Characterization of miRNA editing during cortical development. A. Cumulative counts (TPM) of editing at each position of all mature miRNA sequences at different developmental stages. The editing events were enriched at “seed” sequence (position 2 to 8) and flanking region (position 12 to 15) of miRNAs. B. Summary of miRNA editing at different stages detected by deep-sequencing. There are more edited miRNAs and modified positions at P28 than other stages. The number of highly edited miRNAs (TPM > 50) gradually elevated during development. C-D: The percentage of total edited miRNA reads among total miRNA reads was much higher after P7 than earlier stages (C). Similar tendency was also observed for miRNAs of high editing events (>50 TPM) (D). E. Developmental changes of the expression of wild type (WT) and “A” to “I” edited miRNA-376b at position 6 (A/G: 6). The level of edited form exceeded that of WT from P7. F. Summary of biological processes that may be regulated by WT and edited (A/G:6) miRNA-376b. All target genes of the wild type and edited miRNAs were predicted by TargetScan and statistically over-represented GO annotations were included (P < 0.01). Note that GO terms of WT are those involved in early development of cortex. Those GO terms unique to edited miRNA targets are associated with establishment and maintenance of neural circuitry. G. Validation of “A” to “I” editing of miRNA-376b at position 6. RNAs from P7 rat cortex were reverse transcribed and then amplified by PCR. The PCR product was sequenced. A heterozygous change A-G was detected at position 6 (arrow).