Visualisation of metabolic tissues in zebrafish. (A–A″″′) Pancreas. The insulin (ins) promoter drives the expression of GFP in β-cells. (A) Schematic of construct used. (A′) Fluorescent image of a 3-day-old ins:EGFP embryo showing expression within the islet of the pancreas. (A″) Rendered composite of confocal images of a 10-day-old ins:EGFP embryo following immunofluorescence to detect insulin, with overlaid 20× brightfield. (A″′–A″″′) Close-up images of EGFP fluorescence (A″′), immunofluorescence to detect insulin (A″″) and merged image demonstrating colocalization of EGFP with insulin (A″″′). Reproduced with permission (Pisharath et al., 2007). (B,B′) Liver. (B) A transgenic zebrafish that allows researchers to visualise glucose production in the liver. A 2.8-kb fragment of the phosphoenolpyruvate carboxykinase (pck1) promoter drives expression of a fluorescent protein (venus). Reproduced with permission (Gut et al., 2012). (B′) Confocal analysis of the liver parenchyma of a 1.5-month-old live LiPan/Tg[fli:EGFP transgenic zebrafish. Hepatocytes express the dsRed RFP reporter gene under a liver-specific lfabp promoter and the vasculature is labelled in green. Reproduced with permission (Korzh et al., 2008). (C–C″) Adipose. Low (C) and high (C′) power image of juvenile fish stained with Oil Red O, indicating the location of the adipocytes close to the intestine and pancreas. (C″) Confocal imaging of lipid droplets in juvenile fish stained with LipidTox. Images are authors’ own.

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