Fig. 5: ErbB4–Slitrk3 interaction is important for inhibitory synapse formation and transmission.

A–C ErbB4-ΔRLD-expressing HEK293T cells could not induce gephyrin puncta. HEK293T cells expressing K751M, ΔRLD, or empty vector (Mock) were co-cultured with hippocampal neurons (DIV9) and stained for MAP2 and gephyrin. Scale bar, 10 μm (A). Quantitative analysis of the intensity (B) and size (C) of gephyrin puncta in A. n = 30 cells for Mock, n = 19 cells for K751M, and n = 23 cells for ΔRLD. D–G Perisomatic gephyrin puncta number and size were decreased in primary hippocampal neurons infected with RLD-expressing virus. Schematic of lentivirus vector expressing Flag-RLD-IgG and experimental timeline (D). Hippocampal neurons at DIV2 were infected with the virus expressing RLD or empty vector (Control) for 10 days and then fixed and stained with gephyrin and GFP antibodies. Representative images of gephyrin+ inhibitory synapses onto perisoma of cultured PyNs (E). Scale bar, 20 μm. Quantitative analysis of perisomatic gephyrin puncta number (F) and size (G) in E. n = 30 neurons for Control, n = 30 neurons for RLD. H–J AIS gephyrin puncta number and size were decreased in primary hippocampal neurons infected with RLD-expressing virus. Representative images of gephyrin+ AIS inhibitory synapses of cultured PyNs. Boxed areas were enlarged in the respective right images (H). Scale bar, 20 μm for lower magnification images and 10 μm for enlarged images of boxed areas. Quantitative analysis of perisomatic gephyrin puncta number (I) and size (J) in H. n = 24 neurons for Control, n = 24 neurons for RLD. K–Q RLD injection decreased inhibitory synaptic transmission in hippocampal CA1 PyNs. Schematics of whole-cell patch-clamp recordings of PyNs in CA1 from IgG or RLD-IgG-injected K751M mice (K). Representative traces of sIPSCs (L) and mIPSCs (O). Scale bars, 15 pA, 2 s. Cumulative probability plots and histogram summary of sIPSCs and mIPSCs interevent intervals (M, P), as well as amplitudes (N, Q). n = 10 neurons from three IgG-injected mice and n = 9 neurons from three RLD-IgG-injected mice. Data were shown as mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001. Student’s t test.