Fig. 6
Pin1 KO Leads to Developmental Axon Growth Defects in the Peripheral Nervous System and CNS (A-H) Axons of the cranial and spinal nerves are less extensive and complex in Pin1 KO embryos. The cranial (A-D) and spinal (E-F) nerves were analyzed in E12.5 Pin1 WT (A, C, E, and G) and KO (B, D, F, and H) embryos by whole-mount immunohistochemistry for neurofilaments. In Pin1 KO embryos, stunted neurite processes are found in the ophthalmic branch of the trigeminal nerve (B and D, arrows) and in the lateral branches of the cervical spinal nerves (F and H, arrows). (I-M) Entorhino-hippocampal perforant projections are significantly shorter in Pin1 KO embryos at E15.5. Horizontal sections of E15.5 embryos were stained for neurofilament light subunit (NF-L) (green) to trace growth of entorhinal perforant projections toward the stratum lacunosum-moleculare (s.l-m) of the hippocampus proper in Pin1+/- (I) and KO (J) mice. The dashed lines indicate borders of the developing dentate gyrus. (K and L) Pin1 KO shorter perforant projections are associated with reduced CRMP2A level (red) in growth cones, as indicated by arrows. (M) Schematic drawing of the entorhino-hippocampal perforant pathway at E15.5 in the presence or absence of Pin1 as shown in (I)-(L). CP, cortical plate; EC, entorhinal cortex; DG, dentate gyrus; CA1, CA3, hippocampal regions. (N and O) Developmental defects are corrected later during development of Pin1 KO mice. Entorhinal perforant projections are detected in s.l-m of both Pin1 WT (N, arrow) and KO (O, arrow) newborn mice. Lower levels of CRMP2A are present in perforant projections in s.l-m in Pin1 KO mice (O). Scale bars represent 100 µm (I, J, N, and O) and 50 ¼m (K and L). See also Figure S5. |