Home
This Title All WIREs
WIREs RSS Feed
How to cite this WIREs title:
WIREs Dev Biol
Impact Factor: 3.754

Kidney organogenesis in the zebrafish: insights into vertebrate nephrogenesis and regeneration

Full article on Wiley Online Library:   HTML PDF

Can't access this content? Tell your librarian.

Abstract Vertebrates form a progressive series of up to three kidney organs during development—the pronephros, mesonephros, and metanephros. Each kidney derives from the intermediate mesoderm and is comprised of conserved excretory units called nephrons. The zebrafish is a powerful model for vertebrate developmental genetics, and recent studies have illustrated that zebrafish and mammals share numerous similarities in nephron composition and physiology. The zebrafish embryo forms an architecturally simple pronephros that has two nephrons, and these eventually become a scaffold onto which a mesonephros of several hundred nephrons is constructed during larval stages. In adult zebrafish, the mesonephros exhibits ongoing nephrogenesis, generating new nephrons from a local pool of renal progenitors during periods of growth or following kidney injury. The characteristics of the zebrafish pronephros and mesonephros make them genetically tractable kidney systems in which to study the functions of renal genes and address outstanding questions about the mechanisms of nephrogenesis. Here, we provide an overview of the formation and composition of these zebrafish kidney organs, and discuss how various zebrafish mutants, gene knockdowns, and transgenic models have created frameworks in which to further delineate nephrogenesis pathways. WIREs Dev Biol 2013, 2:559–585. doi: 10.1002/wdev.92 This article is categorized under: Gene Expression and Transcriptional Hierarchies > Regulatory Mechanisms Vertebrate Organogenesis > From a Tubular Primordium: Non-Branched Vertebrate Organogenesis > From a Tubular Primordium: Branched

This WIREs title offers downloadable PowerPoint presentations of figures for non-profit, educational use, provided the content is not modified and full credit is given to the author and publication.

Download a PowerPoint presentation of all images


Glomerular and interrenal gland development. (a) Anatomical location of the podocyte and interrenal fields in the zebrafish embryo that is enlarged in panels b–e, in which nephrons are shown in a region of the embryo trunk that is just ventral to the spinal cord, notochord, and midline somites. (b) Several partially overlapping gene expression domains define the podocyte and interrenal precursors during late somitogenesis, wt1a (light purple) is expressed in a broad field adjacent to somites 1–3, wt1b is restricted to an area of cells (dark green) adjacent to somite 3, and nr5a1a is expressed in scattered cells (dark purple) littered throughout the wt1a/b fields. (c) By the 28 somite stage, the nr5a1a+ cells have formed bilateral clusters just caudal to the wt1b+ cells (wt1a domain no longer indicated). (d) At 30–36 hpf, the podocytes migrate to the midline and join together, and the interrenal cells also migrate to the midline. (e) By 48 hpf, the podocytes have recruited vasculature to form a glomerulus (G), and the interrenal gland (IR) remains a single conglomerate.

[ Normal View | Magnified View ]

Nephron gene regulatory network. The signals and transcription factors that are thought to direct pronephros lineages are indicated; black arrows indicate positive/inductive signals and red lines indicate inhibitory roles. Nephron segment abbreviations are: podocytes (P) (dark green), neck (N) (light green), proximal convoluted tubule (PCT) (orange), proximal straight tubule (PST) (yellow), distal early (DE) (light blue), corpuscle of Stannius (CS) (red), distal late (DL) (dark blue), and pronephric duct (PD) (black), with the cloaca (C) (purple). The PST and DE segments are comprised of a mosaic pattern of two epithelial cell populations (not shown in segment bar): single‐ciliated solute transporter cells and multiciliated cells (MCC). The differentiation of MCC versus a transporter cell fate is regulated by Notch signaling, shown with blue arrows.

[ Normal View | Magnified View ]

Emergence of nephron progenitor subdomains. (a) The renal progenitor cell field develops from the IM directly adjacent to the field of paraxial mesoderm (PM) (dorsal view). The PM cells, which are patterned through pathways that include the activities of ntla, tbx16, and cdx genes, secrete retinoic acid (RA). RA secretion (purple arrows) is highest in the rostral PM during the late gastrula to early somitogenesis stages, leading to the hypothesis that the renal progenitor cell field is exposed to a gradient of RA that is highest in rostral regions adjacent to where the first few somites will form. (b–e) Gene expression subdomains in the renal progenitor cell field are as indicated: rostral (light blue), central (turquoise), and caudal (dark blue). These domains are speculated to represent major subdivisions of the nephron progenitors, though this pattern of subdomains is actually an intricate, nested pattern that is both complex and dynamic. Gene expression domains fluctuate through to the 28 somite stage, when segment boundaries can be detected based on discrete domains of solute transporter transcripts. (b) At the 5 somite stage, the rostral domain contains a subset of wt1a+ cells (area of wide blue cross‐hatchings in the rostral field), that includes the podocyte progenitors. (c) By the 8 somite stage, the rostral and caudal fields have overlapping boundaries, where a region of cells co‐expresses jag2 and mecom (dark blue cross‐hatchings). (d) By the 15 somite stage, irx3b expression is detected, and has been the basis of support for the notion of a central domain identity at this timepoint. The podocyte lineage (green box) is distinct from the tubular populations, based on the specific expression of foxc1a, hey1, lhx1a, mafba, and wt1b in cells located adjacent to somite 3; a broader region still expresses wt1a, likely including interrenal progenitors (wide blue cross‐hatchings adjacent to somite 2) (See also Figure ). (e) By the 28 somite stage, segments have emerged as abutting domains that are defined by the expression of specific solute transporter gene transcripts and/or transcription factors, though most transcription factors examined to date mark multiple segments. Nephron segment abbreviations are: podocytes (P) (dark green), neck (N) (light green), proximal convoluted tubule (PCT) (orange), proximal straight tubule (PST) (yellow), distal early (DE) (light blue), corpuscle of Stannius (CS) (red), distal late (DL) (dark blue), and pronephric duct (PD) (black), with the cloaca (C) (purple).

[ Normal View | Magnified View ]

Specification, axial positioning, and maintenance of the renal progenitor cell field. (a) Ventral mesoderm fates arise upon BMP signaling during D–V axis specification. Fate map studies at the embryonic shield stage have determined the locale (blue) from which the blood, angioblasts, and pronephros cell lineages arise. Blood and angioblasts arise from the ventral‐most mesoderm, with pronephros fates partially intermingled but also occupying a slightly more lateral position. (b) Mesoderm specification events that promote IM fates (blue) involve the actions of T‐box factors, such as ntla and tbx16, which are expressed during late gastrula (epiboly) stages and throughout somitogenesis (not depicted). (c) Mesodermal patterning by the cdx factors is responsible for setting the axial position of the IM field (blue) which is evident by the tailbud stage. Patterning events in adjacent tissues also affect pronephros progenitors, such as osr1 activity, which leads to the maintenance of pax2a‐expression in the rostral renal progenitor cell field through its effects in regulating endoderm and angioblast lineages.

[ Normal View | Magnified View ]

The zebrafish pronephros arises from the IM. (a) Tail‐bud stage embryo with intermediate mesoderm (IM) (blue) situated between the paraxial mesoderm (PM) (grey) and lateral plate mesoderm (LPM) (white). (b) The 5 somite stage embryo exhibits several cell fields in close proximity to the renal progenitor cell field: domains of tal1+ cells that are thought to give rise to angioblasts, a tal1+/gata1a+ co‐expressing domain that is thought to give rise to primitive blood cells, and the field of renal progenitors which likely co‐express pax2a, pax8, and lhx1a. (c) The 28 somite stage embryo exhibits a pronephros comprised of two parallel nephrons that consist of numerous segment domains, known as the podocytes (P) (dark green), neck (N) (light green), proximal convoluted tubule (PCT) (orange), proximal straight tubule (PST) (yellow), distal early (DE) (light blue), corpuscle of Stannius (CS) (red), distal late (DL) (dark blue), and pronephric duct (PD) (black), which drains the body via the cloaca (C) (purple).

[ Normal View | Magnified View ]

Tubule epithelium development. (a) At 24 hpf (the 28 somite stage), the nephron tubules have undergone a mesenchymal to epithelial transition (MET), and are visible as bilateral tubule units in cross section. (b) Immunohistochemistry image of cryosection from a cdh17::eGFP embryo, with the right nephron tubule shown enlarged in (b′). (b′) Digital zoom (6.25թ of a single nephron tubule cross section, with the nephrons visible as GFP+ cells, with tubulin (light blue) detected at the apical epithelial surface (red), and nuclei stained with DAPI (blue), 60X magnification. White bar indicates 5 µm. (c) At 48 hpf, the nephron tubule epithelium has further differentiated, and single or multiple ciliated organelles are present in cells of the PST and DE, depicted in a sagittal section schematic (note: cell number in PST domain is not representative of actual PST segment cell number); epithelium maturation coincides with the onset of glomerular filtration, and subsequent fluid flow within the tubule (blue arrow).

[ Normal View | Magnified View ]

Timeline of renal development in the zebrafish. (Top) Colored bar denotes major developmental events, as marked by somite(s) number or days post fertilization (dpf). (Bottom) Black bars denote approximate time period for the various events of pronephros and mesonephros formation.

[ Normal View | Magnified View ]

The adult mesonephros. (a) (Top) Adult zebrafish with pink box indicating dorsal body wall location of the mesonephros. (Middle) Schematic dorsal view of the mesonephros, with head, trunk and tail regions; the approximate positions of the ventrally‐located interrenal glands are indicated with an asterisk (*). (Bottom) Schematic of branched tubular network in the mesonephros. Branched pinwheel arrays of nephrons plumb into large collecting ducts. The interstitial stroma includes hematopoietic stem cells (HSC) (light blue), blood cells (pink; specific lineages not designated), and renal progenitors (green). The stroma may also include other mesenchymal cell type(s) yet to be identified. (b) Histological section of a paraffin‐embedded adult kidney stained with hematoxylin and eosin (60ՠmagnification). The glomerulus (G), tubule (T) and blood (b) fractions are indicated with black arrows.

[ Normal View | Magnified View ]

Mesonephros development: addition of nephrons to the pronephros. (a) (Top) At approximately 10–14 dpf (corresponding to ∼4 mm in length), juvenile zebrafish larvae begin mesonephros development, which is indicated in region of the pronephros enlarged below. (Bottom left panel) Single lhx1a+ mesenchymal cells first appear in association with the distal tubule near the swim bladder, in a region indicated by asterisk (green). (Bottom right panel) Over time, the progressive addition of mesonephros tubules (pink) leads to a dense collection of nephrons that plumb into the pair of pronephros nephrons (blue). (b) The process of tubulogenesis is indicated. Single lhx1a+ cells multiply and form aggregates in close juxtaposition to the existing pronephros tubule. Over several days, the lhx1a+ cells rapidly expand and generate a nephron tubule that eventually displays polarized gene expression domains of lhx1a (green), pax8 (purple), and wt1b (pink) expressing cells.

[ Normal View | Magnified View ]

Morphogenesis of the pronephros proximal tubule. (a) The proximal convoluted tubule (PCT) exhibits receptor mediated endocytosis and shows uptake of solutes, as visualized by absorption of 40 kD fluorescein isothiocyanate (FITC) dextran conjugates. (Top) A brightfield image of a 4 dpf embryo that was injected with FITC‐dextran at 2 dpf, shown laterally, (middle) view of the PCT through FITC filter, and (bottom) enlarged view of a single PCT. (b) PCT coiling morphogenesis, shown in dorsal view after whole mount in situ hybridization to detect slc20a1a transcripts (stained in purple). (Top) 3 dpf embryo shows ‘coat hanger’ hooks of the rostral PCT, (middle) 4 dpf embryo where coiling has now occurred, and (bottom) 5 dpf embryo where the PCT has multiple loops and coils.

[ Normal View | Magnified View ]

Browse by Topic

Vertebrate Organogenesis > From a Tubular Primordium: Non-Branched
Vertebrate Organogenesis > From a Tubular Primordium: Branched
Gene Expression and Transcriptional Hierarchies > Regulatory Mechanisms