2.6.6.ScRNA-seq data pre-processing
The single cell transcriptomic data of the 9 samples of human embryonic tooth germ including incisors and molars from PCW12 to PCW18 were acquired from the GEO database (GSE184749). The quality control screening was used for low-quality cells filtration (≤200 genes or ≥20,000 genes, >10% mitochondrial genes). In total, 23530 cells were adopted for further analyses. PCA was performed for normalization based on the top 2000 highly variable genes, then R package harmony was applied to correct the batch effect. UMAP method was applied for dimensional reduction.