Fig. 1

Mosaic labeling of KV cells.

(A) A dorsal view of the tailbud in a live zebrafish embryo at the 8-somite stage (8 ss) of development. Kupffer’s vesicle (KV) is positioned at the end of the notochord. The inset shows GFP-labeled KV cells surrounding the fluid-filled KV lumen in a Tg(sox17:GFP-CAAX) transgenic embryo at 8 ss. This is the middle plane of the KV. Scale = 10 μm. (B) Schematic of cell shape changes during KV remodeling. KV-ant cells (blue) and KV-post cells (red) have similar shapes at 2 ss, but then undergo regional cell shape changes such that KV-ant cells are elongated and KV-post cells are wide and thin by 8 ss. These cell shape changes result in asymmetric positioning of motile cilia that generate fluid flows for left-right patterning. (C) Structure of the ubi:zebrabow and sox17:Cre^ERT2 transgenes and the possible recombination outcomes of the ‘zebrabow’ transgene by Cre recombinase activity in KV cell lineages. (D) Time course of mosaic labeling of KV cells. Brief treatment of double transgenic Tg(sox17:Cre^ERT2); Tg(ubi:Zebrabow) embryos with 4-OHT from the dome stage to the shield stage generates low levels of Cre activity that changes expression of default RFP to expression of YFP in a subset of KV cells. (E) Mosaic labeled YFP⁺ KV cells at the middle plane of KV at 8 ss. (F) 3D reconstructed KV cells (green) and KV lumen (magenta) at 8 ss. Scale = 10 μm. (G–H) Morphometric parameters of 3D rendered KV-ant (G) and KV-post (H) cells: length = axis spanning from apical to basal side of the cell, height = axis spanning from dorsal to ventral side of the cell, and width = axis connecting lateral sides of the cell. Scale = 5 μm.