(A) Enrichment of specific mRNAs in FMRP-immunoprecipitates from wild-type mouse brain extracts relative to those derived from FMR1 KO mice (age 3 months) measured by RT-qPCR. RNA-samples are identical to those used in Figure 1. Statistical analysis by Student’s t-test: ** p < 0.01, ** p < 0.001. n = 6 immunoprecipitations from individual mice each group. (B) Enrichment of rat mRNAs in FMRP-immunoprecipitates from wild-type rat brain mixed with FMR1 KO mouse brain during homogenization.indicates in vivo interaction of FMRP with specific mRNAs (see text). Statistical analysis using Fisher’s exact test ** p < 0.01, *** p < 0.001. n = 29 to 45. Dashed line indicates the frequency (~17%) of rat cDNAs in the input material averaged among all tested genes. See also Supplemental Figure S7. (C, D) Hippocampal neurons (DIV4+3) were cotransfected with FF-luc 3’UTR reporters for the indicated NMDA receptor subunits as well as RR-luc and shRNA constructs targeting ZnT3, FMRP, AGO1 or EGFP (see Supplemental Figure S3). Graphs indicate expression of the reporter constructs normalized to the effect of each shRNA on a control FF-luc construct. Statistical analysis: (C) One-way ANOVA with Dunnett’s post test: * p < 0.05, ** p < 0.01. n = 24 to 72. (D) Student’s test comparing the response of both NR2A reporter variants: * p < 0.05, ** p < 0.01, *** p < 0.001. n = 18. See also Supplemental Figures S6, S7 and S8.