Overview of structure and function of mammalian cilia

Tumor cell-intrinsic Piezo2 drives radioresistance by impairing CD8+ T cell stemness maintenance

Changes in mechanosensitive ion channels following radiation have seldom been linked to therapeutic sensitivity or specific factors involved in antitumor immunity. Here, in this study, we found that the mechanical force sensor, Piezo2, was significantly upregulated in tumor cells after radiation, and Piezo2 knockout in tumor cells enhanced tumor growth suppression by radiotherapy. Specifically, loss of Piezo2 in tumor cells induced their IL-15 expression via unleashing JAK2/STAT1/IRF-1 axis after radiation. This increase in IL-15 activates IL-15Rα on tumor-infiltrating CD8+ T cells, thereby leading to their augmented effector and stem cell-like properties, along with reduced terminal exhausted feature. Importantly, Piezo2 expression was negatively correlated with CD8 infiltration, as well as with radiosensitivity of patients with rectum adenocarcinoma receiving radiotherapy treatment. Together, our findings reveal that tumor cell-intrinsic Piezo2 induces radioresistance by dampening the IRF-1/IL-15 axis, thus leading to impaired CD8+ T cell-dependent antitumor responses, providing insights into the further development of combination strategies to treat radioresistant cancers.

Calaxin is a key factor for calcium-dependent waveform control in zebrafish sperm

Calcium is critical for regulating the waveform of motile cilia and flagella. Calaxin is currently the only known molecule involved in the calcium-dependent regulation in ascidians. We have recently shown that Calaxin stabilizes outer arm dynein (OAD), and the knockout of Calaxin results in primary ciliary dyskinesia phenotypes in vertebrates. However, from the knockout experiments, it was not clear which functions depend on calcium and how Calaxin regulates the waveform. To address this question, here, we generated transgenic zebrafish expressing a mutant E130A-Calaxin deficient in calcium binding. E130A-Calaxin restored the OAD reduction of calaxin -/- sperm and the abnormal movement of calaxin -/- left-right organizer cilia, showing that Calaxin's stabilization of OADs is calcium-independent. In contrast, our quantitative analysis of E130A-Calaxin sperms showed that the calcium-induced asymmetric beating was not restored, linking Calaxin's calcium-binding ability with an asymmetric flagellar beating for the first time. Our data show that Calaxin is a calcium-dependent regulator of the ciliary beating and a calcium-independent OAD stabilizer.

Characterization of pathogenic genetic variants in Russian patients with primary ciliary dyskinesia using gene panel sequencing and transcript analysis

BACKGROUND

Primary ciliary dyskinesia (PCD) is a group of rare genetically heterogeneous disorders caused by defective cilia and flagella motility. The clinical phenotype of PCD patients commonly includes chronic oto-sino-pulmonary disease, infertility, and, in about half of cases, laterality defects due to randomization of left-right body asymmetry. To date, pathogenic variants in more than 50 genes responsible for motile cilia structure and assembly have been reported in such patients. While multiple population-specific mutations have been described in PCD cohorts from different countries, the data on genetic spectrum of PCD in Russian population are still extremely limited.

RESULTS

The present study provides a comprehensive clinical and genetic characterization of 21 Russian families with PCD living in various country regions. Anomalies of ciliary beating in patients` respiratory epithelial cells were confirmed by high-speed video microscopy. In the most cases, custom-designed panel sequencing allowed to uncover causative variants in well-known or rarely mentioned PCD-related genes, including DNAH5, DNAH11, CFAP300, LRRC6, ZMYND10, CCDC103, HYDIN, ODAD4, DNAL1, and OFD1. The variations comprised common mutations, as well as novel genetic variants, some of which probably specific for Russian patients. Additional targeted analysis of mRNA transcripts from ciliated cells enabled us to specify functional effects of newly identified genetic variants in DNAH5 (c.2052+3G>T, c.3599-2A>G), HYDIN (c.10949-2A>G, c.1797C>G), and ZMYND10 (c.510+1G>C) on splicing process. In particular, the splice site variant c.2052+3G>T, detected in four unrelated families, resulted in skipping of exon 14 in DNAH5 transcripts and, according to haplotype analysis of affected probands, was proposed as an ancestral founder mutation in Udmurt population.

CONCLUSIONS

The reported data provide a vital insight into genetic background of primary ciliary dyskinesia in the Russian population. The findings clearly illustrate the utility of gene panel sequencing coupled with transcriptional analysis in identification and clinical interpretation of novel genetic variants.

Multiciliogenesis: Tricking the cell-cycle machinery to build hundreds of cilia

Multiciliated cells produce over a hundred motile cilia anchored to the membrane by modified centrioles. Recent work has characterized an alternative cell cycle used by this post-mitotic cell type to generate additional centrioles without undergoing cell division.

CilioGenics: an integrated method and database for predicting novel ciliary genes

Uncovering the full list of human ciliary genes holds enormous promise for the diagnosis of cilia-related human diseases, collectively known as ciliopathies. Currently, genetic diagnoses of many ciliopathies remain incomplete (1-3). While various independent approaches theoretically have the potential to reveal the entire list of ciliary genes, approximately 30% of the genes on the ciliary gene list still stand as ciliary candidates (4,5). These methods, however, have mainly relied on a single strategy to uncover ciliary candidate genes, making the categorization challenging due to variations in quality and distinct capabilities demonstrated by different methodologies. Here, we develop a method called CilioGenics that combines several methodologies (single-cell RNA sequencing, protein-protein interactions (PPIs), comparative genomics, transcription factor (TF) network analysis, and text mining) to predict the ciliary capacity of each human gene. Our combined approach provides a CilioGenics score for every human gene that represents the probability that it will become a ciliary gene. Compared to methods that rely on a single method, CilioGenics performs better in its capacity to predict ciliary genes. Our top 500 gene list includes 258 new ciliary candidates, with 31 validated experimentally by us and others. Users may explore the whole list of human genes and CilioGenics scores on the CilioGenics database (https://ciliogenics.com/).

Primary cilia abnormalities participate in the occurrence of spontaneous abortion through TGF-β/SMAD2/3 signaling pathway

Spontaneous abortion is the most common complication in early pregnancy, the exact etiology of most cases cannot be determined. Emerging studies suggest that mutations in ciliary genes may be associated with progression of pregnancy loss. However, the involvement of primary cilia on spontaneous abortion and the underlying molecular mechanisms remains poorly understood. We observed the number and length of primary cilia were significantly decreased in decidua of spontaneous abortion in human and lipopolysaccharide (LPS)-induced abortion mice model, accompanied with increased expression of proinflammatory cytokines interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α. The length of primary cilia in human endometrial stromal cell (hESC) was significantly shortened after TNF-α treatment. Knocking down intraflagellar transport 88 (IFT88), involved in cilia formation and maintenance, promoted the expression of TNF-α. There was a reverse regulatory relationship between cilia shortening and TNF-α expression. Further research found that shortened cilia impair decidualization in hESC through transforming growth factor (TGF)-β/SMAD2/3 signaling. Primary cilia were impaired in decidua tissue of spontaneous abortion, which might be mainly caused by inflammatory injury. Primary cilia abnormalities resulted in dysregulation of TGF-β/SMAD2/3 signaling transduction and decidualization impairment, which led to spontaneous abortion.

Further evidence from DNAH12 supports favorable fertility outcomes of infertile males with dynein axonemal heavy chain gene family variants

Male infertility is a major concern affecting reproductive health. Biallelic deleterious variants of most DNAH gene family members have been linked to male infertility, with intracytoplasmic sperm injection (ICSI) being an efficacious way to achieve offspring. However, the association between DNAH12 and male infertility is still limited. Here, we identified one homozygous variant and two compound heterozygous variants in DNAH12 from three infertile Chinese men. Semen analysis revealed severe asthenozoospermia, abnormal morphology, and structure of sperm flagella. Furthermore, the Dnah12 knock-out mouse revealed severe spermatogenesis failure and validated the same male infertility phenotype. Favorable fertility outcomes were achieved through ICSI in three human individuals and Dnah12 knock-out mice. Collectively, our study indicated that biallelic variants of DNAH12 can induce male infertility in both human beings and mice. Notably, evidence from DNAH12 enhanced that ICSI was an optimal intervention to achieve favorable fertility outcomes for infertile males with DNAH gene family variants.

The Odad3 Gene Is Necessary for Spermatozoa Development and Male Fertility in Mice

Odad3 gene loss-of-function mutation leads to Primary Ciliary Dyskinesia (PCD), a disease caused by motile cilia dysfunction. Previously, we demonstrated that knockout of the Odad3 gene in mice replicates several features of PCD, such as hydrocephalus, defects in left-right body symmetry, and male infertility, with a complete absence of sperm in the reproductive tract. The majority of Odad3 knockout animals die before sexual maturation due to severe hydrocephalus and failure to thrive, which precludes fertility studies. Here, we performed the expression analysis of the Odad3 gene during gonad development and in adult testes. We showed that Odad3 starts its expression during the first wave of spermatogenesis, specifically at the meiotic stage, and that its expression is restricted to the germ cells in the adult testes, suggesting that Odad3 plays a role in spermatozoa formation. Subsequently, we conditionally deleted the Odad3 gene in adult males and demonstrated that even partial ablation of the Odad3 gene leads to asthenoteratozoospermia with multiple morphological abnormalities of sperm flagella (MMAF) in mice. The analysis of the seminiferous tubules in Odad3-deficient mice revealed defects in spermatogenesis with accumulation of seminiferous tubules at the spermiogenesis and spermiation phases. Furthermore, analysis of fertility in heterozygous Odad3+/- knockout mice revealed a reduction in sperm count and motility as well as abnormal sperm morphology. Additionally, Odad3+/- males exhibited a shorter fertile lifespan. Overall, these results suggest the important role of Odad3 and Odad3 gene dosage in male fertility. These findings may have an impact on the genetic and fertility counseling practice of PCD patients carrying Odad3 loss-of-function mutations.

Astrocyte-Specific Inhibition of the Primary Cilium Suppresses C3 Expression in Reactive Astrocyte

C3-positive reactive astrocytes play a neurotoxic role in various neurodegenerative diseases. However, the mechanisms controlling C3-positive reactive astrocyte induction are largely unknown. We found that the length of the primary cilium, a cellular organelle that receives extracellular signals was increased in C3-positive reactive astrocytes, and the loss or shortening of primary cilium decreased the count of C3-positive reactive astrocytes. Pharmacological experiments suggested that Ca2+ signalling may synergistically promote C3 expression in reactive astrocytes. Conditional knockout (cKO) mice that specifically inhibit primary cilium formation in astrocytes upon drug stimulation exhibited a reduction in the proportions of C3-positive reactive astrocytes and apoptotic cells in the brain even after the injection of lipopolysaccharide (LPS). Additionally, the novel object recognition (NOR) score observed in the cKO mice was higher than that observed in the neuroinflammation model mice. These results suggest that the primary cilium in astrocytes positively regulates C3 expression. We propose that regulating astrocyte-specific primary cilium signalling may be a novel strategy for the suppression of neuroinflammation.

Deciphering vesicle-assisted transport mechanisms in cytoplasm to cilium trafficking

The cilium, a pivotal organelle crucial for cell signaling and proper cell function, relies on meticulous macromolecular transport from the cytoplasm for its formation and maintenance. While the intraflagellar transport (IFT) pathway has traditionally been the focus of extensive study concerning ciliogenesis and ciliary maintenance, recent research highlights a complementary and alternative mechanism-vesicle-assisted transport (VAT) in cytoplasm to cilium trafficking. Despite its potential significance, the VAT pathway remains largely uncharacterized. This review explores recent studies providing evidence for the dynamics of vesicle-related diffusion and transport within the live primary cilium, employing high-speed super-resolution light microscopy. Additionally, we analyze the spatial distribution of vesicles in the cilium, mainly relying on electron microscopy data. By scrutinizing the VAT pathways that facilitate cargo transport into the cilium, with a specific emphasis on recent advancements and imaging data, our objective is to synthesize a comprehensive model of ciliary transport through the integration of IFT-VAT mechanisms.

Prominin 1 and Tweety Homology 1 both induce extracellular vesicle formation

Prominin-1 (Prom1) is a five-transmembrane-pass integral membrane protein that associates with curved regions of the plasma membrane. Prom1 interacts with membrane cholesterol and actively remodels the plasma membrane. Membrane bending activity is particularly evident in photoreceptors, where Prom1 loss-of-function mutations cause failure of outer segment homeostasis, leading to cone-rod retinal dystrophy (CRRD). The Tweety Homology (Ttyh) protein family has been proposed to be homologous to Prominin, but it is not known whether Ttyh proteins have an analogous membrane-bending function. Here, we characterize the membrane-bending activity of human Prom1 and Ttyh1 in native bilayer membranes. We find that Prom1 and Ttyh1 both induce formation of extracellular vesicles (EVs) in cultured mammalian cells and that the EVs produced are physically similar. Ttyh1 is more abundant in EV membranes than Prom1 and produces EVs with membranes that are more tubulated than Prom1 EVs. We further show that Prom1 interacts more stably with membrane cholesterol than Ttyh1 and that this may contribute to membrane bending inhibition in Prom1 EVs. Intriguingly, a loss-of-function mutation in Prom1 associated with CRRD induces particularly stable cholesterol binding. These experiments provide mechanistic insight into Prominin function in CRRD and suggest that Prom and Ttyh belong to a single family of functionally related membrane-bending, EV-generating proteins.

Assessment and Comparison of Early Developmental Toxicity of Six Per- and Polyfluoroalkyl Substances with Human Embryonic Stem Cell Models

Per- and polyfluoroalkyl substances (PFAS) are extensively utilized in varieties of products and tend to accumulate in the human body including umbilical cord blood and embryos/fetuses. In this study, we conducted an assessment and comparison of the potential early developmental toxicity of perfluorooctanoic acid (PFOA), undecafluorohexanoic acid (PFHxA), heptafluorobutyric acid, perfluorooctanesulfonate (PFOS), perfluorohexanesulfonate, and perfluorobutyric acid at noncytotoxic concentrations relevant to human exposure using models based on human embryonic stem cells in both three-dimensional embryoid body (EB) and monolayer differentiation configurations. All six compounds influenced the determination of cell fate by disrupting the expression of associated markers in both models and, in some instances, even led to alterations in the formation of cystic EBs. The expression of cilia-related gene IFT122 was significantly inhibited. Additionally, PFOS and PFOA inhibited ciliogenesis, while PFOA specifically reduced the cilia length. Transcriptome analysis revealed that PFOS altered 1054 genes and disrupted crucial signaling pathways such as WNT and TGF-β, which play integral roles in cilia transduction and are critical for early embryonic development. These results provide precise and comprehensive insights into the potential adverse health effects of these six PFAS compounds directly concerning early human embryonic development.

IFT27 regulates the long-term maintenance of photoreceptor outer segments in zebrafish

Approximately a quarter of Retinitis Pigmentosa (RP) is caused by mutations in transport-related genes in cilia. IFT27 (Intraflagellar Transport 27), a core component of the ciliary intraflagellar transport (IFT) system, has been implicated as a significant pathogenic gene in RP. The pathogenic mechanisms and subsequent pathology related to IFT27 mutations in RP are largely obscure. Here, we utilized TALEN technology to create an ift27 knockout (ift27-/-) zebrafish model. Electroretinography (ERG) detection showed impaired vision in this model. Histopathological examinations disclosed that ift27 mutations cause progressive degeneration of photoreceptors in zebrafish, and this degeneration was late-onset. Immunofluorescence labeling of outer segments showed that rods degenerated before cones, aligning with the conventional characterization of RP. In cultured human retinal pigment epithelial cells, we found that IFT27 was involved in maintaining ciliary morphology. Furthermore, decreased IFT27 expression resulted in the inhibition of the Hedgehog (Hh) signaling pathway, including decreased expression of key factors in the Hh pathway and abnormal localization of the ciliary mediator Gli2. In summary, we generated an ift27-/- zebrafish line with retinal degeneration which mimicked the symptoms of RP patients, highlighting IFT27's integral role in the long-term maintenance of cilia via the Hh signaling pathway. This work may furnish new insights into the treatment or delay of RP caused by IFT27 mutations.

Cerebral furin deficiency causes hydrocephalus in mice

Furin is a pro-protein convertase that moves between the trans-Golgi network and cell surface in the secretory pathway. We have previously reported that cerebral overexpression of furin promotes cognitive functions in mice. Here, by generating the brain-specific furin conditional knockout (cKO) mice, we investigated the role of furin in brain development. We found that furin deficiency caused early death and growth retardation. Magnetic resonance imaging showed severe hydrocephalus. In the brain of furin cKO mice, impaired ciliogenesis and the derangement of microtubule structures appeared along with the down-regulated expression of RAB28, a ciliary vesicle protein. In line with the widespread neuronal loss, ependymal cell layers were damaged. Further proteomics analysis revealed that cell adhesion molecules including astrocyte-enriched ITGB8 and BCAR1 were altered in furin cKO mice; and astrocyte overgrowth was accompanied by the reduced expression of SOX9, indicating a disrupted differentiation into ependymal cells. Together, whereas alteration of RAB28 expression correlated with the role of vesicle trafficking in ciliogenesis, dysfunctional astrocytes might be involved in ependymal damage contributing to hydrocephalus in furin cKO mice. The structural and molecular alterations provided a clue for further studying the potential mechanisms of furin.

Hydrodynamic synchronization of elastic cilia: How surface effects determine the characteristics of metachronal waves

Cilia are hairlike microactuators whose cyclic motion is specialized to propel extracellular fluids at low Reynolds numbers. Clusters of these organelles can form synchronized beating patterns, called metachronal waves, which presumably arise from hydrodynamic interactions. We model hydrodynamically interacting cilia by microspheres elastically bound to circular orbits, whose inclinations with respect to a no-slip wall model the ciliary power and recovery stroke, resulting in an anisotropy of the viscous flow. We derive a coupled phase-oscillator description by reducing the microsphere dynamics to the slow timescale of synchronization and determine analytical metachronal wave solutions and their stability in a periodic chain setting. In this framework, a simple intuition for the hydrodynamic coupling between phase oscillators is established by relating the geometry of flow near the surface of a cell or tissue to the directionality of the hydrodynamic coupling functions. This intuition naturally explains the properties of the linear stability of metachronal waves. The flow near the surface stabilizes metachronal waves with long wavelengths propagating in the direction of the power stroke and, moreover, metachronal waves with short wavelengths propagating perpendicularly to the power stroke. Performing simulations of phase-oscillator chains with periodic boundary conditions, we indeed find that both wave types emerge with a variety of linearly stable wave numbers. In open chains of phase oscillators, the dynamics of metachronal waves is fundamentally different. Here the elasticity of the model cilia controls the wave direction and selects a particular wave number: At large elasticity, waves traveling in the direction of the power stroke are stable, whereas at smaller elasticity waves in the opposite direction are stable. For intermediate elasticity both wave directions coexist. In this regime, waves propagating towards both ends of the chain form, but only one wave direction prevails, depending on the elasticity and initial conditions.

Midbody remnant regulates the formation of primary cilia and their roles in tumor growth

Recent studies have shown that the formation of the primary cilium is associated with a specific cellular organelle known as the midbody remnant (MBR), which is a point-like organelle formed by shedding of the midbody at the end of mitosis. MBRs move along the cell surface close to the center body and regulate it to form primary cilia at the top of the centriole. Primary cilia can act as an organelle to inhibit tumorigenesis, and it is lost in a variety of tumors. Studies have shown that the accumulation of MBRs in tumor cells affects ciliogenesis; in addition, both MBRs and primary cilia are degraded in tumor cells through the autophagy pathway, and MBRs can also transfer tumor signaling pathway factors to primary cilia affecting tumorigenesis. In this article, the basic structure and the formation process of MBR and primary cilia are reviewed and the mechanism of MBRs regulating ciliogenesis is elaborated. The significance of MBR-mediated ciliogenesis in tumorigenesis and its potential as a target for cancer treatment are discussed.

Advancing Primary Ciliary Dyskinesia Diagnosis through High-Speed Video Microscopy Analysis

Primary ciliary dyskinesia (PCD) is an inherited disorder that impairs motile cilia, essential for respiratory health, with a reported prevalence of 1 in 16,309 within Hispanic populations. Despite 70% of Puerto Rican patients having the RSPH4A [c.921+3_921+6del (intronic)] founder mutation, the characterization of the ciliary dysfunction remains unidentified due to the unavailability of advanced diagnostic modalities like High-Speed Video Microscopy Analysis (HSVA). Our study implemented HSVA for the first time on the island as a tool to better diagnose and characterize the RSPH4A [c.921+3_921+6del (intronic)] founder mutation in Puerto Rican patients. By applying HSVA, we analyzed the ciliary beat frequency (CBF) and pattern (CBP) in native Puerto Rican patients with PCD. Our results showed decreased CBF and a rotational CBP linked to the RSPH4A founder mutation in Puerto Ricans, presenting a novel diagnostic marker that could be implemented as an axillary test into the PCD diagnosis algorithm in Puerto Rico. The integration of HSVA technology in Puerto Rico substantially enhances the PCD evaluation and diagnosis framework, facilitating prompt detection and early intervention for improved disease management. This initiative, demonstrating the potential of HSVA as an adjunctive test within the PCD diagnostic algorithm, could serve as a blueprint for analogous developments throughout Latin America.

Tektin bundle interacting protein, TEKTIP1, functions to stabilize the tektin bundle and axoneme in mouse sperm flagella

Tektins are microtubule inner proteins (MIPs) and localize at the inside lumen of doublet microtubules (DMTs) of cilia/flagella. TEKTIP1, a newly identified protein by cryo-electron microscopy (cryo-EM), is proposed to be localized at the center of the tektin bundle and hypothesized to recruit tektins or stabilize the bundle. However, the physiological role of TEKTIP1 is unknown. In this study, we generated Tektip1-knockout (Tektip1-/-) mice and showed that they were male subfertile primarily due to reduced sperm motility. A high percentage of sperm from Tektip1-/- mice showed moderately disorganized axoneme structures and abnormal flagellar waveforms. TEKTIP1 predominately interacted with TEKT3 among tektins. Loss of TEKTIP1 partially disturbed the organization of tektin bundle by mainly affecting the native status of TEKT3 and its interaction with other tektins. Collectively, our study reveals the physiological role and potential molecular mechanism of TEKTIP1 in axonemal structure and sperm motility, highlights the importance of MIPs in stabilizing DMTs, and suggests a potential relevance of TEKTIP1 deficiency to human asthenospermia. Tektip1-/- mice will be an excellent animal model to study the DMT organization of sperm flagella using cryo-EM in future.

CRP inhibits the osteoblastic differentiation of OPCs via the up-regulation of primary cilia and repression of the Hedgehog signaling pathway

Inflammation disrupts bone metabolism and leads to bone damage. C-reactive protein (CRP) is a typical inflammation marker. Although CRP measurement has been conducted for many decades, how osteoblastic differentiation influences molecular mechanisms remains largely unknown. The present study attempted to investigate the effects of CRP on primary cultured osteoblast precursor cells (OPCs) while elucidating the underlying molecular mechanisms. OPCs were isolated from suckling Sprague-Dawleyrats. Fewer OPCs were observed after recombinant C-reactive protein treatment. In a series of experiments, CRP inhibited OPC proliferation, osteoblastic differentiation, and the OPC gene expression of the hedgehog (Hh) signaling pathway. The inhibitory effect of CRP on OPC proliferation occurred via blockade of the G1-S transition of the cell cycle. In addition, the regulation effect of proto cilium on osteoblastic differentiation was analyzed using the bioinformatics p. This revealed the primary cilia activation of recombinant CRP effect on OPCs through in vitro experiments. A specific Sonic Hedgehog signaling agonist (SAG) rescued osteoblastic differentiation inhibited by recombinant CRP. Moreover, chloral hydrate, which removes primary cilia, inhibited the Suppressor of Fused (SUFU) formation and blocked Gli2 degradation. This counteracted osteogenesis inhibition caused by CRP. Therefore, these data depict that CRP can inhibit the proliferation and osteoblastic differentiation of OPCs. The underlying mechanism could be associated with primary cilia activation and Hh pathway repression.

To squeeze or not: Regulation of cell size by mechanical forces in development and human diseases

Physical constraints, such as compression, shear stress, stretching and tension play major roles during development and tissue homeostasis. Mechanics directly impact physiology, and their alteration is also recognized as having an active role in driving human diseases. Recently, growing evidence has accumulated on how mechanical forces are translated into a wide panel of biological responses, including metabolism and changes in cell morphology. The aim of this review is to summarize and discuss our knowledge on the impact of mechanical forces on cell size regulation. Other biological consequences of mechanical forces will not be covered by this review. Moreover, wherever possible, we also discuss mechanosensors and molecular and cellular signaling pathways upstream of cell size regulation. We finally highlight the relevance of mechanical forces acting on cell size in physiology and human diseases.

CP110 and CEP135 Localize Near the Proximal Centriolar Remnants of Mice Spermatozoa

Centrioles form centrosomes that organize microtubules, assist in cell structure, and nucleate cilia that provide motility and sensation. Within the sperm, the centrosome consists of two centrioles (proximal and distal centriole) and a pericentriolar material known as the striated column and capitulum. The distal centriole nucleates the flagellum. Mice spermatozoa, unlike other mammal spermatozoa (e.g., human and bovine), have no ultra-structurally recognizable centrioles, but their neck has the centriolar proteins POC1B and FAM161A, suggesting mice spermatozoa have remnant centrioles. Here, we examine whether other centriolar proteins, CP110 and CEP135, found in the human and bovine spermatozoa centrioles are also found in the mouse spermatozoa neck. CP110 is a tip protein controlling ciliogenesis, and CEP135 is a centriole-specific structural protein in the centriole base of canonical centrioles found in most cell types. Here, we report that CP110 and CEP135 were both located in the mice spermatozoa neck around the proximal centriolar remnants labeled by POC1B, increasing the number of centriolar proteins found in the mice spermatozoa neck, further supporting the hypothesis that a remnant proximal centriole is present in mice.

Functional and structural significance of the inner-arm-dynein subspecies d in ciliary motility

Motile cilia play various important physiological roles in eukaryotic organisms including cell motility and fertility. Inside motile cilia, large motor-protein complexes called "ciliary dyneins" coordinate their activities and drive ciliary motility. The ciliary dyneins include the outer-arm dyneins, the double-headed inner-arm dynein (IDA f/I1), and several single-headed inner-arm dyneins (IDAs a, b, c, d, e, and g). Among these single-headed IDAs, one of the ciliary dyneins, IDA d, is of particular interest because of its unique properties and subunit composition. In addition, defects in this subspecies have recently been associated with several types of ciliopathies in humans, such as primary ciliary dyskinesia and multiple morphologic abnormalities of the flagellum. In this mini-review, we discuss the composition, structure, and motor properties of IDA d, which have been studied in the model organism Chlamydomonas reinhardtii, and further discuss the relationship between IDA d and human ciliopathies. In addition, we provide future perspectives and discuss remaining questions regarding this intriguing dynein subspecies.

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 emerging functions of intraflagellar transport 52 in ciliary transport and ciliopathies

Ciliary transport in eukaryotic cells is an intricate and conserved process involving the coordinated assembly and functioning of a multiprotein intraflagellar transport (IFT) complex. Among the various IFT proteins, intraflagellar transport 52 (IFT52) plays a crucial role in ciliary transport and is implicated in various ciliopathies. IFT52 is a core component of the IFT-B complex that facilitates movement of cargoes along the ciliary axoneme. Stable binding of the IFT-B1 and IFT-B2 subcomplexes by IFT52 in the IFT-B complex regulates recycling of ciliary components and maintenance of ciliary functions such as signal transduction and molecular movement. Mutations in the IFT52 gene can disrupt ciliary trafficking, resulting in dysfunctional cilia and affecting cellular processes in ciliopathies. Such ciliopathies caused by IFT52 mutations exhibit a wide range of clinical features, including skeletal developmental abnormalities, retinal degeneration, respiratory failure and neurological abnormalities in affected individuals. Therefore, IFT52 serves as a promising biomarker for the diagnosis of various ciliopathies, including short-rib thoracic dysplasia 16 with or without polydactyly. Here, we provide an overview of the IFT52-mediated molecular mechanisms underlying ciliary transport and describe the IFT52 mutations that cause different disorders associated with cilia dysfunction.

The prescription design and key properties of nasal gel for CNS drug delivery: A review

Central nervous system (CNS) diseases are among the major health problems. However, blood-brain barrier (BBB) makes traditional oral and intravenous delivery of CNS drugs inefficient. The unique direct connection between the nose and the brain makes nasal administration a great potential advantage in CNS drugs delivery. However, nasal mucociliary clearance (NMCC) limits the development of drug delivery systems. Appropriate nasal gel viscosity alleviates NMCC to a certain extent, gels based on gellan gum, chitosan, carbomer, cellulose and poloxamer have been widely reported. However, nasal gel formulation design and key properties for alleviating NMCC have not been clearly discussed. This article summarizes gel formulations of different polymers in existing nasal gel systems, and attempts to provide a basis for researchers to conduct in-depth research on the key characteristics of gel matrix against NMCC.

Genetic variants in primary cilia-related genes associated with the prognosis of first-line chemotherapy in colorectal cancer

BACKGROUND

Primary cilia are antenna-like organelles that conduct physical and chemical signals, which affect cell proliferation, migration, and differentiation. Some researchers have reported the correlation between primary cilia-related genes and prognosis of colorectal cancer (CRC).

METHODS

The association between single nucleotide polymorphisms (SNPs) of primary cilia-related genes and outcome after the first-line chemotherapy was explored by the Cox regression model. Expression qualitative trait locus (eQTL) analysis was performed to explore the impact of SNPs on gene expression. Tumor Immune Estimation Resource and TISIDB databases were used for investigating the relevance between ODF2L and tumor infiltration immune cells and immunomodulators.

RESULTS

We identified that rs4288473 C allele of ODF2L had poor progression-free survival (PFS) and overall survival (OS) of CRC patients in the additive model (adjusted HRPFS  = 1.39, 95% CI = 1.14-1.70, p = 1.36 × 10-3 , and adjusted HROS  = 1.31, 95% CI = 1.03-1.65, p = 2.62 × 10-2 ). The stratified analysis indicated that rs4288573 CC/CT genotype was involved with poor prognosis in the irinotecan-treated subgroup (PPFS  = 1.03 × 10-2 , POS  = 3.29 × 10-3 ). Besides, ODF2L mRNA expression level was notably up-regrated in CRC tissues. The C allele of rs4288573 was notably related to higher ODF2L mRNA expression levels based on eQTL analysis. Functionally, knockdown of ODF2L inhibited cell proliferation and decrease the chemoresistance of HCT-116 and DLD-1 cells to irinotecan.

CONCLUSION

Our study indicates that rs4288573 in ODF2L is a potential predictor of the chemotherapy prognosis of CRC.

A historical perspective of macroautophagy regulation by biochemical and biomechanical stimuli

Macroautophagy is a lysosomal degradative pathway for intracellular macromolecules, protein aggregates, and organelles. The formation of the autophagosome, a double membrane-bound structure that sequesters cargoes before their delivery to the lysosome, is regulated by several stimuli in multicellular organisms. Pioneering studies in rat liver showed the importance of amino acids, insulin, and glucagon in controlling macroautophagy. Thereafter, many studies have deciphered the signaling pathways downstream of these biochemical stimuli to control autophagosome formation. Two signaling hubs have emerged: the kinase mTOR, in a complex at the surface of lysosomes which is sensitive to nutrients and hormones; and AMPK, which is sensitive to the cellular energetic status. Besides nutritional, hormonal, and energetic fluctuations, many organs have to respond to mechanical forces (compression, stretching, and shear stress). Recent studies have shown the importance of mechanotransduction in controlling macroautophagy. This regulation engages cell surface sensors, such as the primary cilium, in order to translate mechanical stimuli into biological responses.

Functions of cilia in cardiac development and disease

Errors in embryonic cardiac development are a leading cause of congenital heart defects (CHDs), including morphological abnormalities of the heart that are often detected after birth. In the past few decades, an emerging role for cilia in the pathogenesis of CHD has been identified, but this topic still largely remains an unexplored area. Mouse forward genetic screens and whole exome sequencing analysis of CHD patients have identified enrichment for de novo mutations in ciliary genes or non-ciliary genes, which regulate cilia-related pathways, linking cilia function to aberrant cardiac development. Key events in cardiac morphogenesis, including left-right asymmetric development of the heart, are dependent upon cilia function. Cilia dysfunction during left-right axis formation contributes to CHD as evidenced by the substantial proportion of heterotaxy patients displaying complex CHD. Cilia-transduced signaling also regulates later events during heart development such as cardiac valve formation, outflow tract septation, ventricle development, and atrioventricular septa formation. In this review, we summarize the role of motile and non-motile (primary cilia) in cardiac asymmetry establishment and later events during heart development.

Integrative analysis of transcriptomic and metabolomic profiles reveals enhanced arginine metabolism in androgen-independent prostate cancer cells

BACKGROUND

Prostate cancer is a common solid tumor that affects a significant number of men worldwide. Conventional androgen deprivation therapy (ADT) increases the risk of developing castration-resistant prostate cancer (CRPC). Effective clinical management of patients with CRPC is challenging due to the limited understanding.

METHODS

In this study, transcriptomic and metabolomic profiles of androgen-dependent prostate cancer cell line LNCaP and the androgen-independent cells developed from LNCaP cells (LNCaP-ADR) were investigated using RNA-sequencing and LC-MS/MS, respectively. The differentially expressed genes and metabolites were analyzed, and integrative analysis of transcriptomic and metabolomic data was further conducted to obtain a comprehensive understanding of the metabolic characteristics in LNCaP-ADR cells. Quantitative real-time PCR (QPCR) was employed to ascertain the mRNA expression levels of the selected differentially expressed genes.

RESULTS

The arginine and proline metabolism pathway was identified as a commonly altered pathway at both the transcriptional and metabolic levels. In the LNCaP-ADR cells, significant upregulation was observed for metabolites including 5-Aminopentanoic acid, L-Arginine, L-Glutamic acid, N-Acetyl-L-alanine, and Pyrrole-2-carboxylic acid at the metabolic level. At the transcriptional level, MAOA, ALDH3A2, ALDH2, ARG1, CKMT2, and CNDP1 were found to be significantly upregulated in the LNCaP-ADR cells. Gene set enrichment analysis (GSEA) identified various enriched gene sets in the LNCaP-ADR cells, encompassing inflammatory response, 9plus2 motile cilium, motile cilium, ciliary plasm, cilium or flagellum-dependent cell motility, cilium movement, cilium, response to endoplasmic reticulum stress, PTEN DN.V1 DN, SRC UP.V1 UP, IL15 UP.V1 DN, RB DN.V1 DN, AKT UP MTOR DN.V1 UP, VEGF A UP.V1 UP, and KRAS.LUNG.BREAST UP.V1 UP.

CONCLUSIONS

These findings highlight the substantial association between the arginine and proline metabolism pathway and CRPC, emphasizing the need to prioritize strategies that target dysregulated metabolites and differentially expressed genes as essential interventions in the clinical management of CRPC.

ALS-linked C9orf72-SMCR8 complex is a negative regulator of primary ciliogenesis

Massive GGGGCC (G4C2) repeat expansion in C9orf72 and the resulting loss of C9orf72 function are the key features of ~50% of inherited amyotrophic lateral sclerosis and frontotemporal dementia cases. However, the biological function of C9orf72 remains unclear. We previously found that C9orf72 can form a stable GTPase activating protein (GAP) complex with SMCR8 (Smith-Magenis chromosome region 8). Herein, we report that the C9orf72-SMCR8 complex is a major negative regulator of primary ciliogenesis, abnormalities in which lead to ciliopathies. Mechanistically, the C9orf72-SMCR8 complex suppresses the primary cilium as a RAB8A GAP. Moreover, based on biochemical analysis, we found that C9orf72 is the RAB8A binding subunit and that SMCR8 is the GAP subunit in the complex. We further found that the C9orf72-SMCR8 complex suppressed the primary cilium in multiple tissues from mice, including but not limited to the brain, kidney, and spleen. Importantly, cells with C9orf72 or SMCR8 knocked out were more sensitive to hedgehog signaling. These results reveal the unexpected impact of C9orf72 on primary ciliogenesis and elucidate the pathogenesis of diseases caused by the loss of C9orf72 function.

Doublet microtubule inner junction protein FAP20 recruits tubulin to the microtubule lattice

Doublet microtubules of eukaryotic cilia and flagella are made up of a complete A- and an incomplete B-tubule that are fused together. Of the two fusion points, the outer junction is made of tripartite tubulin connections, while the inner junction contains non-tubulin elements. The latter includes flagellar-associated protein 20 (FAP20) and Parkin co-regulated gene protein (PACRG) that together link the A- and B-tubule at the inner junction. While structures of doublet microtubules reveal molecular details, their assembly is poorly understood. In this study, we purified recombinant FAP20 and characterized its effects on microtubule dynamics. We use in vitro reconstitution and cryo-electron microscopy to show that FAP20 recruits free tubulin to the existing microtubule lattice. Our cryo-electron microscopy reconstruction of microtubule:FAP20:tubulin complex reveals the mode of tubulin recruitment by FAP20 onto microtubules, providing insights into assembly steps of B-tubule closure during doublet microtubule formation.

The centrosome - diverse functions in fertilization and development across species

The centrosome is a non-membrane-bound organelle that is conserved across most animal cells and serves various functions throughout the cell cycle. In dividing cells, the centrosome is known as the spindle pole and nucleates a robust microtubule spindle to separate genetic material equally into two daughter cells. In non-dividing cells, the mother centriole, a substructure of the centrosome, matures into a basal body and nucleates cilia, which acts as a signal-transducing antenna. The functions of centrosomes and their substructures are important for embryonic development and have been studied extensively using in vitro mammalian cell culture or in vivo using invertebrate models. However, there are considerable differences in the composition and functions of centrosomes during different aspects of vertebrate development, and these are less studied. In this Review, we discuss the roles played by centrosomes, highlighting conserved and divergent features across species, particularly during fertilization and embryonic development.

Leukemia inhibitory factor shortens primary cilia by upregulating C-C motif chemokine 2 in human neural stem/progenitor cells

Primary cilia on neural stem/progenitor cells (NSPCs) play an important role in determining cell fate, although the regulatory mechanisms involved in the ciliogenesis remain largely unknown. In this study, we analyzed the effect of the leukemia inhibitory factor (LIF) for the primary cilia in immortalized human NSPCs. LIF withdrawal elongated the primary cilia length, whereas the addition of LIF shortened it. Microarray gene expression analysis revealed that differentially expressed genes (DEGs) associated with LIF treatment were related with the multiple cytokine signaling pathways. Among the DEGs, C-C motif chemokine 2 (CCL2) had the highest ranking and its increase in the protein concentration in the NSPCs-conditioned medium after the LIF treatment was confirmed by ELISA. Interestingly, we found that CCL2 was a negative regulator of cilium length, and LIF-induced shortening of primary cilia was antagonized by CCL2-specific antibody, suggesting that LIF could influence cilia length via upregulating CCL2. The shortening effect of LIF and CCL2 on primary cilia was also observed in SH-SY5Y cells. The results of the study suggested that the LIF-CCL2 axis may well be a regulator of NSPCs and its primary cilia length, which could affect multiple cellular processes, including NSPC proliferation and differentiation.

The role of cilia during organogenesis in zebrafish

Cilia are hair-like organelles that protrude from the surface of eukaryotic cells and are present on the surface of nearly all human cells. Cilia play a crucial role in signal transduction, organ development and tissue homeostasis. Abnormalities in the structure and function of cilia can lead to a group of human diseases known as ciliopathies. Currently, zebrafish serves as an ideal model for studying ciliary function and ciliopathies due to its relatively conserved structure and function of cilia compared to humans. In this review, we will summarize the different types of cilia that present in embryonic and adult zebrafish, and provide an overview of the advantages of using zebrafish as a vertebrate model for cilia research. We will specifically focus on the roles of cilia during zebrafish organogenesis based on recent studies. Additionally, we will highlight future prospects for ciliary research in zebrafish.

A novel strategy to increase the therapeutic potency of GBM chemotherapy via altering parenchymal/cerebral spinal fluid clearance rate

Patients with glioblastoma (GBM) face a poor prognosis with a median survival of less than two years. Escalating the dose of chemotherapy is often impossible due to patient comorbidities; thus, we focused on modulating brain clearance as a mechanism to enhance drug accumulation. Given the recently identified interconnectivity between brain parenchymal fluid and cerebral spinal fluid (CSF), we reasoned enhancing drug concentration in the CSF also increases drug concentration in the parenchyma where a GBM resides. To improve drug accumulation in the CSF, we impair the motility of ependymal cell cilia. We identified FDA-approved therapeutics that interact with cilia as a "side effect." Therapeutics that inhibit airway cilia also inhibit ependymal cilia. Multiple cilia-inhibiting drugs, when administered in combination with GBM chemotherapy temozolomide (TMZ), significantly improved the overall survival of mice bearing orthotopic GBM. Combining TMZ with lidocaine results in 100% of animals surviving tumor-free to the study endpoint. This treatment results in a ~ 40-fold increase in brain TMZ levels and is well-tolerated. Mice bearing MGMT methylated, human PDX orthotopic GBM also responded with 100% of animals surviving tumor-free to the study endpoint. Finally, even mice bearing TMZ-resistant, orthotopic GBM responded to the combination treatment with 40% of animals surviving tumor-free to the study endpoint, implying this strategy can sensitize TMZ-resistant GBM. These studies offer a new concept for treating malignant brain tumors by improving the accumulation of TMZ in the CNS. In the future, this regimen may also improve the treatment of additional encephalopathies treated by brain-penetrating therapeutics. SIGNIFICANCE: We exploit the interconnectivity of parenchymal and cerebral spinal fluid to enhance the amount of temozolomide that accumulates in the central nervous system to improve the survival of mice bearing brain tumors.

Lipid raft interacting galectin 8 regulates primary ciliogenesis

Primary cilium is a specialized sensory organelle that transmits environmental information into cells. Its length is tightly controlled by various mechanisms such as the frequency or the cargo size of the intraflagellar transport trains which deliver the building materials such as tubulin subunits essential for the growing cilia. Here, we show the sialoglycan interacting galectin 8 regulates the process of primary ciliogenesis. As the epithelia become polarized, there are more galectin 8 being apically secreted and these extracellular galectin 8 molecules apparently bind to a lipid raft enriched domain at the base of the primary cilia through interacting with lipid raft components, such as GD3 ganglioside and scaffold protein caveolin 1. Furthermore, the binding of galectin 8 at this critical region triggers rapid growth of primary cilia by perturbing the barrier function of the transition zone (TZ). Our study also demonstrates the functionality of this barrier depends on intact organization of lipid rafts at the cilia as genetically knockout of Cav1 and pharmacologically inhibition of lipid raft both phenocopy the effect of apical addition of recombinant galectin 8; that is, rapid elongation of primary cilia and redistribution of cilia proteins from TZ to the growing axoneme. Indeed, as cilia elongated, endogenous galectin 8, caveolin 1, and TZ component, TMEM231, also transited from the TZ to the growing axoneme. We also noted that the interaction between caveolin 1 and TMEM231 could be perturbed by exogenous galectin 8. Taken together, we proposed that galectin 8 promoted primary cilia elongation through impeding the barrier function of the TZ by interfering with the interaction between caveolin 1 and TMEM231.

Paralog-specific TTC30 regulation of Sonic hedgehog signaling

The intraflagellar transport (IFT) machinery is essential for cilia assembly, maintenance, and trans-localization of signaling proteins. The IFT machinery consists of two large multiprotein complexes, one of which is the IFT-B. TTC30A and TTC30B are integral components of this complex and were previously shown to have redundant functions in the context of IFT, preventing the disruption of IFT-B and, thus, having a severe ciliogenesis defect upon loss of one paralog. In this study, we re-analyzed the paralog-specific protein complexes and discovered a potential involvement of TTC30A or TTC30B in ciliary signaling. Specifically, we investigated a TTC30A-specific interaction with protein kinase A catalytic subunit α, a negative regulator of Sonic hedgehog (Shh) signaling. Defects in this ciliary signaling pathway are often correlated to synpolydactyly, which, intriguingly, is also linked to a rare TTC30 variant. For an in-depth analysis of this unique interaction and the influence on Shh, TTC30A or B single- and double-knockout hTERT-RPE1 were employed, as well as rescue cells harboring wildtype TTC30 or the corresponding mutation. We could show that mutant TTC30A inhibits the ciliary localization of Smoothened. This observed effect is independent of Patched1 but associated with a distinct phosphorylated PKA substrate accumulation upon treatment with forskolin. This rather prominent phenotype was attenuated in mutant TTC30B. Mass spectrometry analysis of wildtype versus mutated TTC30A or TTC30B uncovered differences in protein complex patterns and identified an impaired TTC30A-IFT57 interaction as the possible link leading to synpolydactyly. We could observe no impact on cilia assembly, leading to the hypothesis that a slight decrease in IFT-B binding can be compensated, but mild phenotypes, like synpolydactyly, can be induced by subtle signaling changes. Our systematic approach revealed the paralog-specific influence of TTC30A KO and mutated TTC30A on the activity of PRKACA and the uptake of Smoothened into the cilium, resulting in a downregulation of Shh. This downregulation, combined with interactome alterations, suggests a potential mechanism of how mutant TTC30A is linked to synpolydactyly.

Oxidative Stress Induces Skin Pigmentation in Melasma by Inhibiting Hedgehog Signaling

There is growing evidence that oxidative stress plays a role in melasma and disrupts primary cilia formation. Additionally, primary cilia have been suggested to have an inhibitory role in melanogenesis. This study examined the potential link between oxidative stress, skin hyperpigmentation, and primary cilia. We compared the expression levels of the nuclear factor E2-related factor 2 (NRF2), intraflagellar transport 88 (IFT88), and glioma-associated oncogene homologs (GLIs) in skin samples from patients with melasma, both in affected and unaffected areas. We also explored the roles of NRF2, IFT88, and GLIs in ciliogenesis and pigmentation using cultured adult human keratinocytes, with or without melanocytes. Our findings revealed decreased levels of NRF2, heme oxygenase-1, IFT88, and GLIs in lesional skin from melasma patients. The knockdown of NRF2 resulted in reduced expressions of IFT88 and GLI1, along with fewer ciliated cells. Furthermore, NRF2, IFT88, or GLI1 knockdown led to increased expressions in protease-activated receptor-2 (PAR2), K10, involucrin, tyrosinase, and/or melanin. These effects were reversed by the smoothened agonist 1.1. Calcium also upregulated these proteins, but not NRF2. The upregulation of involucrin and PAR2 after NRF2 knockdown was mitigated with a calcium chelator. In summary, our study suggests that oxidative stress in NRF2-downregulated melasma keratinocytes impedes ciliogenesis and related molecular processes. This inhibition stimulates keratinocyte differentiation, resulting in melanin synthesis and melanosome transfer, ultimately leading to skin hyperpigmentation.

CEP104/FAP256 and associated cap complex maintain stability of the ciliary tip

Cilia are essential organelles that protrude from the cell body. Cilia are made of a microtubule-based structure called the axoneme. In most types of cilia, the ciliary tip is distinct from the rest of the cilium. Here, we used cryo-electron tomography and subtomogram averaging to obtain the structure of the ciliary tip of the ciliate Tetrahymena thermophila. We show that the microtubules at the tip are highly crosslinked with each other and stabilized by luminal proteins, plugs, and cap proteins at the plus ends. In the tip region, the central pair lacks typical projections and twists significantly. By analyzing cells lacking a ciliary tip-enriched protein CEP104/FAP256 by cryo-electron tomography and proteomics, we discovered candidates for the central pair cap complex and explained the potential functions of CEP104/FAP256. These data provide new insights into the function of the ciliary tip and the mechanisms of ciliary assembly and length regulation.

Targeting the hedgehog pathway in MET mutation cancers and its effects on cells associated with cancer development

The mutation of MET plays a crucial role in the initiation of cancer, while the Hedgehog (Hh) pathway also plays a significant role in cell differentiation and the maintenance of tumor stem cells. Conventional chemotherapy drugs are primarily designed to target the majority of cell populations within tumors rather than tumor stem cells. Consequently, after a brief period of remission, tumors often relapse. Moreover, the exclusive targeting of tumor stemness cell disregards the potential for other tumor cells to regain stemness and acquire drug resistance. As a result, current drugs that solely target the HGF/c-MET axis and the Hh pathway demonstrate only moderate efficacy in specific types of cancer. Mounting evidence indicates that these two pathways not only play important roles in cancer but also exert significant influence on the development of resistance to single-target therapies through the secretion of their own ligands. In this comprehensive review, we analyze and compare the potential impact of the Hh pathway on the tumor microenvironment (TME) in HGF/c-MET-driven tumor models, as well as the interplay between different cell types. Additionally, we further substantiate the potential and necessity of dual-pathway combination therapy as a critical target in MET addicted cancer treatment. Video Abstract.

Functions of actin-binding proteins in cilia structure remodeling and signaling

Cilia are microtubule-based organelles found on the surfaces of many types of cells, including cardiac fibroblasts, vascular endothelial cells, human retinal pigmented epithelial-1 (RPE-1) cells, and alveolar epithelial cells. These organelles can be classified as immotile cilia, referred to as primary cilia in mammalian cells, and motile cilia. Primary cilia are cellular sensors that detect extracellular signals; this is a critical function associated with ciliopathies, which are characterized by the typical clinical features of developmental disorders. Cilia are extensively studied organelles of the microtubule cytoskeleton. However, the ciliary actin cytoskeleton has rarely been studied. Clear evidence has shown that highly regulated actin cytoskeleton dynamics contribute to normal ciliary function. Actin-binding proteins (ABPs) play vital roles in filamentous actin (F-actin) morphology. Here, we discuss recent progress in understanding the roles of ABPs in ciliary structural remodeling and further downstream ciliary signaling with a focus on the molecular mechanisms underlying actin cytoskeleton-related ciliopathies.

Knockout of the BRAP homolog in mice leads to abnormal tracheal cilia

Both bombesin receptor-activated protein (BRAP) and its mouse homolog have been found to be expressed in bronchial epithelia but with unclear functions. Using electron microscopy combined with histological assays, we found that BRAP homolog deficiency in mice led to abnormal tracheal cilia. Rab-3A-interacting protein (Rabin8), a protein that might play a role in cilia development, was screened by yeast two-hybrid and further verified to have interaction with human BRAP by co-immunoprecipitation and pulldown assays. The expression levels of Rabin8, together with acetylated α-tubulin, a marker of cilia, were either downregulated by knockdown of BRAP or upregulated by overexpression of BRAP in cultured immortalized human bronchial epithelial cells. These results reveal a role for BRAP in airway cilia formation.

On the role of calcium diffusion and its rapid buffering in intraflagellar signaling

We have considered the realistic mechanism of rapid Ca2+ (calcium ion) buffering within the wave of calcium ions progressing along the flagellar axoneme. This buffering is an essential part of the Ca2+ signaling pathway aimed at controlling the bending dynamics of flagella. It is primarily achieved by the mobile region of calmodulin molecules and by stationary calaxin, as well as by the part of calmodulin bound to calcium/calmodulin-dependent kinase II and kinase C. We derived and elaborated a model of Ca2+ diffusion within a signaling wave in the presence of these molecules which rapidly buffer Ca2+. This approach has led to a single nonlinear transport equation for the Ca2+ wave that contains the effects brought about by both as necessary buffers for signaling. The presence of mobile buffer calmodulin gives rise to a transport equation that is not strictly diffusive but also exhibits a sink-like effect. We solved straightforwardly the final transport equation in an analytical framework and obtained the implied function of calcium concentration. The effective diffusion coefficient depends on local Ca2+ concentration. It is plausible that these buffers' presence can impact Ca2+ wave speed and shape, which are essential for decoding Ca2+ signaling in flagella. We present the solution of the transport equation for a few specified cases with physiologically reasonable sets of parameters involved.

Identification of genetic variants associated with anterior cruciate ligament rupture and AKC standard coat color in the Labrador Retriever

Canine anterior cruciate ligament (ACL) rupture is a common complex disease. Prevalence of ACL rupture is breed dependent. In an epidemiological study, yellow coat color was associated with increased risk of ACL rupture in the Labrador Retriever. ACL rupture risk variants may be linked to coat color through genetic selection or through linkage with coat color genes. To investigate these associations, Labrador Retrievers were phenotyped as ACL rupture case or controls and for coat color and were single nucleotide polymorphism (SNP) genotyped. After filtering, ~ 697 K SNPs were analyzed using GEMMA and mvBIMBAM for multivariate association. Functional annotation clustering analysis with DAVID was performed on candidate genes. A large 8 Mb region on chromosome 5 that included ACSF3, as well as 32 additional SNPs, met genome-wide significance at P < 6.07E-7 or Log10(BF) = 3.0 for GEMMA and mvBIMBAM, respectively. On chromosome 23, SNPs were located within or near PCCB and MSL2. On chromosome 30, a SNP was located within IGDCC3. SNPs associated with coat color were also located within ADAM9, FAM109B, SULT1C4, RTDR1, BCR, and RGS7. DZIP1L was associated with ACL rupture. Several significant SNPs on chromosomes 2, 3, 7, 24, and 26 were located within uncharacterized regions or long non-coding RNA sequences. This study validates associations with the previous ACL rupture candidate genes ACSF3 and DZIP1L and identifies novel candidate genes. These variants could act as targets for treatment or as factors in disease prediction modeling. The study highlighted the importance of regulatory SNPs in the disease, as several significant SNPs were located within non-coding regions.

Experimental and molecular support for Cfap70 as a causative gene of 'multiple morphological abnormalities of the flagella' with male infertility†

Multiple morphological abnormalities of the flagella, a severe form of asthenozoospermia, can lead to male infertility. Recent studies have implicated an association between human CFAP70 deficiency and multiple morphological abnormalities of the flagella; however, the underlying biological mechanism and supporting experimental evidence in animal models remain unclear. To address this gap, we used CRISPR/Cas9 technology to generate Cfap70-deficient mice to investigate the relationship between Cfap70 deficiency and multiple morphological abnormalities of the flagella. Our findings show that the loss of CFAP70 leads to multiple morphological abnormalities of the flagella and spermiogenesis defects. Specifically, the lack of CFAP70 impairs sperm flagellum biogenesis and head shaping during spermiogenesis. Late-step spermatids from Cfap70-deficient mouse testis exhibited club-shaped sperm heads and abnormal disassembly of the manchette. Furthermore, we found that CFAP70 interacts with DNAI1 and DNAI2; Cfap70 deficiency also reduces the level of AKAP3 in sperm flagella, indicating that CFAP70 may participate in the flagellum assembly and transport of flagellar components. These findings provide compelling evidence implicating Cfap70 as a causative gene of multiple morphological abnormalities of the flagella and highlight the consequences of CFAP70 loss on flagellum biogenesis.

PIH1D3-knockout rats exhibit full ciliopathy features and dysfunctional pre-assembly and loading of dynein arms in motile cilia

Background: Recessive mutation of the X-linked gene, PIH1 domain-containing protein 3 (PIH1D3), causes familial ciliopathy. PIH1D3 deficiency is associated with the defects of dynein arms in cilia, but how PIH1D3 specifically affects the structure and function of dynein arms is not understood yet. To gain insights into the underlying mechanisms of the disease, it is crucial to create a reliable animal model. In humans, rats, and mice, one copy of the PIH1D3 gene is located on the X chromosome. Interestingly, mice have an additional, intronless copy of the Pih1d3 gene on chromosome 1. To develop an accurate disease model, it is best to manipulate the X-linked PIH1D3 gene, which contains essential regulatory sequences within the introns for precise gene expression. This study aimed to develop a tailored rat model for PIH1D3-associated ciliopathy with the ultimate goal of uncovering the intricate molecular mechanisms responsible for ciliary defects in the disease. Methods: Novel Pih1d3-knockout (KO) rats were created by using TALEN-mediated non-homologous DNA recombination within fertilized rat eggs and, subsequently, underwent a comprehensive characterization through a battery of behavioral and pathological assays. A series of biochemical and histological analyses were conducted to elucidate the identity of protein partners that interact with PIH1D3, thus shedding light on the intricate molecular mechanisms involved in this context. Results: PIH1D3-KO rats reproduced the cardinal features of ciliopathy including situs inversus, defects in spermatocyte survival and mucociliary clearance, and perinatal hydrocephalus. We revealed the novel function of PIH1D3 in cerebrospinal fluid circulation and elucidated the mechanism by which PIH1D3 deficiency caused communicating hydrocephalus. PIH1D3 interacted with the proteins required for the pre-assembly and uploading of outer (ODA) and inner dynein arms (IDA), regulating the integrity of dynein arm structure and function in cilia. Conclusion: PIH1D3-KO rats faithfully reproduced the cardinal features of ciliopathy associated with PIH1D3 deficiency. PIH1D3 interacted with the proteins responsible for the pre-assembly and uploading of dynein arms in cilia, and its deficiency led to dysfunctional cilia and, thus, to ciliopathy by affecting the pre-assembly and uploading of dynein arms. The resultant rat model is a valuable tool for the mechanistic study of PIH1D3-caused diseases.

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.

Convergence of Calcium Channel Regulation and Mechanotransduction in Skeletal Regenerative Biomaterial Design

Cells are known to perceive their microenvironment through extracellular and intracellular mechanical signals. Upon sensing mechanical stimuli, cells can initiate various downstream signaling pathways that are vital to regulating proliferation, growth, and homeostasis. One such physiologic activity modulated by mechanical stimuli is osteogenic differentiation. The process of osteogenic mechanotransduction is regulated by numerous calcium ion channels-including channels coupled to cilia, mechanosensitive and voltage-sensitive channels, and channels associated with the endoplasmic reticulum. Evidence suggests these channels are implicated in osteogenic pathways such as the YAP/TAZ and canonical Wnt pathways. This review aims to describe the involvement of calcium channels in regulating osteogenic differentiation in response to mechanical loading and characterize the fashion in which those channels directly or indirectly mediate this process. The mechanotransduction pathway is a promising target for the development of regenerative materials for clinical applications due to its independence from exogenous growth factor supplementation. As such, also described are examples of osteogenic biomaterial strategies that involve the discussed calcium ion channels, calcium-dependent cellular structures, or calcium ion-regulating cellular features. Understanding the distinct ways calcium channels and signaling regulate these processes may uncover potential targets for advancing biomaterials with regenerative osteogenic capabilities.

ODF2 Negatively Regulates CP110 Levels at the Centrioles/Basal Bodies to Control the Biogenesis of Primary Cilia

Primary cilia are essential sensory organelles that develop when an inhibitory cap consisting of CP110 and other proteins is eliminated. The degradation of CP110 by the ubiquitin-dependent proteasome pathway mediated by NEURL4 and HYLS1 removes the inhibitory cap. Here, we investigated the suitability of rapamycin-mediated dimerization for centriolar recruitment and asked whether the induced recruitment of NEURL4 or HYLS1 to the centriole promotes primary cilia development and CP110 degradation. We used rapamycin-mediated dimerization with ODF2 to induce their targeted recruitment to the centriole. We found decreased CP110 levels in the transfected cells, but independent of rapamycin-mediated dimerization. By knocking down ODF2, we showed that ODF2 controls CP110 levels. The overexpression of ODF2 is not sufficient to promote the formation of primary cilia, but the overexpression of NEURL4 or HYLS1 is. The co-expression of ODF2 and HYLS1 resulted in the formation of tube-like structures, indicating an interaction. Thus, ODF2 controls primary cilia formation by negatively regulating the concentration of CP110 levels. Our data suggest that ODF2 most likely acts as a scaffold for the binding of proteins such as NEURL4 or HYLS1 to mediate CP110 degradation.

Exome sequencing in a Romanian Bardet-Biedl syndrome cohort revealed an overabundance of causal BBS12 variants

Bardet-Biedl syndrome (BBS), is an emblematic ciliopathy hallmarked by pleiotropy, phenotype variability, and extensive genetic heterogeneity. BBS is a rare (~1/140,000 to ~1/160,000 in Europe) autosomal recessive pediatric disorder characterized by retinal degeneration, truncal obesity, polydactyly, cognitive impairment, renal dysfunction, and hypogonadism. Twenty-eight genes involved in ciliary structure or function have been implicated in BBS, and explain the molecular basis for ~75%-80% of individuals. To investigate the mutational spectrum of BBS in Romania, we ascertained a cohort of 24 individuals in 23 families. Following informed consent, we performed proband exome sequencing (ES). We detected 17 different putative disease-causing single nucleotide variants or small insertion-deletions and two pathogenic exon disruptive copy number variants in known BBS genes in 17 pedigrees. The most frequently impacted genes were BBS12 (35%), followed by BBS4, BBS7, and BBS10 (9% each) and BBS1, BBS2, and BBS5 (4% each). Homozygous BBS12 p.Arg355* variants were present in seven pedigrees of both Eastern European and Romani origin. Our data show that although the diagnostic rate of BBS in Romania is likely consistent with other worldwide cohorts (74%), we observed a unique distribution of causal BBS genes, including overrepresentation of BBS12 due to a recurrent nonsense variant, that has implications for regional diagnostics.