2014 年 24 巻 2 号 p. 1-7
Medaka has been developed as a model animal that can be used to apply both forward and reverse genetic approaches. Large-scale mutagenesis screening for developmental processes, full-length cDNA/Expressed sequence Tag(EST) sequencing and genome sequencing projects have made it possible to use medaka as an effective model for research studies using a forward genetic approach. Currently, it is possible to identify the causal genes in medaka mutants within one to two years. Moreover, the TILLING library and high-throughput screening of mutations by highresolution melting (HRM) facilitate the identification of mutations in a particular gene and can produce medaka with mutations in the particular gene of interest. In addition to this reverse genetics approach, genome editing with the use of engineered nucleases, such as TALEN and CRISPR/CAS9, can be applicable to medaka. Recently, knock-in expression with a GFP cassette at the de novo locus was reported in zebrafish, and this can also be applied to medaka. Therefore, most methods for forward and reverse genetic approaches are equivalent or easier with the medaka model than other animal models such as the mouse and rat.
Although constant environments (fixed temperature and day/night cycle) are the general condition for animal experiments, organisms in nature live in fluctuating environments. Thus, studies on phenotype/genotype interactions in fluctuating environments represent the future for the biological and biomedical sciences. In this context, numerous features of medaka, such as their adaptability to variable temperature (4 to 40 ℃), tolerance to high-salinity environments without acclimatization, ability to measure the light/dark cycle and adaptation to seasonal change, can provide important information for analyses of phenotype, genotype and environmental interaction. For these reasons, we believe that medaka, a model animal established in Japan, is a good candidate for experimental animal studies of phenotype and genotype interactions in changing environments.