Alpha-synuclein spreading in M83 mice brain revealed by detection of pathological α-synuclein by enhanced ELISA

Background: The accumulation of misfolded proteins appears as a fundamental pathogenic process in human neurodegenerative diseases. In the case of synucleinopathies such as Parkinson's disease (PD) or dementia with Lewy bodies (DLB), the intraneuronal deposition of aggregated alpha-synuclein (aS) is a major characteristic of the disease, but the molecular basis distinguishing the disease-associated protein (aSD) from its normal counterpart remains poorly understood. However, recent research suggests that a prion-like mechanism could be involved in the inter-cellular and inter-molecular propagation of aggregation of the protein within the nervous system. Results: Our data confirm our previous observations of disease acceleration in a transgenic mouse line (M83) overexpressing a mutated (A53T) form of human aS, following inoculation of either brain extracts from sick M83 mice or fibrillar recombinant aS. A similar phenomenon is observed following a "second passage" in the M83 mouse model, including after stereotactic inoculations into the hippocampus or cerebellum. For further molecular analyses of aSD, we designed an ELISA test that identifies aSD specifically in sick mice and in the brain regions targeted by the pathological process in this mouse model. aSD distribution, mainly in the caudal brain regions and spinal cord, overall appears remarkably uniform, whatever the conditions of experimental challenge. In addition to specific detection of aSD immunoreactivity using an antibody against Ser129 phosphorylated aS, similar results were observed in ELISA with several other antibodies against the C-terminal part of aS, including an antibody against non phosphorylated aS. This also indicated consistent immunoreactivity of the murine aS protein specifically in the affected brain regions of sick mice. Conclusions: Prion-like behaviour in propagation of the disease-associated aS was confirmed with the M83 transgenic mouse model, that could be followed by an ELISA test. The ELISA data question their possible relationship with the conformational differences between the disease-associated aS and its normal counterpart.