# CD271 orchestrates skin structure, differentiation, and inflammation via PI3K/Akt and PKCα/ERK pathways

## TL;DR

The study shows that CD271 regulates skin structure and inflammation through specific signaling pathways, and its absence leads to skin abnormalities and immune responses.

## Contribution

The paper introduces two novel mouse models to study CD271's role in skin biology and disease.

## Key findings

- CD271 deletion in keratinocytes causes epidermal hyperproliferation and delayed differentiation.
- KO skin shows increased inflammatory cytokines and immune cell recruitment.
- CD271 regulates skin homeostasis via PI3K/Akt and PKCα/ERK pathways.

## Abstract

The involvement of the neurotrophin network in pathological skin conditions, such as psoriasis or squamous cancer, by their common neurotrophin receptor CD271 has become recently evident. Depending on the specific ligand and co-receptor interacting with it, CD271 mediates various cellular responses in keratinocytes. In vitro analysis shows that it is implicated in the transition from human interfollicular keratinocyte stem cells to transient amplifying cells. However, no in vivo models are available to dissect the complexity of these mechanisms, including the effect on the inflammatory response. Here, we develop and characterize two novel mouse models, the CD271cKO and the CD271ciKO, where CD271 is conditionally absent in keratinocytes during development or after topical induction, respectively. By histology, functional assay, transcriptomics and molecular analysis, we identified substantial skin changes correlated to CD271 deletion, including epidermal hyperproliferation, “activated” keratinocyte signature, and a delayed in the differentiation process, mostly linked to PI3K/Akt and mitogenic pathways-dependent processes. KO keratinocyte displays upregulation of Ki67, PCNA, KRT5, KRT6, and ERK phosphorylation, as well as major expression of IL1α, Cxcl15, and TGFβ. KO skin resemble dysplastic skin conditions, including the recruitment of immune cells, particularly T cells, macrophages, and neutrophils, and release of inflammatory cytokines involved in TNF, JAK/Stat, IL17, and PI3k/Akt signaling pathways. Overall, our data defines CD271 as a crucial regulator of skin homeostasis. Therefore, our models represent an exceptionally useful tool for the characterization of skin pathophysiology linked to CD271 and possibly for developing appropriate therapies.