Higher levels of myelin phospholipids in brains of neuronal a-Synuclein transgenic mice precede myelin loss

alpha-Synuclein is a protein involved in the pathogenesis of synucleinopathies, including Parkinson's disease (PD), dementia with Lewy bodies (DLB) and multiple system atrophy (MSA). We investigated the role of neuronal alpha-Syn in myelin composition and abnormalities. The phospholipid content of purified myelin was determined by P-31 NMR in two mouse lines modeling PD, PrP-A53T alpha-Syn and Thy-1 wt-alpha-Syn. Significantly higher levels of phospholipids were detected in myelin purified from brains of these alpha-Syn transgenic mouse models than in control mice. Nevertheless, myelin ultrastructure appeared intact. To further investigate the effect of alpha-Syn on myelin abnormalities, we systematically analyzed the striatum, a brain region associated with neurodegeneration in PD. An age and diseasedependent loss of myelin basic protein (MBP) signal was detected by immunohistochemistry in striatal striosomes (patches). The age-dependent loss of MBP signal was associated with lower P25a levels in oligodendrocytes. In addition, we found that alpha-Syn inhibited oligodendrocyte maturation and the formation of membranous sheets in vitro. Based on these results we concluded that neuronal alpha-Syn is involved in the regulation and/ or maintenance of myelin phospholipid. However, axonal hypomyelination in the PD models is evident only in progressive stages of the disease and associated with alpha-Syn toxicity.