Fig. 4

Disruption of nephrogenic cell aggregate formation in Fgf signaling inhibited kidneys. (A) Adult Tg(lhx1a:EGFP) fish at 5 dpi exhibit condensed, dome-shaped cell aggregates on distal tubules. (B) Treatment of regenerating fish from 3 to 5 days post injury with the Fgfr1 inhibitor PD166866 followed by imaging at 5 dpi showed delayed formation of tight adherent nephrogenic cell domes and the appearance of cell lamellopodia (arrowheads in B). (C–D) Tight, condensed lhx1a:EGFP ​+ ​nephrogenic cell aggregates seen in control injured kidneys (C) did not form in fish treated with PD166866 from 3 to 7 dpi (D); instead lhx1a:EGFP ​+ ​cells remained stellate-shaped and disorganized. (E) 6 dpi lhx1a:EGFP ​+ ​nephrogenic cell aggregates display a rosette shape with a zo-1 positive apical lumen (inset) extending in the direction of nephron growth (red arrowhead; proximal). (F) 24 ​h PD166866 treatment from day 5–6 induces filopodia and lamellopodia formation (white arrowheads) and reduction in apical zo-1 localization (white arrow) with a ring of remnant zo-1 only in distal cells (red arrowhead). (G) Juvenile Tg(lhx1a:EGFP) fish at 42 dpf produce nephrogenic aggregates in their developing kidneys identical to injury-induced, dome-shaped aggregates (arrowhead in G). (H) Treatment of juveniles from 35 to 42 dpf with PD166866 results in the loss of domed aggregates and appearance of single cells and stellate cell clusters (arrowheads in H), indicating a loss of adhesion. Scale bars in Z-projections (A–F) are 10 μm and 100 μm in (G,H).