This project examines gene expression and PD susceptibility differences between dopamine (DA) neurons in the substantia nigra (A9) that are vulnerable to PD, compared to those spared in the same midbrain tissue region A10 (VTA). In this Project, we discovered new gene and molecular candidates for neuroprotection by specific lasercapture and genomic analysis of characteristic midbrain DA neurons. We are providing many named examples of RT-PCR validated genes obtained from the microarray analyses, plus several uncoded tables of their genetic PD linkage (collaboration with Duke U Udall Center). Several specific neuropeptide genes are elevated in DA neurons located in the A10, including vasoactive intestinal peptide (VIP) and cholecysteokinin (CCK-8), CGRP and GRP. Interestingly, many genes and molecules we have found to have differential gene expression such as FGF1, PP2A regulatory subunit B, Gamma isoform, RAB3, RAB5A, RAB11, RAB1, RAB14, GTP-binding protein rah are also linked to PD susceptibility genetic loci. We propose to test such genes for functional effects in PD focused models. As a first step in such an evaluation, we expose or express the molecules in alpha-synuclein overexpressing PC 12 cells, one of four in vitro culture models, to determine their effects on neurotoxicity. We have now found several peptides preferentially expressed in A10 DA neurons also to be neuroprotective in alpha-synuclein in vitro systems, and DA neuron primary rodent and human cell culture and animal models. This supports the hypotheses and point to a potential relevance of these genes in PD. In contrast to A10 elevated genes, delivery of the GIRK2 gene (an A9 DA neuron elevated gene) via lentivirus, increases the vulnerability of PC12 cells and primary DA neurons to MPP+ toxicity. The molecules differentially expressed in A9/A10 DA neurons with potential genetic PD linkage or particular neurodegenerative or regenerative properties can now be tested systematically by tissue culture and animal models, to identify new pathways and substances providing insights to the pathogeneses and novel therapies for PD. This Project is internally enhanced by the Cores and externally by the Duke U collaboration of the NIH Udall Center consortium. This project's systematic and PD focused approach, and new preliminary data support the hypothesis that genetic profiles of A9 and A10 cells can be useful to (1) test and explain relative vulnerability between these neuronal phenotypes, (2) serve as powerful leads to PD focused research of genetic convergence analysis of human PD susceptibility and (3) innovative neuroprotection studies for novel treatments of PD patients.
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