Medaka as a model teleost: characteristics and approaches of genetic modification

The medaka is a small freshwater fish found in ponds and rivers in Japan and has been a familiar pet since the 17th century. It has also been used as a model of basic biology for more than 100 years. Recently, because of the development of molecular genetic tools, the medaka has drawn attention because of its amenability to genetic modification. In this chapter, we will introduce a brief history, biological features, and application techniques for genetic modification, including disruption and foreign gene introduction. In addition to such basic approaches involving the generation of transgenic and knockout medaka, we will introduce several techniques for increasing the efficiency and range of possible applications: bacterial artificial chromosome/Fosmid-based vector construction, the dual promoter method, transposase, and phiC31 integrase. Lastly, we will introduce several gene knock-in techniques that involve Cas9/clustered regularly interspaced short palindromic repeats-mediated genome cleavage and the following of various DNA repair pathways.