SkinChronicles, No 13, May 2026, by Joseph Inns

Studies into hair follicle stem cells (HFSC) have been dominated by transcription factor and signalling gradient frameworks to explain how the bulge compartment is specified. Peters and colleagues make a case for exploring membrane lipid composition to better understand how HFSC fate is determined.

They use epidermis specific deletion of ceramide synthase 4 (CerS4), an enzyme which produces long chain ceramides, sphingolipids with important barrier functions. By leveraging parallel transcriptomics, proteomics and lipidomics of FACS purified CD34+ HFSCs they reveal the molecular consequences of CerS4 loss across these regulatory layers. They identified a coherent shift in long chain ceramides, Wnt pathway activity and stem cell marker expression that no single modality would have resolved alone. Loss of these lipids rerouted HFSC precursors into upper hair follicle and inner bulge fates through hyperactivation of non-canonical Wnt signalling. This example of multi-omics integration demonstrates how complementary methodologies can reveal biological shifts that may otherwise remain hidden.

They note a resemblance to atopic dermatitis in the CerS4 epidermis depletion model, with disrupted hair follicle architecture and barrier function leading to a Th2 immune signature. The authors explain how ceramide production is an important element in atopic dermatitis, but the findings also have relevance for the broader hair follicle development field and may help us understand monogenic skin conditions such as Ichthyosis where the skin barrier is altered and tumour syndromes which are thought to arise from the HFSC compartment. The skin barrier is written in lipids and proteins, not just in RNA.

Highlighted paper: Thompson, S.M., Yaple, V.S., Searle, G.H. et al. Rete ridges form via evolutionarily distinct mechanisms in mammalian skin. Nature 651, 135–145 (2026). https://doi.org/10.1038/s41586-025-10055-5