(A) Schematic representation of the MS2 mRNA reporter with motifs inserted upstream of the sv40 3′ UTR. Green box is motif 1, blue box is motif 2, and red box is motif 3. (B) Schematic representation of the primary sequences used to test the sufficiency of the motifs in (A). Green underline is motif 1, blue underline is motif 2, and red underline is motif 3. Top to bottom correspond to fmr1, eif4ebp2, and mbpa sequences. (C) Representative images of MS2 system after motifs from the mbpa, eif4ebp2, or fmr1 3′ UTRs were inserted into the MS2 mRNA reporter. Asterisks mark cell bodies. (D) Quantification of mRNA abundance in myelin sheaths from (A–C). (E) Quantification of mRNA abundance in myelin sheaths from individual insertions of each motif. Statistical analysis evaluated with Wilcoxon test. Scale bars, 10 μm. A minimum (n) of 6 embryos and 35 sheaths were used in each condition (D and E). The underlying numerical data can be found in S1 and S4 Data. 3' UTR, 3' untranslated region.