a, Quantification of the number of Homer1+/Synapsin1+ puncta in co-cultured neurons after treatment with different agents (untreated: n = 51 control, 43 PMDS cells; TSA: n = 11/12, VPA: n = 25/29, Nif: n = 9/8, IGF2: n = 31/40, IGF1: n = 35/32). b, Images of co-cultured control (green) and PMDS (red) neurons after IGF1 treatment. Scale bars = 20 (top) and 5 (bottom) μm. c, Recordings (top) and quantification of amplitude and frequency (bottom) of spontaneous EPSCs recorded in IGF1-treated cultures at −70 mV (n = 18 control and 25 PMDS cells). d, Recordings (top) and quantification of amplitudes (bottom) of evoked AMPA- (measured at the peak, Vh = −70 mV) and NMDA-EPSCs (measured 50 ms post-stimulus, Vh = +60 mV) acquired in IGF1-treated cultures (n = 14 control and 21 PMDS cells). Dashed lines represent data originally presented in . e, Images of co-cultured control (green) and PMDS (red) neurons in untreated (top) and IGF1-treated (bottom) cultures, immunostained with antibodies against GFP, mKate2, Shank3, and PSD95. Scale bars = 20 (left) and 5 (right) μm. f, Quantification of the number of Shank3+, PSD95+, and Shank3/PSD95+ puncta in co-cultured control (w/o, n = 25 cells; IGF1, 21 cells) and PMDS (w/o, n = 33 cells; IGF1, 25 cells) neurons. Values were normalized to the mean values acquired from control neurons in untreated cultures. g, Mean normalized traces (left) and quantification of the decay kinetics (right) of NMDA-EPSCs recorded from control (w/o, n = 9; IGF1, 12) and PMDS (w/o, n = 18; IGF1, 18, GFP-Shank3, 6) neurons. Data presented as means ± SEMs; *p < 0.05, **p < 0.01, ***p < 0.001, one-way ANOVA with Bonferroni’s test. h, Cartoon depicting possible mechanisms for the recovery of synaptic transmission in PMDS neurons.