Dysregulated lipid metabolism and hypomyelination in postnatal peroxisome-deficient Pex2 knockout Zellweger mice

Tanja Eberhart¹Khanichi N Charles²Brenda Salumbides-Torres²Nia Price²Steven J. Fliesler^3,4Phyllis L Faust⁵Werner Josef Kovacs^1*

• ¹Institute of Molecular Health Sciences, ETH Zurich, Zurich, Switzerland
• ²Department of Biology, San Diego State University, San Diego, United States
• ³Departments of Ophthalmology and Biochemistry and Graduate Program in Neuroscience, The University at Buffalo - The State University of New York (SUNY), Buffalo, United States
• ⁴Research Service, Veterans Administration Western New York Healthcare System, Buffalo, United States
• ⁵Department of Pathology and Cell Biology, Vagelos College of Physicians and Surgeons, Columbia University, New York, United States

ABSTRACT Peroxisomes are dynamic organelles that play a crucial role in cellular metabolism, particularly in fatty acid degradation, cholesterol homeostasis and reactive oxygen species metabolism. Their dysfunction is associated with severe neurological disorders, including Zellweger spectrum disorders (ZSD) and X-linked adrenoleukodystrophy (X-ALD). In this study, we investigated the relationship between cholesterol homeostasis and myelination in postnatal peroxisome-deficient Pex2 knockout mice. We dissected the central nervous system (CNS) of 10-day-old (P10) control and Pex2-/- mice into five regions: spinal cord, brainstem, cerebellum, diencephalon and cerebral cortex. Catalase activity, a marker enzyme of peroxisomes, was significantly increased in CNS regions of Pex2-/- mice, indicating an oxidative imbalance. Proteomic analysis revealed significant alterations in peroxisomal proteins and pathways related to neurodegenerative diseases, cholesterol and fatty acid metabolism and mRNA processing. Cholesterol biosynthesis was particularly dysregulated: enzyme activities, mRNA, and protein levels were reduced in white matter regions but increased in the cerebral cortex. The elevated desmosterol levels in the brain of Pex2-/- mice indicate impaired cholesterol synthesis. Sphingolipid metabolism was also altered in the peroxisome-deficient CNS, as the protein levels of enzymes dihydroceramide desaturase 1, ceramide synthase 2, fatty acid 2-hydroxylase, and UDP-glycosyltransferase 8 were significantly decreased. Myelination was significantly reduced throughout the CNS, as evidenced by decreased activities of the myelin marker 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP) and decreased mRNA and protein levels of myelin-associated proteins. The consistent decrease in ribosomal protein S6 phosphorylation in the CNS of Pex2-/- mice suggests that decreased mechanistic target of rapamycin complex 1 (mTORC1) activity contributes to hypomyelination. Gene expression analysis revealed an upregulation of pro-inflammatory cytokines and altered expression of some homeostatic and disease-associated microglial (DAM) genes. However, full DAM activation was not yet observed in Pex2-/- mice at P10. In conclusion, this study shows that systemic peroxisome deficiency leads to severe hypomyelination and dysregulation of cholesterol and fatty acid metabolism in the CNS, providing new insights into the pathophysiology of peroxisomal disorders.