Extended Data Fig. 6: FateMap on treatment-naive primary human melanocytes reveals between-clone diversity.

a. (left) UMAP of all barcoded naive primary melanocyte cells. Cells are colored by clusters determined using Seurat’s FindClusters command (“Seurat clusters, resolution = 0.6”). (right) On the UMAP, we recolored each cell by its expression for a select subset of genes that were identified as differentially expressed in drug resistant cells via the Seurat pipeline. b. Six representative examples demonstrate that a clone is constrained largely in a specific transcriptional cluster such that cells within a clone are more transcriptionally similar to each other than cells in other clones. c. Average pairwise correlation between cells within a clone was estimated based on the expression levels of the top 500 most variable genes. Each point represents the average value for Spearman’s correlation coefficient for all possible pairs of cells within a clone. For each clone, a paired control was created by randomly sampling an equivalent number of cells from the whole population. Higher average correlation coefficient in clones indicates higher transcriptional similarity among cells within a clone, as compared to cells that are not clones. Wilcoxon signed rank test (paired, two-sided) was used to compare the difference in average correlation coefficient. d. UMAP of all barcoded naive primary melanocyte cells. 2,868 cells are colored by whether they are a singleton (i.e. clone size = 1). Cluster 10 is enriched for singletons and displays high expression of S100B, a marker identified to be associated with single cell colonies by FateMap. e. UMAPs of representative twin clones (sharing the same barcode) across the two splits A (2,868 cells) and B (3,333 cells). The twins largely end up with the same transcriptional fate type. This observation suggests that primary melanocyte cells derived from the same clone have similar transcriptional states and are constrained in the gene expression space.