Development of microglia-targeting adeno-associated viral vectors as tools to study microglial behavior in vivo
Yukihiro Okada, Nobutake Hosoi, Yasunori Matsuzaki, Yuuki Fukai, Akito Hiraga, Junichi Nakai, Keisuke Nitta, Yoichiro Shinohara, Ayumu Konno, Hirokazu Hirai
Abstract
Abstract Here we describe the microglia-targeting adeno-associated viral (AAV) vectors containing a 1.7-kb putative promoter region of microglia/macrophage-specific ionized calcium-binding adaptor molecule 1 ( Iba1 ), along with repeated miRNA target sites for microRNA (miR)-9 and miR-129-2-3p. The 1.7-kb genomic sequence upstream of the start codon in exon 1 of the Iba1 ( Aif1 ) gene, functions as microglia preferential promoter in the striatum and cerebellum. Furthermore, ectopic transgene expression in non-microglial cells is markedly suppressed upon adding two sets of 4-repeated miRNA target sites for miR-9 and miR-129-2-3p, which are expressed exclusively in non-microglial cells and sponged AAV-derived mRNAs. Our vectors transduced ramified microglia in healthy tissues and reactive microglia in lipopolysaccharide-treated mice and a mouse model of neurodegenerative disease. Moreover, live fluorescent imaging allowed the monitoring of microglial motility and intracellular Ca 2+ mobilization. Thus, microglia-targeting AAV vectors are valuable for studying microglial pathophysiology and therapies, particularly in the striatum and cerebellum.