shHDAC6 strongly reduces neurite outgrowth in SH-SY5Y cells. Parental SH-SY5Y cells were left untreated (Ctrl) or treated with 0.2 or 1.5 × 105 TU of lentiviral particles encoding for shRNA against HDAC6 (shHDAC6). TDP-43 silenced shTDP cells were included for comparison (B). A and B, Western blots show the protein levels of HDAC6 (upper panel) and TDP-43 (middle panel). GAPDH was used as a loading control. C, shown are representative images of cells that were treated with the neurite outgrowth protocol indicated in Figure 1B and stained with Alexa568-phalloidin (red). Nuclei were counterstained with Hoechst (blue). D, cells were exposed to RA for 4d, fixed and labeled with Alexa568-phalloidin (red) and anti-HDAC6 (green). Nuclei were counterstained with Hoechst (blue). Scale bars correspond to 20 μm.