A novel mouse model for investigating α-synuclein aggregates in oligodendrocytes: implications for the glial cytoplasmic inclusions in multiple system atrophy.

The aggregated alpha-synuclein (αsyn) in oligodendrocytes (OLGs) is one of the pathological hallmarks in multiple system atrophy (MSA). We have previously reported that αsyn accumulates not only in neurons but also in OLGs long after the administration of αsyn preformed fibrils (PFFs) in mice. However, detailed spatial and temporal analysis of oligodendroglial αsyn aggregates was technically difficult due to the background neuronal αsyn aggregates. The aim of this study is to create a novel mouse that easily enables sensitive and specific detection of αsyn aggregates in OLGs and the comparable analysis of the cellular tropism of αsyn aggregates in MSA brains. To this end, we generated transgenic (Tg) mice expressing human αsyn-green fluorescent protein (GFP) fusion proteins in OLGs under the control of the 2', 3'-cyclic nucleotide 3'-phosphodiesterase (CNP) promoter (CNP-SNCAGFP Tg mice). Injection of αsyn PFFs in these mice induced distinct GFP-positive aggregates in the processes of OLGs as early as one month post-inoculation (mpi), and their number and size increased in a centripetal manner. Moreover, MSA-brain homogenates (BH) induced significantly more oligodendroglial αsyn aggregates than neuronal αsyn aggregates compared to DLB-BH in CNP-SNCAGFP Tg mice, suggestive of their potential tropism of αsyn seeds for OLGs. In conclusion, CNP-SNCAGFP Tg mice are useful for studying the development and tropism of αsyn aggregates in OLGs and could contribute to the development of therapeutics targeting αsyn aggregates in OLGs.