S100-family proteins are upregulated in canine and human Discoid Lupus Erythematosus 

Discoid lupus erythematosus (DLE) is an autoimmune disorder characterized by skin lesions and scarring hair loss. Pet dogs can develop DLE just like their human companions. We sought to compare gene expression in lesional skin biopsies compared to healthy margin controls in both human and veterinary DLE patients with the goal of identifying conserved drivers of disease. We determined differentially expressed genes (DEGs) in canine DLE compared to healthy margin skin using NanoString's canine Immune-Oncology panel of 800 genes as well as bulk RNA sequencing. We compared these datasets to published human DLE datasets, and performed comparative transcriptomics analysis to align DEGs. S100 family proteins were among the highest upregulated DEGs. We utilized immunohistochemistry to confirm protein level expression, which was highest in the epidermis. Given these findings, we hypothesize that S100 family members are key mediators of interface dermatitis in both canine and human DLE. Future studies are planned to understand the mechanistic significance of S100 in DLE immunopathogenesis.