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Mucolipidosis type IV (MLIV; OMIM 252,650) is an autosomal recessive lysosomal disorder caused by mutations in MCOLN1. MLIV causes psychomotor impairment and progressive vision loss. The major hallmarks of postnatal brain MRI are hypomyelination and thin corpus callosum. Human brain pathology data is scarce and demonstrates storage of various inclusion bodies in all neuronal cell types. The current study describes novel fetal brain MRI and neuropathology findings in a fetus with MLIV. Fetal MRI was performed at 32 and 35 weeks of gestation due to an older sibling with spastic quadriparesis, visual impairment and hypomyelination. Following abnormal fetal MRI results, the parents requested termination of pregnancy according to Israeli regulations. Fetal autopsy was performed after approval of the high committee for pregnancy termination. A genetic diagnosis of MLIV was established in the fetus and sibling. Sequential fetal brain MRI showed progressive curvilinear hypointensities on T2-weighted images in the frontal deep white matter and a thin corpus callosum. Fetal brain pathology exhibited a thin corpus callosum and hypercellular white matter composed of reactive astrocytes and microglia, multifocal white matter abnormalities with mineralized deposits, and numerous aggregates of microglia with focal intracellular iron accumulation most prominent in the frontal lobes. This is the first description in the literature of brain MRI and neuropathology in a fetus with MLIV. The findings demonstrate prenatal white matter involvement with significant activation of microglia and astrocytes and impaired iron metabolism.
Asunto(s)
Mucolipidosis , Canales de Potencial de Receptor Transitorio , Sustancia Blanca , Femenino , Humanos , Hierro/metabolismo , Mucolipidosis/diagnóstico por imagen , Mucolipidosis/genética , Embarazo , Diagnóstico Prenatal , Canales de Potencial de Receptor Transitorio/genética , Canales de Potencial de Receptor Transitorio/metabolismo , Sustancia Blanca/metabolismoRESUMEN
Alterations in mitochondrial dynamics (fission, fusion, and movement) are implicated in many neurodegenerative diseases, from rare genetic disorders such as Charcot-Marie-Tooth disease, to common conditions including Alzheimer's disease. However, the relationship between altered mitochondrial dynamics and neurodegeneration is incompletely understood. Here we show that disease associated MFN2 proteins suppressed both mitochondrial fusion and transport, and produced classic features of segmental axonal degeneration without cell body death, including neurofilament filled swellings, loss of calcium homeostasis, and accumulation of reactive oxygen species. By contrast, depletion of Opa1 suppressed mitochondrial fusion while sparing transport, and did not induce axonal degeneration. Axon degeneration induced by mutant MFN2 proteins correlated with the disruption of the proper mitochondrial positioning within axons, rather than loss of overall mitochondrial movement, or global mitochondrial dysfunction. We also found that augmenting expression of MFN1 rescued the axonal degeneration caused by MFN2 mutants, suggesting a possible therapeutic strategy for Charcot-Marie-Tooth disease. These experiments provide evidence that the ability of mitochondria to sense energy requirements and localize properly within axons is key to maintaining axonal integrity, and may be a common pathway by which disruptions in axonal transport contribute to neurodegeneration.
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Axones/ultraestructura , GTP Fosfohidrolasas/genética , Mitocondrias/patología , Proteínas Mitocondriales/genética , Degeneración Nerviosa/genética , Neuronas/citología , Mutación Puntual/genética , Proteínas Adaptadoras del Transporte Vesicular/metabolismo , Animales , Arginina/genética , Calcio/metabolismo , Desoxiglucosa/metabolismo , Embrión de Mamíferos , Fluoresceínas , GTP Fosfohidrolasas/metabolismo , Ganglios Espinales/citología , Regulación de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica/genética , Glutamina/genética , Proteínas Fluorescentes Verdes/genética , Proteínas Fluorescentes Verdes/metabolismo , Humanos , Mitocondrias/efectos de los fármacos , Mitocondrias/ultraestructura , Degeneración Nerviosa/patología , Degeneración Nerviosa/prevención & control , Proteínas del Tejido Nervioso/metabolismo , Neuronas/ultraestructura , ARN Interferente Pequeño/farmacología , Ratas , Especies Reactivas de Oxígeno/metabolismo , Bloqueadores de los Canales de Sodio/uso terapéutico , Tetrodotoxina/uso terapéutico , TransfecciónRESUMEN
BACKGROUND: Mucolipidosis IV (MLIV) is an autosomal recessive pediatric disease that leads to motor and cognitive deficits and loss of vision. It is caused by a loss of function of the lysosomal channel transient receptor potential mucolipin-1 and is associated with an early pro-inflammatory brain phenotype, including increased cytokine expression. The goal of the current study was to determine whether blood cytokines are linked to motor dysfunction in patients with MLIV and reflect brain inflammatory changes observed in an MLIV mouse model. METHODS: To determine the relationship between blood cytokines and motor function, we collected plasma from MLIV patients and parental controls concomitantly with assessment of motor function using the Brief Assessment of Motor Function and Modified Ashworth scales. We then compared these profiles with cytokine profiles in brain and plasma samples collected from the Mcoln1-/- mouse model of MLIV. RESULTS: We found that MLIV patients had prominently increased cytokine levels compared to familial controls and identified profiles of cytokines correlated with motor dysfunction, including IFN-γ, IFN-α2, and IP-10. We found that IP-10 was a key differentiating factor separating MLIV cases from controls based on data from human plasma, mouse plasma, and mouse brain. CONCLUSIONS: Our data indicate that MLIV is characterized by increased blood cytokines, which are strongly related to underlying neurological and functional deficits in MLIV patients. Moreover, our data identify the interferon pro-inflammatory axis in both human and mouse signatures, suggesting that interferon signaling is an important aspect of MLIV pathology.
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Mucolipidosis , Canales de Potencial de Receptor Transitorio , Animales , Quimiocina CXCL10/metabolismo , Citocinas/metabolismo , Modelos Animales de Enfermedad , Humanos , Interferones/metabolismo , Ratones , Mucolipidosis/genética , Mucolipidosis/metabolismo , Mucolipidosis/patología , Canales de Potencial de Receptor Transitorio/metabolismoRESUMEN
Background and Objectives: Mucolipidosis type IV (MLIV) is an ultra-rare lysosomal disorder initially described as a static neurodevelopmental condition. However, patient caregivers frequently report progressive muscular hypertonicity and functional decline. We evaluated a cohort of patients with MLIV to determine whether neurologic disability correlates with age. Methods: We performed a cross-sectional, observational study of 26 patients with MLIV in the United States and Israel ranging in age from 2 to 40 years. Medical history was obtained from caregivers, and patients underwent a full neurologic examination. The Brief Assessment of Motor Function (BAMF), Gross Motor Function Classification System, and modified Ashworth scales were applied. Caregivers identified developmental skills on the Oregon Project for Visually Impaired and Blind Children checklist that their child had lost the ability to perform. Results: Three patients were clinically classified as mildly affected and the remaining 23 patients as typical, severely affected cases. Timing of first symptom onset ranged from 1.5 months to 8 years of age (median 7.25 months). Across typical patients, modified Ashworth scores demonstrated a positive age dependence illustrating worsening spasticity across the lifespan. Signs of extrapyramidal motor dysfunction were also qualitatively observed. In parallel, gross and fine motor function assessed with the BAMF and Gross Motor Function Classification System scales declined across age. All typical patients had restricted tongue mobility and lacked rotary jaw movement when chewing, but BAMF scores for deglutition declined only in the oldest patients. In contrast, scores for articulation were low in all patients and did not correlate with age. Finally, loss of developmental skills frequently occurred in early adolescence. Discussion: This cross-sectional natural history study of MLIV demonstrates worse motor function in older patients. These data support a neurodegenerative component of MLIV that manifests as developmental regression in the second decade of life. Whether the emergence of functional decline results from the cumulative, nonlinear interactions of steadily progressive neurodegenerative processes or reflects an inflection from impaired CNS development to degeneration is uncertain. However, understanding the relationship between CNS pathology and clinical course of disease will be imperative to guiding future interventional trials and optimizing patient care.
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Molybdenum cofactor deficiency and isolated sulfite oxidase deficiency are two rare genetic disorders that are caused by impairment of the mitochondrial enzyme sulfite oxidase. Sulfite oxidase is catalyzing the terminal reaction of cellular cysteine catabolism, the oxidation of sulfite to sulfate. Absence of sulfite oxidase leads to the accumulation of sulfite, which has been identified as a cellular toxin. However, the molecular pathways leading to the production of sulfite are still not completely understood. In order to identify novel treatment options for both disorders, the understanding of cellular cysteine catabolism - and its alterations upon loss of sulfite oxidase - is of utmost importance. Here we applied a new detection method of sulfite in cellular extracts to dissect the contribution of cytosolic and mitochondrial glutamate oxaloacetate transaminase (GOT) in the transformation of cysteine sulfinic acid to sulfite and pyruvate. We found that the cytosolic isoform GOT1 is primarily responsible for the production of sulfite. Moreover, loss of sulfite oxidase activity results in the accumulation of sulfite, H2S and persulfidated cysteine and glutathione, which is consistent with an increase of SQR protein levels. Surprisingly, none of the known H2S-producing pathways were found to be upregulated under conditions of sulfite toxicity suggesting an alternative route of sulfite-induced shift from oxidative to H2S dependent cysteine catabolism.
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Sulfito-Oxidasa , Sulfitos , Glutamatos , Oxaloacetatos , Sulfito-Oxidasa/genética , Transaminasas/genéticaRESUMEN
Pediatric traumatic brain injury (TBI) is a major cause of concern worldwide. Non-accidental traumatic (NAT) brain injury is common in infants. Since infants may present with varied presentations post-NAT, a healthy suspicion is required for effective diagnosis. Infants with NAT and, rarely, accidental subdural hemorrhage may exhibit a clinicoradiologically dissociative presentation, with their behavior appearing to reflect better function than what becomes apparent with maturation. Injury to the developing brain can result in extensive damage consistent with the "big black brain" phenomenon, which predicts poor prognosis. Sequential magnetic resonance imaging (MRI) is important to understand insults to the developing brain for follow-up and prognostication. Pediatric traumatic brain injury (TBI) is a major cause of concern worldwide. NAT brain injury is common in infants, who may present with varied presentations post-NAT, hence, a healthy suspicion is required for effective diagnosis. Infants with NAT and, rarely, an accidental subdural hemorrhage may exhibit a clinicoradiologically dissociative presentation with their behavior appearing to reflect better function than what becomes apparent with maturation. Injury to the developing brain can result in extensive damage consistent with the "big black brain" phenomenon, which predicts poor prognosis. Sequential MRI is important to understand insults to the developing brain for follow-up and prognostication.
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[This corrects the article DOI: 10.7759/cureus.8011.].
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OBJECTIVE: To define the phenotypic spectrum of isolated sulfite oxidase (ISOD) and molybdenum cofactor deficiency (MoCD), aiming to promote timely diagnosis and assist in future clinical trial design. METHODS: We analyzed clinical, radiographic, biochemical, and genetic data from 146 patients reported in the literature. RESULTS: We stratified patients into 2 phenotypic subgroups based on clinical and radiographic characteristics. In the first (Class I), patients presented early in life (age 1-50 days) with acute onset of neurologic symptoms and development of diffuse brain injury with cystic leukomalacia. Patients in the second subgroup (Class II) presented later in life (age 30 days-23 years) with prominent movement abnormalities and selective injury of the basal ganglia and cerebellum. A significant difference in survival estimates correlated with milder disease severity among Class II patients. Substantial overlap in sulfur-containing metabolite levels prevented discrimination of subgroups based on diagnostic biomarkers, but genotype-phenotype correlations suggested that residual SUOX activity may contribute to milder phenotypes. CONCLUSIONS: Patients with SUOX and MoCD gravitate toward 1 of 2 distinct clinicoradiographic profiles. Patient stratification may help promote accurate diagnosis, prognostication, and aid in the design of future clinical trials.
RESUMEN
Molybdenum cofactor deficiency (MoCD) is an autosomal recessive disorder belonging to the large family of inborn errors in metabolism. Patients typically present with encephalopathy and seizures early after birth and develop severe neurodegeneration within the first few weeks of life. The main pathomechanism underlying MoCD is the loss of function of sulfite oxidase (SO), a molybdenum cofactor (Moco) dependent enzyme located in mitochondrial intermembrane space. SO catalyzes the oxidation of sulfite (SO3 2-) to sulfate (SO4 2-) in the terminal reaction of cysteine catabolism, and in the absence of its activity, sulfurous compounds such as SO3 2-, S-sulfocysteine, and thiosulfate accumulate in patients. Despite growing evidence that these compounds affect neuronal and mitochondrial function, the molecular basis of neuronal dysfunction and cell death in MoCD is still poorly understood. Here we show that mitochondria are severely affected by the loss of SO activity. SO-deficient mouse embryonic fibroblasts display reduced growth rates and impaired ATP production when cultured in galactose, which is an indicator of mitochondrial dysfunction. We also found that mitochondria in SO-deficient cells form a highly interconnected network compared to controls while displaying a slight decrease in motility and unchanged mitochondrial mass. Moreover, we show that the mitochondrial network is directly influenced by SO3 2-, as a moderate elevation of SO3 2- lead to the formation of an interconnected mitochondrial network, while high SO3 2- levels induced fragmentation. Finally, we found a highly interconnected mitochondrial network in MoCD patient-derived fibroblasts, similar to our findings in mouse-derived fibroblasts. We therefore conclude that altered mitochondrial dynamics are an important contributor to the disease phenotype and suggest that MoCD should be included among the mitochondrial disorders.