Alterations of Striatal Projection Neurons in Parkinson's disease

National Institute On Aging

Investigators

Linked publications & trials

Abstract

To examine whether there are any gross anatomical changes of striosome SPNs in the Pitx3ak/ak mice, we first crossbred two different striosome SPN reporter mouse lines, Nr4a1-GFP68 and Sepw1-Cre/Ai27D, into Pitx3ak/ak background, respectively, and then checked the projections of striosome SPNs to different target brain regions. We found in both Nr4a1-GFP/Pitx3ak/ak and Sepw1-Cre/Ai27D/ Pitx3ak/ak lines that the striosomal projection to SNr was drastically reduced, while the projection to GPe increased compared to control mice. Since the striosome dSPNs project to SNr and iSPNs project to GPe, these observations suggest a reduction of striosome dSPN and an increase in iSPN numbers in the Pitx3ak/ak mice. In support of this notion, our RNAscope in situ hybridization experiments revealed a significant decrease of the number of striosome dSPNs and relative increase of striosome iSPNs in Pitx3ak/ak mice. Together, these findings demonstrate the reconfiguration of striosome SPNs subtypes in response to PD-like dopamine depletion, which fosters the dominance of striosome indirect pathway over the direct pathway. To further determine the gene expression changes at single cell level in the striatum of Pitx3ak/ak mice, we conducted single nuclei RNA sequencing (snRNAseq) on striatal tissues isolated from Pitx3ak/ak and littermate control mice. Our preliminary analyses of the snRNAseq data supported the early findings from the RNAscope and immunostaining studies. Pitx3ak/ak mice also display profound impairments in the rotarod motor skill learning task69. To examine whether there are any alterations of neuronal activity in the striosome dSPNs and iSPNs, we applied an intersectional mouse genetics approach to generate Cre and Flp DNA recombinase dual-controlled mice, which allow for genetic manipulation of striosome dSPNs and iSPNs specifically. We will employ two-photon imaging and fiber photometry to record the neuronal activity from these neuronal subpopulations during motor skill learning. Additionally, we will adopt optogenetics or chemogenetics to rebalance the activity of striosome dSPNs and iSPNs, and to rescue the motor learning impairments in Pitx3ak/ak mice. Lastly, we will adapt findings from Pitx3ak/ak mice to investigation of other PD-related mouse models that develop age-dependent loss of SNc DANs to ascertain whether the remodeling of striosome direct and indirect pathway neurons also occurs in those mice. Together, these studies will help us to better understand the pathogenetic mechanisms of striatal neurons in PD.