Uncovering the molecular mechanisms underlying spinal cord regeneration

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About 1200 people a year are left paralysed in the UK due to a Spinal Cord Injury (or SCI). This is because injuries involving the central nervous system (CNS) have very poor capacities to regenerate, thus resulting in a permanent loss of function. However, whilst SCI can be devastating to humans the tadpole of the frog Xenopus can regenerate their CNS (spinal cord) completely following amputation or injury. Our goal is to understand how neuronal regeneration occurs in Xenopus to open new therapeutic avenues for patients suffering a SCI or peripheral neuropathies. Recently, we have identified the transcription factor Foxm1 as being specifically upregulated in the regenerating spinal cord in Xenopus (Love et al. 2011). Preliminary data indicate that knocking down foxm1 expression impairs tail re-growth upon amputation, leads to a reduction of proliferation and an increase of neuronal progenitors in the regenerating spinal cord. We have also generated a knockout of foxm1 in Xenopus using the Crispr/Cas9 technology. The first aim of this project will be to use our foxm1 knockout line to investigate further the role of Foxm1 during spinal cord regeneration. Our second aim will be to perform an RNAseq experiments to identify new genes involved in spinal cord regeneration in a Foxm1 dependent and independent manner. These datasets will allow us to start uncovering the molecular mechanisms underlying spinal cord regeneration following tail amputation in Xenopus. Since the ultimate goal of this project will be to improve our understanding of why amphibians have greater capacity for neuronal regeneration than mammals, the third aim of this project will be to compare our findings in tadpoles with those in mammals, using the sciatic nerve crush in rodents as an experimental model of nerve regeneration. It has previously been shown that Foxm1 expression is upregulated at the site of injury following sciatic nerve crush, but its role in regeneration is unknown. We will first establish which cell type(s) expressed Foxm1 (Schwann cells or axons in the nerve). We will then test if the genes we have identified as being regeneration and Foxm1 dependant in Xenopus are also upregulated upon sciatic nerve crush. Finally, we will use genetic tools such as conditional Foxm1 knock-out mice to assess its role in regeneration.Altogether, these experiments will greatly improve our understanding of the molecular mechanisms underlying neuronal regeneration. We hope that it will ultimately open new research avenues to improve neuronal regeneration in mammals and humans.