To determine genes associated with specific phases of SST cell maturation, we performed differential expression (DEX) analysis of SST-expressing clusters using the R package limma (Ritchie et al., 2015). At D54, four clusters of SST+ cells were present, two of which were CORT+ (Figure 4,5). Cortistatin (CORT), a neuropeptide expressed by a subset of cortical interneurons, was previously implicated in regulation of slow-wave sleep (de Lecea et al., 1997). The CORT+ clusters (nCTX.54.CORT, nCTX.54.CORT/NEFL) appeared more mature than the CORT− clusters (nCTX.54.SST, nCTX.54.SST/GRIA2), due to CXCR4 expression in the latter, and increased expression of GRIA2, SATB1 and MEF2C in the former (Figure 4A, 5C). We looked for differentially expressed genes across these clusters to determine the signatures of SST cell maturation. We identified 2304 DEX genes (FDR < 0.05), with the majority (90%) upregulated in the CORT+ populations (see Table S3 for complete list of differentially expressed genes). We plotted the top 50 DEX genes ranked by test significance (Figure 6A), and the 29 genes enriched in maturing SST cells includes a number of genes implicated in migration (DAB1, CNTNAP2,
