor-dependent enzyme activities results in a greatly improved neurodevelopmental outcome when started sufficiently early. The possibility of MoCD type A needs to be urgently explored in every encephalopathic neonate to avoid any delay in appropriate cPMP substitution, and to maximise treatment benefit.

FUNDING

German Ministry of Education and Research; Orphatec/Colbourne Pharmaceuticals.

Diagnostic approach to microcephaly in childhood: a two-center study and review of the literature

AIM

The aim of this study was to assess the diagnostic approach to microcephaly in childhood and to identify the prevalence of the various underlying causes/disease entities.

METHOD

We conducted a retrospective study on a cohort of 680 children with microcephaly (399 males, 281 females; mean age at presentation 7-8mo, range 1mo-5y) from patients presenting to Charité - University Medicine Berlin (n=474) and University Hospital Dresden (n=206). Patient discharge letters were searched electronically to identify cases of microcephaly, and then the medical records of these patients were used to analyze parameters for distribution.

RESULTS

The putative aetiology for microcephaly was ascertained in 59% of all patients, leaving 41% without a definite diagnosis. In the cohort of pathogenetically defined microcephaly, genetic causes were identified in about half of the patients, perinatal brain damage accounted for 45%, and postnatal brain damage for 3% of the cases. Microcephaly was associated with intellectual impairment in 65% of participants, epilepsy was diagnosed in 43%, and ophthalmological disorders were found in 30%. Brain magnetic resonance imaging revealed abnormalities in 76% of participants.

INTERPRETATION

Microcephaly remains a poorly defined condition, and a uniform diagnostic approach is urgently needed. A definite aetiological diagnosis is important in order to predict the prognosis and offer genetic counselling. Identifying gene mutations as causes of microcephaly increases our knowledge of brain development and the clinical spectrum of microcephaly. We therefore propose a standardized initial diagnostic approach to microcephaly.

Early features in neuroimaging of two siblings with molybdenum cofactor deficiency

We report the features of neuroimaging within 24 hours after birth in 2 siblings with molybdenum cofactor deficiency. The first sibling was delivered by emergency cesarean section because of fetal distress and showed pedaling and crawling seizures soon after birth. Brain ultrasound revealed subcortical multicystic lesions in the frontal white matter, and brain MRI at 4 hours after birth showed restricted diffusion in the entire cortex, except for the area adjacent to the subcortical cysts. The second sibling was delivered by elective cesarean section. Cystic lesions were seen in the frontal white matter on ultrasound, and brain MRI showed low signal intensity on T1-weighted image and high signal intensity on T2-weighted image in bifrontal white matter within 24 hours after birth, at which time the infant sucked sluggishly. Clonic spasm appeared at 29 hours after birth. The corpus callosum could not be seen clearly on ultrasound or MRI in both infants. Cortical atrophy and white matter cystic lesions spread to the entire hemisphere and resulted in severe brain atrophy within ~1 month in both infants. Subcortical multicystic lesions on ultrasound and a cortex with nonuniform, widespread, restricted diffusion on diffusion-weighted images are early features of neuroimaging in patients with molybdenum cofactor deficiency type A.

Low-molecular-mass metal complexes in the mouse brain

The presence of labile low-molecular-mass (LMM, defined as <10 kDa) metal complexes in cells and super-cellular structures such as the brain has been inferred from chelation studies, but direct evidence is lacking. To evaluate the presence of LMM metal complexes in the brain, supernatant fractions of fresh mouse brain homogenates were passed through a 10 kDa cutoff membrane and subjected to size-exclusion liquid chromatography under anaerobic refrigerated conditions. Fractions were monitored for Mn, Fe, Co, Cu, Zn, Mo, S and P using an on-line ICP-MS. At least 30 different LMM metal complexes were detected along with numerous P- and S- containing species. Reproducibility was assessed by performing the experiment 13 times, using different buffers, and by examining whether complexes changed with time. Eleven Co, 2 Cu, 5 Mn, 4 Mo, 3 Fe and 2 Zn complexes with molecular masses <4 kDa were detected. One LMM Mo complex comigrated with the molybdopterin cofactor. Most Cu and Zn complexes appeared to be protein-bound with masses ranging from 4-20 kDa. Co was the only metal for which the "free" or aqueous complex was reproducibly observed. Aqueous Co may be sufficiently stable in this environment due to its relatively slow water-exchange kinetics. Attempts were made to assign some of these complexes, but further efforts will be required to identify them unambiguously and to determine their functions. This is among the first studies to detect low-molecular-mass transition metal complexes in the mouse brain using LC-ICP-MS.

Molybdenum cofactor deficiency: review of 12 cases (MoCD and review)

Molybdenum cofactor deficiency is a rare inborn error of metabolism. The major clinical symptoms are intractable neonatal seizures, progressive encephalopathy, facial dysmorphic features and feeding difficulties. Most of the patients are misdiagnosed as hypoxic ischemic encephalopathy. The majority of patients have mutations in the MOCS1 and MOCS2 genes. Although the therapeutic treatment strategies have not been improved, genetic analysis is essential to elucidate the disease. Here, we report a review of 12 patients with Molybdenum cofactor deficiency reported from Turkey.

Neonatal neuroimaging findings in inborn errors of metabolism

Individually, metabolic disorders are rare, but overall they account for a significant number of neonatal disorders affecting the central nervous system. The neonatal clinical manifestations of inborn errors of metabolism (IEMs) are characterized by nonspecific systemic symptoms that may mimic more common acute neonatal disorders like sepsis, severe heart insufficiency, or neonatal hypoxic-ischemic encephalopathy. Certain IEMs presenting in the neonatal period may also be complicated by sepsis and cardiomyopathy. Early diagnosis is mandatory to prevent death and permanent long-term neurological impairments. Although neuroimaging findings are rarely specific, they play a key role in suggesting the correct diagnosis, limiting the differential diagnosis, and may consequently allow early initiation of targeted metabolic and genetic laboratory investigations and treatment. Neuroimaging may be especially helpful to distinguish metabolic disorders from other more common causes of neonatal encephalopathy, as a newborn may present with an IEM prior to the availability of the newborn screening results. It is therefore important that neonatologists, pediatric neurologists, and pediatric neuroradiologists are familiar with the neuroimaging findings of metabolic disorders presenting in the neonatal time period.

Clinical neuroimaging features and outcome in molybdenum cofactor deficiency

Molybdenum cofactor deficiency predominantly affects the central nervous system. There are limited data on long-term outcome or brain magnetic resonance imaging (MRI) features. We examined the clinical, brain MRI, biochemical, genetic, and electroencephalographic features and outcome in 8 children with a diagnosis of molybdenum cofactor deficiency observed in our institution over 10 years. Two modes of presentation were identified: early (classical) onset with predominantly epileptic encephalopathy in 6 neonates, and late (atypical) with global developmental impairment in 2 children. Children in both groups had varying degrees of motor, language, and visual impairment. There were no deaths. Brain MRI demonstrated cerebral infarction in all but one child in the atypical group. Distinctive features were best observed on early brain MRI: acute symmetrical involvement of the globus pallidi and subthalamic regions coexisting with older cerebral hemisphere infarction, chronic lesions suggestive of a prenatal insult, pontocerebellar hypoplasia with retrocerebellar cyst, and presence of a distinctive band at the cortical/subcortical white matter. Sequential imaging revealed progressive pontine atrophy and enlargement of retrocerebellar cyst. The brain MRI of one child with atypical presentation (verbal dyspraxia, lens dislocation) showed symmetrical cerebellar deep nuclei signal abnormality without cerebral infarction. Imaging pattern on early brain MRI (<1 week) may prompt the diagnosis, potentially allowing early treatment and disease modifications.