A holey pursuit: lumen formation in the developing kidney

The formation of polarized epithelial tubules is a hallmark of kidney development. One of the fundamental principles in tubulogenesis is that epithelia coordinate the polarity of individual cells with the surrounding cells and matrix. A central feature in this process is the segregation of membranes into spatially and functionally distinct apical and basolateral domains, and the generation of a luminal space at the apical surface. This review examines our current understanding of the cellular and molecular mechanisms that underlie the establishment of apical–basal polarity and lumen formation in developing renal epithelia, including the roles of cell–cell and cell–matrix interactions and polarity complexes. We highlight growing evidence from animal models, and correlate these findings with models of tubulogenesis from other organ systems, and from in vitro studies.