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New insights into the neuropathogenesis of molybdenum cofactor deficiency
Michael S Salman1, Cameron Ackerley, Christof Senger
1Department of Neurology, Hospital for Sick Children, Toronto, ON, Canada.
Background:
Molybdenum cofactor deficiency (MOCOD) is a rare, progressive neurodegenerative disorder caused by sulphite oxidase enzyme deficiency. The neuropathological findings are consistent with a toxic insult to the brain that causes severe neuronal loss, reactive astrogliosis and spongiosis. The mechanisms responsible for these changes are unknown.
Methods:
The case is a male infant with MOCOD who died at nine months of age from pneumonia. At autopsy, a complete neuropathological examination was performed including conventional immunohistochemical staining. In addition, brain sections were stained cytochemically with shikata and orcein which stain for disulphide bonds. The elemental composition of cortical cells was then analyzed in the scanning electron microscope using backscatter electron imaging and energy dispersive X-ray spectrometry.
Results:
Neurons demonstrated cytoplasmic staining with shikata and orcein cytochemically when compared to control sections. Energy dispersive X-ray spectrometry analysis of these neurons confirmed the presence of excess sulphur and unexpectedly revealed excess magnesium accumulation. None of these findings was found in an age-matched control.
Conclusions:
In MOCOD we found abnormal accumulation of sulphur and magnesium in neurons. It is postulated that sulphur-containing compound(s) that are formed as a result of MOCOD cause excitotoxic neuronal injury in the presence of excess magnesium.
Insights
Molybdenum cofactor deficiency (MOCOD) leads to excess sulfur and magnesium in brain neurons. This accumulation may cause excitotoxic injury, contributing to neurodegeneration in this rare disorder.
Area of Science:
- Neuroscience
- Biochemistry
- Pathology
Background:
- Molybdenum cofactor deficiency (MOCOD) is a rare, progressive neurodegenerative disorder resulting from sulphite oxidase enzyme deficiency.
- Neuropathological findings in MOCOD include severe neuronal loss, reactive astrogliosis, and spongiosis, suggesting a toxic brain insult.
- The underlying mechanisms driving these neuropathological changes in MOCOD remain largely unknown.
Observation:
- Autopsy of a male infant with MOCOD revealed neuropathological examination including cytochemical staining for disulphide bonds and elemental analysis of cortical cells.
- Neurons in the MOCOD brain exhibited cytoplasmic staining with shikata and orcein, indicating alterations in disulphide bonds.
- Scanning electron microscopy with energy dispersive X-ray spectrometry identified excess sulphur and magnesium accumulation within the neurons of the affected infant.
Findings:
- Abnormal accumulation of sulphur and magnesium was detected in the neurons of an infant with Molybdenum cofactor deficiency (MOCOD).
- Cytochemical staining revealed abnormal disulphide bond patterns in the neurons of the MOCOD patient.
- Elemental analysis confirmed significantly higher concentrations of sulphur and magnesium in the neurons compared to age-matched controls.
Implications:
- The study postulates that sulphur-containing compounds, resulting from MOCOD, may induce excitotoxic neuronal injury in the presence of excess magnesium.
- These findings suggest a novel mechanism contributing to the neurodegenerative pathology observed in Molybdenum cofactor deficiency.
- Further research into the role of sulphur and magnesium metabolism in MOCOD could lead to new therapeutic strategies.