c-JUN REPROGRAMS SCHWANN CELLS OF INJURED NERVES TO GENERATE A REPAIR CELL ESSENTIAL FOR REGENERATION

The striking PNS regenerative response to injury rests on the plasticity of adult Schwann cells and their ability to transit between differentiation states, a highly unusual feature in mammals. Using mice with inactivation of Schwann cell c-Jun, we show that the injury response involves c-Jun dependent natural reprograming of differentiated cells to generate a distinct Schwann cell state specialized to promote regeneration. Transected distal stumps of c-Jun mutants show 172 disregulated genes, resulting in abnormal expression of growth factors, adhesion molecules and cytoskeletal changes that lead to neuronal death, inhibition of axon growth and striking failures of functional repair after injury. These observations provide a molecular basis for understanding Schwann cell plasticity and nerve regeneration. They offer conclusive support for the notion that Schwann cells control repair in the PNS, using dedicated transcriptional controls to generate a distinct repair cell, a transition that shows similarities to transdifferentiation seen in other systems. Total RNA was purified from a 10mm segment of the distal stump and uninjured contralateral nerve from c-Jun mutants and control mice 7 days after nerve cut. For each condition (injured/uninjured) and genotype (control/ knock-out) 2 independent samples (replicates) were generated from pooled nerves of 4/6 mice resulting in a total of 8 samples: CTRL.cut.R1, CTRL.cut.R2, CTRL.uncut.R1, CTRL.uncut.R2, KO.cut.R1, KO.cut.R2, KO.uncut.R1,KO.uncut.R2.