Expression and Manipulation of the APC-\u03b2-Catenin Pathway During Peripheral Neuron Regeneration

Arul Duraikannu,Douglas W Zochodne,Ambika Chandrasekhar,Jose A Martinez

doi:10.1038/s41598-018-31167-1

Abstract

Molecules and pathways that suppress growth are expressed in postmitotic neurons, a potential advantage in mature neural networks, but a liability during regeneration. In this work, we probed the APC (adenomatous polyposis coli)-β-catenin partner pathway in adult peripheral sensory neurons during regeneration. APC had robust expression in the cytoplasm and perinuclear region of adult DRG sensory neurons both before and after axotomy injury. β-catenin was expressed in neuronal nuclei, neuronal cytoplasm and also in perineuronal satellite cells. In injured dorsal root ganglia (DRG) sensory neurons and their axons, we observed paradoxical APC upregulation, despite its role as an inhibitor of growth whereas β-catenin was downregulated. Inhibition of APC in adult sensory neurons and activation of β-catenin, LEF/TCF transcriptional factors were associated with increased neuronal plasticity in vitro. Local knockdown of APC, at the site of sciatic nerve crush injury enhanced evidence for electrophysiological, behavioural and structural regeneration in vivo. This was accompanied by upregulation of β-catenin. Collectively, the APC-β-catenin-LEF/TCF transcriptional pathway impacts intrinsic mechanisms of axonal regeneration and neuronal plasticity after injury, offering new options for addressing axon regeneration.

Highlights

Manipulating the intrinsic properties of neurons and providing them with an accelerated growth pattern at the outset of regeneration is a newer approach toward improving these outcomes
To examine the distribution of adenomatous polyposis coli (APC) protein in normal or injured nerve tissue, we examined transverse cryosections of immunostained dorsal root ganglia (DRG) and sciatic nerves coupled with Western immunoblotting
APC immunostaining was present in normal DRG sensory neurons, colabelling with neurofilament 200 (NF200) (Fig. 1C,D) and spinal motor neurons (Supplemental Fig. 1)

Summary

Introduction

Manipulating the intrinsic properties of neurons and providing them with an accelerated growth pattern at the outset of regeneration is a newer approach toward improving these outcomes. The Wnt signaling pathway, widely expressed, is of importance in peripheral and central neurons[3] It has, for example, been linked to neurogenesis, neuron positioning, axon and dendrite development, synaptogenesis and myelin compaction[4,5]. Additional, roles of Wnt signaling have been identified in axon guidance of corticospinal tract (CST) axons[6] and in neuroprotection and regeneration after optic nerve injury[7] Specific molecules within this pathway include the tumor suppressor gene adenomatous polyposis coli (APC), frequently mutated in colorectal cancer[8]. Conditional ablation of β-catenin in neural stem cells and their progeny impair dentate gyrus neurogenesis[15,16] In later stages it has roles in the mature central nervous system, including regulation of the neuronal cytoskeleton and synaptic differentiation[13], axon guidance and neuronal cell survival. Roles identified to date include cell cycle control of neuronal PC12 (pheochromocytoma) cells[25], apoptosis of neural crest cells[26], neurite formation[25], and receptor accumulation in synapses[27]

Methods

Results

Conclusion