Figure 1

Signalling activated through the TrkB-SHC docking site supports survival of geniculate neurons. (A) Counts of geniculate ganglion neurons in E12.5, E14.5, and P4 Trkb^S/S animals and respective control littermates (Trkb^+/+). Neuronal loss is detected already at E12.5 and increases at later stages (E12.5, Trkb^S/S 702 ± 47 (n = 3) vs. Trkb^+/+ 869 ± 51 (n = 4), P <0.01; E14.5, Trkb^S/S 398 ± 142 (n = 3) vs. Trkb^+/+ 915 ± 81 (n = 3), P <0.001; P4, Trkb^S/S 261 ± 32 (n = 2) vs. Trkb^+/+ 789 ± 38 (n = 4), P <0.001). (B) Mutation at the PLCγ-docking site does not affect geniculate neuron survival at any stage analysed (E12.5, Trkb^P/P 934 ± 75 (n = 2) vs. Trkb^W/W 936 ± 62 (n = 4), P = 0.975; E14.5, Trkb^P/P 878 ± 77 (n = 6) vs. Trkb^W/W 815.5 ± 67 (n = 3), P = 0.279; P4, Trkb^P/P 790 ± 76 (n = 3) vs. Trkb^W/W 799 ± 37 (n = 3), P = 0.852). Survival analysis of geniculate neurons from Trkb^D/D showed substantial loss already at E12.5 (E12.5, Trkb^D/D 183 ± 27 (n = 3) vs. Trkb^W/W 936 ± 62 (n = 4), P <0.001; E14.5, Trkb^D/D 84 ± 5 (n = 3) vs. Trkb^W/W 815.5 ± 67 (n = 3), P <0.001). Values shown are mean ± s.d., and the P statistic from unpaired Student’s t-tests. (C–F) Representative images of Nissl-stained sections of geniculate ganglions from Trkb^+/+_,Trkb^S/S, Trkb^W/W, and Trkb^P/P mice at P4. Scale bars 50 μm.