NPC2 and breast cancer: Based on transcriptional and epigenetic levels of their respective DEGs in the other NPC subpopulations and related enriched functions, we identified NPC4, which exhibited high specific expression of POU4F2, GAP43 and SNCG, as the RGC lineage precursors, NPC2 with highly specific expression of TFAP2C, PTF1A, and PRDM13 as HC/AC lineage precursors, and the remaining NPC subclusters (NPC1, 5, 6, and 7) with highly specific expression of OTX2, RXRG, and other related genes as BC/PH lineage precursors (Figure 5B; Figures S7E and S8A, Supporting Information).