Inclusion of a portion of the native SNCA 3′UTR reduces toxicity of human S129A SNCA on striatal‐projecting dopamine neurons in rat substantia Nigra

Abstract

Experimental models of Parkinson's disease (PD) created by aberrant expression of the alpha-synuclein (SNCA) coding region have been reported. However, noncoding regions function in normal physiology and recent in vitro studies have shown that microRNAs-7 and -153 regulate SNCA expression by binding the 3'UTR. Here, effects of different hSNCA forms were examined in vivo. Adult, male rats were injected into one substantia nigra (SN) with AAV-wtSNCA, AAV-S129A hSNCA, or AAV-S129D hSNCA either with or without a portion of the native 3'UTR. DA neurons in SN that maintained striatal (ST) projections at the end of treatment were retrogradely labeled by bilateral ST fluorogold (FG) injections and FG-positive DA neurons in SN were counted. At 5 weeks, hSNCA coding vectors reduced numbers of FG-positive neurons in injected SN compared with uninjected SN (wtSNCA, p = 0.05; S129A/D hSNCA, p = 0.01). At 7 and 9 weeks, wtSNCA- and S129D hSNCA-treated rats exhibited recovery, but S129A hSNCA-injected rats did not (p = 0.01). In contrast, numbers of FG-positive neurons were unaffected by hSNCA expression when the 3'UTR was included. When FG-positive neurons were expressed as the ratio of numbers in injected to uninjected sides, the S129A hSNCA coding vector resulted in the highest decrease at 9 weeks versus wtSNCA (p = 0.05) or S129D hSNCA (p = 0.01). Inclusion of the 3'UTR resulted in no significant differences in FG-positive neuron ratios. These data suggest that inclusion of the 3'UTR protects against S129A hSNCA-induced loss of nigrostriatal-projecting DA neurons in vivo and that mis-regulation of hSNCA expression and function at noncoding regions contribute to PD pathogenesis.