Increased N-acetylaspartate in model mouse of Pelizaeus-Merzbacher disease

Area of Science:

• Neuroscience
• Biochemistry
• Medical Imaging

Background:

• Pelizaeus-Merzbacher disease (PMD) is a rare, inherited neurological disorder caused by mutations in the proteolipid protein 1 (PLP1) gene, leading to impaired myelin formation in the central nervous system.
• The myelin synthesis-deficient (msd) mouse model recapitulates key pathological features of PMD, including hypomyelination and neurological deficits.
• Understanding the underlying biochemical alterations in the msd mouse brain is crucial for developing diagnostic markers and therapeutic strategies for PMD.

Purpose of the Study:

• To investigate the levels and biochemical pathways of N-acetylaspartate (NAA) and N-acetylaspartylglutamate (NAAG) in the brain of msd mice, a model for PMD.
• To correlate neurochemical changes with histological findings of hypomyelination and astrogliosis in the msd mouse model.
• To explore the potential of NAA and NAAG as biomarkers for PMD using magnetic resonance spectroscopy (MRS).

Main Methods:

• Magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopy (¹H-MRS) were employed to analyze the thalamus of msd and wildtype mice.
• High-performance liquid chromatography (HPLC) was utilized for independent quantification of NAA and NAAG.
• Immunohistochemical analysis was performed using antibodies against myelin basic protein (Mbp), glial fibrillary acidic protein (Gfap), NG2, and neuronal nuclei (NeuN) to assess cellular composition and myelination status.

Main Results:

• ¹H-MRS revealed elevated total NAA (tNAA), creatine, glutamine, and glutamate, alongside decreased choline (Cho) in msd mice compared to controls.
• HPLC analysis confirmed increased levels of both NAA and NAAG in the brains of msd mice.
• Histological examination showed significant hypomyelination and astrogliosis in msd brains, while oligodendrocyte progenitor cells and neurons were present in normal numbers in the thalamus.

Conclusions:

• The neurochemical abnormalities in msd mice suggest a primary increase in NAA, potentially leading to a secondary increase in NAAG.
• Elevated tNAA and reduced Cho, detectable by ¹H-MRS, may serve as significant biomarkers for PMD.
• These neurochemical signatures could aid in distinguishing PMD from other neurological conditions characterized by decreased tNAA.