Article

Chung, C.Y. et al. Cell type-specific gene expression of midbrain dopaminergic neurons reveals molecules involved in their vulnerability and protection. Hum. Mol. Genet. 14, 1709-1725

Harvard University, Cambridge, Massachusetts, United States
Human Molecular Genetics (Impact Factor: 6.39). 08/2005; 14(13):1709-25. DOI: 10.1093/hmg/ddi178
Source: PubMed

ABSTRACT

Molecular differences between dopamine (DA) neurons may explain why the mesostriatal DA neurons in the A9 region preferentially degenerate in Parkinson's disease (PD) and toxic models, whereas the adjacent A10 region mesolimbic and mesocortical DA neurons are relatively spared. To characterize innate physiological differences between A9 and A10 DA neurons, we determined gene expression profiles in these neurons in the adult mouse by laser capture microdissection, microarray analysis and real-time PCR. We found 42 genes relatively elevated in A9 DA neurons, whereas 61 genes were elevated in A10 DA neurons [> 2-fold; false discovery rate (FDR) < 1%]. Genes of interest for further functional analysis were selected by criteria of (i) fold differences in gene expression, (ii) real-time PCR validation and (iii) potential roles in neurotoxic or protective biochemical pathways. Three A9-elevated molecules [G-protein coupled inwardly rectifying K channel 2 (GIRK2), adenine nucleotide translocator 2 (ANT-2) and the growth factor IGF-1] and three A10-elevated peptides (GRP, CGRP and PACAP) were further examined in both alpha-synuclein overexpressing PC12 (PC12-alphaSyn) cells and rat primary ventral mesencephalic (VM) cultures exposed to MPP+ neurotoxicity. GIRK2-positive DA neurons were more vulnerable to MPP+ toxicity and overexpression of GIRK2 increased the vulnerability of PC12-alphaSyn cells to the toxin. Blocking of ANT decreased vulnerability to MPP+ in both cell culture systems. Exposing cells to IGF-1, GRP and PACAP decreased vulnerability of both cell types to MPP+, whereas CGRP protected PC12-alphaSyn cells but not primary VM DA neurons. These results indicate that certain differentially expressed molecules in A9 and A10 DA neurons may play key roles in their relative vulnerability to toxins and PD.

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    • "Parkinson's diseases31323334. Hence, PACAP is able to protect against neurotoxic agents several cell types such as PC12 cells, GIRK2-positive and GIRK2-negative dopamine neurons of primary ventral midbrain cultures, as well as Neuro-2a neuroblastoma cells[35,31]. It has been clearly established that PACAP modulates several pathways involved in apoptosis to promote neuroprotective effects. "
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    • "We opted for a 96.96 dynamic array to evaluate 96 cells, each for the expression of 96 key genes, an approach used previously to discriminate stem cell identities (Buganim et al., 2012; Guo et al., 2010). We selected 96 gene candidates based on reported differential expression between SNc and VTA (Chung et al., 2005; Greene et al., 2005; Grimm et al., 2004), with a positive bias toward genes with validated midbrain mRNA expression as shown by in situ hybridization in public databases (Table S1). In addition, we evaluated the expression of housekeeping genes (Actb, Gapdh, and Hprt), genes linked to PD (Atp13a2, Lrrk2, Park2, Park7, Pink1, and Snca), as well as validated DA neuronal markers (Ddc, Th, Slc6a3, and Slc18a2). "
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    • "The human SN/VTA presents high complexity and is composed of several dopaminergic neuronal subpopulations that differ in their neurodevelopmental origin (Zecevic and Verney 1995; Puelles and Verney 1998; Verney et al. 2001), genetic and neurochemical profile (Haber et al. 1995; Grimm et al. 2004; Thuret et al. 2004; Chung et al. 2005; Luk et al. 2013), projection sites (van Domburg and ten Donkelaar 1991; Damier et al. 1999a; Nieuwenhuys et al. 2008), and susceptibility to disease (Gibb and Lees 1991; Damier et al. 1999b; Hauser et al. 2005; approximately all SN/VTA neuronal populations located rostral to the exit of the 3 rd cranial nerve and to the transition between the parvocellular and magnocellular parts of the red nucleus (see for anatomical details van Domburg and ten Donkelaar 1991; Damier et al. 1999a; Nieuwenhuys et al. 2008). In addition, detailed neuropathological studies in Parkinson's disease have shown that diencephalic SN/VTA dopaminergic neurons are significantly more resilient to neuronal death than the mesencephalic ones (Damier et al. 1999b), thus supporting the validity of using developmental criteria to define SN/VTA sub-regions for neuropathological studies in the adult brain. "
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