Delta-like 1-mediated cis-inhibition of Jagged1/2 signalling inhibits differentiation of human epidermal cells in culture

Victor A Negri,Fiona M Watt,Gernot Walko,Lisa M Renz,Meike E W Logtenberg,Bénédicte Oules

doi:10.1038/s41598-019-47232-2

Abstract

Epidermal homeostasis depends on a balance between self-renewal of stem cells and terminal differentiation of their progeny. Notch signalling is known to play a role in epidermal stem cell patterning and differentiation. However, the molecular mechanisms are incompletely understood. Here we demonstrate dynamic patterns of Notch ligand and receptor expression in cultured human epidermis. Notch2 and 3 act together to promote differentiation, while Notch1 decreases stem cell proliferation. The Notch ligand Jagged1 triggers differentiation when presented on an adhesive substrate or on polystyrene beads and over-rides the differentiation inhibitory effect of cell spreading. In contrast, Delta-like 1 (Dll1) overexpression abrogates the pro-differentiation effect of Jagged1 in a cell autonomous fashion. We conclude that Dll1 expression by stem cells not only stimulates differentiation of neighbouring cells in trans, but also inhibits differentiation cell autonomously. These results highlight the distinct roles of different Notch receptors and ligands in controlling epidermal homeostasis.

Highlights

Mammalian epidermis comprises a multi-layered epithelium, termed inter-follicular epidermis (IFE), with various associated appendages including hair follicles, sebaceous glands, and sweat glands[1]
We demonstrate that different Notch receptors and ligands play overlapping but distinct roles in controlling terminal differentiation in the human IFE and provide new mechanistic insights into how Notch signalling is regulated to maintain a balance between stem cell (SC) renewal and differentiation
When human epidermal SCs are deprived of extracellular matrix (ECM) adhesion by culturing them in suspension (0 h), they rapidly transit through a commitment stage (4 h) to undergo terminal differentiation by 12 h in suspension[20]

Summary

Introduction

Mammalian epidermis comprises a multi-layered epithelium, termed inter-follicular epidermis (IFE), with various associated appendages including hair follicles, sebaceous glands, and sweat glands[1]. Once terminal differentiation has been triggered, committed progenitors (CPs) detach from the basement membrane and become sorted into the suprabasal layers There, they undergo a programmed series of morphological and biochemical changes that include the synthesis of the differentiation-specific keratins K1 and K10, as well as involucrin (IVL), transglutaminase (TGM) 1, periplakin (PPL), and loricrin[6]. Notch signalling is activated via interaction with ligands (such as Jagged[1], Jagged[2] and Dll1) that are themselves transmembrane proteins and results in two successive proteolytic cleavages of the Notch receptor[7,8]. We demonstrate that different Notch receptors and ligands play overlapping but distinct roles in controlling terminal differentiation in the human IFE and provide new mechanistic insights into how Notch signalling is regulated to maintain a balance between SC renewal and differentiation

Methods

Results

Conclusion