Overexpression of KLF genes in retinal ganglion cells. Rattus norvegicus

Adult mammalian CNS neurons undergo a developmental switch in intrinsic axon growth ability associated with their failure to regenerate axons after injury. Krüppel-like transcription factors (KLF) regulate intrinsic axon growth ability, but signaling regulation upstream and downstream is poorly understood. Here we find that suppressing expression of KLF9, an axon growth suppressor normally upregulated 250-fold in retinal ganglion cell (RGC) development, promotes long-distance optic nerve regeneration in vivo. We identify a novel binding partner, MAPK10/JNK3, critical for KLF9’s axon growth suppressive activity. Additionally, by screening genes regulated by KLFs in RGCs, we identify dual-specificity phosphatase 14 (Dusp14) as key to limiting axon growth and regenerative ability downstream of KLF9, associated with its dephosphorylation of MAPKs critical to neurotrophic signaling of RGC axon elongation. These results now link intrinsic and extrinsic regulation of axon growth and suggest new therapeutic strategies to promote axon regeneration in the adult CNS. Overall design: RGCs from early postnatal rats were purified and KLF9, -16, -7, and -11 genes and control, FLAG-tagged mCherry gene were transduced using lentivirus. RNA was then extracted using RNEasy (Qiagen) and processed for hybridization onto Affymetrix Rat Genome 230 2.0 Arrays.