Fig. 3. In vivo Sema3A silencing in motoneurons alters motor axon tracts. (A) In toto NgCAM immunostaining (lateral view) on pShSema3A-EGFP embryo showing the reduction of MMC axon length (bracket) and ventral nerve thickness (arrowheads) on the electroporated side compared with the control side. (B) Horizontal cross sections at the cervical-brachial level of spinal nerves labeled with NF160kD or NgCAM from pShSema3A-EGFP or pShScramble-EGFP embryos. (C) Histogram of normalized spinal nerve thickness in control and pShSema3A-EGFP HH25 embryos (spinal nerve sections from three pShScramble-EGFP embryos and eight pShSema3A-EGFP embryos; ^*, P<0.0001 with Mann-Whitney test). (D) Transverse sections at the cervical-brachial level of pShSema3A-EGFP and pShScramble-EGFP HH24 embryos stained with NF160kD. (E) Histogram of the ratio of the length of EGFP⁺ fibers to NF⁺ fibers within the dorsal ramus, as illustrated (dorsal rami from five pShScramble-EGFP and seven pShSema3A-EGFP embryos; ^*, P<0.0001 with Mann-Whitney test). (F) Histogram of the length of NF⁺/EGFP^- fibers of dorsal rami in pShScramble and pShSema3A conditions (arbitrary units). Error bars indicate s.e.m. Scale bars: 100 µm.