Fig. 4: Induced GABAergic synapses mature rapidly, in parallel with glutamatergic synapses.
From: Induction of synapse formation by de novo neurotransmitter synthesis
a Experimental protocol for b–k; Ngn2-induced human neurons were additionally infected with viruses expressing V57 factors, and analyzed every 15 days starting from post-induction day 15 until day 60. b Summary graphs of Cm (left) and Rm (right) values, at different time-points of neuronal maturation. c Example images (left) and average density or size (right) of Synapsin puncta constituted on Tuj1-positive neurites, as measured from NV57 neurons at different stages of their in vitro development (see annotated). d, e Sample traces (left) and average parameters (right, event frequency or amplitude) of AMPAR-mediated sEPSCs d and GABAAR sIPSCs e recorded in the presence of PTX and CNQX, respectively, at day 15–60. f, g Stimulation-evoked EPSCs (f, with PTX) and IPSCs (g, with CNQX) recorded at indicated time-points; example traces (left), average amplitudes (middle), and percentage of cells with detectable responses (right). h, i Same as c, except for vGLUT (h) or vGAT (i) puncta formed on MAP2-positive dendritic branches. j. Representative images (left) and Mander’s coefficients (right) of co-localization between Synapsin puncta and either vGLUT or vGAT signals. Neurites were visualized by co-expression of soluble EGFP. Both vGLUT and vGAT signals individually occupy only a fraction of Synapsin-positive total synapses at day 60. k Same as j, except for co-localization between Synapsin and either Homer or Gephyrin, at day 60. All data represent means ± SEM. Summary graphs also denote the total number of field-of-views analyzed (for immunostaining) or neurons patched (for electrophysiology)/independent batches, and individual data-points (open circles). Statistical significance for normally distributed data (Skewness and Kurtosis values between −2 and 2) in panels j and k was calculated by two-tailed, unpaired, Student’s t-test, with ***P < 0.005; **P < 0.01. For all group-wise comparisons (time-course, b–i), one-way ANOVA was performed, and P-values were stated.
