The Park lab studies how stem/progenitor cells differentiate into specific cell types using the mouse kidney as a model system. The nephron, the functional unit of the kidney, is composed of at least 15 distinct cell types. Since all of the cell types found in the nephron originate from the common nephron progenitor cells, the mouse kidney serves as an excellent system to study cell fate decisions of stem/progenitor cells. We aim to (1) determine the roles of developmental signaling pathways (Wnt, Notch, Tgf/Bmp, Fgf, Hedgehog, and retinoic acid) in nephron formation, (2) identify transcription factors that define cell identities for each cell type found in the nephron, and (3) elucidate how these transcription factors coordinate with signaling pathways in gene regulatory networks. Understanding how multipotent nephron progenitors develop into different nephron segments will not only help build functional nephrons in vitro for potential cell/tissue replacement therapy but also provide insight into how cellular identities are maintained in healthy kidneys and disrupted in diseased or injured kidneys.