The roles of epidermal Blimp-1 in atopic dermatitis

Abstract Keratinocytes are the main cell type constructing the epidermis of animals, which can further differentiate into corneocytes and express multiple innate immune receptors. B lymphocyte-induced maturation protein-1 (Blimp-1) plays a crucial rule in directing cornification of keratinocytes. We previously reported that keratinocyte-specific deletion of Prdm1, the gene encoding Blimp-1, induced spontaneous inflammation in the skin of adult mice. We further found that deletion of Prdm1in keratinocytes in Balb/c genetic background caused hyper-production of type 2 cytokines and thymic stromal lymphopoietin (TSLP) in the skin, and staphylococci colonization, which are characteristics of atopic dermatitis (AD). Since K5-CreER+Prdm1f/f(CKO) mice in Balb/c background exhibited AD-like symptoms, we wondered whether they are more susceptible to the disease progression in a murine AD model induced by MC903, a vitamin D3 analog enhancing TSLP production by keratinocytes. We found that CKO mice showed more immune cell infiltration in ear skin, developed more severe epidermal hyperplasia, and induced more TSLP secretion in the skin following topical application of MC903. Recent studies showed that staphylococci colonization activated the transcription of endogenous retroviruses (ERVs) in murine skin, while excess ERV expression led to skin inflammation. As staphylococci colonized on our CKO mouse skin, we hypothesized that enhanced ERV expression may also link to skin inflammation of CKO mice. Indeed, both in vivoand in vitrodeletion of Prdm1in keratinocytes resulted in elevated levels of ERV transcripts. We are studying the contribution of elevated ERV transcripts in Blimp-1-reduction-mediated AD-like skin inflammation.