Selective rab11 transport and the intrinsic regenerative ability of CNS axons

Abstract

Neurons lose intrinsic axon regenerative ability with maturation, but the mechanism remains unclear. Using an in-vitro laser axotomy model, we show a progressive decline in the ability of cut CNS axons to form a new growth cone and then elongate. Failure of regeneration was associated with increased retraction after axotomy. Transportation into axons becomes selective with maturation; we hypothesized that selective exclusion of molecules needed for growth may contribute to regeneration decline. With neuronal maturity rab11 vesicles (which carry many molecules involved in axon growth) became selectively targeted to the somatodendritic compartment and excluded from axons by predominant retrograde transport However, on overexpression rab11 was mistrafficked into proximal axons, and these axons showed less retraction and enhanced regeneration after axotomy. These results suggest that the decline of intrinsic axon regenerative ability is associated with selective exclusion of key molecules, and that manipulation of transport can enhance regeneration.

Functional Genome-wide Screen Identifies Pathways Restricting Central Nervous System Axonal Regeneration

“…Rab 11 has been implicated in regulating the traffic of inhibitory proteins from axons to dendrites (Koseki et al, 2017). There is a link between endoplasmic reticulum (ER) and endosome contact in mediating axonal extension (Raiborg et al, 2015).…”

PI 3-kinase delta enhances axonal PIP3 to support axon regeneration in the adult CNS

“…In this model, axon regeneration ability is progressively lost with maturity, and molecules that promote regeneration may differ from those that promote developmental outgrowth . In vitro laser axotomy was used to sever the axons of E18 cortical neurons cultured to DIV 15-18, at which stage cortical neurons have a limited capacity for regeneration Koseki et al, 2017). Expression of either p110δ or p110α H1047R led to a sharp increase in the percentage of axons regenerating after axotomy compared with GFP expressing controls (rising from 16% for control neurons to 61% for p110α H1047R expressors, and 57% for cells expressing p110δ).…”

“…Laser axotomy of cortical neurons was performed as described previously Koseki et al, 2017) Regeneration was classed as the development of a new growth cone followed by axon extension for a minimum of 50 µm.…”

“…Adult central nervous system (CNS) neurons have a weak capacity for axon regeneration, meaning that injuries in the brain, spinal cord and optic nerve have devastating consequences (Curcio and Bradke, 2018;He and Jin, 2016). In most CNS neurons, regenerative capacity declines dramatically with development, both in vitro (Goldberg et al, 2002;Koseki et al, 2017) and in vivo (Kalil and Reh, 1979;Wu et al, 2007), so that regenerative ability is lost as axons mature. Conversely, peripheral nervous system (PNS) neurons maintain regenerative potential through adult life.…”

“…Cells were transfected at 10 DIV, and experiments (imaging or axotomy) were performed between 14 and 17 DIV. Cortical neurons were transfected by oscillating nanomagnetic transfection (magnefect nano system, nanoTherics, Stoke-On-Trent, UK) as previously described(Franssen et al, 2015).hESC dopaminergic neuron culture RC17 hESC cell culture has been have been previously described in detail before(De Sousa et al, 2016;Koseki et al, 2017). Cells (RRID:CVCL_L206) were sourced from Roslin Cells, Scottish Centre for Regenerative Medicine, Edinburgh, United Kingdom.…”