Affiliations: Neuroscience Research Australia, Sydney, NSW, Australia | School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia
Note:  Correspondence to: Dr W. S. Kim, Neuroscience Research Australia, Barker Street, Randwick, NSW, 2031, Australia. Tel.: +61 2 9399 1084; Fax: +61 2 9399 1005; E-mail: [email protected]
Abstract: Background: Multiple system atrophy (MSA) is a fatal neurodegenerative disease of unknown aetiology characterised by the accumulation of insoluble α-synuclein (α-syn) aggregates in the cytoplasm of myelin-producing oligodendrocytes. Dysfunction of the lipid-rich myelin membrane may precede α-syn pathology in MSA pathogenesis. ATP-binding cassette transporter A8 (ABCA8) is a little-studied lipid transporter, which has recently been found to be highly expressed in oligodendrocyte-rich white matter regions of the human brain. ABCA8 expression promotes sphingomyelin production in oligodendrocytes in vitro, suggesting a role in myelin formation and maintenance. Objective: We hypothesise that aberrant ABCA8 expression in oligodendrocytes plays a role in the early pathogenesis of MSA by impacting myelin stability and regulation of α-syn and p25α. Methods: We measured the expression of ABCA8, α-syn and p25α in MSA brains in disease-affected grey matter (GM, putamen and cerebellum), disease-affected white matter (WM, under the motor cortex) and an unaffected brain region (visual cortex). We transfected human oligodendrocytes with ABCA8 and assessed its impact on α-syn and p25α expression. Results: ABCA8 expression was significantly increased in the disease-affected GM and WM with no significant change in the unaffected brain region. α-syn and p25α expression were significantly increased in the disease-affected WM and GM respectively. Overexpression of ABCA8 in oligodendrocytes caused significant increases in both α-syn and p25α expression. Conclusions: These data suggest a direct relationship between the levels of ABCA8 and the ectopic expression of α-syn and increased expression of p25α. As these data reflect results found in MSA, we hypothesise that increased ABCA8 may precipitate MSA pathology.
Keywords: Multiple system atrophy, ABCA8, α-synuclein, p25α, oligodendrocyte, human brain