The primary cilium coordinates signaling pathways in cell cycle control and migration during development and tissue repair

Autosomal Dominant Polycystic Kidney Disease: Extrarenal Involvement

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disorder, but kidneys are not the only organs involved in this systemic disorder. Individuals with the condition may display additional manifestations beyond the renal system, involving the liver, pancreas, and brain in the context of cystic manifestations, while involving the vascular system, gastrointestinal tract, bones, and cardiac valves in the context of non-cystic manifestations. Despite kidney involvement remaining the main feature of the disease, thanks to longer survival, early diagnosis, and better management of kidney-related problems, a new wave of complications must be faced by clinicians who treated patients with ADPKD. Involvement of the liver represents the most prevalent extrarenal manifestation and has growing importance in the symptom burden and quality of life. Vascular abnormalities are a key factor for patients' life expectancy and there is still debate whether to screen or not to screen all patients. Arterial hypertension is often the earliest onset symptom among ADPKD patients, leading to frequent cardiovascular complications. Although cardiac valvular abnormalities are a frequent complication, they rarely lead to relevant problems in the clinical history of polycystic patients. One of the newest relevant aspects concerns bone disorders that can exert a considerable influence on the clinical course of these patients. This review aims to provide the "state of the art" among the extrarenal manifestation of ADPKD.

Extraciliary OFD1 Is Involved in Melanocyte Survival through Cell Adhesion to ECM via Paxillin

Primary cilia play a significant role in influencing cell fate, including apoptosis in multiple cell types. In the lesional epidermis of vitiligo patients, a reduced number of ciliated cells was observed. Our study also revealed a downregulation of oral-facial digital syndrome type 1 (OFD1) in the affected skin of vitiligo patients. However, it remains unknown whether primary cilia are involved in the control of melanocyte apoptosis. While both intraflagellar transport 88 (IFT88) and retinitis pigmentosa GTPase regulator-interacting protein-1 like (RPGRIP1L) are associated with ciliogenesis in melanocytes, only the knockdown of OFD1, but not IFT88 and RPGRIP1L, resulted in increased melanocyte apoptosis. OFD1 knockdown led to a decrease in the expression of proteins involved in cell-extracellular matrix (ECM) interactions, including paxillin. The OFD1 amino acid residues 601-1012 interacted with paxillin, while the amino acid residues 1-601 were associated with ciliogenesis, suggesting that the OFD1 domains responsible for paxillin binding are distinct from those involved in ciliogenesis. OFD1 knockdown, but not IFT88 knockdown, inhibited melanocyte adhesion to the ECM, a defect that was restored by paxillin overexpression. In summary, our findings indicate that the downregulation of OFD1 induces melanocyte apoptosis, independent of any impairment in ciliogenesis, by reducing melanocyte adhesion to the ECM via paxillin.

Spatiotemporal Mapping of Brain Cilia Reveals Region-Specific Oscillation of Length and Orientation

In this study, we conducted high-throughput spatiotemporal analysis of primary cilia length and orientation across 22 mouse brain regions. We developed automated image analysis algorithms, which enabled us to examine over 10 million individual cilia, generating the largest spatiotemporal atlas of cilia. We found that cilia length and orientation display substantial variations across different brain regions and exhibit fluctuations over a 24-hour period, with region-specific peaks during light-dark phases. Our analysis revealed unique orientation patterns of cilia at 45 degree intervals, suggesting that cilia orientation within the brain is not random but follows specific patterns. Using BioCycle, we identified circadian rhythms of cilia length in five brain regions: nucleus accumbens core, somatosensory cortex, and three hypothalamic nuclei. Our findings present novel insights into the complex relationship between cilia dynamics, circadian rhythms, and brain function, highlighting cilia crucial role in the brain's response to environmental changes and regulation of time-dependent physiological processes.

Transfusion of Adult, but Not Neonatal, Platelets Promotes Monocyte Trafficking in Neonatal Mice

BACKGROUND

Thrombocytopenia is common in preterm neonates. Platelet transfusions are sometimes given to thrombocytopenic neonates with the hope of reducing the bleeding risk, however, there are little clinical data to support this practice, and platelet transfusions may increase the bleeding risk or lead to adverse complications. Our group previously reported that fetal platelets expressed lower levels of immune-related mRNA compared with adult platelets. In this study, we focused on the effects of adult versus neonatal platelets on monocyte immune functions that may have an impact on neonatal immune function and transfusion complications.

METHODS

Using RNA sequencing of postnatal day 7 and adult platelets, we determined age-dependent platelet gene expression. Platelets and naive bone marrow-isolated monocytes were cocultured and monocyte phenotypes determined by RNA sequencing and flow cytometry. An in vivo model of platelet transfusion in neonatal thrombocytopenic mice was used in which platelet-deficient TPOR (thrombopoietin receptor) mutant mice were transfused with adult or postnatal day 7 platelets and monocyte phenotypes and trafficking were determined.

RESULTS

Adult and neonatal platelets had differential immune molecule expression, including Selp. Monocytes incubated with adult or neonatal mouse platelets had similar inflammatory (Ly6Chi) but different trafficking phenotypes, as defined by CCR2 and CCR5 mRNA and surface expression. Blocking P-sel (P-selectin) interactions with its PSGL-1 (P-sel glycoprotein ligand-1) receptor on monocytes limited the adult platelet-induced monocyte trafficking phenotype, as well as adult platelet-induced monocyte migration in vitro. Similar results were seen in vivo, when thrombocytopenic neonatal mice were transfused with adult or postnatal day 7 platelets; adult platelets increased monocyte CCR2 and CCR5, as well as monocyte chemokine migration, whereas postnatal day 7 platelets did not.

CONCLUSIONS

These data provide comparative insights into adult and neonatal platelet transfusion-regulated monocyte functions. The transfusion of adult platelets to neonatal mice was associated with an acute inflammatory and trafficking monocyte phenotype that was platelet P-sel dependent and may have an impact on complications associated with neonatal platelet transfusions.

Osteoclastogenesis Requires Primary Cilia Disassembly and Can Be Inhibited by Promoting Primary Cilia Formation Pharmacologically

The primary cilium is a solitary, sensory organelle with many roles in bone development, maintenance, and function. In the osteogenic cell lineage, including skeletal stem cells, osteoblasts, and osteocytes, the primary cilium plays a vital role in the regulation of bone formation, and this has made it a promising pharmaceutical target to maintain bone health. While the role of the primary cilium in the osteogenic cell lineage has been increasingly characterized, little is known about the potential impact of targeting the cilium in relation to osteoclasts, a hematopoietic cell responsible for bone resorption. The objective of this study was to determine whether osteoclasts have a primary cilium and to investigate whether or not the primary cilium of macrophages, osteoclast precursors, serves a functional role in osteoclast formation. Using immunocytochemistry, we showed the macrophages have a primary cilium, while osteoclasts lack this organelle. Furthermore, we increased macrophage primary cilia incidence and length using fenoldopam mesylate and found that cells undergoing such treatment showed a significant decrease in the expression of osteoclast markers tartrate-resistant acid phosphatase, cathepsin K, and c-Fos, as well as decreased osteoclast formation. This work is the first to show that macrophage primary cilia resorption may be a necessary step for osteoclast differentiation. Since primary cilia and preosteoclasts are responsive to fluid flow, we applied fluid flow at magnitudes present in the bone marrow to differentiating cells and found that osteoclastic gene expression by macrophages was not affected by fluid flow mechanical stimulation, suggesting that the role of the primary cilium in osteoclastogenesis is not a mechanosensory one. The primary cilium has been suggested to play a role in bone formation, and our findings indicate that it may also present a means to regulate bone resorption, presenting a dual benefit of developing ciliary-targeted pharmaceuticals for bone disease.

Cilia-associated wound repair mediated by IFT88 in retinal pigment epithelium

Primary cilia are conserved organelles that integrate extracellular cues into intracellular signals and are critical for diverse processes, including cellular development and repair responses. Deficits in ciliary function cause multisystemic human diseases known as ciliopathies. In the eye, atrophy of the retinal pigment epithelium (RPE) is a common feature of many ciliopathies. However, the roles of RPE cilia in vivo remain poorly understood. In this study, we first found that mouse RPE cells only transiently form primary cilia. We then examined the RPE in the mouse model of Bardet-Biedl Syndrome 4 (BBS4), a ciliopathy associated with retinal degeneration in humans, and found that ciliation in BBS4 mutant RPE cells is disrupted early during development. Next, using a laser-induced injury model in vivo, we found that primary cilia in RPE reassemble in response to laser injury during RPE wound healing and then rapidly disassemble after the repair is completed. Finally, we demonstrated that RPE-specific depletion of primary cilia in a conditional mouse model of cilia loss promoted wound healing and enhanced cell proliferation. In summary, our data suggest that RPE cilia contribute to both retinal development and repair and provide insights into potential therapeutic targets for more common RPE degenerative diseases.

Effects of pharmacological primary cilium disturbance in the context of in vitro 2D and 3D malignant pleura mesothelioma

INTRODUCTION

Primary cilium (PC) is a single non-motile antenna-like organelle composed of a microtubule core axon originating from the mother centriole of the centrosome. The PC is universal in all mammalian cells and protrudes to the extracellular environment receiving mechanochemical cues that it transmits in the cell.

AIM

To investigate the role of PC in mesothelial malignancy in the context of two-dimensional (2D) and three-dimensional (3D) phenotypes.

MATERIALS AND METHODS

The effect of pharmacological deciliation [using ammonium sulphate (AS) or chloral hydrate (CH)] and PC elongation [using lithium chloride (LC)] on cell viability, adhesion, and migration (2D cultures) as well as in mesothelial sphere formation, spheroid invasion and collagen gel contraction (3D cultures) was investigated in benign mesothelial MeT-5A cells and in malignant pleural mesothelioma (MPM) cell lines, M14K (epithelioid) and MSTO (biphasic), and primary malignant pleural mesothelioma cells (pMPM).

RESULTS

Pharmacological deciliation or elongation of the PC significantly affected cell viability, adhesion, migration, spheroid formation, spheroid invasion and collagen gel contraction in MeT-5A, M14K, MSTO cell lines and in pMPM cells compared to controls (no drug treatment).

CONCLUSIONS

Our findings indicate a pivotal role of the PC in functional phenotypes of benign mesothelial cells and MPM cells.

Characterization of Primary Cilia Formation in Human ESC-Derived Retinal Organoids

Objectives

Primary cilia are conserved organelles found in polarized mammalian cells that regulate neuronal growth, migration, and differentiation. Proper cilia formation is essential during eye development. Our previous reports found that both amacrine and retinal ganglion cells (RGCs) contain primary cilia in primate and rodent retinas. However, whether primary cilia are present in the inner retina of human retinal organoids remains unknown. The purpose of this study is to characterize the primary cilia distribution in human embryonic stem cell (hESC-derived retinal organoid development.

Materials and Methods

Retinal organoids were differentiated from a hESC line, harvested at various developmental timepoints (day 44-day 266), and immunostained with antibodies for primary cilia, including Arl13b (for the axoneme), AC3, and Centrin3 (for the basal body). AP2α, Prox1, GAD67, Calretinin, GFAP, PKCα, and Chx10 antibodies as well as Brn3b-promoted tdTomato expression were used to visualize retinal cell types.

Results

A group of ciliated cells were present in the inner aspects of retinal organoids from day 44 to day 266 in culture. Ciliated Chx10-positive retinal progenitor cells, GFAP-positive astrocytes, and PKCα-positive rod-bipolar cells were detected later during development (day 176 to day 266). Ciliation persisted during all stages of retinal developmental in AP2α-positive amacrine cells, but it was decreased in Brn3b-positive retinal ganglion cells (RGCs) at later time points. Additionally, AC3-positive astrocytes significantly decreased during the later stages of organoid formation.

Conclusions

Amacrine cells in retinal organoids retain cilia throughout development, whereas RGC ciliation gradually and progressively decreases with organoid maturation.

Heterogeneity of the NIH3T3 Fibroblast Cell Line

The embryonic mouse fibroblast cell line NIH3T3 is widely used in life science research, including the study of cell cycle control and primary cilia. Fibroblasts are the most important cell type in connective tissue, as they produce components of the extracellular matrix and determine tissue architecture. However, they are very heterogeneous and consist of subtypes specific to their organ of residence, among others. The NIH3T3 cell line was derived from whole mouse embryos that developed to pre-birth and is therefore most likely composed of different fibroblast subtypes. Furthermore, prolonged proliferation may have influenced their cellular composition. A heterogeneous cell population is unsuitable for any sophisticated research project. We found that the proportion of ciliated cells in the total NIH3T3 cell population was highly variable and asked whether this was a consequence of cellular heterogeneity and what molecular signatures were associated with it. We have established sub-cell lines by clonal expansion of single cells and characterized them morphologically and molecularly. Eventually, a myofibroblast-like and a fibroblast-like cell line were generated that differ in ciliation and proliferation. These homogeneous cell lines are valuable for a more detailed study of their molecular signatures, not least to uncover further the molecular pathways that contribute to the formation of the primary cilium.

The influence zone: a critical performance measure for negative pressure wound therapy systems

This article provides an introduction to the theory of, what is termed, the 'influence zone' in the context of negative pressure wound therapy (NPWT). It is a quantitative bioengineering performance measure for NPWT systems, to indicate their effectiveness, namely, how far from the wound bed edges a specific system is able to deliver effective mechano-stimulation into the periwound, and at which intensity. The influence zone therefore provides objective and standardised metrics of one of the fundamental modes of action of NPWT systems: the ability to effectively and optimally deform both the wound and periwound macroscopically and microscopically. Most important is the mechanical deformation of the periwound area to activate cells responsible for tissue repair, particularly (myo)fibroblasts. Notably, the influence zone must extend sufficiently into the periwound to stimulate (myo)fibroblasts in order that they migrate and progress the wound healing process, facilitating the formation of scar tissue, without overstretching the periwound tissues so as not cause or escalate further cell and tissue damage. The inclusion of the influence zone theory within research to investigate the efficacy of NPWT systems facilitates systematic comparisons of commercially available and potentially new systems. This approach has the capacity to guide not only research and development work, but also clinical decision-making. Recently published research found that inducing an effective influence zone first and foremost requires continuous delivery of the intended pressure to the wound bed.

Electrical waveform dependent osteogenesis on PVDF/BaTiO3 composite using a customized and programmable cell stimulator

Directing cellular functionalities using biomaterial-based bioelectronic stimulation remains a significant constraint in translating research outcomes to address specific clinical challenges. Electrical stimulation is now being clinically used as a therapeutic treatment option to promote bone tissue regeneration and to improve neuromuscular functionalities. However, the nature of the electrical waveforms during the stimulation and underlying biophysical rationale are still not scientifically well explored. Furthermore, bone-mimicking implant-based bioelectrical regulation of osteoinductivity has not been translated to clinics. The present study demonstrates the role of the waveform in electrical signal to direct differentiation of stem cells on an electroactive polymeric substrate, using monophasic DC, square wave, and biphasic wave. In this regard, an in-house electrical stimulation device has been fabricated for the uninterrupted delivery of programmed electrical signals to stem cells in culture. To provide a functional platform for stem cells to differentiate, barium titanate (BaTiO₃ , BT) reinforced PVDF has been developed with mechanical properties similar to bone. The electrical stimulation of human mesenchymal stem cells (hMSCs) on PVDF/BT composite inhibited proliferation rate at day 7, indicating early commitment for differentiation. The phenotypical characteristics of DC stimulated hMSCs provided signatures of differentiation towards osteogenic lineage, which was subsequently confirmed using ALP assay, collagen deposition, matrix mineralization, and genetic expression. Our findings suggest that DC stimulation induced early osteogenesis in hMSCs with a higher level of intracellular reactive oxygen species (ROS), whereas the stimulation with square wave directed late osteogenesis with a lower ROS regeneration. In summary, the present study critically analyzes the role of electrical stimulation and its waveforms in regulating osteogenesis, without external biochemical differentiation inducers, on a bone-mimicking functional substrate. Such a strategy can potentially be adopted to develop orthopedic implant-based bioelectronic medicine for bone regeneration. This article is protected by copyright. All rights reserved.

Primary cilium in kidney development, function and disease

The primary cilium is a hair-like, microtubule-based organelle that is covered by the cell membrane and extends from the surface of most vertebrate cells. It detects and translates extracellular signals to direct various cellular signaling pathways to maintain homeostasis. It is mainly distributed in the proximal and distal tubules and collecting ducts in the kidney. Specific signaling transduction proteins localize to primary cilia. Defects in cilia structure and function lead to a class of diseases termed ciliopathies. The proper functioning of primary cilia is essential to kidney organogenesis and the maintenance of epithelial cell differentiation and proliferation. Persistent cilia dysfunction has a role in the early stages and progression of renal diseases, such as cystogenesis and acute tubular necrosis (ATN). In this review, we focus on the central role of cilia in kidney development and illustrate how defects in cilia are associated with renal disease progression.

Spatially resolved transcriptomics reveals the architecture of the tumor-microenvironment interface

During tumor progression, cancer cells come into contact with various non-tumor cell types, but it is unclear how tumors adapt to these new environments. Here, we integrate spatially resolved transcriptomics, single-cell RNA-seq, and single-nucleus RNA-seq to characterize tumor-microenvironment interactions at the tumor boundary. Using a zebrafish model of melanoma, we identify a distinct "interface" cell state where the tumor contacts neighboring tissues. This interface is composed of specialized tumor and microenvironment cells that upregulate a common set of cilia genes, and cilia proteins are enriched only where the tumor contacts the microenvironment. Cilia gene expression is regulated by ETS-family transcription factors, which normally act to suppress cilia genes outside of the interface. A cilia-enriched interface is conserved in human patient samples, suggesting it is a conserved feature of human melanoma. Our results demonstrate the power of spatially resolved transcriptomics in uncovering mechanisms that allow tumors to adapt to new environments.

A primary cilium in oligodendrocytes: a fine structure signal of repairs in thalamic Osmotic Demyelination Syndrome (ODS)

A murine osmotic demyelination syndrome (ODS) model of the central nervous system included the relay thalamic ventral posterolateral (VPL) and ventral posteromedial (VPM) nuclei. Morphologic comparisons between treatments have revealed oligodendrocyte changes and, already 12 hours following the osmolality restoration, some heavily contrasted oligodendrocytes formed a unique intracellular primary cilium. This unique structure, found in vivo, in mature CNS oligodendrocytes, could account for a local awakening of some of the developmental proteome as it can be expressed in oligodendrocyte precursor cells. This resilience accompanied the emergence of arl13b protein expression along with restoration of nerve cell body axon hillocks shown in a previous issue of this journal. Additionally, the return of several thalamic oligodendrocyte fine features (nucleus, organelles) was shown 36 h later, including some mitosis. Those cell restorations and recognized translational activities comforted that local repairs could again take place, due to oligodendrocyte resilience after ODS instead or added to a postulated immigration of oligodendrocyte precursor cells distant from the sites of myelinolysis.

Advances in the Diagnosis and Treatment of Primary Ciliary Dyskinesia: A Review

IMPORTANCE

Primary ciliary dyskinesia (PCD) is a rare, inherited condition involving motile cilia that line the upper and lower respiratory tracts, leading to chronic infections of the paranasal sinuses, middle ear, and bronchi that begin during infancy. Unfortunately, despite its early presentation, PCD is often recognized late.

OBSERVATIONS

People with PCD have diverse clinical manifestations, including chronic upper and lower respiratory tract disease, laterality defects, and subfertility. Through efforts of multinational clinical collaboratives, 4 cardinal features have been described that identify people who likely have PCD: unexplained neonatal respiratory distress, left-right laterality defects, daily wet cough, and nonseasonal rhinosinusitis beginning before 6 months of age. Recent advances in the understanding of the genetics and pathogenesis of the disease have led to a revolution in the approach to screening and diagnostic testing. Moreover, PCD has a broad clinical spectrum, and genotype-phenotype associations are beginning to be recognized.

CONCLUSIONS AND RELEVANCE

A high index of suspicion remains critical in diagnosing PCD. Children who have at least 2 of the major clinical features should be considered for further evaluation. Nevertheless, while newer tools have improved diagnostic capabilities, there is no single test that will diagnose every person with the disease. In people suspected of having PCD, nasal nitric oxide measurement is a useful screen, followed by diagnostic genetic testing and if negative, ciliary ultrastructural analysis. Despite otolaryngologic manifestations being common in infancy and persisting into adulthood, they have been understudied. Indeed, there are few randomized clinical trials examining the medicosurgical approaches to respiratory disease.

Understanding Primary Ciliary Dyskinesia and Other Ciliopathies

Ciliopathies are a collection of disorders related to cilia dysfunction. Cilia are specialized organelles that project from the surface of most cells. Motile and primary (sensory) cilia are essential structures and have wide ranging functions. Our understanding of the genetics, pathophysiology, and clinical manifestations of motile ciliopathies, including primary ciliary dyskinesia (PCD), has rapidly advanced since the disease was linked to ciliary ultrastructural defects nearly five decades ago. We will provide an overview of different types of cilia, their role in child health and disease, focusing on motile ciliopathies, and describe recent advances that have led to improved diagnostics and may yield therapeutic targets to restore ciliary structure and function.

Human myelomeningocele risk and ultra-rare deleterious variants in genes associated with cilium, WNT-signaling, ECM, cytoskeleton and cell migration

Myelomeningocele (MMC) affects one in 1000 newborns annually worldwide and each surviving child faces tremendous lifetime medical and caregiving burdens. Both genetic and environmental factors contribute to disease risk but the mechanism is unclear. This study examined 506 MMC subjects for ultra-rare deleterious variants (URDVs, absent in gnomAD v2.1.1 controls that have Combined Annotation Dependent Depletion score ≥ 20) in candidate genes either known to cause abnormal neural tube closure in animals or previously associated with human MMC in the current study cohort. Approximately 70% of the study subjects carried one to nine URDVs among 302 candidate genes. Half of the study subjects carried heterozygous URDVs in multiple genes involved in the structure and/or function of cilium, cytoskeleton, extracellular matrix, WNT signaling, and/or cell migration. Another 20% of the study subjects carried heterozygous URDVs in candidate genes associated with gene transcription regulation, folate metabolism, or glucose metabolism. Presence of URDVs in the candidate genes involving these biological function groups may elevate the risk of developing myelomeningocele in the study cohort.

Functional inhibition of fatty acid binding protein 4 ameliorates impaired ciliogenesis in GCs

Ciliogenesis is often impaired in some cancer cells, leading to acceleration of cancer phenotypes such as cell migration and proliferation. From the investigation of primary cilia of 16 gastric cancer cells (GCs), we found that GCs could be grouped into four primary cilia (PC)-positive GCs and 12 PC-negative GCs. The proliferation of the PC-positive GCs was lower than that of PC-negative GCs. To explore the role of fatty acid binding protein 4 (FABP4), which is a known oncogenic factor, in ciliogenesis, FABP4 expression and function were inhibited by transfection of cells with short interfering RNA targeting FABP4 (siFABP4) or FABP4 inhibitor treatment. Notably, the proliferation and migration of the cilia-forming GCs was effectively suppressed by inhibition of FABP4. In addition, the primary cilia in GCs were restored by a factor greater than two, suggesting a negative role of FABP4 in ciliogenesis in these GCs and FABP4 as a potential anticancer target.

Primary Ciliary Signaling in the Skin-Contribution to Wound Healing and Scarring

Primary cilia (PC) are solitary, post-mitotic, microtubule-based, and membrane-covered protrusions that are found on almost every mammalian cell. PC are specialized cellular sensory organelles that transmit environmental information to the cell. Signaling through PC is involved in the regulation of a variety of cellular processes, including proliferation, differentiation, and migration. Conversely, defective, or abnormal PC signaling can contribute to the development of various pathological conditions. Our knowledge of the role of PC in organ development and function is largely based on ciliopathies, a family of genetic disorders with mutations affecting the structure and function of PC. In this review, we focus on the role of PC in their major signaling pathways active in skin cells, and their contribution to wound healing and scarring. To provide comprehensive insights into the current understanding of PC functions, we have collected data available in the literature, including evidence across cell types, tissues, and animal species. We conclude that PC are underappreciated subcellular organelles that significantly contribute to both physiological and pathological processes of the skin development and wound healing. Thus, PC assembly and disassembly and PC signaling may serve as attractive targets for antifibrotic and antiscarring therapies.

Physiological and Pathophysiological Aspects of Primary Cilia-A Literature Review with View on Functional and Structural Relationships in Cartilage

Cilia are cellular organelles that project from the cell. They occur in nearly all non-hematopoietic tissues and have different functions in different tissues. In mesenchymal tissues primary cilia play a crucial role in the adequate morphogenesis during embryological development. In mature articular cartilage, primary cilia fulfil chemo- and mechanosensitive functions to adapt the cellular mechanisms on extracellular changes and thus, maintain tissue homeostasis and morphometry. Ciliary abnormalities in osteoarthritic cartilage could represent pathophysiological relationships between ciliary dysfunction and tissue deformation. Nevertheless, the molecular and pathophysiological relationships of ‘Primary Cilia’ (PC) in the context of osteoarthritis is not yet fully understood. The present review focuses on the current knowledge about PC and provide a short but not exhaustive overview of their role in cartilage.

Primary cilia defects causing mitral valve prolapse

Mitral valve prolapse (MVP) affects 1 in 40 people and is the most common indication for mitral valve surgery. MVP can cause arrhythmias, heart failure, and sudden cardiac death, and to date, the causes of this disease are poorly understood. We now demonstrate that defects in primary cilia genes and their regulated pathways can cause MVP in familial and sporadic nonsyndromic MVP cases. Our expression studies and genetic ablation experiments confirmed a role for primary cilia in regulating ECM deposition during cardiac development. Loss of primary cilia during development resulted in progressive myxomatous degeneration and profound mitral valve pathology in the adult setting. Analysis of a large family with inherited, autosomal dominant nonsyndromic MVP identified a deleterious missense mutation in a cilia gene, DZIP1 A mouse model harboring this variant confirmed the pathogenicity of this mutation and revealed impaired ciliogenesis during development, which progressed to adult myxomatous valve disease and functional MVP. Relevance of primary cilia in common forms of MVP was tested using pathway enrichment in a large population of patients with MVP and controls from previously generated genome-wide association studies (GWAS), which confirmed the involvement of primary cilia genes in MVP. Together, our studies establish a developmental basis for MVP through altered cilia-dependent regulation of ECM and suggest that defects in primary cilia genes can be causative to disease phenotype in some patients with MVP.

Desert hedgehog-primary cilia cross talk shapes mitral valve tissue by organizing smooth muscle actin

Non-syndromic mitral valve prolapse (MVP) is the most common heart valve disease affecting 2.4% of the population. Recent studies have identified genetic defects in primary cilia as causative to MVP, although the mechanism of their action is currently unknown. Using a series of gene inactivation approaches, we define a paracrine mechanism by which endocardially-expressed Desert Hedgehog (DHH) activates primary cilia signaling on neighboring valve interstitial cells. High-resolution imaging and functional assays show that DHH de-represses smoothened at the primary cilia, resulting in kinase activation of RAC1 through the RAC1-GEF, TIAM1. Activation of this non-canonical hedgehog pathway stimulates α-smooth actin organization and ECM remodeling. Genetic or pharmacological perturbation of this pathway results in enlarged valves that progress to a myxomatous phenotype, similar to valves seen in MVP patients. These data identify a potential molecular origin for MVP as well as establish a paracrine DHH-primary cilium cross-talk mechanism that is likely applicable across developmental tissue types.

The Role of Calmodulin in Tumor Cell Migration, Invasiveness, and Metastasis

Calmodulin (CaM) is the principal Ca²⁺ sensor protein in all eukaryotic cells, that upon binding to target proteins transduces signals encoded by global or subcellular-specific changes of Ca²⁺ concentration within the cell. The Ca²⁺/CaM complex as well as Ca²⁺-free CaM modulate the activity of a vast number of enzymes, channels, signaling, adaptor and structural proteins, and hence the functionality of implicated signaling pathways, which control multiple cellular functions. A basic and important cellular function controlled by CaM in various ways is cell motility. Here we discuss the role of CaM-dependent systems involved in cell migration, tumor cell invasiveness, and metastasis development. Emphasis is given to phosphorylation/dephosphorylation events catalyzed by myosin light-chain kinase, CaM-dependent kinase-II, as well as other CaM-dependent kinases, and the CaM-dependent phosphatase calcineurin. In addition, the role of the CaM-regulated small GTPases Rac1 and Cdc42 (cell division cycle protein 42) as well as CaM-binding adaptor/scaffold proteins such as Grb7 (growth factor receptor bound protein 7), IQGAP (IQ motif containing GTPase activating protein) and AKAP12 (A kinase anchoring protein 12) will be reviewed. CaM-regulated mechanisms in cancer cells responsible for their greater migratory capacity compared to non-malignant cells, invasion of adjacent normal tissues and their systemic dissemination will be discussed, including closely linked processes such as the epithelial–mesenchymal transition and the activation of metalloproteases. This review covers as well the role of CaM in establishing metastatic foci in distant organs. Finally, the use of CaM antagonists and other blocking techniques to downregulate CaM-dependent systems aimed at preventing cancer cell invasiveness and metastasis development will be outlined.

The Bardet-Biedl syndrome protein complex regulates cell migration and tissue repair through a Cullin-3/RhoA pathway

Cell motility and migration play critical roles in various physiological processes and disease states. Here, we show that the BBBsome, a macromolecule composed of eight Bardet-Biedl syndrome (BBS) proteins including BBS1, is a critical determinant of cell migration and wound healing. Fibroblast cells derived from mice or humans harboring a homozygous missense mutation (BBS1^M390R/M390R) that disrupt the BBSome exhibit defects in migration and wound healing. Furthermore, we demonstrate that BBS1^M390R/M390R mice have significantly delayed wound closure. In line with this, we provide data suggesting that BBS1^M390R/M390R fibroblasts have impaired platelet-derived growth factor-AA (PDGF) receptor-α signaling, a key regulator of directional cell migration acting as a chemoattractant during postnatal migration responses such as wound healing. In addition, we show that BBS1^M390R/M390R fibroblasts have upregulated RhoA expression and activity. The relevance of RhoA upregulation is demonstrated by the ability of RhoA-kinase inhibitor Y27632 to partially rescue the migration defect of BBS1^M390R/M390R fibroblasts cells. We also show that accumulation of RhoA protein in BBS1^M390R/M390R fibroblasts cells is associated with reduction and inactivation of the ubiquitin ligase Cullin-3. Consistent with this, Cullin-3 inhibition with MLN4924 is sufficient to reduce migration of normal fibroblasts. These data implicate the BBSome in cell motility and tissue repair through a mechanism that involves PDGF receptor signaling and Cullin-3-mediated control of RhoA.

Novel functions of the primary cilium in bone disease and cancer

The primary cilium, a sensory organelle that emanates from the cell surface of most mammalian cell types during growth arrest, has attracted the attention of many researchers over the past decade. Recently, a large number of new findings have assigned novel functions and roles to the primary cilium in signal transduction and related diseases, which has greatly augmented the importance of the cilium in human health and development. Here, we review emerging evidence supporting the primary cilium as a sensory organelle in signal transduction in microgravity, electromagnetic field sensing, chemosensation and tumorigenesis. We also present an overview of signal transduction crosstalk associated with the primary cilium in bone disease and cancer, including primary cilium-related Ca²⁺ signaling, parathyroid hormone signaling, cAMP signaling, BMP/Smad1/5/8 signaling and Wnt signaling. We anticipate that emerging discoveries about the function of the primary cilium will provide novel insight into the molecular mechanisms of stimulus sensation, signal transduction and pathogenesis.

The Role of Primary Cilia in the Crosstalk between the Ubiquitin⁻Proteasome System and Autophagy

Protein degradation is a pivotal process for eukaryotic development and homeostasis. The majority of proteins are degraded by the ubiquitin⁻proteasome system and by autophagy. Recent studies describe a crosstalk between these two main eukaryotic degradation systems which allows for establishing a kind of safety mechanism. If one of these degradation systems is hampered, the other compensates for this defect. The mechanism behind this crosstalk is poorly understood. Novel studies suggest that primary cilia, little cellular protrusions, are involved in the regulation of the crosstalk between the two degradation systems. In this review article, we summarise the current knowledge about the association between cilia, the ubiquitin⁻proteasome system and autophagy.

Ciliary gene RPGRIP1L is required for hypothalamic arcuate neuron development

Intronic polymorphisms in the α-ketoglutarate-dependent dioxygenase gene (FTO) that are highly associated with increased body weight have been implicated in the transcriptional control of a nearby ciliary gene, retinitis pigmentosa GTPase regulator-interacting protein-1 like (RPGRIP1L). Previous studies have shown that congenital Rpgrip1l hypomorphism in murine proopiomelanocortin (Pomc) neurons causes obesity by increasing food intake. Here, we show by congenital and adult-onset Rpgrip1l deletion in Pomc-expressing neurons that the hyperphagia and obesity are likely due to neurodevelopmental effects that are characterized by a reduction in the Pomc/Neuropeptide Y (Npy) neuronal number ratio and marked increases in arcuate hypothalamic-paraventricular hypothalamic (ARH-PVH) axonal projections. Biallelic RPGRIP1L mutations result in fewer cilia-positive human induced pluripotent stem cell-derived (iPSC-derived) neurons and blunted responses to Sonic Hedgehog (SHH). Isogenic human ARH-like embryonic stem cell-derived (ESc-derived) neurons homozygous for the obesity-risk alleles at rs8050136 or rs1421085 have decreased RPGRIP1L expression and have lower numbers of POMC neurons. RPGRIP1L overexpression increases POMC cell number. These findings suggest that apparently functional intronic polymorphisms affect hypothalamic RPGRIP1L expression and impact development of POMC neurons and their derivatives, leading to hyperphagia and increased adiposity.

Positioning of the Centrosome and Golgi Complex

For over a century, the centrosome has been an organelle more easily tracked than understood, and the study of its peregrinations within the cell remains a chief underpinning of its functional investigation. Increasing attention and new approaches have been brought to bear on mechanisms that control centrosome localization in the context of cleavage plane determination, ciliogenesis, directional migration, and immunological synapse formation, among other cellular and developmental processes. The Golgi complex, often linked with the centrosome, presents a contrasting case of a pleiomorphic organelle for which functional studies advanced somewhat more rapidly than positional tracking. However, Golgi orientation and distribution has emerged as an area of considerable interest with respect to polarized cellular function. This chapter will review our current understanding of the mechanism and significance of the positioning of these organelles.

The Roles of Primary Cilia in Cardiovascular Diseases

Primary cilia are microtubule-based organelles found in most mammalian cell types. Cilia act as sensory organelles that transmit extracellular clues into intracellular signals for molecular and cellular responses. Biochemical and molecular defects in primary cilia are associated with a wide range of diseases, termed ciliopathies, with phenotypes ranging from polycystic kidney disease, liver disorders, mental retardation, and obesity to cardiovascular diseases. Primary cilia in vascular endothelia protrude into the lumen of blood vessels and function as molecular switches for calcium (Ca²⁺) and nitric oxide (NO) signaling. As mechanosensory organelles, endothelial cilia are involved in blood flow sensing. Dysfunction in endothelial cilia contributes to aberrant fluid-sensing and thus results in vascular disorders, including hypertension, aneurysm, and atherosclerosis. This review focuses on the most recent findings on the roles of endothelial primary cilia within vascular biology and alludes to the possibility of primary cilium as a therapeutic target for cardiovascular disorders.

Cilium structure, assembly, and disassembly regulated by the cytoskeleton

The cilium, once considered a vestigial structure, is a conserved, microtubule-based organelle critical for transducing extracellular chemical and mechanical signals that control cell polarity, differentiation, and proliferation. The cilium undergoes cycles of assembly and disassembly that are controlled by complex inter-relationships with the cytoskeleton. Microtubules form the core of the cilium, the axoneme, and are regulated by post-translational modifications, associated proteins, and microtubule dynamics. Although actin and septin cytoskeletons are not major components of the axoneme, they also regulate cilium organization and assembly state. Here, we discuss recent advances on how these different cytoskeletal systems­ affect cilium function, structure, and organization.

Calcium channels in primary cilia

PURPOSE OF REVIEW

Primary cilia have become important organelles implicated in embryonic development, organogenesis, health, and diseases. Although many studies in cell biology have focused on changes in ciliary length or ciliogenesis, the most common readout for evaluating ciliary function is intracellular calcium.

RECENT FINDINGS

Recent tools have allowed us to examine intracellular calcium in more precise locations, that is, the cilioplasm and cytoplasm. Advances in calcium imaging have also allowed us to identify which cilia respond to particular stimuli. Furthermore, direct electrophysiological measurement of ionic currents within a cilium has provided a wealth of information for understanding the sensory roles of primary cilia.

SUMMARY

Calcium imaging and direct measurement of calcium currents demonstrate that primary cilia are sensory organelles that house several types of functional calcium channels. Although intracellular calcium now allows a functional readout for primary cilia, discussions on the relative contributions of the several channel types have just begun. Perhaps, all of these calcium channels are required and necessary to differentiate stimuli in different microenvironments.

SPEN, a new player in primary cilia formation and cell migration in breast cancer

Background

The primary cilium is a microtubule-based and nonmotile organelle functioning as a cellular antenna that is involved in the regulation of cell proliferation, differentiation, and migration. In breast cancer cells, the primary cilium is a structure that decreases in incidence with increasing degrees of transformation and may be biologically more important in estrogen receptor (ERα)-negative breast cancer cells. Split ends (SPEN) is an ERα corepressor that we have identified as a tumor suppressor protein in ERα-positive breast cancer cells whose hormone-independent roles in breast cancer have never been explored.

Methods

We determined the hormone-independent transcriptional program regulated by the ERα cofactor SPEN in breast cancer using DNA microarrays. The biological functions regulated by SPEN independently of hormones were studied in vitro in ERα-positive and ERα-negative breast cancer cells. Finally, we examined the clinical relevance of SPEN expression in cohorts of breast cancer samples with outcome data.

Results

We found that SPEN is coexpressed with a number of genes involved in ciliary biology, including the ciliogenic transcription factor RFX3, in a hormone-independent manner. SPEN reexpression in T47D cells containing a nonsense mutation in SPEN restored the primary cilium, whereas its knockdown in MCF10A and Hs578T cells considerably decreased primary cilia levels. We also report that SPEN regulates migration in breast cells, but only in those harboring primary cilia, and that KIF3A silencing, a critical factor in primary cilia, partially reverses SPEN’s effects, suggesting that SPEN may coordinate cellular movement through primary cilia-dependent mechanisms. Finally, we found that high SPEN RNA levels were predictive of early metastasis in two independent cohorts of 77 (HR 2.25, P = 0.03) and 170 (HR = 2.23, P = 0.004) patients with ERα-negative breast cancer.

Conclusions

Together, our data demonstrate a role for SPEN in the regulation of primary cilia formation and cell migration in breast cancer cells, which may collectively explain why its expression is associated with time to metastasis in cohorts of patients with ERα-negative breast cancers.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-017-0897-3) contains supplementary material, which is available to authorized users.

A role for primary cilia in aortic valve development and disease

BACKGROUND

Bicuspid aortic valve (BAV) disease is the most common congenital heart defect, affecting 0.5-1.2% of the population and causing significant morbidity and mortality. Only a few genes have been identified in pedigrees, and no single gene model explains BAV inheritance, thus supporting a complex genetic network of interacting genes. However, patients with rare syndromic diseases that stem from alterations in the structure and function of primary cilia ("ciliopathies") exhibit BAV as a frequent cardiovascular finding, suggesting primary cilia may factor broadly in disease etiology.

RESULTS

Our data are the first to demonstrate that primary cilia are expressed on aortic valve mesenchymal cells during embryonic development and are lost as these cells differentiate into collagen-secreting fibroblastic-like cells. The function of primary cilia was tested by genetically ablating the critical ciliogenic gene Ift88. Loss of Ift88 resulted in abrogation of primary cilia and increased fibrogenic extracellular matrix (ECM) production. Consequentially, stratification of ECM boundaries normally present in the aortic valve were lost and a highly penetrant BAV phenotype was evident at birth.

CONCLUSIONS

Our data support cilia as a novel cellular mechanism for restraining ECM production during aortic valve development and broadly implicate these structures in the etiology of BAV disease in humans. Developmental Dynamics 246:625-634, 2017. © 2017 Wiley Periodicals, Inc.

Wnt Signaling as Master Regulator of T-Lymphocyte Responses: Implications for Transplant Therapy

T cell-mediated immune responses to the grafted tissues are the major reason for failed organ transplantation. The regulation of T cell responses is complex and involves major histocompatibility complex molecules on transplanted organs, cytokines, regulatory cells, and antigen-presenting cells. The evolutionary conserved Wnt signal transduction pathway has long been known for its importance in development of stem cells and immature T cells in the thymus. Recent evidence indicates the Wnt pathway as a master regulator of T cell immune responses via governing the balance between T helper 17/regulatory T cells and by regulating the formation of effector and memory cytotoxic CD8 T cell responses. In doing so, Wnt signals influence the outcome of immune responses in transplantation settings.

A novel role for primary cilia in airway remodeling

Primary cilia (PC) are solitary cellular organelles that play critical roles in development, homeostasis, and disease pathogenesis by modulating key signaling pathways such as Sonic Hedgehog and calcium flux. The antenna-like shape of PC enables them also to facilitate sensing of extracellular and mechanical stimuli into the cell, and a critical role for PC has been described for mesenchymal cells such as chondrocytes. However, nothing is known about the role of PC in airway smooth muscle cells (ASMCs) in the context of airway remodeling. We hypothesized that PC on ASMCs mediate cell contraction and are thus integral in the remodeling process. We found that PC are expressed on ASMCs in asthmatic lungs. Using pharmacological and genetic methods, we demonstrated that PC are necessary for ASMC contraction in a collagen gel three-dimensional model both in the absence of external stimulus and in response to the extracellular component hyaluronan. Mechanistically, we demonstrate that the effect of PC on ASMC contraction is, to a small extent, due to their effect on Sonic Hedgehog signaling and, to a larger extent, due to their effect on calcium influx and membrane depolarization. In conclusion, PC are necessary for the development of airway remodeling by mediating calcium flux and Sonic Hedgehog signaling.

Crosstalk of cell polarity signaling pathways

Cell polarity, the asymmetric organization of cellular components along one or multiple axes, is present in most cells. From budding yeast cell polarization induced by pheromone signaling, oocyte polarization at fertilization to polarized epithelia and neuronal cells in multicellular organisms, similar mechanisms are used to determine cell polarity. Crucial role in this process is played by signaling lipid molecules, small Rho family GTPases and Par proteins. All these signaling circuits finally govern the cytoskeleton, which is responsible for oriented cell migration, cell shape changes, and polarized membrane and organelle trafficking. Thus, typically in the process of cell polarization, most cellular constituents become polarized, including plasma membrane lipid composition, ion concentrations, membrane receptors, and proteins in general, mRNA, vesicle trafficking, or intracellular organelles. This review gives a brief overview how these systems talk to each other both during initial symmetry breaking and within the signaling feedback loop mechanisms used to preserve the polarized state.

Primary cilium is required for the stimulating effect of icaritin on osteogenic differentiation and mineralization of osteoblasts in vitro

OBJECTIVE

Icaritin, one effective metabolite of Herba Epimedii-derived flavonoid icariin, has a strong osteogenic activity. However, its action mechanism remains unclear. Since primary cilia have been shown to play a pivotal role in regulating the osteogenesis, we hypothesized primary cilia are indispensable in mediating icaritin osteogenic effect.

MATERIALS AND METHODS

Primary rat calvarial osteoblasts were transfected with siRNA1 targeting intraflagellar transport protein 88 (IFT88), a protein required for ciliogenesis, to prevent formation of primary cilium and were treated with 10^-6 M icaritin.

RESULTS

Alkaline phosphatase (ALP) activity was significantly increased after 3 days in cells transfected with scrambled siRNA control and treated by icaritin (SC+I group) compared to cells transfected with scrambled siRNA control only (SC group). ALP activity after IFT88 siRNA1 transfection and icaritin treatment (siRNA1+I group) was significantly lower than that of SC+I group. Formation of ALP positively stained colonies after 6 days, osteocalcin secretion after 9 days and formation of calcified nodules after 12 days displayed a similar tendency among the three groups. mRNA expression of osteogenesis-related genes ALP, BMP-2, COL1α, RUNX-2 and OSX after 24 h was significantly increased in SC+I group, but was not different with SC group in siRNA1+I group. Protein levels of BMP-2, COL1α, RUNX-2 and OSX after 48 h showed the similar tendency with gene expression.

CONCLUSION

Primary cilia are important in mediating icaritin-stimulated osteogenic differentiation and may be a novel target for pharmacological therapies for bone loss.

Pulsed electromagnetic fields stimulate osteogenic differentiation and maturation of osteoblasts by upregulating the expression of BMPRII localized at the base of primary cilium

Pulsed electromagnetic fields (PEMFs) have been considered as a potential candidate for the prevention and treatment of osteoporosis, however, the mechanism of its action is still elusive. We have previously reported that 50Hz 0.6mT PEMFs stimulate osteoblastic differentiation and mineralization in a primary cilium- dependent manner, but did not know the reason. In the current study, we found that the PEMFs promoted osteogenic differentiation and maturation of rat calvarial osteoblasts (ROBs) by activating bone morphogenetic protein BMP-Smad1/5/8 signaling on the condition that primary cilia were normal. Further studies revealed that BMPRII, the primary binding receptor of BMP ligand, was readily and strongly upregulated by PEMF treatment and localized at the bases of primary cilia. Abrogation of primary cilia with small interfering RNA sequence targeting IFT88 abolished the PEMF-induced upregulation of BMPRII and its ciliary localization. Knockdown of BMPRII expression level with RNA interference had no effects on primary cilia but significantly decreased the promoting effect of PEMFs on osteoblastic differentiation and maturation. These results indicated that PEMFs stimulate osteogenic differentiation and maturation of osteoblast by primary cilium-mediated upregulation of BMPRII expression and subsequently activation of BMP-Smad1/5/8 signaling, and that BMPRII is the key component linking primary cilium and BMP-Smad1/5/8 pathway. This study has thus revealed the molecular mechanism for the osteogenic effect of PEMFs.

The cilia-regulated proteasome and its role in the development of ciliopathies and cancer

The primary cilium is an essential structure for the mediation of numerous signaling pathways involved in the coordination and regulation of cellular processes essential for the development and maintenance of health. Consequently, ciliary dysfunction results in severe human diseases called ciliopathies. Since many of the cilia-mediated signaling pathways are oncogenic pathways, cilia are linked to cancer. Recent studies demonstrate the existence of a cilia-regulated proteasome and that this proteasome is involved in cancer development via the progression of oncogenic, cilia-mediated signaling. This review article investigates the association between primary cilia and cancer with particular emphasis on the role of the cilia-regulated proteasome.

Concise Review: Primary Cilia: Control Centers for Stem Cell Lineage Specification and Potential Targets for Cell-Based Therapies

Directing stem cell lineage commitment prevails as the holy grail of translational stem cell research, particularly to those interested in the application of mesenchymal stem cells and adipose-derived stem cells in tissue engineering. However, elucidating the mechanisms underlying their phenotypic specification persists as an active area of research. In recent studies, the primary cilium structure has been intimately associated with defining cell phenotype, maintaining stemness, as well as functioning in a chemo, electro, and mechanosensory capacity in progenitor and committed cell types. Many hypothesize that the primary cilium may indeed be another important player in defining and controlling cell phenotype, concomitant with lineage-dictated cytoskeletal dynamics. Many of the studies on the primary cilium have emerged from disparate areas of biological research, and crosstalk amongst these areas of research is just beginning. To date, there has not been a thorough review of how primary cilia fit into the current paradigm of stem cell differentiation and this review aims to summarize the current cilia work in this context. The goal of this review is to highlight the cilium's function and integrate this knowledge into the working knowledge of stem cell biologists and tissue engineers developing regenerative medicine technologies. Stem Cells 2016;34:1445-1454.

Primary ciliary dyskinesia and associated sensory ciliopathies

Primary ciliary dyskinesia (PCD) is a genetic disease of motile cilia, which belongs to a group of disorders resulting from dysfunction of cilia, collectively known as ciliopathies. Insights into the genetics and phenotypes of PCD have grown over the last decade, in part propagated by the discovery of a number of novel cilia-related genes. These genes encode proteins that segregate into structural axonemal, regulatory, as well as cytoplasmic assembly proteins. Our understanding of primary (sensory) cilia has also expanded, and an ever-growing list of diverse conditions has been linked to defective function and signaling of the sensory cilium. Recent multicenter clinical and genetic studies have uncovered the heterogeneity of motile and sensory ciliopathies, and in some cases, the overlap between these conditions. Here, we will describe the genetics and pathophysiology of ciliopathies in children, focusing on PCD, review emerging genotype-phenotype relationships, and diagnostic tools available for the clinician.

Crescerin uses a TOG domain array to regulate microtubules in the primary cilium

Primary cilia are critical organelles involved in development, sensation, and signaling. Crescerin, a conserved protein family in ciliated and flagellated eukaryotes, uses a TOG domain array with tubulin polymerization activity to regulate cilia microtubules and facilitate proper cilia length, ultrastructure, and function.

Eukaryotic cilia are cell-surface projections critical for sensing the extracellular environment. Defects in cilia structure and function result in a broad range of developmental and sensory disorders. However, mechanisms that regulate the microtubule (MT)-based scaffold forming the cilia core are poorly understood. TOG domain array–containing proteins ch-TOG and CLASP are key regulators of cytoplasmic MTs. Whether TOG array proteins also regulate ciliary MTs is unknown. Here we identify the conserved Crescerin protein family as a cilia-specific, TOG array-containing MT regulator. We present the crystal structure of mammalian Crescerin1 TOG2, revealing a canonical TOG fold with conserved tubulin-binding determinants. Crescerin1's TOG domains possess inherent MT-binding activity and promote MT polymerization in vitro. Using Cas9-triggered homologous recombination in Caenorhabditis elegans, we demonstrate that the worm Crescerin family member CHE-12 requires TOG domain–dependent tubulin-binding activity for sensory cilia development. Thus, Crescerin expands the TOG domain array–based MT regulatory paradigm beyond ch-TOG and CLASP, representing a distinct regulator of cilia structure.

Correlation between cell migration and reactive oxygen species under electric field stimulation

Cell migration is an essential process involved in the development and maintenance of multicellular organisms. Electric fields (EFs) are one of the many physical and chemical factors known to affect cell migration, a phenomenon termed electrotaxis or galvanotaxis. In this paper, a microfluidics chip was developed to study the migration of cells under different electrical and chemical stimuli. This chip is capable of providing four different strengths of EFs in combination with two different chemicals via one simple set of agar salt bridges and Ag/AgCl electrodes. NIH 3T3 fibroblasts were seeded inside this chip to study their migration and reactive oxygen species (ROS) production in response to different EF strengths and the presence of β-lapachone. We found that both the EF and β-lapachone level increased the cell migration rate and the production of ROS in an EF-strength-dependent manner. A strong linear correlation between the cell migration rate and the amount of intracellular ROS suggests that ROS are an intermediate product by which EF and β-lapachone enhance cell migration. Moreover, an anti-oxidant, α-tocopherol, was found to quench the production of ROS, resulting in a decrease in the migration rate.

Tectonic‑1 contributes to the growth and migration of prostate cancer cells in vitro

Tectonic‑1 (TCTN1) is an upstream gene involved in embryonic development. The aim of the present study was to investigate the effect of the TCTN1 gene on the viability and migration of prostate cancer cells. Lentivirus‑mediated short hairpin RNA (shRNA) was constructed to silence the expression of TCTN1 in PC‑3 and DU145 prostate cancer cells. Cell viability and proliferation were measured using MTT and colony formation assays, and the distribution of cells in phases of the cell cycle was determined using flow cytometry. Cell migration was detected using a Transwell assay. The results demonstrated that TCTN1 was widely expressed in several human prostate cancer cell lines. Knockdown of the TCTN1 gene by RNA interference markedly suppressed cell viability and colony formation in the PC‑3 and DU145 cell lines. Cell cycle progression was also arrested by TCTN1 silencing. In addition, knockdown of the TCTN1 gene led to the inhibition of cell migration in the two cell lines. These findings confirmed the direct association between the TCTN1 gene and prostate cancer growth in vitro. With further understanding and clinical investigation, this indicates the potential for future development of a novel marker for early detection and gene therapy for prostate cancer.

CSPP-L Associates with the Desmosome of Polarized Epithelial Cells and Is Required for Normal Spheroid Formation

Deleterious mutations of the Centrosome/Spindle Pole associated Protein 1 gene, CSPP1, are causative for Joubert-syndrome and Joubert-related developmental disorders. These disorders are defined by a characteristic mal-development of the brain, but frequently involve renal and hepatic cyst formation. CSPP-L, the large protein isoform of CSPP1 localizes to microtubule ends of the mitotic mid-spindle and the ciliary axoneme, and is required for ciliogenesis. We here report the microtubule independent but Desmoplakin dependent localization of CSPP-L to Desmosomes in apical-basal polarized epithelial cells. Importantly, siRNA conferred depletion of CSPP-L or Desmoplakin promoted multi-lumen spheroid formation in 3D-cultures of non-ciliated human colon carcinoma Caco-2 cells. Multi-lumen spheroids of CSPP1 siRNA transfectants showed disrupted apical cell junction localization of the cytoskeleton organizing RhoGEF ECT2. Our results hence identify a novel, non-ciliary role for CSPP-L in epithelial morphogenesis.

Alström syndrome: current perspectives

Alström syndrome (ALMS) is a rare genetic disorder that has been included in the ciliopathies group, in the last few years. Ciliopathies are a growing group of diseases associated with defects in ciliary structure and function. The development of more powerful genetic approaches has been replaced the strategies to follow for getting a successful molecular diagnosis for these patients, especially for those without the typical ALMS phenotype. In an effort to deepen the understanding of the pathogenesis of ALMS disease, much work has been done, in order to establish the biological implication of ALMS1 protein, which is still being elucidated. In addition to its role in ciliary function and structure maintenance, this protein has been implicated in intracellular trafficking, regulation of cilia signaling pathways, and cellular differentiation, among others. All these progresses will lead to identifying therapeutic targets, thus opening the way to future personalized therapies for human ciliopathies.

Adult Stem Cell Responses to Nanostimuli

Adult or mesenchymal stem cells (MSCs) have been found in different tissues in the body, residing in stem cell microenvironments called "stem cell niches". They play different roles but their main activity is to maintain tissue homeostasis and repair throughout the lifetime of an organism. Their ability to differentiate into different cell types makes them an ideal tool to study tissue development and to use them in cell-based therapies. This differentiation process is subject to both internal and external forces at the nanoscale level and this response of stem cells to nanostimuli is the focus of this review.