O12 Transcriptional analysis of epidermolysis bullosa patient samples identifies key signatures of disease heterogeneity

Abstract Introduction and aims Epidermolysis bullosa (EB) is a family of rare, incurable, inherited disorders characterized by extreme skin and mucosal fragility. The two most severe forms are dystrophic EB (DEB), caused by genetic variance in type-VII collagen, and junctional EB (JEB), caused by genetic variance in genes encoding basement membrane proteins laminin 332 (α3, β3, γ2), type XVII collagen or integrin α6β4. Despite clinical similarities, there are dramatic differences in the life expectancies of patients with these subtypes. Patients with RDEB survive to early or midadulthood, comparatively patients with JEB rarely survive beyond the first year of life. We aim to explore the disparity in life expectancy using a transcriptomic and an in vivo approach. Methods We performed bulk RNA sequencing on 7 DEB and 13 JEB samples (3 LAMA3, 8 LAMB3 and 2 LAMC2) to identify molecular and cellular differences underpinning these diseases. Principal component analysis and differential gene expression (DEG) analysis was conducted to explore the relatedness between subtypes. Immunohistochemistry was used to validate these findings in mouse models of EB. Results Three distinct clusters of samples were grouped by condition; one DEB and two JEB clusters separated by LAMA3 and LAMC2 mutations. Pathway and gene ontology (GO) analysis of DEGs indicated an upregulation in cell death, proinflammatory pathways and interleukins (ILs) (IL-1, IL-11, CXCL12 and β-defensins) which stimulate the adaptive immune response. In addition, an abundance of transcriptional factors linked to wound healing (MMP2, COL1A1), collagen remodelling (LOX), fibrosis (TGFβ) and epidermal development (EPPK1, TGM1, FLG and KRT14) were upregulated in patients with JEB compared with those with DEB. These changes have been validated in mouse models of EB at Queen Mary University of London. Conclusions We have identified and validated significant changes between EB subtypes. The use of pathway and GOterm analysis identified altered pathways and molecular drivers that could be used as a novel approach for therapeutic treatments for EB.