Concordant Signaling Pathways Produced by Pesticide Exposure in Mice Correspond to Pathways Identified in Human Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative disease in which the etiology of 90 percent of the patients is unknown. Pesticide exposure is a major risk factor for PD, and paraquat (PQ), pyridaben (PY) and maneb (MN) are amongst the most widely used pesticides. We studied mRNA expression using transcriptome sequencing (RNA-Seq) in the ventral midbrain (VMB) and striatum (STR) of PQ, PY and paraquat+maneb (MNPQ) treated mice, followed by pathway analysis. We found concordance of signaling pathways between the three pesticide models in both the VMB and STR as well as concordance in these two brain areas. The concordant signaling pathways with relevance to PD pathogenesis were e.g. axonal guidance signaling, Wnt/β-catenin signaling, as well as pathways not previously linked to PD, e.g. basal cell carcinoma, human embryonic stem cell pluripotency and role of macrophages, fibroblasts and endothelial cells in rheumatoid arthritis. Human PD pathways previously identified by expression analysis, concordant with VMB pathways identified in our study were axonal guidance signaling, Wnt/β-catenin signaling, IL-6 signaling, ephrin receptor signaling, TGF-β signaling, PPAR signaling and G-protein coupled receptor signaling. Human PD pathways concordant with the STR pathways in our study were Wnt/β-catenin signaling, axonal guidance signaling and G-protein coupled receptor signaling. Peroxisome proliferator activated receptor delta (Ppard) and G-Protein Coupled Receptors (GPCRs) were common genes in VMB and STR identified by network analysis. In conclusion, the pesticides PQ, PY and MNPQ elicit common signaling pathways in the VMB and STR in mice, which are concordant with known signaling pathways identified in human PD, suggesting that these pathways contribute to the pathogenesis of idiopathic PD. The analysis of these networks and pathways may therefore lead to improved understanding of disease pathogenesis, and potential novel therapeutic targets

Overlapping signaling pathways between human PD transcriptome studies and signaling pathways in STR of PQ, PY and MNPQ mouse models of PD.

<p>All human IPA analysis were performed by <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036191#pone.0036191-Sutherland1" target="_blank">[18]</a>.</p><p><b>x</b> = Common Pathways.</p><p>SN: Substantia nigra, BA9: Brodman area 9, SFG: Superior frontal gyrus, L SN: Lateral substantia nigra, M SN: Medial substantia nigra, PU: Putamen, OC: Occipital cortex.</p

Pesticide induced loss of TH+ neurons and increased α-synuclein immunoreactivity.

<p>A) Immunostaining of SN of PQ, PY, MNPQ and wild type (WT) mice with tyrosine hydroxylase antibody. B) Percent loss of TH+ neurons and fold increase of α-synuclein immunoreactivity compared to wild type control mice.</p

Common genes in the STR between PQ, PY and MNPQ mouse models of PD.

<p>A) Venn diagram of 500 up-regulated STR transcripts from PQ, PY and MNPQ models of PD. B) Venn diagram of 500 down-regulated STR transcripts from PQ, PY and MNPQ models of PD. C) Common up-regulated genes in the STR of PQ, PY and MNPQ models of PD. D) Common down-regulated genes in the STR of PQ, PY and MNPQ models of PD.</p

Global gene network in VMB of PQ, PY and MNPQ mouse models of PD.

<p>The genes from the most significant network of each individual pesticide mouse model were overlayed to generate global gene networks in the VMB. Down-regulated genes are highlighted in green, up-regulated genes are highlighted in red. The focus molecules-G protein coupled receptors (GPCRs) members, Kelch-like ECH-associated protein 1 (<i>Keap1</i>) and peroxisome proliferator-activated receptor delta (<i>Pparδ</i>) are down-regulated in VMB.</p

Validation of RNA-Seq gene expression fold changes by Taqman real time PCR.

<p>A) Gene expression fold changes in VMB. B) Gene expression fold changes in the STR.</p

Taqman assays used for quantitative RT-PCR.

<p>Taqman assays used for quantitative RT-PCR.</p

Venn diagram of top ten signaling pathways in PQ, PY and MNPQ models of PD.

<p>A) Signaling pathways in VMB. B) Signaling pathways in STR. C) Common overlapping pathways in VMB and STR are underlined. Considering the top ten canonical pathways there are six pathways common in VMB of PQ, PY and MNPQ mouse models. There are three pathways common in STR of PQ, PY and MNPQ mouse models. All the three common canonical pathways in STR overlap with pathways common in the VMB between the three pesticide models.</p

Global gene network in STR of PQ, PY and MNPQ mouse models of PD.

<p>The genes from the most significant network of each individual pesticide mouse model were overlayed to generate global gene networks in the STR. Down-regulated genes are highlighted in green, up-regulated genes are highlighted in red. The focus molecules- G protein coupled receptors (GPCRs) members and <i>Pparδ</i> are down-regulated while <i>Atxn1</i> is up-regulated.</p

The phenotypic spectrum of rapid-onset dystonia-parkinsonism (RDP) and mutations in the ATPIA3 gene

Rapid-onset dystonia-parkinsonism (RDP) (also known as DYT12) is characterized by the abrupt onset of dystonia and parkinsonism and is caused by mutations in the ATP1A3 gene. We obtained clinical data and sequenced the ATP1A3 gene in 49 subjects from 21 families referred with 'possible' RDP, and performed a genotype-phenotype analysis. Of the new families referred for study only 3 of 14 families (21%) demonstrated a mutation in the ATP1A3 gene, but no new mutations were identified beyond our earlier report of 6. Adding these to previously reported families, we found mutations in 36 individuals from 10 families including 4 de novo mutations and excluded mutations in 13 individuals from 11 families. The phenotype in mutation positive patients included abrupt onset of dystonia with features of parkinsonism, a rostrocaudal gradient, and prominent bulbar findings. Other features found in some mutation carriers included common reports of triggers, minimal or no tremor at onset, occasional mild limb dystonia before the primary onset, lack of response to dopaminergic medications, rare abrupt worsening of symptoms later in life, stabilization of symptoms within a month and minimal improvement overall. In comparing ATP1A3 mutation positive and negative patients, we found that tremor at onset of symptoms, a reversed rostrocaudal gradient, and significant limb pain exclude a diagnosis of RDP. A positive family history is not required. Genetic testing for the ATP1A3 gene is recommended when abrupt onset, rostrocaudal gradient and prominent bulbar findings are presen