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Kidney International May 2008Nephrons possess a segmental organization where each segment is specialized for the secretion and reabsorption of particular solutes. The developmental control of... (Review)
Review
Nephrons possess a segmental organization where each segment is specialized for the secretion and reabsorption of particular solutes. The developmental control of nephron segment patterning remains one of the enigmas within the field of renal biology. Achieving an understanding of the mechanisms that direct nephron segmentation has the potential to shed light on the causes of kidney birth defects and renal diseases in humans. Researchers studying embryonic kidney development in zebrafish and Xenopus have recently demonstrated that the pronephric nephrons in these vertebrates are segmented in a similar fashion as their mammalian counterparts. Further, it has been shown that retinoic acid signaling establishes proximodistal segment identities in the zebrafish pronephros by modulating the expression of renal transcription factors and components of signaling pathways that are known to direct segment fates during mammalian nephrogenesis. These findings present the zebrafish model as an excellent genetic system in which to interrogate the conserved developmental pathways that control nephron segmentation in both lower vertebrates and mammals.
Topics: Animals; Models, Animal; Nephrons; Organogenesis; Tretinoin; Zebrafish
PubMed: 18322540
DOI: 10.1038/ki.2008.37 -
PLoS Genetics Oct 2007Kidney function depends on the nephron, which comprises a blood filter, a tubule that is subdivided into functionally distinct segments, and a collecting duct. How these...
Kidney function depends on the nephron, which comprises a blood filter, a tubule that is subdivided into functionally distinct segments, and a collecting duct. How these regions arise during development is poorly understood. The zebrafish pronephros consists of two linear nephrons that develop from the intermediate mesoderm along the length of the trunk. Here we show that, contrary to current dogma, these nephrons possess multiple proximal and distal tubule domains that resemble the organization of the mammalian nephron. We examined whether pronephric segmentation is mediated by retinoic acid (RA) and the caudal (cdx) transcription factors, which are known regulators of segmental identity during development. Inhibition of RA signaling resulted in a loss of the proximal segments and an expansion of the distal segments, while exogenous RA treatment induced proximal segment fates at the expense of distal fates. Loss of cdx function caused abrogation of distal segments, a posterior shift in the position of the pronephros, and alterations in the expression boundaries of raldh2 and cyp26a1, which encode enzymes that synthesize and degrade RA, respectively. These results suggest that the cdx genes act to localize the activity of RA along the axis, thereby determining where the pronephros forms. Consistent with this, the pronephric-positioning defect and the loss of distal tubule fate were rescued in embryos doubly-deficient for cdx and RA. These findings reveal a novel link between the RA and cdx pathways and provide a model for how pronephric nephrons are segmented and positioned along the embryonic axis.
Topics: Animals; Cloning, Molecular; Gene Expression Regulation; Gene Expression Regulation, Developmental; Homeodomain Proteins; In Situ Hybridization; Kidney; Mice; Models, Biological; Mutation; Phenotype; Protein Structure, Tertiary; Transcription Factors; Tretinoin; Zebrafish
PubMed: 17953490
DOI: 10.1371/journal.pgen.0030189 -
Genesis (New York, N.Y. : 2000) Sep 2016Cilia arose early during eukaryotic evolution, and their structural components are highly conserved from the simplest protists to complex metazoan species. In recent... (Review)
Review
Cilia arose early during eukaryotic evolution, and their structural components are highly conserved from the simplest protists to complex metazoan species. In recent years, the role of cilia in the ontogeny of vertebrate organs has received increasing attention due to a staggering correlation between human disease and dysfunctional cilia. In particular, the presence of cilia in both the developing and mature kidney has become a deep area of research due to ciliopathies common to the kidney, such as polycystic kidney disease (PKD). Interestingly, mutations in genes encoding proteins that localize to the cilia cause similar cystic phenotypes in kidneys of various vertebrates, suggesting an essential role for cilia in kidney organogenesis and homeostasis as well. Importantly, the genes so far identified in kidney disease have conserved functions across species, whose kidneys include both primary and motile cilia. Here, we aim to provide a comprehensive description of cilia and their role in kidney development, as well as highlight the usefulness of the zebrafish embryonic kidney as a model to further understand the function of cilia in kidney health.
Topics: Animals; Cilia; Humans; Kidney; Morphogenesis
PubMed: 27389733
DOI: 10.1002/dvg.22957 -
Cells Sep 2015The nephron is the basic structural and functional unit of the vertebrate kidney. To ensure kidney functions, the nephrons possess a highly segmental organization where... (Review)
Review
The nephron is the basic structural and functional unit of the vertebrate kidney. To ensure kidney functions, the nephrons possess a highly segmental organization where each segment is specialized for the secretion and reabsorption of particular solutes. During embryogenesis, nephron progenitors undergo a mesenchymal-to-epithelial transition (MET) and acquire different segment-specific cell fates along the proximo-distal axis of the nephron. Even if the morphological changes occurring during nephrogenesis are characterized, the regulatory networks driving nephron segmentation are still poorly understood. Interestingly, several studies have shown that the pronephric nephrons in Xenopus and zebrafish are segmented in a similar fashion as the mouse metanephric nephrons. Here we review functional and molecular aspects of nephron segmentation with a particular interest on the signaling molecules and transcription factors recently implicated in kidney development in these three different vertebrate model organisms. A complete understanding of the mechanisms underlying nephrogenesis in different model organisms will provide novel insights on the etiology of several human renal diseases.
PubMed: 26378582
DOI: 10.3390/cells4030483 -
Developmental Dynamics : An Official... Dec 2015Development of the pronephros in Xenopus laevis is largely dependent on retinoic acid signaling at the time of kidney field specification with the simultaneous...
BACKGROUND
Development of the pronephros in Xenopus laevis is largely dependent on retinoic acid signaling at the time of kidney field specification with the simultaneous occurrence of a necessary calcium signaling. At the crossroads of these two signaling pathways, we studied the role of Hspa9 (heat shock 70 kDa protein 9) encoding a mitochondrial chaperone in pronephros development.
RESULTS
We first showed that Hspa9 is highly expressed in the pronephros territory and elongating nephric duct. We then observed that upon reduced retinoic acid signaling hspa9 expression was reduced as pax8 and pax2. Overexpression of hspa9 enlarged the pax8 positive pronephros territory, leading to a larger pronephric tubule. Loss of function of hspa9 in the kidney field using morpholino approach severely reduced pax8 expression and pronephros formation. Phenotypic rescue was achieved by co-injection of the full-length murine Hspa9 mRNA. However, no rescue was observed when Hspa9 mRNA lacking the mitochondrial-targeting sequence was injected, as this truncated form is able to interfere with pronephros formation when injected solely.
CONCLUSIONS
Hspa9 is an important mediator for pronephros development through modulation of pax8. Mitochondrial functions of hspa9 are likely to be involved in specification of pronephric cell fate.
Topics: Animals; Gene Expression Regulation, Developmental; HSP70 Heat-Shock Proteins; Mitochondrial Proteins; Paired Box Transcription Factors; Pronephros; Signal Transduction; Tretinoin; Xenopus Proteins; Xenopus laevis
PubMed: 26335666
DOI: 10.1002/dvdy.24344 -
Journal of Developmental Biology Oct 2022The Wilms' tumor suppressor gene, , encodes a zinc finger-containing transcription factor that binds to a GC-rich motif and regulates the transcription of target genes....
The Wilms' tumor suppressor gene, , encodes a zinc finger-containing transcription factor that binds to a GC-rich motif and regulates the transcription of target genes. was first identified as a tumor suppressor gene in Wilms' tumor, a pediatric kidney tumor, and has been implicated in normal kidney development. The WT1 protein has transcriptional activation and repression domains and acts as a transcriptional activator or repressor, depending on the target gene and context. In , an ortholog of has been isolated and shown to be expressed in the developing embryonic pronephros. To investigate the role of in pronephros development in embryos, we mutated by CRISPR/Cas9 and found that the expression of pronephros marker genes was reduced. In reporter assays in which known WT1 binding sequences were placed upstream of the gene, WT1 activated transcription of the gene. The injection of wild-type or artificially altered transcriptional activity of mRNA disrupted the expression of pronephros marker genes in the embryos. These results suggest that the appropriate amounts and activity of WT1 protein are required for normal pronephros development in embryos.
PubMed: 36412640
DOI: 10.3390/jdb10040046 -
Development (Cambridge, England) Dec 1998The zebrafish pronephric kidney provides a simplified model of nephron development and epithelial cell differentiation which is amenable to genetic analysis. The...
The zebrafish pronephric kidney provides a simplified model of nephron development and epithelial cell differentiation which is amenable to genetic analysis. The pronephros consists of two nephrons with fused glomeruli and paired pronephric tubules and ducts. Nephron formation occurs after the differentiation of the pronephric duct with both the glomeruli and tubules being derived from a nephron primordium. Fluorescent dextran injection experiments demonstrate that vascularization of the zebrafish pronephros and the onset of glomerular filtration occurs between 40 and 48 hpf. We isolated fifteen recessive mutations that affect development of the pronephros. All have visible cysts in place of the pronephric tubule at 2-2.5 days of development. Mutants were grouped in three classes: (1) a group of twelve mutants with defects in body axis curvature and manifesting the most rapid and severe cyst formation involving the glomerulus, tubule and duct, (2) the fleer mutation with distended glomerular capillary loops and cystic tubules, and (3) the mutation pao pao tang with a normal glomerulus and cysts limited to the pronephric tubules. double bubble was analyzed as a representative of mutations that perturb the entire length of the pronephros and body axis curvature. Cyst formation begins in the glomerulus at 40 hpf at the time when glomerular filtration is established suggesting a defect associated with the onset of pronephric function. Basolateral membrane protein targeting in the pronephric duct epithelial cells is also severely affected, suggesting a failure in terminal epithelial cell differentiation and alterations in electrolyte transport. These studies reveal the similarity of normal pronephric development to kidney organogenesis in all vertebrates and allow for a genetic dissection of genes needed to establish the earliest renal function.
Topics: Animals; Crosses, Genetic; DNA-Binding Proteins; Embryo, Nonmammalian; Embryonic Induction; Female; Gene Expression Regulation, Developmental; Kidney; Kidney Glomerulus; Kidney Tubules; Male; Mutagenesis; Nephrons; PAX2 Transcription Factor; Phenotype; Transcription Factors; WT1 Proteins; Zebrafish; Zebrafish Proteins; Zinc Fingers
PubMed: 9806915
DOI: 10.1242/dev.125.23.4655 -
Developmental Biology Jun 2006The ecotropic viral integration site 1 (Evi1) and related MEL1 (MDS1/Evi1-like gene 1) genes are zinc finger oncogenic transcription factors involved in myeloid...
The ecotropic viral integration site 1 (Evi1) and related MEL1 (MDS1/Evi1-like gene 1) genes are zinc finger oncogenic transcription factors involved in myeloid leukaemia. Here, we show that in Xenopus, Evi1 and MEL1 have partially overlapping restricted embryonic expression profiles. Within the pronephros, Evi1 and MEL1 are sequentially expressed within the distal tubule and duct compartments, Evi1 transcription being detected prior to any sign of pronephric morphogenesis. In the pronephros of zebrafish embryos, Evi1 expression is restricted to the posterior portion of the duct, the anterior portion having characteristics of proximal tubules. In the Xenopus pronephros, Evi1 expression is upregulated by retinoid signaling and repressed by overexpression of xWT1 and by Notch signaling. Overexpression of Evi1 from late neurula stage specifically inhibits the expression of proximal tubule and glomus pronephric markers. We show that the first zinc finger and CtBP interaction domains are required for this activity. Overexpression of a hormone-inducible Evi1-VP16 antimorphic fusion with activation at neurula stage disrupts distal tubule and duct formation and expands the expression of glomus markers. Although overexpression of this construct also causes in many embryos a reduction of proximal tubule markers, embryos with expanded and ectopic staining have been also observed. Together, these data indicate that Evi1 plays a role in the proximo-distal patterning of the pronephros and suggest that it may do so by functioning as a CtBP dependent repressor.
Topics: Amino Acid Sequence; Animals; Carrier Proteins; Gene Expression Regulation, Developmental; Kidney; Membrane Proteins; Morphogenesis; Sequence Alignment; Thyroid Hormones; Transcription Factors; Transcription, Genetic; Up-Regulation; Xenopus Proteins; Xenopus laevis; Thyroid Hormone-Binding Proteins
PubMed: 16574097
DOI: 10.1016/j.ydbio.2006.02.040 -
Scientific Reports Nov 2023The transcription factor Six2 plays a crucial role in maintaining self-renewing nephron progenitor cap mesenchyme (CM) during metanephric kidney development. In mouse...
The transcription factor Six2 plays a crucial role in maintaining self-renewing nephron progenitor cap mesenchyme (CM) during metanephric kidney development. In mouse and human, expression at single-cell resolution has detected Six2 in cells as they leave the CM pool and differentiate. The role Six2 may play in these cells as they differentiate remains unknown. Here, we took advantage of the zebrafish pronephric kidney which forms directly from intermediate mesoderm to test six2b function during pronephric tubule development and differentiation. Expression of six2b during early zebrafish development was consistent with a role in pronephros formation. Using morpholino knock-down and CRISPR/Cas9 mutagenesis, we show a functional role for six2b in the development of proximal elements of the pronephros. By 48 h post-fertilization, six2b morphants and mutants showed disrupted pronephric tubule morphogenesis. We observed a lower-than-expected frequency of phenotypes in six2b stable genetic mutants suggesting compensation. Supporting this, we detected increased expression of six2a in six2b stable mutant embryos. To further confirm six2b function, F crispant embryos were analyzed and displayed similar phenotypes as morphants and stable mutants. Together our data suggests a conserved role for Six2 during nephrogenesis and a role in the morphogenesis of the proximal tubule.
Topics: Animals; Humans; Mice; Morphogenesis; Nephrons; Pronephros; Zebrafish; Zebrafish Proteins
PubMed: 37952044
DOI: 10.1038/s41598-023-47046-3 -
Developmental Biology Jan 2006Prostaglandin G/H synthases (PGHS), commonly referred to as cyclooxygenases (COX-1 and COX-2), catalyze a key step in the synthesis of biologically active prostaglandins... (Review)
Review
Prostaglandin G/H synthases (PGHS), commonly referred to as cyclooxygenases (COX-1 and COX-2), catalyze a key step in the synthesis of biologically active prostaglandins (PGs), the conversion of arachidonic acid (AA) into prostaglandin H(2) (PGH(2)). PGs have important functions in a variety of physiologic and pathologic settings, including inflammation, cardiovascular homeostasis, reproduction, and carcinogenesis. However, an evaluation of prostaglandin function in early development has been difficult due to the maternal contribution of prostaglandins from the uterus. The emergence of zebrafish as a model system has begun to provide some insights into the roles of this signaling cascade during vertebrate development. In zebrafish, COX-1 derived prostaglandins are required for two distinct stages of development, namely during gastrulation and segmentation. During gastrulation, PGE(2) signaling promotes cell motility, without altering the cell shape or directional migration of gastrulating cells. During segmentation, COX-1 signaling is also required for posterior mesoderm development, including the formation of vascular tube structures, angiogenesis of intersomitic vessels, and pronephros morphogenesis. We propose that deciphering the role for prostaglandin signaling in zebrafish development could yield insight and ultimately address the mechanistic details underlying various disease processes that result from perturbation of this pathway.
Topics: Animals; Eicosanoids; Embryonic Development; Gene Expression Regulation, Developmental; Mice; Models, Animal; Models, Biological; Prostaglandin-Endoperoxide Synthases; Prostaglandins; Receptors, Prostaglandin; Signal Transduction; Zebrafish
PubMed: 16310177
DOI: 10.1016/j.ydbio.2005.10.013