Photomicrographs of dissociated adult wild type (A, C) and PlexinA2-/- (B,D) DRG cells immunostained for ßIII-tubulin after being cultured for 18 hours on substrates coated without (A, B) or with 300 μg Sema6A (C, D). Neurite outgrowth was quantitated for wild type and PlexinA2-/- DRGs on subtrates coated with the indicated amounts of Sema6A per well (E). Increasing the concentration of Sema6A significantly attenuated neurite outgrowth from wild type DRG cells, while PlexinA2-/- DRG cells were insensitive to Sema6A mediated inhibition (mean sem from n = 4 independent mouse cultures; * P<0.05, ANOVA). Photomicrograph of a 15 μm section of wild type DRG from an adult mouse demonstrates PlexinA2 expression by a majority of large and small diameter sensory neurons (F, G). CGRP, Calcitonin gene related peptide; IB4, Griffonia Simplicifolia I-B4. Scale bar A = 100 μm, F = 50 μm.