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.