Extended Data Fig. 1: Melanocytes are spatially associated with the zebrafish kidney but dispensable for steady-state haematopoiesis.

a, Top right panel, schematic of an embryo. The black boxed area contains the kidney and is enlarged in the other panels. Left panel containing 4 images, zebrafish positive for Tg(cdh17:GFP) (green, labelling the kidney tubule) and Tg(runx:mcherry) (red, labelling HSPCs) are depicted at 7 dpf. The boxed areas in the left images are enlarged in the corresponding fluorescence panels in the middle; these panels show the head kidney containing the haematopoietic marrow (indicated by the dashed outline). The white arrow highlights the melanocyte umbrella. Scale bars,100 μm (bright field) and 50 μm (fluorescence). Bottom right panels, the kidney marrow of a 6-dpf larva positive for Tg(mitfa:GFP) (green, labelling melanocytes) and Tg(runx:mcherry) (red, labelling HSPCs) is shown from a lateral view (bottom right, large panel) and from an orthogonal view (transverse section; bottom right, small panel). The scale bar represents 20 μm. b, Whole-mount in situ hybridization of cmyb at different time points, a representative larva at 5 dpf is shown. Arrows indicate (from cranial to caudal) the thymus, the kidney and the caudal haematopoietic tissue; the enlarged portion of the image (dashed box) shows the thymus and the kidney. The experiment was performed with n = 10 wild-type and 10 mitfa^−/− larvae at 5 dpf and 10 wild-type and 7 mitfa^−/− larvae at 7.5 dpf. c, Flow cytometric analysis of the percentage of HSPCs that were positive for Tg(runx:mCherry) as a proportion of live cells in the kidney marrow of adult fish. Data are mean ± s.d.; n.s., not significant. d–f, Relative abundance of progenitors, myelomonocytes and lymphocytes in adult wild-type fish and mitfa, roy^−/− and casper^−/− pigment mutants as assessed by flow cytometry as previously described³⁰. c–f, n = 6 wild-type, 6 mitfa^−/−, 3 roy^−/− and 4 casper^−/− fish. Data are mean ± s.d.; analysis by ANOVA.

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