Fig. 1. PTPRT regulates synaptic formation and dendritic arborization in hippocampal neurons. (A) Tissue distribution patterns of PTPRT revealed by Western blot analysis. Monoclonal antibodies specific for PTPRT were used. Br, brain; Ht, heart; Lv, liver; Lu, lung; Kd, kidney; Ts, testis; Tm, thymus; Sp, spleen; Sm, skeletal muscle. PSD-95 and β-catenin were used as controls. (B) Developmental pattern of PTPRT in the rat brain. E, embryonic; P, postnatal days. PSD-95 was used as a control. (C, D) PTPRT co-localized to neuronal synapses stained with synaptophysin and PSD-95. Scale bar, 20 μm. (E) The number of excitatory synapses (vGLUT-positive PSD-95 clusters). Mean ± SEM. n = 30 dendrites for control, 31 for WT-RT (wild-type), and 30 for 2cs-RT (inactive). Scale bar, 10 μm. (F) The number of inhibitory synapses (vGAT-positive gephyrin clusters). Mean ± SEM. n = 27 dendrites for control, 28 for WT-RT, and 28 for 2cs-RT. Scale bar, 10 μm. (G) PTPRT knock-down of PTPRT in cultured neurons decreased the frequency, but not amplitude, of mEPSCs (n = 12 for control and n = 10 for shRNA). (H) Attenuated dendritic arborization upon knockdown of PTPRT. When rat hippocampal neurons were transfected with PTPRT-shRNA, the numbers of dendrites and arborization were decreased significantly and rescued by the addition of Resc PTPRT in this context. Mean ± SEM of data from 9 control neurons, 10 PTPRTshRNA neurons, and 9 PTPRT-shRNA + Resc PTPRT neurons are shown. Scale bar, 100 μm.