Targeting β-actin and GAP-43 mRNAs into axons using the STAT3α 3′UTR selectively modulates axonal growth phenotypes. Targeting β-actin and GAP-43 mRNAs into axons using the STAT3α 3′UTR selectively modulates axonal growth phenotypes. A, Representative images of naive DRG neurons cotransfected with GFP and mCherry, cell body-restricted β-actin · mCh-3′Stat3αshort or GAP43 · mCh-3′Stat3αshort, or axonally localizing β-actin · mCh-3′Stat3αlong or GAP43 · mCh-3′Stat3αlong constructs are shown. NF + P immunostaining is shown in A, and mCherry signal for the cell bodies is shown in the insets. Neurons expressing the axonally targeted GAP43 · mCh-3′Stat3αlong mRNA require montage images to capture full axon projection. Scale bar, 100 μm. B, Representative high-magnification images for GFP (green) and NF + P signals (blue) along mid-axon shaft for neurons transfected as in A are shown. Scale bar, 10 μm. C–E, Quantification of indicated growth parameters for neurons transfected as in A are shown. There is a significant increase in axon length with transfection of axonally targeted GAP43 · mCh-3′Stat3αlong transfection compared with mCherry, GAP43 · mCh-3′Stat3αshort, β-actin · mCh-3′Stat3αlong, and β-actin · mCh-3′Stat3αshort transfections (C). Axon branching (D) and filopodia (E) are significantly increased with expression of β-actin · mCh-3′Stat3αlong transfection compared with mCherry, GAP43 · mCh-3′Stat3αshort, GAP43 · mCh-3′Stat3αlong, and β-actin · mCh-3′Stat3αshort transfections (*p ≤ 0.05 for indicated value vs mCherry and GAP43 · mCh-3′γ-actin by student's t test). Christopher J. Donnelly et al. J. Neurosci. 2013;33:3311-3322 ©2013 by Society for Neuroscience