Biology subjects

Bufler, P.

Publications and source records attributed to Bufler, P..

3 recordsLinked to original sources

bioRxiv2025

Kidney-specific Wdr72 deletion leads to incomplete distal renal tubular acidosis through impaired V-ATPase B1 subunit localization

BackgroundDistal renal tubular acidosis (dRTA) is a rare kidney disorder characterized by impaired urinary acidification due to defective proton secretion in type A intercalated cells of the collecting duct. Recently, pathogenic variants in the human gene encoding the WD Repeat Domain 72 protein (WDR72) have been reported in patients with dRTA, yet the physiological role of WDR72 in the kidney remains unknown. MethodsTo elucidate the renal function of Wdr72, we generated a kidney-specific knockout mouse model (Wdr72fl/fl;Pax8-Cre+) and assessed acid-base homeostasis under baseline, acute, and chronic acid loading. ResultsWdr72fl/fl;Pax8-Cre+ mice displayed persistently elevated urinary pH, reduced titratable acid and net acid excretion under basal and acid-loaded conditions, consistent with incomplete dRTA. While the systemic pH remained unchanged compared to controls under standard diet, chronic acid load led to mild hyperchloremic, hypokalemic metabolic acidosis. Notably, urinary NH excretion was increased upon acid loading accompanied by upregulation of key ammoniagenesis enzymes, which was detected even under basal conditions, consistent with a compensatory activation of proximal tubular acid excretion pathways. The total and membranous abundance of the V-ATPase B1 subunit decreased markedly within the kidney, despite unchanged transcript levels, suggesting a defect in V-ATPase trafficking or assembly. In addition, morphometric analyses revealed an increased proportion of type A intercalating cells that failed to expand upon acid loading, indicating defective adaptive plasticity. ConclusionsKidney-specific Wdr72 deletion impairs distal urinary acidification through reduced V-ATPase abundance and membranous targeting, altered intercalated cell morphology, and limited adaptive remodeling, resulting in incomplete dRTA. Upregulation of renal ammoniagenesis partially compensates the acidification defect. These findings highlight WDR72 as a key regulator of distal nephron acid-base homeostasis and offer mechanistic insight into WDR72-associated dRTA. Key PointsO_LIKidney-specific deletion of Wdr72 reduced Atp6v1b1 membranous localization in intercalated cells. C_LIO_LIKidney-specific Wdr72 knockout altered intercalated cell morphology, and limited their adaptive remodeling. C_LIO_LIThe lack of the renal Wdr72 resulted in incomplete dRTA, compensated partially by elevated ammoniagenesis. C_LI

molecular biology↗

bioRxiv2024

Fetal Liver-like Organoids Recapitulate Blood-Liver Niche Development and Multipotent Hematopoiesis from Human Pluripotent Stem Cells

The fetal liver is a hematopoietic organ, hosting a diverse and evolving progenitor population. While human liver organoids derived from pluripotent stem cells (PSCs) mimic aspects of embryonic and fetal development, they typically lack the complex hematopoietic niche and the interaction between hepatic and hematopoietic development. We describe the generation of human Fetal Liver-like Organoids (FLOs), that model human hepato-hematopoietic interactions previously characterized in mouse models. Developing FLOs first integrate a yolk sac-like hemogenic endothelium into hepatic endoderm and mesoderm specification. As the hepatic and hematopoietic lineages differentiate, the FLO culture model establishes an autonomous niche capable of driving subsequent progenitor differentiation without exogenous factors. Consistent with yolk sac-derived waves, hematopoietic progenitor cells (HPCs) within FLOs exhibit multipotency with a preference for myeloid lineage commitment, while retaining fetal B and T cell differentiation potential. We reconstruct in FLOs the embryonic monocyte-to-macrophage and granulocyte immune trajectories within the FLO microenvironment and assess their functional responses in the liver niche. In vivo, FLOs demonstrate a liver engraftment bias of hematopoietic cells, recapitulating a key phenomenon of human hematopoietic ontogeny. Our findings highlight the intrinsic capacity of liver organoids to support hematopoietic development, establishing FLOs as a platform for modeling and manipulating human blood-liver niche interactions during critical stages of development and disease.

developmental biology↗

bioRxiv2024

Dissecting compounded hepatocyte injury in a model of MASLD progression from human induced pluripotent stem cells

Drug discovery for multifactorial diseases like metabolic dysfunction-associated steatotic liver disease (MASLD) remains challenging due to inadequate models and untargeted drug screenings. We combined stem-cell-based modeling with computational drug predictions identifying flavin pathways as therapeutic targets in MASLD. For disease stage-specific discovery, we established a MASLD testing model, compounding metabolic triggers to intensify mitochondrial crisis. In vitro injuries included adipo- and myokines, immune cell co-culture, and genomic risk factors. Benchmarking experiments revealed similarities with advanced human MASLD. To query therapeutic compounds, protein-protein-interaction networks, weighted gene co-expression, and knowledge graph-based analyses independently predicted flavin adenine dinucleotide (FAD) as an anti-MASLD factor. Dysregulated flavoproteomes in vitro and in vivo-in pediatric and adult MASLD patients- supported our flavin network-focused strategy. We established therapeutic FAD concentrations to mitigate metabolic injury and fibro-inflammation in human multicellular liver organoids and other assays. We enhanced therapeutic FAD effects through genetic mitochondrial biogenic augmentation and identified orally available flavo-active compounds--including Aspirin--restoring mitochondrial respiration. Our study demonstrates how integrating stem cell-derived disease modeling with computed drug predictions can expedite therapeutic discovery.

cell biology↗