Characterization of AIMP2 variant-linked mouse model of Parkinson's disease - PROJECT SUMMARY The accumulation of the aminoacyl-tRNA synthetase complex interacting multifunctional protein-2 (AIMP2) has been found to be pathogenic in Parkinson's disease (PD) patients. This accumulation has been observed in the brains of Parkin knockout mice and in postmortem brains from both juvenile PD patients with Parkin deletion and sporadic PD patients. The overexpression of AIMP2 results in a selective, progressive, and age-dependent loss of dopamine neurons through the activation of poly (ADP-ribose) polymerase-1 (PARP1). Additionally, our recent discovery shows that AIMP2 has a self-aggregating tendency which results in toxicity. AIMP2 aggregates act as a catalyst for the aggregation and spread of α-synuclein, pointing to a pathological role in PD. Significantly, a recent human genetics study on PD identified rare variants in the AIMP2 gene that are linked to late-onset PD (LOPD). However, there have been no investigations on the pathological effects of AIMP2 variants in mammals, due to the lack of suitable mammal models. Hence, mouse models are required to study the pathogenic mechanisms underlying PD caused by AIMP2 mutations. Our preliminary studies using variants such as wild type (WT), R26Q, R65C, D86E, L165F, L165V, P177L, T203M, and I213T have revealed that the R65C variant is more susceptible to insoluble redistribution, aggregation formation, and cytotoxicity than the WT AIMP2 and other variants. Based on these findings, we propose in aim 1 to create an R65C AIMP2 knock-in (KI) mouse model using CRISPR technology. The motor phenotype and brain pathology of the mouse model will be characterized. Our recent publication has shown that AIMP2 has a tendency to self-aggregate and interact with α-synuclein, leading to an acceleration of coaggregation both in vitro and in vivo. Furthermore, preliminary studies have indicated that the R65 variant causes the rapid formation of α-synuclein aggregates and an increase in toxicity when AIMP2 and α-synuclein are co-expressed in cell cultures. Based on these findings, we hypothesize that the R65C AIMP2 variant contributes to the transmission of pathological α-synuclein induced by α-synuclein preformed fibrils (PFF). To test this, in aim 2, we will examine the impact of the R65C AIMP2 variant on Lewy body pathology caused by α-synuclein PFF. For this purpose, we will inject α-synuclein PFF into the striatum of the R65C AIMP2 knock-in mice. We will prioritize examining Lewy body pathology using these mice. The completion of this study will greatly enhance our understanding of the underlying pathogenesis of AIMP2- related PD and provide a valuable resource for the PD research community in the form of an AIMP2-linked PD mouse model for future studies on pathogenic mechanisms and the development of treatments. Additionally, it will shed new light on the study of sporadic PD.
