O20 Dissecting junctional epidermolysis bullosa heterogeneity

Abstract

Abstract Introduction and aims Epidermolysis bullosa (EB) is a family of rare, incurable, inherited disorders that are characterized by extreme skin and mucosal fragility. One of the most severe forms is junctional EB (JEB). JEB is caused by mutations in genes encoding the skin basement membrane proteins laminin 332 (α3, β3, γ2), type XVII collagen or integrin α6β4. Despite similarities between the disease pathology of JEB and other forms of EB there is a dramatic reduction in life expectancy for patients with JEB. Patients with JEB rarely survive beyond the first year of life. To investigate this disparity, we have optimized a previously published conditional tamoxifen induced knockout JEB mouse model (Lama3flx/flxK14CreERT). This mouse model recapitulates all key features of JEB, such as thickening of the epidermis and visible blistering owing to the loss of laminin α3 at the basement membrane. Methods Single-cell (sc)RNA-Seq analysis was conducted on pooled skin samples from a healthy (control) and JEB mouse model (n = 3 per genotype). Immunofluorescent staining was conducted to confirm scRNA-Seq analysis including markers for skin differentiation (K14, transglutaminase 1, loricrin), proliferation (Ki67), basement membrane (laminin α3, laminin β3, laminin γ2, collagen VII) and immune markers (F4/80, Ly6-G/C, CD3, CD79). Results We can see large differences in cellular populations across the two conditions. With increased T- and B-immune-cell subpopulations in the JEB model compared with the healthy control. Utilizing CellChatDB we identified disease-specific signalling pathways that identify activated T- and B-cell populations interacting with JEB macrophage populations via proinflammatory pathways. Conclusions We have utilized an in vivo mouse model to gain insight into the molecular and cellular differences in a JEB diseased phenotype. Identifying changes in cellular pathways could be used as a targeted approach to identify a beneficial therapeutic treatment for JEB.