, 2000). We observed clear differences between wild-type and knockout mice 6 days after crush injury in distal segments of the nerve. CB-839 order Wild-type nerve revealed robust

axonal YFP at 2 mm distal to the crush site, while the signal in knockout nerve was much reduced (Figures 7D and 7E). Thus, both behavioral and histological parameters show delayed regeneration of sensory neurons that specifically lack Importin β1 in the axonal compartment. Our results reveal a central role for locally translated Importin β1 in retrograde axonal signaling after nerve injury. The cell body response to axonal injury in sensory neurons is dependent on the transport of injury signals from lesion site to soma (Rishal and Fainzilber, 2010). Three different types of signaling modalities have been suggested to act in this pathway, including growth factor and receptor complexes (Brock et al., 2010), jun kinase and associated molecules together with the adaptor Sunday Driver ( Cavalli et al., 2005), and importin-dependent signals ( Rishal and Fainzilber, 2010). The complexity and robustness of this system was recently emphasized by a study implicating

approximately hundreds of signaling proteins and thousands of genes in the retrograde injury response in rat sciatic nerve ( Michaelevski et al., 2010). The fact that axonal loss of Importin β1 affects over 60% of the genes activated in the cell body response to injury is striking and supports find more a major role for importin-dependent

transport in the injury response mechanism, as is indeed reflected in the delayed recovery from peripheral nerve lesion seen in the knockout mice. Although injury-regulated expression of the affected genes and Idoxuridine subsequent regeneration are not completely repressed in the Importin β1 long 3′ UTR knockout, the largely attenuated gene regulation and delayed functional recovery we observe most likely reflects the fact that cargo proteins can still bind Importin αs at lower affinity in the absence of Importin β1 ( Lott and Cingolani, 2011). Partial redundancy of multiple retrograde signaling pathways might also play a role ( Abe and Cavalli, 2008; Ibanez, 2007; Michaelevski et al., 2010), and the fact that approximately one-third of the injury-responsive transcripts in our arrays were regulated similarly in wild-type and knockout animals highlights the participation of both Importin β1-dependent and -independent pathways in retrograde injury signaling. Local protein synthesis in axons has been proposed as a critical aspect of importin-dependent retrograde injury signaling. At least four components or regulators of the complex are thought to be locally translated in axons, including Importin β1 itself (Hanz et al.