OTULIN maintains skin homeostasis by controlling keratinocyte death and stem cell identity

Esther Hoste,Kodi Ravichandran,Mozes Sze,Geert Van Loo,Arne Martens,Sophia Maschalidi,Lien Verboom,Maria Kasper,Hanna-Kaisa Vikkula,Yvan Saeys,Lisette Van Hove,Niels Vandamme,Kim Lecomte,Karl Annusver,Kevin Verstaen,Tino Hochepied,Jana Roels

doi:10.1038/s41467-021-25944-2

Abstract

OTULIN is a deubiquitinase that specifically cleaves linear ubiquitin chains. Here we demonstrate that the ablation of Otulin selectively in keratinocytes causes inflammatory skin lesions that develop into verrucous carcinomas. Genetic deletion of Tnfr1, knockin expression of kinase-inactive Ripk1 or keratinocyte-specific deletion of Fadd and Mlkl completely rescues mice with OTULIN deficiency from dermatitis and tumorigenesis, thereby identifying keratinocyte cell death as the driving force for inflammation. Single-cell RNA-sequencing comparing non-lesional and lesional skin reveals changes in epidermal stem cell identity in OTULIN-deficient keratinocytes prior to substantial immune cell infiltration. Keratinocytes lacking OTULIN display a type-1 interferon and IL-1β response signature, and genetic or pharmacologic inhibition of these cytokines partially inhibits skin inflammation. Finally, expression of a hypomorphic mutant Otulin allele, previously shown to cause OTULIN-related autoinflammatory syndrome in humans, induces a similar inflammatory phenotype, thus supporting the importance of OTULIN for restraining skin inflammation and maintaining immune homeostasis.

Highlights

OTULIN is a deubiquitinase that cleaves linear ubiquitin chains
Dermatitis in ΔKerOTULIN skin was further confirmed by the marked presence of CD11b- and F4/80-positive macrophages in ΔKerOTULIN skin lesions (Fig. 1e), and aberrant keratinocyte differentiation could be demonstrated in both lesional and non-lesional skin of ΔKerOTULIN mice based on abnormal Keratin-6 (K6) and filaggrin staining of skin sections (Fig. 1e)
These inflammatory lesions develop into verrucous carcinomas, an uncommon variant of squamous cell carcinomas, that are characterized by exophytic epidermal outgrowths and marked melanophagy, a phenotype that was not observed in mice lacking components of the linear ubiquitin chain assembly complex (LUBAC) complex

Summary

Introduction

OTULIN is a deubiquitinase that cleaves linear ubiquitin chains. Here we demonstrate that the ablation of Otulin selectively in keratinocytes causes inflammatory skin lesions that develop into verrucous carcinomas. LUBAC, which consists of the proteins SHARPIN, HOIP, and HOIL-1, is the only currently known E3 ligase complex responsible for M1 ubiquitin chain formation[5,6,7], and mice deficient for SHARPIN or lacking HOIL-1 or HOIP in keratinocytes develop severe dermatitis[8,9,10]. Mice deficient for OTULIN or expressing a catalytically inactive OTULIN mutant die midgestation as a result of aberrant cell death mediated by TNFR1-signaling and receptor-interacting protein kinase 1 (RIPK1) kinase activity[13,17]. TNF can induce inflammation by promoting cell death In these circumstances, a different molecular complex is assembled, resulting in the formation of an apoptosis-inducing complex IIa, consisting of FADD (Fas-associated death domain) and caspase-8, or complex

Methods

Results

Conclusion