019 Investigating OX40L and its role in mediating cutaneous and systemic autoimmune disease

Systemic lupus erythematosus (SLE) is a devastating systemic inflammatory disease, with prominent female bias. Recent literature suggests the OX40/OX40L costimulatory pathway may play an important role in development of SLE. GWAS have identified TNFSF4 (OX40L) as an SLE susceptibility locus. OX40L stimulation of T cells through the OX40 receptor has been shown to promote a T follicular helper (Tfh) phenotype, and Ox40l knockout has been demonstrated to ameliorate the SLE phenotype in transgenic and induced lupus mouse models. We recently reported a mouse model (K5-Vgll3) where epidermal overexpression of the female-biased transcription cofactor Vgll3 results in upregulation of Ox40l in epidermis as well as development of SLE. To address the role of OX40L in this model, we demonstrate that Ox40l KO results in decreased disease severity, consistent with this pathway being important for propagating VGLL3-mediated inflammation. To investigate the link between VGLL3 and OX40L expression in SLE skin, we created an N/TERT VGLL3-Myc-DDK overexpression cell system. IP-mass spectrometry of VGLL3 complexes identified transcription factor TEAD1, previously reported to bind upstream of OX40L, as a top VGLL3 interactor. Assessing OX40L and OX40 expression via immunofluorescence and single-cell RNA-seq (scRNA-seq), we found increased expression of OX40L on KCs and OX40 on CD4+ T cells in both K5-Vgll3 and SLE skin compared to controls. ScRNA-seq also showed that OX40+ T cells in K5-Vgll3 and lupus skin were skewed towards a Tfh/T peripheral helper (Tph) phenotype. Similarly, spatial-seq identified a population of Tfh/Tph-like population in SLE skin not present in healthy controls. Overall, our data indicates cutaneous VGLL3 controls transcriptional regulation of OX40L through TEAD1, and OX40L expression is required to mediate downstream SLE-like inflammation, possibly through promoting Tfh/Tph-like cells in SLE compared to healthy skin.