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PubMed1994

Expression of the LIM class homeobox gene Xlim-1 in pronephros and CNS cell lineages of Xenopus embryos is affected by retinoic acid and exogastrulation.

The LIM class homeobox gene Xlim-1 is expressed in Xenopus embryos in the lineages leading to (i) the notochord, (ii) the pronephros, and (iii) certain cells of the central nervous system (CNS). In its first expression phase, Xlim-1 mRNA arises in the Spemann organizer region, accumulates in prechordal mesoderm and notochord during gastrulation, and decays in these tissues during neurula stages except that it persists in the posterior tip of the notochord. In the second phase, expression in lateral mesoderm begins at late gastrula, and converges to the pronephros at tailbud stages. Expression in a central location of the neural plate also initiates at late gastrula, expands anteriorly and posteriorly, and becomes established in the lateral regions of the spinal cord and hindbrain at tailbud stages. Thus Xlim-1 expression precedes morphogenesis, suggesting that it may be involved in cell specification in these lineages. Enhancement of Xlim-1 expression by retinoic acid (RA) was first detectable in the dorsal mesoderm at initial gastrula. During gastrulation and early neurulation, RA strongly enhanced Xlim-1 expression in all three lineages and also expanded its expressing domains; this overexpression correlated well with RA phenotypes such as enlarged pronephros and hindbrain-like structure. Exogastrulation reduced Xlim-1 expression in the lateral mesoderm and ectoderm but not in the notochord, suggesting that the second phase of Xlim-1 expression requires mesoderm/ectoderm interactions. RA treatment of exogastrulae did not revert this reduction.

Animals↗

PubMed1993

[Ontogeny of the pronephros and mesonephros in the South African clawed frog, Xenopus laevis Daudin, with special reference to the appearance and movement of the renin-immunopositive cells].

Development of the pronephros and mesonephros of Xenopus laevis was morphologically studied in the larvae immediately after hatch (stage 35/36) to the end of metamorphosis (stage 66) together with the appearance of renin-immunopositive cells. The pronephros consisted of 3 pairs of pronephric tubules at stage 35/36 and became functional at stage 37/38 with the opening of the pronephric ducts to the cloaca. It increased thereafter in volume, but became degenerative at stage 56, lost a part of the pronephric ducts at stage 60, and completely disappeared at stage 64. The mesonephros displayed its anlage at stage 42, and gained the immature renal corpuscles at stage 48. At stage 49, it was equipped with the matured nephrons. The mesonephric tubules differentiated into the neck, proximal, intermediate and distal parts. The collecting tubules and ducts were also observed at this stage. At stage 56, a part of the mesonephric tubules degenerated and were displaced by newly formed tubules. Reorganization of the mesonephros was not completed at the end of metamorphosis. Renin-immunopositive cells did not appear in the pronephros, but were observed at the diverging part of the renal artery from the dorsal aorta, and in the walls of arteries and afferent arterioles within the mesonephros in a low frequency of appearance.

Animals↗

PubMed2000

Notch regulates cell fate in the developing pronephros.

The mechanisms that regulate cell fate within the pronephros are poorly understood but are important for the subsequent development of the urogenital system and show many similarities to nephrogenesis in the definitive kidney. Dynamic expression of Notch-1, Serrate-1, and Delta-1 in the developing Xenopus pronephros suggests a role for this pathway in cell fate segregation. Misactivation of Notch signaling using conditionally active forms of either Notch-1 or RBP-J/Su(H) proteins prevented normal duct formation and the proper expression of genetic markers of duct cell differentiation. Inhibition of endogenous Notch signaling elicited the opposite effect. Taken together with the mRNA expression patterns, these data suggest that endogenous Notch signaling functions to inhibit duct differentiation in the dorsoanterior region of the anlage where cells are normally fated to form tubules. In addition, elevated Notch signaling in the pronephric anlage both perturbed the characteristic pattern of the differentiated tubule network and increased the expression of early markers of pronephric precursor cells, Pax-2 and Wilms' tumor suppressor gene (Wt-1). We propose that Notch signaling plays a previously unrecognized role in the early selection of duct and tubule cell fates as well as functioning subsequently to control tubule cell patterning and development.

Animals↗

PubMed2000

The zebrafish pronephros: a genetic system for studies of kidney development.

The zebrafish, as a model system for vertebrate development, offers distinct experimental advantages for studies of organogenesis. The simplicity of the zebrafish pronephros, the feasibility of isolating large numbers of mutants, and the growth in infrastructure for genomics makes the zebrafish an attractive system for the analysis of kidney development. Mutants affecting several aspects of nephrogenesis, including differentiation of the intermediate mesoderm, nephron patterning, epithelial polarity, and angiogenesis, have been isolated. Analysis of mutant phenotypes and the cloning of mutant genes has revealed: (1) a role for bone morphogenetic proteins in patterning the ventral mesoderm, (2) an essential role for the pax2.1 gene in pronephric development, (3) multiple loci required for establishing epithelial polarity in the pronephric duct, (4) a central role for podocytes in directing glomerulogenesis, and (5) 15 loci associated with cystic maldevelopment in the pronephros. The striking similarities of pronephric cell types to those found in higher vertebrates, as well as the conservation of kidney-specific gene expression patterns, suggest that insights gained from studies in zebrafish will be broadly applicable to cell differentiation in the kidney.

Animals↗

PubMed1990

Modulatory effect of metal ions on the immune response of fish: in vivo and in vitro influence of MnCl2 on NK activity of carp pronephros cells.

The in vivo and in vitro influence of MnCl2 on carp pronephros cells was investigated. Increased cytotoxicity against both YAC-1 and P 815 target cells was observed following an intraperitoneal injection of 40, 80, or 120 micrograms MnCl2/g body wt administrated 24 hr prior to the in vitro 51Cr release assay. Similarly, in vitro treatment of carp pronephros cells, at a final concentration of 60 micrograms/culture, resulted in an increase of NK cell activity in both YAC-1 and P 815 target cell lines. However, a significant decrease in this activity was shown with lower doses of MnCl2 (40 and 20 micrograms/culture).

Animals↗

PubMed2002

The Xenopus pronephros as a model system for the study of kidney development and pathophysiology.

By analysing the expression and function of DN-associated genes during renal development in vivo, it may be possible to shed light on their pathogenic roles in the disease. The embryos of the African clawed frog Xenopus laevis provide a useful model for analysing early embryonic development, particularly organogenesis. Their rapid, external development and the large size of embryos allow for ease of observation and manipulation of the developmental programme. The Xenopus pronephros represents a single nephron, the basic unit of the successive vertebrate renal organs, i.e. the mesonephros and metanephros, and thus provides a useful model of nephrogenesis. Suppression subtractive hybridization was used to identify genes induced when primary cultures of mesangial cells are exposed to high extracellular glucose. Among these genes was the bone morphogenetic protein (BMP) gremlin. Interestingly gremlin is expressed in Xenopus pronephros at stage 27 where it has the potential to interact with BMPs and related regulators of nephrogenesis. Further analysis of the role of gremlin in renal development may shed light on their roles in disease.

Animals↗

PubMed2003

Parallel early development of zebrafish interrenal glands and pronephros: differential control by wt1 and ff1b.

Steroids are synthesized mainly from the adrenal cortex. Adrenal deficiencies are often associated with problems related to its development, which is not fully understood. To better understand adrenocortical development, we studied zebrafish because of the ease of embryo manipulation. The adrenocortical equivalent in zebrafish is called the interrenal, because it is embedded in the kidney. We find that interrenal development parallels that of the embryonic kidney (pronephros). Primordial interrenal cells first appear as bilateral intermediate mesoderm expressing ff1b in a region ventral to the third somite. These cells then migrate toward the axial midline and fuse together. The pronephric primordia are wt1-expressing cells located next to the interrenal. They also migrate to the axial midline and fuse to become glomeruli at later developmental stages. Our gene knockdown experiments indicate that wt1 is required for its initial restricted expression in pronephric primordia, pronephric cell migration and fusion. wt1 also appears to be involved in interrenal development and ff1b expression. Similarly, ff1b is required for interrenal differentiation and activation of the differentiated gene, cyp11a1. Our results show that the zebrafish interrenal and pronephros are situated close together and go through parallel developmental processes but are governed by different signaling events.

Animals↗

PubMed2006

Elucidation of megalin/LRP2-dependent endocytic transport processes in the larval zebrafish pronephros.

Megalin/LRP2 is an endocytic receptor in the proximal tubules of the mammalian kidney that plays a central role in the clearance of metabolites from the glomerular filtrate. To establish a genetic model system for elucidation of molecular components of this retrieval pathway, we characterized orthologous transport processes in the zebrafish. We show that expression of megalin/LRP2 and its co-receptor cubilin is conserved in the larval zebrafish pronephros and demarcates a segment of the pronephric duct that is active in clearance of tracer from the ultrafiltrate. Knock-down of megalin/LRP2 causes lack of Rab4-positive endosomes in the proximal pronephric duct epithelium and abrogates apical endocytosis. Similarly, knock-down of the megalin/LRP2 adaptor Disabled 2 also blocks renal clearance processes. These results demonstrate the conservation of the megalin/LRP2 retrieval pathway between the larval zebrafish pronephros and the mammalian kidney and set the stage for dissection of the renal endocytic machinery in a simple model organism. Using this model system, we provide first genetic evidence that renal tubular endocytosis and formation of endosomes is a ligand-induced process that crucially depends on megalin/LRP2 activity.

Adaptor Proteins, Vesicular Transport↗

PubMed1990

Pronephros and mesonephros--Cohnheim revisited.

Erroneous quotations in the literature and Cohnheim's statement, in his Lectures on General Pathology, that the Wolffian body or mesonephros is the first anlage of the urogenital system prompted this description of the growth of our knowledge of the early development of the kidney. Some of the pertinent older literature is reviewed, and the concept of the holonephros, as opposed to the trinephric view of kidney development, is discussed. Emphasis is placed on the decreasing functional significance of the pronephros with evolutionary development, to the extent that the role of the pronephros in the human is questioned. Cohnheim's seemingly erroneous reference to the development of the kidney is shown to be merely a reflection of the views current at his time.

History, 19th Century↗

PubMed2002

Patterns of apoptosis during degeneration of the pronephros and mesonephros.

PURPOSE: The adult mammalian kidney is preceded developmentally by 2 primitive kidneys. We determine whether apoptosis is involved in the regression of these primitive organs and document its temporospatial characteristics. MATERIALS AND METHODS: Timed pregnant rats were sacrificed at 11 to 16 days of gestation inclusively. The fetuses were histologically examined to determine the timing and pattern of apoptosis in the primitive kidneys, including pronephros and mesonephros. RESULTS: Apoptosis of the pronephros occurred primarily at 12 days of gestation. Apoptosis of the distal mesonephros occurred primarily at 13 days and was completed by 14, which left the proximal mesonephros a functioning kidney during the early period of development. The location and timing of apoptosis were consistent and specific. CONCLUSIONS: Apoptosis appears to be an important mechanism of the normal regression of the primitive kidney and follows a strict temporospatial pattern.

Animals↗

PubMed1975

[Differentiation of the epithelium of the pronephros and the primary kidney in frogs].

The kidneys of tadpoles of different developmental stages were examined in preparations processed histologically and histochemically. It was found that differentiation of the provisory excretory organ tubules in frogs was "shortened" or "accelerated" after P. P. Ivanov's terminology, and developed differently as compared with differentiation of tubules of the definitive organ of excretion -- the primary kidney. When differentiating the epithelium of the proximal portion of the primary kidney nephron passes the stage of the high prismatic false-stratified epithelium. The pronephros tubules do not pass this stage and the epithelium becomes a strict monolayer from the very beginning. No mitoses are observed in the pronephros tubule epithelium even at the earliest differentiation stages. Later on, the beginning of tubule functioning, and with the reduction, and later disappearance of yolk granules in the epithelium solitary mitoses make their appearance. The mitotic activity of the primary kidney tubule epithelium is very high (70%) at the early stage of differentiation. Then its mitotic activity decreases (30%), and after the beginning of the tubule functioning mitoses in its epithelium become solitary.

Animals↗

PubMed1996

Wilms' tumor suppressor gene is involved in the development of disparate kidney forms: evidence from expression in the Xenopus pronephros.

The Wilms' tumor suppressor gene (WT1) is required for the formation of the mammalian metanephros, or adult kidney, and for the normal development of the mesonephros, the major mammalian embryonic kidney. In this report the isolation of a Xenopus gene closely related to the mammalian WT1 gene in both sequence and splicing pattern is described. Expression of this gene, xWT1, is restricted to the developing nephric system until late tadpole stages, which expression also begins to be observed in the heart. Within the nephric system, expression is observed in the dorsal portion of the splanchnic lateral plate in tailbud embryos, and in the glomus of early tadpoles. No expression is observed in the pronephric tubules or pronephric duct. The WT1 gene is therefore expressed in a similar temporal and spatial pattern in the vascularized portion of the amphibian pronephroi and in the mammalian metanephroi, arguing that it probably plays a similar crucial role in the morphogenesis of these very different kidney forms. The absence of expression in the developing pronephric tubules indicates that xWT1 is not required for the epithelialization of the tubular portion of the pronephros.

Animals↗

PubMed1999

Dynamic patterns of gene expression in the developing pronephros of Xenopus laevis.

Data from gene ablation studies in mice have indicated critical roles for Lim-1, Wnt4, WT-1, and Pax-2 in the coordination and execution of kidney patterning and differentiation. However, the precise roles of these molecules, their ordering within a genetic hierarchy, and the manner in which they contribute to establishing the fates of cells of each of the components of the nephron have yet to be elucidated in any system. In this report, the temporal and spatial expression patterns of these genes within the Xenopus pronephric system were examined in detail by single- and double-probe in situ hybridization. We describe restrictions of these gene expression patterns within the pronephros which indicate a model for the partitioning of the common pronephric anlage into its three component parts--the tubules, the glomus, and the duct.

Animals↗

PubMed1988

Morphology of the pronephros of the juvenile brown trout, Salmo trutta.

The pronephros in juvenile brown trout (Salmo trutta) consists of a large ovoid renal corpuscle and a pair of tubules. The corpuscle is retained for 11 months, after which the glomerulus regresses. The glomerular arteries come directly from the dorsal aorta. The interstitium is permeated with venous blood vessels that arise from the anterior cardinal veins and are closely apposed to the tubules. Two distinct segments of the pronephric tubular system are distinguished by the histological and ultrastructural features of their component cells: 1) a short, transitional neck in which cells change from capsular epithelium to columnar epithelium, typical of tubules; 2) the convoluted segment composed of cells similar to first proximal tubular cells of the opisthonephros with well-formed brush borders, apical vesicles that vary in size and number along this segment, and lysosomes. Pinocytosis and exocytosis are also evident in this segment. The tubular system increases in length and in its convolutions until about week 9, when the opisthonephros develops. Distally each tubule connects with a Wolffian duct, with cells marked by the absence of apical inclusions and the presence of a uniform brush border, numerous mitochondria, and elaborate infolding of the basalar membrane. Nephrostomes, which are often characteristic of pronephroi, are not present. Cells with long cilia are found throughout the tubular system but are most characteristic of the neck and Wolffian-duct segments.

Aging↗

PubMed1997

Model systems for the study of kidney development: use of the pronephros in the analysis of organ induction and patterning.

Most vertebrate organs, once formed, continue to perform the function for which they were generated until the death of the organism. The kidney is a notable exception to this rule. Vertebrates, even those that do not undergo metamorphosis, utilize a progression of more complex kidneys as they grow and develop. This is presumably due to the changing conditions to which the organism must respond to retain what Homer Smith referred to as our physiological freedom. To quote, "Recognizing that we have the kind of blood we have because we have the kind of kidneys we have, we must acknowledge that our kidneys constitute the major foundation of our physiological freedom. Only because they work the way they do has it become possible for us to have bones, muscles, glands, and brains. Superficially, it might be said that the function of the kidneys is to make urine; but in a more considered view one can say that the kidneys make the stuff of philosophy itself" ("From Fish to Philosopher," Little, Brown and Co., Boston, 1953). Different kidneys are used to make the stuff of philosophy at different stages of development depending on the age and needs of the organism, rather than the usual approach of simply making embryonic organs larger as the animal grows. Although evolution has provided the higher vertebrates with complex adult kidneys, they continue to utilize simple kidneys in embryogenesis. In lower vertebrates with simple adult kidneys, even more simple versions are used during early developmental stages. In this review the anatomy, development, and gene expression patterns of the embryonic kidney, the pronephros, will be described and compared to the more complex kidney forms. Despite some differences in anatomy, similar developmental pathways seem to be responsible for the induction and the response to induction in both evanescent and permanent kidney forms. Gene expression patterns can, therefore, be added to the morphological and functional data indicating that all forms of the kidney are closely related structures. Given the similarities between the development of simple and complex kidneys, the embryonic kidneys may be an ideal model system in which to investigate the genesis of multicomponent organ systems.

Animals↗

PubMed1983

Chemiluminescence of phagocytic cells isolated from the pronephros of striped bass.

Phagocytosis of bacterial fish pathogens by cells isolated from the pronephros of striped bass (Morone saxatilis) was measured using an assay of chemiluminescence. Results of the assay, which proved to be quite reproducible, indicated that the degree of phagocytosis was related to the number of bacteria employed and to the species of bacteria eliciting the response. Cells from individual fish gave similar phagocytic responses but of different magnitudes.

Animals↗

PubMed1987

Ultrastructural characterization of leucocytes in the pronephros of carp (Cyprinus carpio, L.).

In the pronephros of carp (Cyprinus carpio, L.) the following cells were found and ultrastructurally characterized: erythrocytes; lymphocytes and plasma cells; thrombocytes; neutrophilic, eosinophilic and basophilic granulocytes; phagocytic reticular cells and monocytes and non-phagocytic reticular cells. The cells could be separated on a Percoll continuous density gradient and relatively pure fractions could be obtained. In vitro phagocytosis of bacteria (Bacillus megaterium) was found in monocytes and neutrophilic granulocytes, while basophilic and eosinophilic granulocytes engulfed bacterial cells without actual endocytotic uptake.

Animals↗

PubMed1989

Effects of metal ions on cyprinid fish immune response: in vitro effects of Zn2+ and Mn2+ on the mitogenic response of carp pronephros lymphocytes.

Lymphocytes from the pronephros of carp (Cyprinus carpio L) have been subjected to transformation by mitogens, concanavalin A (Con A), phytohemagglutinin (PHA), and lipopolysaccharides (LPS), with Zn or Mn at varying concentrations. Addition of Zn2+ (10(-7) to 10(-3) M) to mitogen-stimulated T and B cells enhanced [3H]thymidine incorporation. Addition of 10(-5) M Zn2+ inhibited the response to Con A, PHA, and LPS. At this concentration, Zn was toxic. Addition of Mn2+ (10(-7) to 10(-3) M) to mitogen-stimulated lymphocytes enhanced [3H]thymidine incorporation. This effect was observed with Con A- and PHA-stimulated lymphocytes, but not with LPS-stimulated lymphocytes. In contrast, addition of 10(-1) M Mn2+ to lymphocyte cultures exerted an inhibitor on the response to Con A or to PHA, while the response to LPS was unaffected. Addition of 10(-1) M Mn2+ to Con A- or PHA-stimulated cultures at different times after initiation of stimulation indicated that Mn2+ was inhibitory only when it was added before the first 16 hr of cultures. The inhibition induced by 10(-1) M Mn2+ could be reversed by adding 2 mM CaCl2 to the culture.

Animals↗