Antibodies against F-spondin inhibit sensory neurite outgrowth on F-spondin–His. F-spondin–His protein (A) and the reelin–His domain protein (A′) were obtained from affinity-purified medium from transfected HEK 293 cells. A single band is observed in a SDS-PAGE gel stained with Coomassie blue (right lane); size markers are shown on the left lane. B, Outgrowth on F-spondin–His. C, Outgrowth on F-spondin–His with R5 IgG. D, Outgrowth on F-spondin–His with R2 IgG.B, C, and D are fluorescence images;B′, C′, and D′ are phase-contrast images.E, Outgrowth on F-spondin–His, BSA, and OVO.F, Outgrowth on laminin and laminin with R5 IgG.G, Outgrowth on F-spondin–His and F-spondin with R5 IgG. H, Outgrowth on F-spondin–His and F-spondin with R2 IgG. Neurite outgrowth on F-spondin–His, laminin, BSA, and ovomucoid substrates: Single neurons isolated from E14 rat dorsal root ganglia were plated on the indicated substrates, cultured for 14 hr, and then fixed and labeled with mAb 3A10. Anti-F-spondin Abs were added: R5 (C, F, G) and R2 (D, H) at the time of plating. For each 3A10-positive neuron, the neurite length was either measured or considered to be 10 μm if no neurite was seen. The percentage of neurons (ordinate) with neurites longer than a given length (in micrometers; abscissa) is plotted (E–H). Scale bar: B–D, 50 μm.