Axonal mRNAs: Characterisation and role in the growth and regeneration of dorsal root ganglion axons and growth cones

Abstract

We have developed a compartmentalised culture model for the purification of axonal mRNA from embryonic, neonatal and adult rat dorsal root ganglia. This mRNA was used un-amplified for RT-qPCR. We assayed for the presence of axonal mRNAs encoding molecules known to be involved in axon growth and guidance. mRNAs for beta-actin, beta-tubulin, and several molecules involved in the control of actin dynamics and signalling during axon growth were found, but mRNAs for microtubule-associated proteins, integrins and cell surface adhesion molecules were absent. Quantification of beta-actin mRNA by means of qPCR showed that the transcript is present at the same level in embryonic, newborn and adult axons. Using the photoconvertible reporter Kaede we showed that there is local translation of beta-actin in axons, the rate being increased by axotomy. Knock down of beta-actin mRNA by RNAi inhibited the regeneration of new axon growth cones after in vitro axotomy, indicating that local translation of actin-related molecules is important for successful axon regeneration.

Caltubin, a Novel Molluscan Tubulin-Interacting Protein, Promotes Axonal Growth and Attenuates Axonal Degeneration of Rodent Neurons

“…Most of the local transcripts are cytoskeletal proteins (e.g., microtubule, microfilament, and intermediate filament proteins) (Kaplan et al, 1992;Eng et al, 1999;Vogelaar et al, 2009), or proteins that regulate cytoskeletal dynamics (e.g., Rho and ␤-thymosin) Verma et al, 2005;van Kesteren et al, 2006). Stabilization and continuous restructuring of the cytoskeleton plays an important role in the processes of neurite formation and regeneration, allowing growth cone formation, vesicle accumulation, and neurite elongation (Spira et al, 2001;Witte et al, 2008).…”

“…Approximately 100 -200 local transcripts have been reported in isolated neurites of various neuronal preparations [e.g., in Aplysia sensory neurons (Moccia et al, 2003;Moroz et al, 2006), in squid axoplasm (Capano et al, 1987;Gioio et al, 1994), and in vertebrate axons (Hengst and Jaffrey, 2007;Willis et al, 2007)]. Many of the local transcripts encode cytoskeletal proteins (e.g., microtubule, microfilament, and intermediate filament proteins) (Kaplan et al, 1992;Eng et al, 1999;Vogelaar et al, 2009) Kesteren et al, 2006), suggesting that regulation of the cytoskeleton through local protein synthesis potentially serves as a conserved mechanism underlying axonal outgrowth and regeneration. Previously, we identified 15 axonally localized mRNAs in Lymnaea pedal A (PeA) neurons (van Kesteren et al, 2006).…”

Molecular and Cellular Mechanisms of Axonal Regeneration After Spinal Cord Injury

“…Local protein synthesis and mRNA localization has been closely associated with successful peripheral nerve regeneration (73). Ribosomes actively translate proteins at the peripheral injury site that both propagate signals back to the soma and supply building blocks for new growth cone formation (31, 33, 74).…”

Mammalian Target of Rapamycin (mTOR) Activation Increases Axonal Growth Capacity of Injured Peripheral Nerves

“…We examined the levels of peripherin and ␤-actin, whose translation after injury has been implicated in axon regeneration (16,34). The basal level of peripherin and ␤-actin in naive sciatic nerve were not significantly different between control and TSC2KO mice (Fig.…”