Figure 5.

eda regulates scale-forming cell (SFC) differentiation via transcriptional regulation of basal epidermal Fgf ligands.

(A) Wild-type dermal and basal epidermal cells plotted in UMAP space and colored by whether they are expressing eda, edar, or shha (shha+ cells also include cells expressing both edar and shha). (B) Wild-type and Eda mutant basal cells plotted in UMAP space and colored by the expression of the signature score of Fgf ligands that are specifically expressed in basal cells (fgf24, fgf20a, fgf20b; specificity score >0.1). (C) Percent of cells expressing the Fgf ligand signature between wild-type and Eda mutant basal cells (error bars estimated via bootstrapping [n = 100]). (D) Scales and dermis visualized in sp7:EGFP; ET37:EGFP double transgenics (green). Heat-shocked control eda^+/- larvae developed well-patterned, uniformly shaped scales (n = 6), whereas heat-shocked control eda^-/- larvae developed no scales (n = 6). Mosaic heat-shock induction of Fgf20a, stringently selected for expression in epidermal cells (magenta) caused mis-patterned and dysmorphic scales to grow in wild-type eda^+/- larvae (n = 25 epidermal clones in six fish) and rescued scale formation in eda^-/- larvae (n = 36 epidermal clones in six fish). Scale bar, 500 μm (D).