Objective: Identification of gene expression changes in the rat substantia nigra pars compacta (SNpc) associated with early alpha-synuclein (a-syn) inclusion formation.

Background: Accumulation of intracellular inclusions (Lewy Bodies) composed primarily of pathological a-syn and degeneration of the nigrostriatal dopamine pathway are hallmark features of Parkinson’s disease (PD). The a-syn preformed fibril (PFF) model recapitulates both of these pathological features in rodents. In the PFF model, phosphorylated a-syn (pSyn) inclusion-containing neurons and reactive microglia (major histocompatibility complex II immunoreactive) peak in the SNpc at 2 months. This is followed by loss of dopaminergic phenotype and ultimately neurodegeneration at 5-6 months post-injection. In the present study, we leverage the early 2-month peak of synucleinopathy and neuroinflammation in the SNpc to detect transcriptomic changes relevant to early PD with the ultimate goal of identifying potential therapeutic targets for neuroprotection.

Method: Three-month-old male and female hTH-EGFP rats received unilateral, intrastriatal injections of sonicated mouse α-syn PFFs (total =16 μg) or an equal volume of vehicle. At 2 months post-injection, GFP was used to visualize the SNpc and guide precise laser capture microdissection (LCM) for the enrichment of nigral dopamine neurons and adjacent cells. Total RNA isolation, followed by ribosomal RNA depletion, and library preparation were performed for RNA-sequencing (RNASeq). Results in a subset of genes are being validated by droplet digital PCR (ddPCR) and in situ hybridization.

Results: In males and females, 2,534 and 1,491 differentially expressed transcripts, respectively, were associated with early synucleinopathy (FDR < 0.2). A total of 326 transcripts were differentially expressed in both sexes, which showed enrichment for disease-relevant biological pathways. Experiments are ongoing to confirm reproducibility via ddPCR and localize transcriptional changes to pSyn inclusion-bearing neurons via in situ hybridization.

Conclusion: Our data reveal that the formation of Lewy body-like inclusions is largely associated with the upregulation of genes associated with immune related pathways, and downregulated genes generally associated with neurotransmission.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/early-synucleinopathy-is-associated-with-differential-regulation-of-neurotransmission-and-immune-related-genes/