FIG. 6.

Reelin-stimulated neurite elongation and branching requires SRF. (A) WT hippocampal neurons derived from P1-to-P3 pups were stained for F-actin (red) and βIII-tubulin (green). Neurons were incubated with control (ctr.) supernatant derived from GFP-expressing HEK293 cells. (B) Srf mutant neurons—in the presence of control supernatant—are, compared to control-treated WT neurons (A), shorter and contain fewer branches. (C) Addition of reelin to WT neurons increases the average neurite length and number of branches (see quantification in panels E and F). (D) In SRF-deficient cultures, exogenous reelin fails to elevate the neurite length and branch number, indicating that reelin signaling requires SRF activity to modulate neuron morphology. (E and F) Quantification of the average neurite length (E) and the average number of branches per neuron (F) under the various conditions. Scale bars in panels A to D, 50 μm.