Fig. 2. Reduction of Λ-profile formation in hippocampal boutons lacking β-actin.

a Sampled EM images showing the flat membrane, Λ-shape, and Ω-shape membrane at hippocampal boutons. The tip of Λ-shape profile could be either pointed or dome-like. b The number of Λ per bouton before (R) and after KCl application in wildtype (WT) or TM4d-Actb^−/− synapses (mean + SEM; each group was from 40–100 synaptic profiles from 5–7 cultures; each culture was from 4–6 mice). p values are 0.678, 0.001, 4.04 × 10⁻⁸, and 3.87 × 10⁻⁹ for R, K⁺, 3 min and 10 min group, respectively (***p < 0.001; **p < 0.01; *p < 0.05, two-tailed unpaired t-test, compared to WT). A schematic showing stimulation and culture fixation time is also shown (lower): EM images were obtained from four conditions in which chemical fixation was applied in the resting condition (R), immediately after 1.5 min application of 90 mM KCl (K⁺), 3 min or 10 min after KCl application. c The number of Ω per bouton before (R) and after KCl application in wildtype (WT) or TM4d-Actb^−/− synapses (mean + SEM; each group was from 40–100 synaptic profiles from 3–8 cultures; each culture was from 4–6 mice). p values are 0.298, 0.465, 0.002, and 0.006 (two-tailed unpaired t-test, compared to WT) for R, K⁺, 3 min and 10 min group, respectively. Source data are provided as a Source Data file.