Citations

Background: Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited disorder leading to kidney failure. Tolvaptan, the only FDA-approved therapy, modestly slows disease progression but is limited by significant adverse effects, highlighting the need for more effective and better-tolerated treatments. Ciliary polycystins are central to ADPKD pathogenesis. We previously demonstrated that a cilia base-localized pool of CDK6 restricts ciliary polycystin abundance by suppressing axonemal polyglutamylation. However, whether CDK6 inhibition can restore polycystin function and suppress ADPKD progression in vivo remains unknown. Methods: Abemaciclib was tested in in vitro 3D cyst assays and ex vivo metanephric organ cultures. In vivo efficacy of early- and late-stage intervention were assessed in F1(129/B6) Pkd1 R3277C/R3277C mice receiving daily abemaciclib. Tolvaptan served as a therapeutic control. Cyst burden, fibrosis in the kidneys, kidney function, and primary cilia of renal epithelial cells were analyzed at study endpoints. Results: CDK6 was prominently upregulated in cyst-lining cells in human and murine PKD kidneys. At doses substantially lower than those used in oncology, abemaciclib robustly suppressed cyst growth in vitro and ex vivo . In vivo , long-term early treatment arrested cyst progression more effectively than tolvaptan without detectable toxicity. Late intervention largely halted cyst growth in females and reversed cyst progression in males. Mechanistically, abemaciclib restored axonemal polyglutamylation and increased ciliary polycystin levels. Conclusions: Abemaciclib has greater therapeutic efficacy and tolerability than tolvaptan in this preclinical model, largely driven by CDK6 inhibition–mediated restoration of axonemal polyglutamylation and increased ciliary polycystin abundance.

Myelodysplastic syndromes (MDS), which are hematopoietic stem cell malignancies, are often accompanied by signs of chronic inflammation, that can in turn drive the pathogenetic process. The precise mechanisms dysregulating inflammatory and innate immune signaling in MDS hematopoietic stem and progenitor cells (HSPCs) remain under investigation. We report that mice lacking Tet2 developed a hyper-inflammatory state, which can be further fueled by LPS-induced inflammation. This chronic inflammation temporarily promotes the self-renewal and myeloid differentiation of Tet2-deficient HSPCs; however, it ultimately accelerates HSC exhaustion and triggers MDS development in chimeric mouse models. Driving this phenotype was the activation of the NLRC4 inflammasome pathway. Notably, Nlrc4 depletion in Tet2-deficient mice impaired MDS development and improved the survival of these mice. These findings uncover a novel mechanistic basis for the MDS-associated inflammation and provide new targeting opportunities in its management.

Key Points Inositol polyphosphate-5-phosphatase E (INPP5E) and type Ig phosphatidylinositol-4-phosphate 5-kinase (PIPKIγ) coordinated the homeostasis of phosphatidylinositol-4-phosphate and phosphatidylinositol-4,5-bisphosphate in primary cilia. Modulating INPP5E or PIPKIγ activity changed the level of polycystin-1 and polycystin-2 in primary cilia. INPP5E inhibition increased the hypomorphic PKD1 variants (PC1-R3277C) in cilia and reduced cystogenesis in the kidney in vitro . Background Autosomal dominant polycystic kidney disease is mainly caused by mutations in PKD1 and PKD2 , which encode polycystin-1 (PC1) and polycystin-2 (PC2), respectively. PC1 and PC2 assemble a cation channel complex enriched in primary cilium, a sensory organelle associated with various developmental diseases, including polycystic kidney disease (PKD). Accumulating evidence supports the necessity of functional polycystin (PC) complex in cilia to prevent cystogenesis in the kidney, indicating that improving their ciliary levels may ameliorate defects underlying PKD pathogenesis. Yet, molecular mechanisms underlying the ciliary targeting and homeostasis of the PC complex are not fully understood. Methods Indirect immunofluorescence microscopy was used to monitor ciliary levels of PC1 and PC2 in renal epithelial cells. Electrophysiology analysis in oocytes was used to determine the channel activity of the PC complex. Cystogenesis in the kidney was measured using in vitro 3D-Matrigel cell models and ex vivo mouse embryonic kidney models. Results Suppressing inositol polyphosphate-5-phosphatase E (INPP5E) or activating type Ig phosphatidylinositol-4-phosphate 5-kinase raised ciliary levels of the PC complex in both normal renal epithelial cells and cells carrying autosomal dominant polycystic kidney disease mutations that interrupt the trafficking of PCs into cilia, including GANAB inactivation and the trafficking PKD1 mutation p.Arg3277Cys (RC). PC1 RC formed a complex with PC2 and exhibited normal channel activity in vitro . An INPP5E that increases PC1 and PC2 in cilia, suppressed in vitro forskolin-induced cystogenesis of inner medullary collecting duct epithelial cell line 3 cells in 3D Matrigel and ex vivo cyst formation in embryonic Pkd1 RC/RC mouse kidneys. Conclusions Our results demonstrated that increasing the ciliary level of PCs, by manipulating a ciliary phosphoinositide signaling axis, enhanced the functionality of PCs and suppressed cystogenesis of renal epithelial cells in vitro .

Abstract Measurable residual disease (MRD) assessment by flow cytometry (FC) plays an essential role in prognosis and therapy escalation of B-cell acute lymphoblastic leukemia (B-ALL). However, the high degree of expertise and manual analysis time required limits the availability of this assay. To overcome this limitation, we developed a data-enhancing artificial intelligence (AI) pipeline that accelerates and simplifies MRD analysis. Unaltered FC files from 171 B-ALL MRD-positive and 89 MRD-negative cases were processed through an AI pipeline trained with 31 expert-gated negative controls. Cluster-informed downsampling reduced FC files from 1.2 million to 155 884 cells per case, on average, (87% cellularity reduction), whereas preserving small MRD populations (median, 100% retention for MRD of <1%) and allowing for true percentage MRD estimates using a correction factor. A deep neural network cell classifier automatically identified normal hematopoietic subsets (macro-averaged F1 score of 0.86); and an AI measure of anomaly discriminated B-ALL from benign mononuclear (area under the curve [AUC] of 0.98) or B-lymphoid cells (AUC of 0.94). Manual analysis of AI-enhanced files was completed in only 1.01 minutes per case, on average (standard deviation of ±0.57); with 100% positive agreement with conventional analysis (for MRD of ≥0.01%), 100% negative agreement, and excellent quantitative correlation (R2 = 0.92). Our cloud-based AI-enhancement solution accelerates B-ALL MRD identification without compromising test performance and has the potential of facilitating B-ALL MRD analysis by more clinical laboratories.

Tubulin polyglutamylation is a posttranslational modification that occurs primarily along the axoneme of cilia. Defective axoneme polyglutamylation impairs cilia function and has been correlated with ciliopathies, including Joubert Syndrome (JBTS). However, the precise mechanisms regulating proper axoneme polyglutamylation remain vague. Here, we show that cyclin-dependent kinase 6 (CDK6), but not its paralog CDK4, localizes to the cilia base and suppresses axoneme polyglutamylation by phosphorylating RAB11 family interacting protein 5 (FIP5) at site S641, a critical regulator of cilia import of glutamylases. S641 phosphorylation disrupts the ciliary recruitment of FIP5 and its association with RAB11, thereby reducing the ciliary import of glutamylases. Encouragingly, the FDA-approved CDK4/6 inhibitor Abemaciclib can effectively restore cilia function in JBTS cells with defective glutamylation. In summary, our study elucidates the regulatory mechanisms governing axoneme polyglutamylation and suggests that developing CDK6-specific inhibitors could be a promising therapeutic strategy to enhance cilia function in ciliopathy patients.

AbstractServing as the cell's sensory antennae, primary cilia are linked to numerous human genetic diseases when they malfunction. DZIP1L, identified as one of the genetic causes of human autosomal recessive polycystic kidney disease (ARPKD), is an evolutionarily conserved ciliary basal body protein. Although it has been reported that DZIP1L is involved in the ciliary entry of PKD proteins, the underlying mechanism remains elusive. Here, an uncharacterized role of DZIP1L is reported in modulating the architecture and function of transition fibers (TFs), striking ciliary base structures essential for selective cilia gating. Using C. elegans as a model, C01G5.7 (hereafter termed DZIP‐1) is identified as the sole homolog of DZIP1L, which specifically localizes to TFs. While DZIP‐1 or ANKR‐26 (the ortholog of ANKRD26) deficiency shows subtle impact on TFs, co‐depletion of DZIP‐1 and ANKR‐26 disrupts TF assembly and cilia gating for soluble and membrane proteins, including the ortholog of ADPKD protein polycystin‐2. Notably, the synergistic role for DZIP1L and ANKRD26 in the formation and function of TFs is highly conserved in mammalian cilia. Hence, the findings illuminate an evolutionarily conserved role of DZIP1L in TFs architecture and function, highlighting TFs as a vital part of the ciliary gate implicated in ciliopathies ARPKD.

Primary cilia are microtube-based organelles that extend from the cell surface and function as biochemical and mechanical extracellular signal sensors. Primary cilia coordinate a series of signaling pathways during development. Cilia dysfunction leads to a pleiotropic group of developmental disorders, termed ciliopathy. Phosphoinositides (PIs), a group of signaling phospholipids, play a crucial role in development and tissue homeostasis by regulating membrane trafficking, cytoskeleton reorganization, and organelle identity. Accumulating evidence implicates the involvement of PI species in ciliary defects and ciliopathies. The abundance and localization of PIs in the cell are tightly regulated by the opposing actions of kinases and phosphatases, some of which are recently discovered in the context of primary cilia. Here, we review several cilium-associated PI kinases and phosphatases, including their localization along cilia, function in regulating the ciliary biology under normal conditions, as well as the connection of their disease-associated mutations with ciliopathies.

Abstract Cellular senescence contributes to tissue homeostasis and age-related pathologies. However, how senescence is initiated in damaged cells remains vague. Here, we discover that irreparable stresses induce transient biogenesis of cilia, which are used by stressed cells to directly communicate with the promyelocytic leukemia nuclear bodies (PML-NBs), the validated stress signaling hub, to initiate senescence responses. Mechanistically, a ciliary ARL13B-ARL3 GTPase cascade negatively regulates the association of transition fiber protein FBF1 and SUMO-conjugating enzyme UBC9. Irreparable stresses downregulate the ciliary ARLs to release UBC9, which SUMOylates FBF1 at the ciliary base. SUMOylated FBF1 then translocates to PML-NBs to promote PML-NB-dependent senescence initiation. Remarkably, Fbf1 suppression effectively subdues global senescence burden and prevents associated health-span decline in irradiation-treated mice. Collectively, our findings assign primary cilia a central role in inducing senescence program and identify them as promising targets to dampen senescence-associated detrimental damage in future senotherapy strategies.