Dr. Young-Yun Kong is a Professor in the Department of Biological Sciences at Seoul National University. He received his bachelor's degree and master's degree at KyungHee University, and Ph.D. degree in the Medical Institute of Bioregulation at the Kyushu University in 1996. During his graduate studies in the laboratory of Dr. Kikuo Nomoto in Japan, he investigated the differential role of CD45 in the T and B lymphocyte function. During his postdoctoral training under the guidance of Dr. Josef Penninger in the Amgen/Ontario Cancer Institute at the University of Toronto, he generated OPGL/RANKL knockout mice and demonstrated that OPGL is a key factor for osteoclastogenesis and lymph node formation. He joined Pohang University of Science and Technology as an assistant Professor in 2000 and generated various mouse genetic models including E3 ubiquitin ligases, Mib1, Mib2, Neur1 and Neur2 that regulate Notch ligands. In mammals, he proved that Mib1 plays an obligatory role in Notch signaling in the various developmental contexts. Using these genetic models, he found that Mind bomb 1-expressing intermediate progenitors generate Notch signaling to maintain radial glial cells during forebrain development. He extended his work to Notch signaling in the generation of hematopoietic stem cells at the aorta-mesonephros-gonad, Notch signaling in the microenvironment that regulates hematopoiesis in the bone marrow, Notch signaling in the lymphopoietic niches that regulate T and marginal zone B cell development, and Notch signaling in the Eph-Ephrin boundary formation of the intestine. He moved to Seoul National University in 2008. Since then, he further extended his work to Notch signaling in renal collecting duct development and found that defect of Notch signaling results in nephrogenic diabetes insipidus. Moreover, his group demonstrated that Notch signaling counteracts WNT/β-catenin signaling through chromatin modification in colorectal cancer. Recently, he has been interested in skeletal muscle stem cells. He found that sex hormones establish a reserve pool of adult muscle stem cells by regulating Notch signaling at puberty. His current studies are attempting to solve the role of sex hormones in the maintenance and re-establishment of muscle stem cells after injury and then finally aging and rejuvenation of muscle stem cells.