Fig. 3: Single-cell profiling reveals a transition to macrophages with a pro-inflammatory signature after UVB irradiation.

A UMAP of single cell clusters derived from WT male no-UVB (WT_Ctrl, n = 1) and WT male UVB day 5 (WT_UV, n = 1). B UMAP of all immune cells subclustered from cells shown in (A). C Cell composition of all immune cell types in WT_Ctrl and WT_UV. D Visualization of marker gene expression in macrophage subpopulations. E Pseudotime analysis of macrophage progression using Monocle 3. Starting timepoint is based on the expression of activation stage marker genes in (D). The inflammatory path and phagocytic path were determined based on the expression pattern of Pro-inflammation and Complement & Phagocytosis marker genes in (D). F UMAP of immune cells based on sample. G Volcano plot of expressed genes in all macrophages. Pro-inflammatory cytokine genes are highlighted. H Violin plots showing Ccl2 and Cxcl2 mRNA expression levels in each immune subtype in WT control and WT UVB samples. I Timeline of diphtheria toxin (DT) administration and melanocyte migration assay using Lysm-Cre; Rosa26-lsl-iDtr mice. J Representative images of Dct staining on DMSO and DT-treated mice (left), and melanocyte migration quantification (right). n = 5 for DMSO and DT group. Arrowheads mark the migrated melanocytes. * marks autofluorescence from the stratum corneum. As the control group, Lysm-Cre; Rosa26-lsl-iDtr mice were treated with DMSO. Statistics: Welch’s t test. Error bar: SEM (J). Scale bar: 100 µm.