Neutrophil‐selective transgenic RNA interference in vivo

Abstract

Tissue specific silencing of genes has applications for genetic engineering. Current strategies rely on Cre/Lox technology in mice requiring the generation of multiple transgenic lines and breeding strategies. Here we pursued a method to silence genes in neutrophils using an miRNA strategy. As proof of principle, we chose CD18 as the target gene since it is an abundantly expressed surface protein. CD18 specific miRNA hairpin driven by the myeloid specific MRP8 promoter resulted in a >90% reduction in CD18 protein levels in neutrophils and monocytes with no observable decrease in T cells and only a partial diminution in macrophages. Neutrophil CD18 silencing resulted in mild neutrophilia, splenomegaly and significant defects in neutrophil trafficking in irritant dermatitis. Our data demonstrate the utility of using miRNA approaches to silence genes in neutrophils which are terminally differentiated cells with a short half life that largely precludes their genetic manipulation in vitro. Furthermore, the mouse model provides a valuable tool to examine the contribution of CD18 on neutrophils to Leukocyte Adhesion Deficiency I (LADI), a complex inherited disorder in which reduced or absent CD18 expression in multiple leukocyte subsets leads to impaired innate and adaptive immune responses.Note: XC, ML and NT contributed equally. Supported by: NIH KO1AR054984 (XC), HL065095 and AR050800 (T.N.M), and a Arthritis Foundation fellowship (NT).