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Mouse models of autosomal dominant polycystic kidney disease (ADPKD) show that intact primary cilia are required for cyst growth following the inactivation of polycystin-1. The signaling pathways underlying this process, termed cilia-dependent cyst activation (CDCA), remain unknown. Using translating ribosome affinity purification RNASeq on mouse kidneys with polycystin-1 and cilia inactivation before cyst formation, we identify the differential ‘CDCA pattern’ translatome specifically dysregulated in kidney tubule cells destined to form cysts. From this, Glis2 emerges as a candidate functional effector of polycystin signaling and CDCA. In vitro changes in Glis2 expression mirror the polycystin- and cilia-dependent changes observed in kidney tissue, validating Glis2 as a cell culture-based indicator of polycystin function related to cyst formation. Inactivation of Glis2 suppresses polycystic kidney disease in mouse models of ADPKD, and pharmacological targeting of Glis2 with antisense oligonucleotides slows disease progression. Glis2 transcript and protein is a functional target of CDCA and a potential therapeutic target for treating ADPKD. Cyst growth in autosomal dominant polycystic kidney disease (ADPKD) is driven by unknown molecular signals that require the presence of intact primary cilia in the absence of the PKD gene products. Here, the authors show that the transcription factor Glis2 is a key effector of this cilia dependent cyst growth pathway and a potential target for therapy in ADPKD

Initiation of cyst formation in autosomal dominant polycystic kidney disease (ADPKD) occurs when kidney tubule cells are rendered null for either PKD1 or PKD2 by somatic ‘second hit’ mutations. Subsequent cyst progression remodels the organ through changes in tubule cell shape, proliferation and secretion. The kidney develops inflammation and fibrosis. We constructed a mouse model in which adult inactivation of either Pkd gene can be followed by reactivation of the gene at a later time. Using this model, we show that re-expression of Pkd genes in cystic kidneys results in rapid reversal of ADPKD. Cyst cell proliferation is reduced, autophagy is activated and cystic tubules with expanded lumina lined by squamoid cells revert to normal lumina lined by cuboidal cells. Increases in inflammation, extracellular matrix deposition and myofibroblast activation are reversed, and the kidneys become smaller. We conclude that phenotypic features of ADPKD are reversible and that the kidney has an unexpected capacity for plasticity controlled at least in part by ADPKD gene function. Re-expression of Pkd genes in cystic kidneys results in rapid reversal of autosomal dominant polycystic kidney disease phenotypes in mice, revealing an unexpected capacity for renal plasticity under the control of Pkd gene function.

Autosomal-dominant polycystic kidney disease (ADPKD) is the most common genetic renal disease, primarily caused by germline mutation of PKD1 or PKD2, leading to end-stage renal disease. The Hippo signaling pathway regulates organ growth and cell proliferation. Herein, we demonstrate the regulatory mechanism of cystogenesis in ADPKD by transcriptional coactivator with PDZ-binding motif (TAZ), a Hippo signaling effector. TAZ was highly expressed around the renal cyst-lining epithelial cells of Pkd1-deficient mice. Loss of Taz in Pkd1-deficient mice reduced cyst formation. In wild type, TAZ interacted with PKD1, which inactivated β-catenin. In contrast, in PKD1-deficient cells, TAZ interacted with AXIN1, thus increasing β-catenin activity. Interaction of TAZ with AXIN1 in PKD1-deficient cells resulted in nuclear accumulation of TAZ together with β-catenin, which up-regulated c-MYC expression. Our findings suggest that the PKD1–TAZ–Wnt–β-catenin–c-MYC signaling axis plays a critical role in cystogenesis and might be a potential therapeutic target against ADPKD.

Polycystic kidney disease is marked by progressive growth of renal tubular epithelia and thus the formation of pathological cysts in the organ over time. Alessandra Boletta and her colleagues now show that this cystic growth has the hallmarks of the Warburg effect (that is, the primary reliance of cells on glycolysis for their energy demands) and that blocking this effect in vivo is sufficient to improve disease progression in two mouse models. Autosomal dominant polycystic kidney disease (ADPKD) is a common genetic disorder characterized by bilateral renal cyst formation 1 . Recent identification of signaling cascades deregulated in ADPKD has led to the initiation of several clinical trials, but an approved therapy is still lacking 2 , 3 . Using a metabolomic approach, we identify a pathogenic pathway in this disease that can be safely targeted for therapy. We show that mutation of PKD1 results in enhanced glycolysis in cells in a mouse model of PKD and in kidneys from humans with ADPKD. Glucose deprivation resulted in lower proliferation and higher apoptotic rates in PKD1 -mutant cells than in nondeprived cells. Notably, two distinct PKD mouse models treated with 2-deoxyglucose (2DG), to inhibit glycolysis, had lower kidney weight, volume, cystic index and proliferation rates as compared to nontreated mice. These metabolic alterations depend on the extracellular signal-related kinase (ERK) pathway acting in a dual manner by inhibiting the liver kinase B1 (LKB1)–AMP-activated protein kinase (AMPK) axis on the one hand while activating the mTOR complex 1 (mTORC1)-glycolytic cascade on the other. Enhanced metabolic rates further inhibit AMPK. Forced activation of AMPK acts in a negative feedback loop, restoring normal ERK activity. Taken together, these data indicate that defective glucose metabolism is intimately involved in the pathobiology of ADPKD. Our findings provide a strong rationale for a new therapeutic strategy using existing drugs, either individually or in combination.

The application of organoids has been limited by the lack of methods for producing uniformly mature organoids at scale. This study introduces an organoid culture platform, called UniMat, which addresses the challenges of uniformity and maturity simultaneously. UniMat is designed to not only ensure consistent organoid growth but also facilitate an unrestricted supply of soluble factors by a 3D geometrically-engineered, permeable membrane-based platform. Using UniMat, we demonstrate the scalable generation of kidney organoids with enhanced uniformity in both structure and function compared to conventional methods. Notably, kidney organoids within UniMat show improved maturation, showing increased expression of nephron transcripts, more in vivo-like cell-type balance, enhanced vascularization, and better long-term stability. Moreover, UniMat’s design offers a more standardized organoid model for disease modeling and drug testing, as demonstrated by polycystic-kidney disease and acute kidney injury modeling. In essence, UniMat presents a valuable platform for organoid technology, with potential applications in organ development, disease modeling, and drug screening. Organoid research can be limited by the lack of methods for producing uniformly mature organoids. Here, the authors present UniMat, an organoid culture platform featuring a 3D geometrically-engineered permeable membrane, which produces uniform and mature organoids by providing both geometrical constraints and unrestricted supply of factors.

Background Ciliopathies are clinically diverse disorders of the primary cilium. Remarkable progress has been made in understanding the molecular basis of these genetically heterogeneous conditions; however, our knowledge of their morbid genome, pleiotropy, and variable expressivity remains incomplete. Results We applied genomic approaches on a large patient cohort of 371 affected individuals from 265 families, with phenotypes that span the entire ciliopathy spectrum. Likely causal mutations in previously described ciliopathy genes were identified in 85% (225/265) of the families, adding 32 novel alleles. Consistent with a fully penetrant model for these genes, we found no significant difference in their “mutation load” beyond the causal variants between our ciliopathy cohort and a control non-ciliopathy cohort. Genomic analysis of our cohort further identified mutations in a novel morbid gene TXNDC15 , encoding a thiol isomerase, based on independent loss of function mutations in individuals with a consistent ciliopathy phenotype (Meckel-Gruber syndrome) and a functional effect of its deficiency on ciliary signaling. Our study also highlighted seven novel candidate genes ( TRAPPC3 , EXOC3L2 , FAM98C , C17orf61 , LRRCC1 , NEK4 , and CELSR2 ) some of which have established links to ciliogenesis. Finally, we show that the morbid genome of ciliopathies encompasses many founder mutations, the combined carrier frequency of which accounts for a high disease burden in the study population. Conclusions Our study increases our understanding of the morbid genome of ciliopathies. We also provide the strongest evidence, to date, in support of the classical Mendelian inheritance of Bardet-Biedl syndrome and other ciliopathies.

Key Points In autosomal dominant polycystic kidney disease (ADPKD), renal cyst formation begins in utero and continues throughout life Renal cysts originate in tubules and contribute to the development of renal insufficiency Individual renal cysts progressively expand at a constant rate that can differ widely from the growth rate of neighbouring cysts Cysts disrupt the renal ultrastructure in the early stages of ADPKD and cause renin-dependent hypertension, albuminuria, interstitial inflammation, fibrosis, and the destruction of functioning nephrons. Evidence indicates that the annual rate of kidney growth in ADPKD is inversely linked to the decline in glomerular filtration rate so can be used to predict future decline in glomerular function Longitudinal studies in thousands of patients have provided evidence to validate the use of total kidney volume as a prognostic marker and as a potential indicator of treatment efficacy in ADPKD The usefulness of total kidney volume (TKV) as a biomarker of disease progression in autosomal dominant polycystic kidney disease is disputed. Here, the authors propose that TKV can be used to monitor treatment efficacy and as a surrogate end point in clinical trials. The rate at which autosomal dominant polycystic kidney disease (ADPKD) progresses to end-stage renal disease varies widely and is determined by genetic and non-genetic factors. The ability to determine the prognosis of children and young adults with ADPKD is important for the effective life-long management of the disease and to enable the efficacy of emerging therapies to be determined. Total kidney volume (TKV) reflects the sum volume of hundreds of individual cysts with potentially devastating effects on renal function. The sequential measurement of TKV has been advanced as a dynamic biomarker of disease progression, yet doubt remains among nephrologists and regulatory agencies as to its usefulness. Here, we review the mechanisms that lead to an increase in TKV in ADPKD, and examine the evidence supporting the conclusion that TKV provides a metric of disease progression that can be used to assess the efficacy of potential therapeutic regimens in children and adults with ADPKD. Moreover, we propose that TKV can be used to monitor treatment efficacy in patients with normal levels of renal function, before the pathologic processes of ADPKD cause extensive fibrosis and irreversible loss of functioning renal tissue.

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive bilateral cyst formation. Multiple cellular pathways including second messenger cAMP signaling are dysregulated in ADPKD, but mechanisms initiating cysts are unknown. ADPKD is caused by mutations in PKD1/PKD2 genes encoding for polycystins that localize to primary cilia—nonmotile, microtubule-based dynamic compartments sensing extracellular chemical/mechanical signals. The compact cylindrical structure of cilia enables tunable signaling amplification regulatable by ciliary length. Severe cystogenesis from polycystin loss is cilia dependent and ciliary elongation is common in cystic epithelia. However, uncoupling the cilium-specific signals repressed by polycystins from downstream cystogenic pathways has proven challenging. Here we aim to understand roles of compartmentalized cAMP signaling in cystogenesis and ciliary length control. We investigated ANKMY2, an Ankyrin repeat MYND domain protein involved in maturation and ciliary localization of membrane adenylyl cyclases—enzymes generating cAMP. In kidney-specific Ankmy2/Pkd1 knockout mice, loss of ANKMY2 suppressed early postnatal cystogenesis and significantly extended survival in an embryonic-onset Pkd1 deletion model. Similarly, in an adult inducible Pkd1 knockout model, ANKMY2 deficiency reduced cyst burden. Mechanistically, ANKMY2 controlled the ciliary trafficking of multiple adenylyl cyclases in mouse and human kidney epithelial cells without disrupting cilia while retaining cellular pools. Ciliary elongation began in dilatated tubules of adult onset ADPKD mice and further increased in cystic kidneys. Both initial and progressive phases of cilia lengthening were ANKMY2-dependent. Our findings indicate that ciliary adenylyl cyclase signaling likely promotes cilia-dependent cyst initiation distinct from cyst progression involving cellular cAMP. Importantly, kidneys lacking ANKMY2 did not show ciliary elongation despite elevated cAMP, suggesting that cilia lengthening during cyst progression could be contingent upon pre-cystic ciliary regulation. These results suggest a critical role for compartmentalized adenylyl cyclase signaling in ADPKD pathogenesis and a framework for identifying ciliary effectors and early subcellular events in cystogenesis.

Diseases affecting the kidney constitute a major health issue worldwide. Their incidence and poor prognosis affirm the urgent need for the development of new therapeutic strategies. Recently, differentiation of pluripotent cells to somatic lineages has emerged as a promising approach for disease modelling and cell transplantation. Unfortunately, differentiation of pluripotent cells into renal lineages has demonstrated limited success. Here we report on the differentiation of human pluripotent cells into ureteric-bud-committed renal progenitor-like cells. The generated cells demonstrated rapid and specific expression of renal progenitor markers on 4-day exposure to defined media conditions. Further maturation into ureteric bud structures was accomplished on establishment of a three-dimensional culture system in which differentiated human cells assembled and integrated alongside murine cells for the formation of chimeric ureteric buds. Altogether, our results provide a new platform for the study of kidney diseases and lineage commitment, and open new avenues for the future application of regenerative strategies in the clinic.

Dysregulated signaling cascades alter energy metabolism and promote cell proliferation and cyst expansion in polycystic kidney disease (PKD). Here we tested whether metabolic reprogramming towards aerobic glycolysis (\"Warburg effect\") plays a pathogenic role in male heterozygous Han:SPRD rats (Cy/+), a chronic progressive model of PKD. Using microarray analysis and qPCR, we found an upregulation of genes involved in glycolysis (Hk1, Hk2, Ldha) and a downregulation of genes involved in gluconeogenesis (G6pc, Lbp1) in cystic kidneys of Cy/+ rats compared with wild-type (+/+) rats. We then tested the effect of inhibiting glycolysis with 2-deoxyglucose (2DG) on renal functional loss and cyst progression in 5-week-old male Cy/+ rats. Treatment with 2DG (500 mg/kg/day) for 5 weeks resulted in significantly lower kidney weights (-27%) and 2-kidney/total-body-weight ratios (-20%) and decreased renal cyst index (-48%) compared with vehicle treatment. Cy/+ rats treated with 2DG also showed higher clearances of creatinine (1.98±0.67 vs 1.41±0.37 ml/min), BUN (0.69±0.26 vs 0.40±0.10 ml/min) and uric acid (0.38±0.20 vs 0.21±0.10 ml/min), and reduced albuminuria. Immunoblotting analysis of kidney tissues harvested from 2DG-treated Cy/+ rats showed increased phosphorylation of AMPK-α, a negative regulator of mTOR, and restoration of ERK signaling. Assessment of Ki-67 staining indicated that 2DG limits cyst progression through inhibition of epithelial cell proliferation. Taken together, our results show that targeting the glycolytic pathway may represent a promising therapeutic strategy to control cyst growth in PKD.