Objective: Identification of changes in gene expression in rat nigral neurons associated with early phases of synucleinopathy.

Background: Early phases of synucleinopathies such as Parkinson’s disease (PD) have been difficult to study as animal models often fail to recapitulate the protracted progression from inclusion formation and accumulation to neurodegeneration. The alpha-synuclein (α-syn) preformed fibril (PFF) synucleinopathy model in rats exhibits distinct and predictable stages throughout the progression of synucleinopathy. Specifically, peak accumulation of α-syn inclusions occurs at 2 months in the substantia nigra pars compacta (SNpc), months prior to the loss of tyrosine hydroxylase immunoreactive (THir) neurons and the ultimate degeneration of the nigrostriatal system. In the present study we leverage this prolonged peritoxic synucleinopathy stage to reveal the genetic signature associated with early synucleinopathy in the SNpc.

Method: Three-month-old male and female Fischer 344 rats received two unilateral, intrastriatal injections of sonicated mouse α-syn PFFs or an equal volume of vehicle. At 2 months post-injection laser capture microdissection (LCM) was used to collect TH neurons from the SNpc followed by RNA sequencing (RNASeq) to identify changes in gene expression. Results in a subset of genes were validated by droplet digital PCR (ddPCR) and western blot.

Results: RNAseq and ddPCR revealed differential expression of genes involved in synaptic transmission. Specifically, genes involved in the composition of synaptic vesicles, vesicle trafficking, and dopamine release were downregulated in early synucleinopathy.  Experiments to determine if these gene changes result in protein changes at the synapse in the striatum are in progress.

Conclusion: Our data reveal that the formation of Lewy body-like inclusions is associated with gene expression changes with potential detrimental effects on nigrostriatal dopamine transmission. The functional consequence of this dysregulation on dopaminergic transmission is presently under investigation.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/genetic-profiling-of-early-synucleinopathy-in-rat-nigrostriatal-dopamine-neurons/