Biology subjects

Oxburgh, L.

Publications and source records attributed to Oxburgh, L..

7 recordsLinked to original sources

bioRxiv2026

Injury-induced Cxcl11 and neutrophil signaling drive zebrafish kidney regeneration by generating a nephrogenic niche of Fgf and Wnt expression

Adult zebrafish regenerate their kidneys after injury by activating quiescent renal stem cells, however the injury signals that activate kidney stem cells are not known. We show here that an innate immune, cytokine response after tubule injury is required and sufficient to induce adult zebrafish kidney regeneration. An injury reporter zebrafish transgenic, Tg(kim1:mScarlet3), revealed that tubule injury occurred specifically in kidney proximal tubules and was associated with a rapid accumulation of neutrophils and macrophages. Injury also activated a Tg(NFkB:GFP) reporter transgene specifically in kidney tubules where RNA seq revealed NFkB target gene and cytokine expression. Inhibition of NFkB signaling with JSH-23 blocked Tg(NFkB:GFP) reporter activation and also inhibited induction of new nephrons. Systemic injection of the immune activators lipopolysaccharide or zymosan into uninjured fish rapidly induced cytokine expression followed by nephrogenic gene expression and the appearance of new, functional nephrons. Analysis of injury-induced cytokines revealed that several paralogs of cxcl11 were strongly expressed throughout the regeneration response and injection of recombinant Cxcl11 was sufficient to induce FGF-dependent kidney stem cell aggregation, but not Wnt-dependent epithelial differentiation. Kidney injury in zebrafish expressing a neutrophil dominant negative rac2D57N transgene activated Fgf signaling but failed to induce wnt9b or downstream Wnt target genes. Nephrogenic gene expression and epithelial tubule formation was rescued by treatment with the canonical Wnt agonist CHIR. Our findings demonstrate that an injury-induced, sterile immune response regulates kidney regeneration by establishing a nephrogenic niche of Fgf and Wnt signaling that supports tissue-resident kidney stem cell differentiation into functional nephrons.

developmental biology↗

bioRxiv2025

Mitochondrial organization in the developing proximal tubule is controlled by LRRK2

The proximal tubule of the nephron resorbs water, amino acids and glucose, and its energy demands are high. Formation of the cellular machinery for energy production is an essential step in proximal tubule epithelial cell (PTC) differentiation, and this report focuses on how mitochondria in nascent PTCs are redistributed from their initial apical position to their ultimate basolateral location. We found that mitochondria move from the apical to basolateral side of the PTC coincident with the initiation of lumen flow and that proximal tubules deficient in filtration (aglomerular mice and kidney organoids) maintain their mitochondria in the apical position, indicating that flow is necessary and sufficient for localization. Further, we show that mitochondrial localization depends on the activity of LRRK2 in vitro and in vivo. Modeling the effect of fluid flow on PTCs demonstrates that LRRK2 activity is regulated by fluid shear stress, providing an explanation for how onset of flow in the newly differentiated proximal tubule may trigger the apical-to-basolateral dissemination of mitochondria that forms the template for subsequent PTC maturation. Our findings indicate that mitochondrial redistribution is one component of a cellular program in the nascent PTC that drives function and that this process is regulated by flow.

developmental biology↗

bioRxiv2025

Multiple Wnt signaling pathways direct epithelial tubule interconnection in the regenerating zebrafish kidney

Epithelial tubule fusion is fundamental for kidney morphogenesis. Differentiating nephron tubules interconnect with collecting system epithelia to generate a lumenal pathway for fluid excretion. In the adult zebrafish kidney, nephrogenesis occurs as a regenerative response to injury and provides a model to explore cell signaling pathways required for tubule interconnection. We show that canonical Wnt signaling at the junction between two tubules induces a mesenchymal, invasive cell phenotype and is required, along with Src kinase and rac1, to generate basal cell protrusions. The Wnt ligands wnt9b and wnt4 are both required for new nephron formation after injury. Mutation in wnt4 or treatment with the canonical Wnt inhibitor IWR1 blocks formation of basal protrusions in forming nephrons. Mutation in the Wnt receptor frizzled9b reveals a fusion-associated non-canonical Wnt pathway that acts to 1) restrict canonical Wnt gene expression, 2) drive Rho kinase-dependent apical constriction of epithelial cells, and 3) position basal protrusions and generate orthogonal tubule lumenal connections. As a result, frizzled9b mutant nephrons fail to fully interconnect with target distal tubules. Our results indicate that canonical and non-canonical Wnt signaling interact in the same cells to orient and drive tubule interconnection in the regenerating zebrafish kidney.

developmental biology↗

bioRxiv2024

Epithelial tubule interconnection driven by HGF-Met signaling in the kidney

The formation of functional epithelial tubules is a central feature of many organ systems. Although the process of tubule formation by epithelial cells is well-studied, the way in which tubules connect with each other (i.e. anastomose) to form functional networks both in vivo and in vitro is not well understood. A key, unanswered question in the kidney is how the renal vesicles of the embryonic kidney connect with the nascent collecting ducts to form a continuous urinary system. We performed a ligand-receptor pair analysis on single cell RNA-seq data from embryonic mouse kidney tubules undergoing anastomosis to select candidates that might mediate this process in vivo. This analysis identified hepatocyte growth factor (HGF), which has known roles in cell proliferation, migration, and tubulogenesis, as one of several possible candidates. To test this possibility, we designed a novel assay to quantitatively examine epithelial tubule anastomosis in vitro using epithelial spheroids with fluorescently-tagged apical surfaces to enable direct visualization of anastomosis. This revealed that HGF is a potent inducer of tubule anastomosis. Tubule anastomosis occurs through a proliferation-independent mechanism that acts through the MAPK signaling cascade and matrix metalloproteinases (MMPs), the latter suggestive of a role in extracellular matrix turnover. Accordingly, treatment of explanted embryonic mouse kidneys with HGF and collagenase was sufficient to induce kidney tubule anastomosis. These results lay the groundwork for investigating how to promote functional interconnections between tubular epithelia, which have important clinical implications for utilizing in vitro grown kidney tissue in transplant medicine.

developmental biology↗

bioRxiv2020

A β-catenin-driven switch in TCF/LEF transcription factor binding to DNA targets sites promotes commitment of mammalian nephron progenitor cells

The canonical Wnt pathway transcriptional co-activator {beta}-catenin regulates self-renewal and differentiation of mammalian nephron progenitor cells (NPCs). We modulated {beta}-catenin levels in NPC cultures using the GSK3 inhibitor CHIR9902 (CHIR) to examine opposing developmental actions of {beta}-catenin. Low CHIR-mediated maintenance and expansion of NPCs is independent of direct engagement of TCF/LEF/ {beta}-catenin transcriptional complexes at low-CHIR dependent cell-cycle targets. In contrast, in high CHIR, TCF7/LEF1/{beta}-catenin complexes replaced TCF7L1/TCF7L2 binding on enhancers of differentiation-promoting target genes. Chromosome confirmation studies showed pre-established promoter-enhancer connections to these target genes in NPCs. High CHIR-associated de novo looping was observed in positive transcriptional feedback regulation to the canonical Wnt pathway. Thus, {beta}-catenins direct transcriptional role is restricted to the induction of NPCs where rising {beta}-catenin levels switch inhibitory TCF7L1/TCF7L2 complexes to activating LEF1/TCF7 complexes at primed gene targets poised for rapid initiation of a nephrogenic program.

developmental biology↗

bioRxiv2020

Proliferation control of kidney interstitial cells

Expansion of interstitial cells in the adult kidney is a hallmark of chronic disease, whereas their proliferation during fetal development is necessary for organ formation. An intriguing difference between adult and neonatal kidneys is that the neonatal kidney has the capacity to control interstitial cell proliferation when the target number has been reached. In this study, we define the consequences of inactivating the TGF{beta}/Smad response in the interstitial cell lineage. We find that pathway inactivation through loss of Smad4 leads to over-proliferation of interstitial cells regionally in the kidney medulla. Genetic and molecular interaction studies showed that Smad3/4 participates in the Wnt/{beta}-catenin signaling pathway, which is responsible for promoting proliferation of interstitial cells. Specifically, Smad4 is required for the expression of the Wnt feedback inhibitor Apcdd1, and based on these findings we propose a model for interstitial cell proliferation control in which the Wnt/{beta}-catenin proliferative signal is attenuated by TGF{beta}/Smad signaling to ensure that proliferation ceases when the target number of interstitial cells has been reached in the neonatal medulla. Summary statementThis study describes a novel function for TGF{beta} signaling in the developing renal interstitium. Mice with Foxd1-Cre-mediated deletion of Smad4 have interstitial expansion and activated Wnt signaling.

developmental biology↗

bioRxiv2019

Asynchronous mixing of kidney progenitor cells potentiates nephrogenesis in organoids

Recent years have seen rapid advances in directed differentiation of human pluripotent stem cells (PSCs) to kidney cells. However, a fundamental difficulty in emulating kidney tissue formation is that kidney development is iterative. Recent studies argue that the human nephron forms through gradual contribution of nephron progenitor cells whose differentiation fates depend on the time at which they are recruited. We show that the majority of PSC-derived nephron progenitor cells differentiated in a short wave in organoid formation and to improve fidelity of PSC-derived organoids, we emulated the asynchronous mix found in the fetal kidney by combining cells differentiated at different times in the same organoid. Asynchronous mixing promoted nephrogenesis, and lineage marking data showed that proximal and distal nephron components preferentially derive from cell populations differentiated at distinct times. When engrafted under the kidney capsule these heterochronic organoids were vascularized and displayed essential features of kidney tissue. Micro-CT and injection of a circulating vascular marker demonstrated that engrafted kidney tissue was connected to the systemic circulation by 2 weeks after engraftment. Proximal tubule glucose uptake was confirmed using intravenous injection of fluorescent dextran. Despite these promising measures of graft function, overgrowth of stromal cells prevented long-term study, and we propose that this is a technical feature of the engraftment procedure rather than a specific shortcoming of the directed differentiation because kidney organoids derived from primary cells and whole embryonic kidneys develop the same stromal overgrowth when engrafted under the kidney capsule.

developmental biology↗