Disrupting β1-integrin clustering impedes BDNF-dependent axon outgrowth. (A) Axon growth assays with BDNF (50 ng/mL) or L-t-LacCer (20 μM) plus BDNF treatments demonstrating representative growth rates during a 60-min period. Scale bar, 10 μm. (B) Quantification of the axon growth rates of vehicle (BSA), BDNF, L-t-LacCer alone, L-t-LacCer plus BDNF, D-e-LacCer (20 μM), D-e-LacCer plus BDNF, β1-integrin function blocking antibody 2999 (Fxn Blk Ab; 5 μg/mL) alone and plus BDNF, control antibody (Control Ab, 5 μg/mL) and Control Ab plus BDNF treatments. Data are the mean ± standard error of the mean. (n > 150, **p < 0.001, ANOVA with Tukey's post hoc analysis). BDNF: brain-derived neurotrophic factor; BSA: bovine serum albumin; D-e-LacCer: D-lactosyl-β1-1'-N-octanoyl-D-erythro-sphingosine; L-t-LacCer: β-D-lactosyl-N-octanoyl-L-threo-sphingosine.