ABSTRACT: Extensive transcriptomic changes associated with paclitaxel-induced peripheral neuropathy in mice: Differential effects in dorsal root ganglia and the sciatic nerve Background: Paclitaxel (Ptx)-induced peripheral neuropathy (PIPN), a common side effect of this anti-cancer drug, causes chronic pain reflecting the molecular changes in the dorsal root ganglion (DRG) of the sciatic nerve (SN). While the subcellular localization and spatio-temporal control of mRNA translation are critical to nerve function, little is known about the transcriptional landscapes of DRG and SN in PIPN. Aim: Transcriptome-wide assessment of Ptx-induced changes in gene expression and mRNA distribution in DRG or SN. Methods: Gene expression microarray analysis of the subcellular transcriptomes of DRG and SN in normal and PIPN mice with Transcriptome Analysis Console followed by analysis with 11 pathway databases. Validation of selected results in cultured cells and animal tissues. Results: In normal mice, transcripts were differentially distributed in DRG and SN. In PIPN, both the gene expression profile and the distribution of the transcripts between DRG and SN were changed compared to normal controls. Functional analysis of gene clusters confirmed changes in pathways known to be affected by Ptx including including cytoskeleton remodeling, cell cycle regulation, immune response and neuronal transmission, as well as less studied pathways such as fatty acid metabolism, Rho GTPases in Wnt signaling, G-protein signal transduction, mRNA splicing and editing. Although the expression and function of cytoskeleton genes is known to be disturbed by Ptx, we found actins, actinins and non-muscle myosins (actomyosin contractility cluster) to be overexpressed by Ptx and accumulated specifically in the SN. For instance, in PIPN, the normalized ratio of SN/DRG mRNA levels for Myh7, Myh2, Actn2, Acta2 and Actb was 32.4, 24.5, 21.9, 3.6 and 3.3 respectively. We also identified transcripts overexpressed and accumulated in PIPN DRGs, with the highest DRG/SN mRNA ratios found for ion channels (ratios in parentheses) SN10a, Kcnd1, Atp1a3, Kcnip3, SN11a, (10.3-21.2); neurotransmitter regulators Syt1, Gabbr2 (14.4, 13.2); fatty acid regulators: Fabp4, Adipoq (22.9, 4.8), some tubulins: Tubb3, Tubb4a, Tubb4b (9.15, 5.5, 2.0) as well as GPCR regulating proteins: Rasgrp1, Gnal, Olfr1098 (16.7, 7.6, 2.0). Furthermore, the Wikipathways integrated with the Transcriptome Analysis Console revealed that GPCRs were the most significantly altered class of genes, predominantly downregulated by Ptx compared to Naive samples in the DRG (320 downregulated, 88 upregulated) and in the SN (469 downregulated, 74 upregulated). In contrast, the comparison of control Naive samples in the DRG versus SN showed minimal changes (21 downregulated, 5 upregulated). These changes were statistically significant with a p-value < 0.001 and a fold change of -2 > FC > 2. Conclusion: Our results show that Ptx not only affects the gene expression but also the subcellular localization of transcripts kept in DRG bodies or over-transported to distal parts of Sciatic Nerve along the longest axon of the body. Cargo trafficking including RNA shuttles among nucleus- cytoplasm-axon terminal of nerves might be one of the most critical processes impaired in PIPN. These results might be used in the future to develop a potential therapeutic strategy focusing on normalization of axon cargo trafficking and PIPN prevention.
