Transient and permanent gene transfer into the brain of the teleost fish medaka ( Oryzias latipes ) using human adenovirus and the Cre‐loxP system

In this study, we demonstrated that human type‐5 adenovirus infected the brain of the teleost fish, medaka ( Oryzias latipes ), in vivo. Injection of adenoviral vector into the mesencephalic ventricle of medaka larvae induced the expression of reporter genes in some parts of the telencephalon, the periventricular area of the mesencephalon and diencephalon, and the cerebellum. Additionally, the Cre‐loxP system works in medaka brains using transgenic medaka carrying a vector containing DsRed2, flanked by loxP sites under control of the β‐actin promoter and downstream promoterless enhanced green fluorescent protein (EGFP). We demonstrated that the presence of green fluorescence depended on injection of adenoviral vector expressing the Cre gene and confirmed that EGFP mRNA was transcribed in the virus‐injected larvae.