Investigating Post-transcriptional Mechanism of Neuropathic Pain

Neuropathic pain is a chronic condition which can arise following damage to the somatosensory system and often involves both hyperalgesia and allodynia. The molecular mechanisms of neuropathic pain remain incompletely understood but require enduring alterations in specific gene programs and protein synthesis affecting neuronal signaling and excitability. We investigate non-coding RNA and RNA-binding protein regulatory pathways in impacting hyperalgesia and neuropathic pain using the mouse spared nerve injury model. Nerve injury alters the expression of many miRNAs, including the highly conserved let-7 family miRNAs, which repress pro-growth mRNAs and are implicated in axon growth, neuronal plasticity, and brain circuit development. The Lin28 RNA binding protein can prevent maturation of let-7 precursor RNAs; consequently, increased Lin28 signaling promotes pro-growth gene expression. The regulation and potential roles of Lin28/let-7 pathway in neuropathic pain remain largely unexplored. In preliminary data, we find that Lin28a loss of function in some, but not other, sensory neuron populations can result in a deficit in mechanical hypersensitivity post-injury. In the SNI mouse model, we evaluate molecular mechanisms underlying pain using single molecule detection. A specific RNA imaging assay, RNAscope in situ hybridization (ISH), is used to amplify single RNA target signals in fixed tissues to allow mapping of the spatiotemporal patterns and cell type specificity of changes. We find that Lin28 mRNAs are elevated in classes of injured neurons relative to uninjured neurons in dorsal route ganglia (DRG) which are ipsilateral at early, 3 day, timepoints post-SNI surgery. In contrast, Lin28 mRNAs are highly elevated following a more protracted time courses post-surgery in the compartment of injured neuronal processes. The spatiotemporal differences in Lin28 mRNA levels across compartments of the nervous system following nerve injury could indicate potential trafficking or local stabilization of Lin28 mRNAs and are the subject of ongoing investigations. Grant support from NIH NS103974.