Figure 1.

Expression of semaphorin receptors Npn-1 and Npn-2, and Plexin-A1, -A2, and -A4 by motor neurons in the chick embryo spinal cord. In situ hybridisations on transverse cryosections (20 μm) of chick embryo spinal cord (hindlimb level) from (b-f) HH stage 20 and (h-l) HH stage 23, show that Npn-1 (b,h), Npn-2 (c,i) and Plexin-A1 (d,j), Plexin-A2 (e,k), and Plexin-A4 (f,l) are all expressed by motor neurons. (a,g) Comparable sections from the same stage embryos immunolabelled with the motor neuron specific antibodies MNR2/islet2 (red) and counterstained with neurofilament antibody (NF; green). Bars = 50 μm.