Next, the iMGL transcriptome was profiled in comparison to human primary fetal microglia (Fetal MG) and adult microglia (Adult MG). CD14+/CD16− monocytes (CD14 M), CD14+/CD16+ inflammatory monocytes (CD16 M), myeloid dendritic cells (Blood DCs), iHPCs, and iPSCs were also examined to compare iMGLs to stem cells and other myeloid molecular signatures. Correlational analysis and Principal Component Analysis (PCA) revealed striking similarity of iMGLs (blue) to Fetal MG (orange) and Adult MG (green) (Figures 2A and S3A). Furthermore, the first principal component PC1 (21.3 % variance, Figure 2A arrows) defines the differentiation time-series from iPSC through iHPC to our iMGL cells while PC2 and PC3 define the dendritic and monocyte trajectories, respectively. Biclustering analysis using 300 microglial, macrophage, and other immune related genes adapted from previous studies (Butovsky et al., 2014; Hickman et al., 2013; Zhang et al., 2014) identified similarities between groups and highlighted common gene clusters, but also uncovered differences between all groups. Again, this analysis showed that iMGLs cluster with microglia, but are distinct from other myeloid cells, iHPCs and iPSCs (Figure 2B).
