Specific and redundant roles for Gli2 and Gli3 in establishing cell fate during hair follicle development
Ectodermal appendage formation requires hedgehog (HH) signal reception, its conduction through the primary cilium and activation of Gli transcription factors (TF). How HH signalling induces cell-type-specific responses through Gli TF in stem cells (SCs) and their ciliadependence remain open questions. Here, we use conditional mouse mutants to genetically dissect the roles of Gli and cilia HH mediators in the skin epithelium. Upon Gli2 depletion, hair follicle (HF) morphogenesis is delayed whereas sebaceous gland (SG) formation is enhanced, suggesting a dual role for Gli2 during appendage formation. By controlling proliferation of SG SCs, Gli2 impacts on the number and size of individual SG lobes. Whereas ablation of Gli3 shows no detectable phenotypes, HF cell fate is blocked in Gli2/3 double knockouts. In addition, loss of cilia phenocopies the loss of Gli2 but not the Gli2/3 mutants. Our study reveals that Gli3 exerts activator and cilia-independent functions in the absence of Gli2. Overall design: Epidermal whole mounts were isolated from the back skin of P2 wild-type and Gli2 epidermal knockout mice using Collagenase/DNase digestion. These epidermal whole mounts were processed into single-cell suspensions, which were subsequently used for single-cell RNA sequencing (scRNA-seq) analysis.