Axonopathy and Reduction of Membrane Resistance: Key Features in a New Murine Model of Human G_M1-Gangliosidosis

• Main Authors: Deborah Eikelberg, Annika Lehmbecker, Graham Brogden, Witchaya Tongtako, Kerstin Hahn, Andre Habierski, Julia B. Hennermann, Hassan Y. Naim, Felix Felmy, Wolfgang Baumgärtner, Ingo Gerhauser
• Format: Article
• Language: English
• Published: MDPI AG 2020-04-01
• Series: Journal of Clinical Medicine
• Subjects: astrogliosis; axonopathy; β-galactosidase deficiency; electrophysiology; G_M1-gangliosidosis; knockout mouse model
• Online Access: https://www.mdpi.com/2077-0383/9/4/1004

G_M1-gangliosidosis is caused by a reduced activity of β-galactosidase (<i>Glb1</i>), resulting in intralysosomal accumulations of G_M1. The aim of this study was to reveal the pathogenic mechanisms of G_M1-gangliosidosis in a new <i>Glb1</i> knockout mouse model. <i>Glb1</i>^−/− mice were analyzed clinically, histologically, immunohistochemically, electrophysiologically and biochemically. Morphological lesions in the central nervous system were already observed in two-month-old mice, whereas functional deficits, including ataxia and tremor, did not start before 3.5-months of age. This was most likely due to a reduced membrane resistance as a compensatory mechanism. Swollen neurons exhibited intralysosomal storage of lipids extending into axons and amyloid precursor protein positive spheroids. Additionally, axons showed a higher kinesin and lower dynein immunoreactivity compared to wildtype controls. <i>Glb1</i>^−/− mice also demonstrated loss of phosphorylated neurofilament positive axons and a mild increase in non-phosphorylated neurofilament positive axons. Moreover, marked astrogliosis and microgliosis were found, but no demyelination. In addition to the main storage material G_M1, G_A1, sphingomyelin, phosphatidylcholine and phosphatidylserine were elevated in the brain. In summary, the current <i>Glb1</i>^−/− mice exhibit a so far undescribed axonopathy and a reduced membrane resistance to compensate the functional effects of structural changes. They can be used for detailed examinations of axon–glial interactions and therapy trials of lysosomal storage diseases.