Role Of Primary Cilia Research Articles

SHCBP1 Overexpression Aggravates Pancreatitis by Triggering the Loss of Primary Cilia.

Primary cilia are microtubule-based organelles that mediate various biological processes. Pancreatic cells are typically ciliated; however, the role of primary cilia in acute pancreatitis (AP) is largely unknown. Here, we report that the loss of primary cilia, mediated by SHCBP1 (SHC1 binding protein), exerted a provocative effect on AP. Primary cilia are extensively lost in inflamed pancreatic cells in vitro and in mouse tissues with AP in vivo. Abrogation of primary cilia aggravated lipopolysaccharide (LPS)-induced inflammation in pancreatic cells. Mechanistically, AP induced the overexpression of SHCBP1 mitotic factor, which is localized to the base of primary cilia. SHCBP1 deficiency relieved LPS- and cerulein-induced pancreatitis by preventing the loss of primary cilia in vitro and in vivo. Collectively, we reveal that inflammation-induced loss of primary cilia aggravates AP. Furthermore, abrogating SHCBP1 to prevent primary cilia loss is an efficient strategy to combat AP.

The role of primary cilia in thyroid diseases.

Primary cilia (PC) are non-motile and microtube-based organelles protruding from the surface of almost all thyroid follicle cells. They maintain homeostasis in thyrocytes and loss of PC can result in diverse thyroid diseases. The dysfunction of structure and function of PC are found in many patients with common thyroid diseases. The alterations are associated with the cause, development, and recovery of the diseases and are regulated by PC-mediated signals. Restoring normal PC structure and function in thyrocytes is a promising therapeutic strategy to treat thyroid diseases. This review explores the function of PC in normal thyroid glands. It summarizes the pathology caused by PC alterations in thyroid cancer (TC), autoimmune thyroid diseases (AITD), hypothyroidism, and thyroid nodules (TN) to provide comprehensive references for further study.

The role of primary cilia in congenital heart defect-associated neurological impairments.

Congenital heart disease (CHD) has, despite significant improvements in patient survival, increasingly become associated with neurological deficits during infancy that persist into adulthood. These impairments afflict a wide range of behavioral domains including executive function, motor learning and coordination, social interaction, and language acquisition, reflecting alterations in multiple brain areas. In the past few decades, it has become clear that CHD is highly genetically heterogeneous, with large chromosomal aneuploidies and copy number variants (CNVs) as well as single nucleotide polymorphisms (SNPs) being implicated in CHD pathogenesis. Intriguingly, many of the identified loss-of-function genetic variants occur in genes important for primary cilia integrity and function, hinting at a key role for primary cilia in CHD. Here we review the current evidence for CHD primary cilia associated genetic variants, their independent functions during cardiac and brain development and their influence on behavior. We also highlight the role of environmental exposures in CHD, including stressors such as surgical factors and anesthesia, and how they might interact with ciliary genetic predispositions to determine the final neurodevelopmental outcome. The multifactorial nature of CHD and neurological impairments linked with it will, on one hand, likely necessitate therapeutic targeting of molecular pathways and neurobehavioral deficits shared by disparate forms of CHD. On the other hand, strategies for better CHD patient stratification based on genomic data, gestational and surgical history, and CHD complexity would allow for more precise therapeutic targeting of comorbid neurological deficits.

Primary cilium participates in radiation-induced bystander effects through TGF-β1 signaling.

Many studies have indicated that tumor growth factor-beta (TGF-β) signaling mediates radiation-induced bystander effects (RIBEs). The primary cilium (PC) coordinates several signaling pathways including TGF-β signaling to regulate diverse cellular processes. But whether the PC participates in TGF-β induced RIBEs remains unclear.The cellular levels of TGF-β1 were detected by western blot analysis and the secretion of TGF-β1 was measured by ELISA kit. The ciliogenesis was altered by CytoD treatment, STIL siRNA transfection, IFT88 siRNA transfection, or KIF3a siRNA transfection, separately, and was detected by western blot analysis and immunofluorescence staining. G0 /G1 phase cells were arrested by serum starvation and S phase cells were induced by double thymidine block. The TGF-β1 signaling was interfered by LY2109761, a TGF-β receptor 1 (TβR1) inhibitor, or TGF-β1 neutral antibody. The DNA damages were induced by TGF-β1 or radiated conditional medium (RCM) from irradiated cells and were reflected by p21 expression, 53BP1 foci, and γH2AX foci.Compared with unirradiated control, both A549 and Beas-2B cells expressed and secreted more TGF-β1 after carbon ion beam or X-ray irradiation. RCM collected from irradiated cells or TGF-β1 treatment caused an increase of DNA damage in cocultured unirradiated Beas-2B cells while blockage of TGF-β signaling by TβR1 inhibitor or TGF-β1 neutral antibody alleviates this phenomenon. IFT88 siRNA or KIF3a siRNA impaired PC formation resulted in an aggravated DNA damage in bystander cells, while elevated PC formation by CytoD or STIL siRNA resulted in a decrease of DNA damage. Furthermore, TGF-β1 induced more DNA damages in S phases cells which showed lower PC formation rate and less DNA damages in G0 /G1 phase cells which showed higher PC formation rate.This study demonstrates the particular role of primary cilia during RCM induced DNA damages through TGF-β1 signaling restriction and thereby provides a functional link between primary cilia and RIBEs.

The role of primary cilia in mechanical transmission of osteocyte based on a 3D finite element model

The primary cilium, as a mechanical receptor of osteocytes, participates in the regulation of osteocyte mechanosensitivity. However, how the length of osteocyte primary cilia changes with fluid shear stress (FSS) are unclear, and how the mechanical transmission within osteocytes altered by primary cilia is not well understood yet. Therefore, the ciliary length changes of osteocyte under 15 ​dyn/cm2 of FSS were experimentally detected, and then 3D finite element models of osteocyte primary cilia containing the basal body and axoneme were built. The results showed that (1) The ciliary length of the CON group, FSS 1h, and FSS 6h were 3.71 ​± ​1.34 ​μm, 3.79 ​± ​1.04 ​μm, and 1.24 ​± ​0.73 ​μm respectively, indicating the different durations of FSS might lead to the adaptive changes of cilium length. The calculations showed (2) when the ciliary length became shorter with the ciliary angle stayed the same, the deformation and stress of the cell membrane and membrane skeleton was increased. However, the deformation and stress of the cilia membrane, basal body, the rotation angles of basal body were decreased, and those of cytoplasm, cytoskeleton, actin cortex and nucleus were also decreased; (3) With the decrease of the ciliary angle, the deformation and stress of the cilia membrane, basal body, as well as the rotation angles of basal body were increased. Those of the cytoplasm, cytoskeleton, actin cortex, and nucleus were also increased except the cell membrane and membrane skeleton. The calculation results suggested the length and angle of the primary cilia, the deformation and stress of intracellular structures in osteocyte were altered with ciliary basal body, indicated the connection between the basal body and cytoskeleton may be a key factor that affected the mechanical transport in osteocytes across the cell membrane. This finally promoted the adaptive change of ciliary length under FSS.

TMIC-09. PRIMARY CILIA REGULATE EXTRACELLULAR VESICLE-MEDIATED IMMUNOSUPPRESSION IN HUMAN GLIOBLASTOMA CELLS

Abstract Glioblastoma is the most common primary malignant brain tumor. Despite maximal safe resection, followed by chemoradiation, median survival is 15 months, and 5-year survival is 6.8%. Efficacy of immunotherapy is limited by glioblastoma-mediated immunosuppression. Extracellular vesicles (EVs) are a heterogeneous group of small membrane-bound particles that are released from all cell types. Glioblastoma-derived EVs regulate the tumor microenvironment and tumor progression in a paracrine manner. They also regulate glioblastoma-mediated systemic immunosuppression in an IL6- and PDL1-dependent manner by inducing myeloid-derived suppressor cells (MDSCs) ultimately resulting in T cell depletion. Primary cilia are ubiquitous microtubule-based organelles that project from the mother centriole and are present on glioblastoma cells. Inhibition of ciliogenesis–through knockdown of KIF3A, IFT88, or ARL13B (structural ciliary proteins required for ciliogenesis)–abolishes IL6 induction in response to chemoradiation and significantly reduces the induction of MDSCs in normal human donor monocytes exposed to glioblastoma-derived EVs. Inhibition of ciliogenesis does not affect the biophysical properties of EVs but our data instead suggest significant alterations in EV packaging and content in response to ciliary loss. These data suggest a novel role for primary cilia in packaging of EV contents and connects these organelles with tumor EV-mediated immunosuppression in glioblastomas. These findings have potential implications for improving the efficacy of immunotherapy in glioblastoma–a universally fatal disease.

Recent advances in primary cilia in bone metabolism.

Primary cilia are microtubule-based organelles that are widespread on the cell surface and play a key role in tissue development and homeostasis by sensing and transducing various signaling pathways. The process of intraflagellar transport (IFT), which is propelled by kinesin and dynein motors, plays a crucial role in the formation and functionality of cilia. Abnormalities in the cilia or ciliary transport system often cause a range of clinical conditions collectively known as ciliopathies, which include polydactyly, short ribs, scoliosis, thoracic stenosis and many abnormalities in the bones and cartilage. In this review, we summarize recent findings on the role of primary cilia and ciliary transport systems in bone development, we describe the role of cilia in bone formation, cartilage development and bone resorption, and we summarize advances in the study of primary cilia in fracture healing. In addition, the recent discovery of crosstalk between integrins and primary cilia provides new insights into how primary cilia affect bone.

Primary cilia: Structure, dynamics, and roles in cancer cells and tumor microenvironment.

Despite the initiation of tumor arises from tumorigenic transformation signaling in cancer cells, cancer cell survival, invasion, and metastasis also require a dynamic and reciprocal association with extracellular signaling from tumor microenvironment (TME). Primary cilia are the antenna-like structure that mediate signaling sensation and transduction in different tissues and cells. Recent studies have started to uncover that the heterogeneous ciliation in cancer cells and cells from the TME in tumor growth impels asymmetric paracellular signaling in the TME, indicating the essential functions of primary cilia in homeostasis maintenance of both cancer cells and the TME. In this review, we discussed recent advances in the structure and assembly of primary cilia, and the role of primary cilia in tumor and TME formation, as well as the therapeutic potentials that target ciliary dynamics and signaling from the cells in different tumors and the TME.

Dendritic cell proliferation by primary cilium in atopic dermatitis.

Introduction: Atopic dermatitis (AD) is a common allergic eczema that affects up to 10% of adults in developed countries. Immune cells in the epidermis, namely, Langerhans cells (LCs), contribute to the pathogenesis of AD, although their exact role(s) in disease remain unclear. Methods: We performed immunostaining on human skin and peripheral blood mononuclear cells (PBMCs) and visualized primary cilium. Result and discussion: We show that human dendritic cells (DCs) and LCs have a previously unknown primary cilium-like structure. The primary cilium was assembled during DC proliferation in response to the Th2 cytokine GM-CSF, and its formation was halted by DC maturation agents. This suggests that the role of primary cilium is to transduce proliferation signaling. The platelet-derived growth factor receptor alpha (PDGFRα) pathway, which is known for transducing proliferation signals in the primary cilium, promoted DC proliferation in a manner dependent on the intraflagellar transport (IFT) system. We also examined the epidermal samples from AD patients, and observed aberrantly ciliated LCs and keratinocytes in immature and proliferating states. Our results identify a potential relationship between the primary cilium and allergic skin barrier disorders, and suggest that targeting the primary cilium may contribute to treating AD.

Brain heterotopia formation by ciliopathic breakdown of neuroepithelial and blood-cerebrospinal fluid barriers.

The developmental functions of primary cilia and the downstream signaling pathways have been widely studied; however, the roles of primary cilia in the developing neurovascular system are not clearly understood. In this study, we found that ablation of genes encoding ciliary transport proteins such as intraflagellar transport homolog 88 (Ift88) and kinesin family member 3a (Kif3a) in cortical radial progenitors led to periventricular heterotopia during late mouse embryogenesis. Conditional mutation of primary cilia unexpectedly caused breakdown of both the neuroepithelial lining and the blood-choroid plexus barrier. Choroidal leakage was partially caused by enlargement of the choroid plexus in the cilia mutants. We found that the choroid plexus expressed platelet-derived growth factor A (Pdgf-A) and that Pdgf-A expression was ectopically increased in cilia-mutant embryos. Cortices obtained from embryos in utero electroporated with Pdgfa mimicked periventricular heterotopic nodules of the cilia mutant. These results suggest that defective ciliogenesis in both cortical progenitors and the choroid plexus leads to breakdown of cortical and choroidal barriers causing forebrain neuronal dysplasia, which may be related to developmental cortical malformation.

The role of primary cilia in pulmonary hypertension

IntroductionVascular remodeling in pulmonary hypertension (PH) is characterized by endothelial dysfunction and smooth muscle cell proliferation and hypertrophy ultimately causing right heart failure and death. Up to now, the molecular mechanisms of PH pathogenesis have not been fully resolved, preventing the development of novel therapies against PH.Based on increased expression and activity levels in both patients and animal models with PH, respectively, PDGF‐BB, TGF‐β and mTOR signaling have been proposed to play critical roles as drivers of lung vascular remodeling. Among other effects, PDGF‐BB, TGF‐β and mTOR signaling cause shortening of the primary cilium – an antenna‐like organelle that functions as a flow‐sensor and signaling hub. Loss or shortening of cilia is characteristically associated with cell proliferation and promotes mTOR signaling, thus potentially establishing a positive feedback loop. Here, we hypothesized that PH is associated with a loss of primary cilia in pulmonary artery endothelial (PAECs) and smooth muscle cells (PASMCs) which in turn drives cell proliferation and thus, remodeling in the pulmonary arterial wall.MethodsPulmonary artery tissue from PH‐patients and non‐PH donors was fixed and stained for acetylated α‐tubulin to determine the number of primary cilia. PAECs and PASMCs from PH patients and non‐PH donors were exposed in vitro to three different characteristic stimuli or mediators, respectively, of PH, namely PDGF‐BB, TGF‐β1, or hypoxia (1%). Cells were fixed and stained for measurement of primary cilia length. IFT88 ‐ an essential structural protein of the primary cilium ‐ was knocked down by siRNA in PAECs and PASMCs to assess the effect of cilium loss on migration and proliferation. Mice with an endothelial‐specific deletion of IFT88 (Cdh5‐CreERT2+, IFT88fl/fl) were housed for 5 weeks in normoxia or hypoxia (10% O2) to test for the role of endothelial primary cilia in the development of PH.ResultsIn pulmonary arteries of PH patients, the number of primary cilia per area was reduced by 80% as compared to healthy donor lungs. Analogously, PASMCs from PH patients had shorter cilia. Following IFT88 knock‐down, PAECs and PASMCs showed increased migration and proliferation as compared to control cells. In both PAECs and PASMCs, stimulation with PDGF‐BB, TGF‐β1, or hypoxia shortened primary cilia as compared to controls. Mice lacking primary cilia in endothelial cells showed a significant increase in right ventricular systolic pressure after 5 weeks of hypoxia as compared to control mice.ConclusionsHere, we demonstrate that PH is associated with a loss of cilia in vivo and reduced cilium length in vitro. Primary cilium loss promotes proliferation and migration of PAECs and PASMCs in vitro, as well as the development of PH in vivo. Cilium loss may as such be an important propagator of vascular remodeling in PH and may present a target for novel therapeutic interventions.

Deletion of kif3a in CK19 positive cells leads to primary cilia loss, biliary cell proliferation and cystic liver lesions in TAA-treated mice.

Loss of primary cilia in epithelial cells is known to cause cystic diseases of the liver and kidney. We have previously shown that during experimental and human cirrhosis that primary cilia were predominantly expressed on biliary cells in the ductular reaction. However, the role of primary cilia in the pathogenesis of the ductular reaction is not fully understood. Primary cilia were specifically removed in biliary epithelial cells (BECs) by the administration of tamoxifen to Kif3af/f;CK19CreERT mice at week 2 of a 20-week course of TAA treatment. Biliary progenitor cells were isolated and grown as organoids from gallbladders. Cells and tissue were analysed using histology, immunohistochemistry and Western blot assays. At the end of 20weeks TAA administration, primary cilia loss in liver BECs resulted in multiple microscopic cystic lesions within an unaltered ductular reaction. These were not seen in control mice who did not receive TAA. There was no effect of biliary primary cilia loss on the development of cirrhosis. Increased cellular proliferation was seen within the cystic structures associated with a decrease in hepatocyte lobular proliferation. Loss of primary cilia within biliary organoids was initially associated with reduced cell passage survival but this inhibitory effect was diminished in later passages. ERK but not WNT signalling was enhanced in primary cilia loss-induced cystic lesions in vivo and its inhibition reduced the expansion of primary cilia deficient biliary progenitor cells in vitro. TAA-treated kif3a BEC-specific knockout mice had an unaltered progression to cirrhosis, but developed cystic lesions that showed increased proliferation.

Ift88 regulates enamel formation via involving Shh signaling.

The ciliopathies are a wide spectrum of human diseases, which are caused by perturbations in the function of primary cilia. Tooth enamel anomalies are often seen in ciliopathy patients; however, the role of primary cilia in enamel formation remains unclear. We examined mice with epithelial conditional deletion of the ciliary protein, Ift88, (Ift88fl / fl ;K14Cre). Ift88fl / fl ;K14Cre mice showed premature abrasion in molars. A pattern of enamel rods which is determined at secretory stage, was disorganized in Ift88mutant molars. Many amelogenesis-related molecules expressing at the secretory stage, including amelogenin and ameloblastin, enamelin, showed significant downregulation in Ift88mutant molar tooth germs. Shh signaling is essential for amelogenesis, which was found to be downregulated in Ift88mutant molar at the secretory stage. Application of Shh signaling agonist at the secretory stage partially rescued enamel anomalies in Ift88mutant mice. Findings in the present study indicate that the function of the primary cilia via Ift88 is critical for the secretory stage of amelogenesis through involving Shh signaling.

The role of primary cilia in zebrafish fin regeneration.

The role of primary cilia in zebrafish fin regeneration.

An investigation of the role of primary cilia in the repairing process after brain injury

An investigation of the role of primary cilia in the repairing process after brain injury

Stromal cells of giant cell tumor of bone show primary cilia in giant cell tumor of bone.

Giant cell tumor of bone (GCTB) is a locally aggressive primary bone neoplasm composed by tumoral stromal cells (SCs) and a reactive component that consists of monocytic/histiocytic cells that give rise by fusion to osteoclast-like multinucleated cells. Recently, specific Histone 3.3 mutations have been demonstrated in SCs of GCTB. Many of the pathways related to bone proliferation and regulation depend on the primary cilium, a microtubule-based organelle that protrudes outside the cell and acts as a sensorial antenna. In the present work, we aimed to study the presence and role of primary cilia in GCTB. Ultrastructural, immunohistochemical, and immunofluorescence studies were performed in order to demonstrate, for the first time, that the primary cilium is located in spindle-shaped SCs of GCTB. Moreover, we showed Hedgehog (Hh) signaling pathway activation in these cells. Hence, primary cilia may play a relevant role in GCTB tumorogenesis through Hh signaling activation in SCs. RESEARCH HIGHLIGHTS: Transmission electron microscopy allows describing and differentiating cellular subpopulations in giant cell tumor of bone (GCTB). The primary cilium is present in some tumoral stromal cells of GCTB. Hedgehog signalling is activated in these cells.

Primary Cilia Are Critical Regulators of White Adipose Tissue Expansion.

The primary cilium is a microtubule-based cellular protrusion found on most mammalian cell types in diverse tissues. It functions as a cellular antenna to sense and transduce a broad range of signals, including odorants, light, mechanical stimuli, and chemical ligands. This diversity in signals requires cilia to display a context and cell type-specific repertoire of receptors. Recently, primary cilia have emerged as critical regulators of metabolism. The importance of primary cilia in metabolic disease is highlighted by the clinical features of human genetic disorders with dysfunctional ciliary signaling, which include obesity and diabetes. This review summarizes the current literature on the role of primary cilia in metabolic disease, focusing on the importance of primary cilia in directing white adipose tissue expansion during obesity.

Primary Cilia Mediate TSH-Regulated Thyroglobulin Endocytic Pathways.

Primary cilia are sensory organelles with a variety of receptors and channels on their membranes. Recently, primary cilia were proposed to be crucial sites for exocytosis and endocytosis of vesicles associated with endocytic control of various ciliary signaling pathways. Thyroglobulin (Tg) synthesis and Tg exocytosis/endocytosis are critical for the functions of thyroid follicular cells, where primary cilia are relatively well preserved. LRP2/megalin has been detected on the apical surface of absorptive epithelial cells, including thyrocytes. LRP2/megalin on thyrocytes serves as a Tg receptor and can mediate Tg endocytosis. In this study, we investigated the role of primary cilia in LRP2/megalin expression in thyroid gland stimulated with endogenous TSH using MMI-treated and Tg-Cre;Ift88flox/flox mice. LRP2/megalin expression in thyroid follicles was higher in MMI-treated mice than in untreated control mice. MMI-treated mice exhibited a significant increase in ciliogenesis in thyroid follicular cells relative to untreated controls. Furthermore, MMI-induced ciliogenesis accompanied increases in LRP2/megalin expression in thyroid follicular cells, in which LRP2/megalin was localized to the primary cilium. By contrast, in Tg-Cre;Ift88flox/flox mice, thyroid with defective primary cilia expressed markedly lower levels of LRP2/megalin. Serum Tg levels were elevated in MMI-treated mice and reduced in Tg-Cre;Ift88flox/flox mice. Taken together, these results indicate that defective ciliogenesis in murine thyroid follicular cells is associated with impaired LRP2/megalin expression and reduced serum Tg levels. Our results strongly suggest that primary cilia harbors LRP2/megalin, and are involved in TSH-mediated endocytosis of Tg in murine thyroid follicles.

FBF1 deficiency promotes beiging and healthy expansion of white adipose tissue.

SUMMARYPreadipocytes dynamically produce sensory cilia. However, the role of primary cilia in preadipocyte differentiation and adipose homeostasis remains poorly understood. We previously identified transition fiber component FBF1 as an essential player in controlling selective cilia import. Here, we establish Fbf1tm1a/tm1a mice and discover that Fbf1tm1a/tm1a mice develop severe obesity, but surprisingly, are not predisposed to adverse metabolic complications. Obese Fbf1tm1a/tm1a mice possess unexpectedly healthy white fat tissue characterized by spontaneous upregulated beiging, hyperplasia but not hypertrophy, and low inflammation along the lifetime. Mechanistically, FBF1 governs preadipocyte differentiation by constraining the beiging program through an AKAP9-dependent, cilia-regulated PKA signaling, while recruiting the BBS chaperonin to transition fibers to suppress the hedgehog signaling-dependent adipogenic program. Remarkably, obese Fbf1tm1a/tm1a mice further fed a high-fat diet are protected from diabetes and premature death. We reveal a central role for primary cilia in the fate determination of preadipocytes and the generation of metabolically healthy fat tissue.

The Role of Primary Cilia in Thyroid Cancer: From Basic Research to Clinical Applications.

Primary cilia (PC) are microtubule-based organelles that are present on nearly all thyroid follicle cells and play an important role in physiological development and in maintaining the dynamic homeostasis of thyroid follicles. PC are generally lost in many thyroid cancers (TCs), and this loss has been linked to the malignant transformation of thyrocytes, which is regulated by PC-mediated signaling reciprocity between the stroma and cancer cells. Restoring PC on TC cells is a possible promising therapeutic strategy, and the therapeutic response and prognosis of TC are associated with the presence or absence of PC. This review mainly discusses the role of PC in the normal thyroid and TC as well as their potential clinical utility.