Fig. 1.

Examples of tip cells. Specialised cells located at the tips of developing organs are found in diverse tissues from primitive Dictyostelium slugs (A) to the mammalian kidney and lung (H and I). In the migrating slug (A,B), prestalk A (pstA) cells populate the apical tip and guide slug migration; the remainder of the slug is composed of prestalk cells, pstO cells and pstAB cells. In the C. elegans gonad, a single distal tip cell (DTC, green in D) is located at each end of the U-shaped gonad arms at the tip of the mitotic region (C,D). In the insect tracheal (E) and renal systems (F), dynamic tip cells (E, arrowhead) with prominent filopodia are found at the distal-most ends of the developing tubes. Tip cells are also observed in the vertebrate vasculature during sprouting angiogenesis (G). Groups of cells located at the growing bud tips regulate branching morphogenesis in the mammalian kidney (H) and lung (I). Figure credits: images reproduced with permission from (B), D Dormann University College London; (C) and (D), J Maciejowski & E Hubbard NYU from http://www.wormatlas.org; (E), M Affolter University of Basel originally published in Curr Biol doi: http://dx.doi.org/10.1016/j.cub.2008.10.062; (G), C Betsholtz, Karolinska Institute ©Betsholtz et al., 2003. Originally published in JCB doi:10.1083/jcb.200302047; (H), F Costantini Columbia originally published in Dev Cell doi; http://dx.doi.org/10.1016/j.devcel.2004.11.008; (I) V. Papaioannou Columbia from PLOS Genetics 2012 doi:10.1371/journal.pgen.1002866.