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Review
. 2018 Dec 5;132(23):2469-2481.
doi: 10.1042/CS20180721. Print 2018 Dec 12.

Investigating the RAS Can Be a Fishy Business: Interdisciplinary Opportunities Using Zebrafish

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Free PMC article
Review

Investigating the RAS Can Be a Fishy Business: Interdisciplinary Opportunities Using Zebrafish

Scott Hoffmann et al. Clin Sci (Lond). .
Free PMC article

Abstract

The renin-angiotensin system (RAS) is highly conserved, and components of the RAS are present in all vertebrates to some degree. Although the RAS has been studied since the discovery of renin, its biological role continues to broaden with the identification and characterization of new peptides. The evolutionarily distant zebrafish is a remarkable model for studying the kidney due to its genetic tractability and accessibility for in vivo imaging. The zebrafish pronephros is an especially useful kidney model due to its structural simplicity yet complex functionality, including capacity for glomerular and tubular filtration. Both the pronephros and mesonephros contain renin-expressing perivascular cells, which respond to RAS inhibition, making the zebrafish an excellent model for studying the RAS. This review summarizes the physiological and genetic tools currently available for studying the zebrafish kidney with regards to functionality of the RAS, using novel imaging techniques such as SPIM microscopy coupled with targeted single cell ablation and synthesis of vasoactive RAS peptides.

Keywords: Renin; SPIM; Zebrafish; optogenetics; transgenics.

Conflict of interest statement

None.

Figures

Figure 1
Figure 1. Interrelationship of Vasculature and nephron in early pronephric kidney
(A and B) 3dpf live Tg(wt1b:GFP;kdrl:mCherry) larvae were anaesthetized, embedded in 1% agar and mounted on a Zeiss Z1 lightsheet microscope, head down and imaged dorsally. The dorsal aorta (DA) can be seen bisecting the image in red, with the pronephric glomerulus (G) in green fused at the midline and the pronephric tubules (T) draining from this. Images were acquired with at 20X/1.0 NA Water Plan Apo objective using dual beam illumination at 488 nm (wt1b:GFP) and 561 nm (kdrl:mCherry), and the images merged and presented as a maximum intensity projection. Scale bars represent 30 μm. (CG) 5dpf live Tg(α-sma:mCherry;wt1b:GFP) larvae were anaesthetized, embedded in 0.5% agar and mounted on an LaVision TrIM Multiphoton microscope, mounted ventrally. Ti:Sapphire laser excited GFP using 860 nm and mCherry with 1100 nm pulsed light through a 25X/1.2NA LWD water-dipping Plan Fluor objective. (C and D) The anterior mesenteric artery (AMA) is shown budding off the dorsal aorta (DA), with main glomerular arterioles (GA) draining blood through the glomerulus (G) and filtering into the tubules (T). Images are shown (C) merged and (D) α-Sma signal as maximum intensity projections. Scale bars represent 20 μm. (E and F) These datasets were rendered in AMIRA to visualize how the vessels were orientated in 3D. (G) Schematic representing the flow of blood (blue arrows) through the glomerular vasculature. Yellow cells represent renin-expressing cells at the AMA location, red cells represent α-Sma-positive cells and green represents the wt1b-GFP-positive glomerulus.
Figure 2
Figure 2. Graphical representation of pronephric zebrafish kidney (∼4dpf; straightened)
(G) Glomerulus, (N) Neck, (PCT) Proximal Convoluted Tubule, (PST) Proximal Straight Tubule, (DE) Distal Early, (DL) Distal Late, (C) Cloaca. Specific segments of the pronephric kidney show conservation of mammalian tubular kidney markers.
Figure 3
Figure 3. Graphical representation of adult zebrafish mesonephric kidney
The mesonephric kidney is segmented into the head, trunk and tail (shown in red) together with a ventral view of the adult kidney in Tg(ren:LifeAct-RFP) fish showing comparative expression of ren:LifeAct-RFP in the head, trunk and tail regions of the kidney.
Figure 4
Figure 4. Renin expression at 5 dpf
Tg(ren:KillerRedmem;kdrl:GFP) larvae were anaesthetized, embedded in 0.5% agar and mounted on a home built SPIM system [104], head down and imaged ventrally using single laser illumination through a 16X/0.8NA water LWD Plan Fluor objective. ren:KillerRedmem expression was excited at 561 nm, kdrl:GFP signal at 488 nm. The posterior mesenteric artery (PMA) buds off the dorsal aorta (DA) and caudal vein (CV). Renin expression is shown extending along the PMA at this time point. Images are maximum intensity projections. Scale bars represent 50 μm.

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