Fig. 6. Impaired development of dorsal forelimb nerve branches in Raldh2^L–/– embryos. (A-D) Combined immunodetection of Epha4 (green) and neurofilaments (red) on transverse sections of E11.5 embryos. (C,D) Epha4 signal alone. Insets show high magnifications of the extremities of the growing dorsal nerves. EphA4 is greatly diminished in the distal tip of the growing dorsal nerves in mutants (thin arrows). Epha4 level in the dorsal limb mesenchyme is not altered in the mutant (arrowheads). (E-H) Nerve patterns in the developing forelimb, using whole-mount anti-neurofilament IHC. (G,H) Details of the growing axons of the ramus profundus of the radialis nerve, viewed after removal of other nerve branches. The corresponding nerve from another, more severely affected mutant, is shown at the same magnification in an inset. nm, nerve medianus; nr: nerve radialis; nr(p), nr(s), profundus and superficialis ramii of the nerve radialis, respectively; nu, nerve ulnaris.