Our body is composed of multiple tissues that contain many types of cells and these tissues cooperatively function to maintain the life. Disruption or dysfunction of some tissues or cells causes disease. To elucidate the function of specific tissues, cell types or genes, particularly in disease progression or tissue homeostasis, in vivo analyses of transgenic knockout or knockin mice is a powerful method. In some cases, transgenic mice exhibit a phenotype similar that of a specific human disease and can be used as a model system for this disease. Our group's aim is to efficiently generate transgenic mice using new technologies, in order to analyze gene function and establish new disease models.