Kif3a deletion prevents primary cilia assembly on oligodendrocyte progenitor cells, reduces oligodendrogenesis and impairs fine motor function

The Relationship between Early Exposure to General Anesthesia and Neurobehavioral Deficits

BACKGROUND

In contemporary medical practice, general anesthesia plays an essential role in pediatric surgical procedures. While modern anesthetic protocols have demonstrated safety and efficacy across various pathological conditions, concerns persist regarding the potential neurotoxic effects associated with early exposure to general anesthesia.

SUMMARY

Current research primarily examines the neurocognitive developmental impacts, with limited focus on neurobehavioral developmental disorders. This review presents a comprehensive analysis of clinical trial results related to five critical neurobehavioral developmental disorders: fine motor disability, attention-deficit hyperactivity disorder, impulse control disorders, autism spectrum disorder, and developmental coordination disorder. Furthermore, this review synthesizes insights from basic research on the potential toxicological mechanisms of general anesthetic agents that could influence clinical neurobehavioral changes. These findings provide valuable guidance for the prudent and safe utilization of anesthetic agents in pediatric patients.

KEY MESSAGES

This review explores the potential connections between general anesthesia and five neurobehavioral disorders, highlighting the importance of cautious anesthetic use in children in light of current research findings.

Pericyte ablation causes hypoactivity and reactive gliosis in adult mice

Capillary pericytes are important regulators of cerebral blood flow, blood-brain barrier integrity and neuroinflammation, but can become lost or dysfunctional in disease. The consequences of pericyte loss or dysfunction is extremely difficult to discern when it forms one component of a complex disease process. To evaluate this directly, we examined the effect of adult pericyte loss on mouse voluntary movement and motor function, and physiological responses such as hypoxia, blood-brain barrier (BBB) integrity and glial reactivity. Tamoxifen delivery to Pdgfrβ-CreERT2:: Rosa26-DTA transgenic mice was titrated to produce a dose-dependent ablation of pericytes in vivo. 100mg/kg of tamoxifen ablated approximately half of all brain pericytes, while two consecutive daily doses of 300mg/kg tamoxifen ablated >80% of brain pericytes. In the open field test, mice with ∼50% pericyte loss spent more time immobile and travelled half the distance of control mice. Mice with >80% pericyte ablation also slipped more frequently while performing the beam walk task. Our histopathological analyses of the brain revealed that blood vessel density was unchanged, but vessel lumen width was increased. Pericyte-ablated mice also exhibited: mild BBB disruption; increased neuronal hypoxia; astrogliosis and increased IBA1+ immunoreactivity, suggestive of microgliosis and/or macrophage infiltration. Our results highlight the importance of pericytes in the brain, as pericyte loss can directly compromise brain health and induce behavioural alterations in mice.

The role of cilia in the development, survival, and regeneration of hair cells

Mutations impacting cilia genes lead to a class of human diseases known as ciliopathies. This is due to the role of cilia in the development, survival, and regeneration of many cell types. We investigated the extent to which disrupting cilia impacted these processes in lateral line hair cells of zebrafish. We found that mutations in two intraflagellar transport (IFT) genes, ift88 and dync2h1, which lead to the loss of kinocilia, caused increased hair cell apoptosis. IFT gene mutants also have a decreased mitochondrial membrane potential, and blocking the mitochondrial uniporter causes a loss of hair cells in wild-type zebrafish but not mutants, suggesting mitochondria dysfunction may contribute to the apoptosis seen in these mutants. These mutants also showed decreased proliferation during hair cell regeneration but did not show consistent changes in support cell number or proliferation during hair cell development. These results show that the loss of hair cells seen following disruption of cilia through either mutations in anterograde or retrograde IFT genes appears to be due to impacts on hair cell survival but not necessarily development in the zebrafish lateral line.

Compartmentalized ciliation changes of oligodendrocytes in aged mouse optic nerve

Primary cilia are microtubule-based sensory organelles that project from the apical surface of most mammalian cells, including oligodendrocytes, which are myelinating cells of the central nervous system (CNS) that support critical axonal function. Dysfunction of CNS glia is associated with aging-related white matter diseases and neurodegeneration, and ciliopathies are known to affect CNS white matter. To investigate age-related changes in ciliary profile, we examined ciliary length and frequency in the retinogeniculate pathway, a white matter tract commonly affected by diseases of aging but in which expression of cilia has not been characterized. We found expression of Arl13b, a marker of primary cilia, in a small group of Olig2-positive oligodendrocytes in the optic nerve, optic chiasm, and optic tract in young and aged C57BL/6 wild-type mice. While the ciliary length and ciliated oligodendrocyte cells were constant in young mice in the retinogeniculate pathway, there was a significant increase in ciliary length in the anterior optic nerve as compared to the aged animals. Morphometric analysis confirmed a specific increase in the ciliation rate of CC1+ /Olig2+ oligodendrocytes in aged mice compared with young mice. Thus, the prevalence of primary cilia in oligodendrocytes in the visual pathway and the age-related changes in ciliation suggest that they may play important roles in white matter and age-associated optic neuropathies.

Uncovering cilia function in glial development

Primary cilia play critical roles in regulating signaling pathways that underlie several developmental processes. In the nervous system, cilia are known to regulate signals that guide neuron development. Cilia dysregulation is implicated in neurological diseases, and the underlying mechanisms remain poorly understood. Cilia research has predominantly focused on neurons and has overlooked the diverse population of glial cells in the brain. Glial cells play essential roles during neurodevelopment, and their dysfunction contributes to neurological disease; however, the relationship between cilia function and glial development is understudied. Here we review the state of the field and highlight the glial cell types where cilia are found and the ciliary functions that are linked to glial development. This work uncovers the importance of cilia in glial development and raises outstanding questions for the field. We are poised to make progress in understanding the function of glial cilia in human development and their contribution to neurological diseases.

Glioblastoma may evade immune surveillance through primary cilia-dependent signaling in an IL-6 dependent manner

Glioblastoma is the most common, malignant primary brain tumor in adults and remains universally fatal. While immunotherapy has vastly improved the treatment of several solid cancers, efficacy in glioblastoma is limited. These challenges are due in part to the propensity of glioblastoma to recruit tumor-suppressive immune cells, which act in conjunction with tumor cells to create a pro-tumor immune microenvironment through secretion of several soluble factors. Glioblastoma-derived EVs induce myeloid-derived suppressor cells (MDSCs) and non-classical monocytes (NCMs) from myeloid precursors leading to systemic and local immunosuppression. This process is mediated by IL-6 which contributes to the recruitment of tumor-associated macrophages of the M2 immunosuppressive subtype, which in turn, upregulates anti-inflammatory cytokines including IL-10 and TGF-β. Primary cilia are highly conserved organelles involved in signal transduction and play critical roles in glioblastoma proliferation, invasion, angiogenesis, and chemoradiation resistance. In this perspectives article, we provide preliminary evidence that primary cilia regulate intracellular release of IL-6. This ties primary cilia mechanistically to tumor-mediated immunosuppression in glioblastomas and potentially, in additional neoplasms which have a shared mechanism for cancer-mediated immunosuppression. We propose potentially testable hypotheses of the cellular mechanisms behind this finding.

Primary cilia control oligodendrocyte precursor cell proliferation in white matter injury via Hedgehog-independent CREB signaling

Remyelination after white matter injury (WMI) often fails in diseases such as multiple sclerosis because of improper recruitment and repopulation of oligodendrocyte precursor cells (OPCs) in lesions. How OPCs elicit specific intracellular programs in response to a chemically and mechanically diverse environment to properly regenerate myelin remains unclear. OPCs construct primary cilia, specialized signaling compartments that transduce Hedgehog (Hh) and G-protein-coupled receptor (GPCR) signals. We investigated the role of primary cilia in the OPC response to WMI. Removing cilia from OPCs genetically via deletion of Ift88 results in OPCs failing to repopulate WMI lesions because of reduced proliferation. Interestingly, loss of cilia does not affect Hh signaling in OPCs or their responsiveness to Hh signals but instead leads to dysfunctional cyclic AMP (cAMP)-dependent cAMP response element-binding protein (CREB)-mediated transcription. Because inhibition of CREB activity in OPCs reduces proliferation, we propose that a GPCR/cAMP/CREB signaling axis initiated at OPC cilia orchestrates OPC proliferation during development and in response to WMI.

Cilia at the Crossroads of Tumor Treating Fields and Chemotherapy

Glioblastoma (GBM), the most common and lethal primary brain tumor in adults, requires multi-treatment intervention which unfortunately barely shifts the needle in overall survival. The treatment options after diagnosis and surgical resection (if possible) include irradiation, temozolomide (TMZ) chemotherapy, and now tumor treating fields (TTFields). TTFields are electric fields delivered locoregionally to the head/tumor via a wearable medical device (Optune®). Overall, the concomitant treatment of TTFields and TMZ target tumor cells but spare normal cell types in the brain. Here, we examine whether primary cilia, microtubule-based "antennas" found on both normal brain cells and GBM cells, play specific roles in sensitizing tumor cells to treatment. We discuss evidence supporting GBM cilia being exploited by tumor cells to promote their growth and treatment resistance. We review how primary cilia on normal brain and GBM cells are affected by GBM treatments as monotherapy or concomitant modalities. We also focus on latest findings indicating a differential regulation of GBM ciliogenesis by TTFields and TMZ. Future studies await arrival of intracranial TTFields models to determine if GBM cilia carry a prognostic capacity.

Kinesin family member 3A induces related diseases via wingless-related integration site/β-catenin signaling pathway

Kinesin family member 3A is an important motor protein that participates in various physiological and pathological processes, including normal tissue development, homeostasis maintenance, tumor infiltration, and migration. The wingless-related integration site/β-catenin signaling pathway is essential for critical molecular mechanisms such as embryonic development, organogenesis, tissue regeneration, and carcinogenesis. Recent studies have examined the molecular mechanisms of kinesin family member 3A, among which the wingless-related integration site/β-catenin signaling pathway has gained attention. The interaction between kinesin family member 3A and the wingless-related integration site/β-catenin signaling pathway is compact and complex but is fascinating and worthy of further study. The upregulation and downregulation of kinesin family member 3A influence many diseases and patient survival through the wingless-related integration site/β-catenin signaling pathway. Therefore, this review mainly focuses on describing the kinesin family member 3A and wingless-related integration site/β-catenin signaling pathways and their associated diseases.

Ultrastructural characteristics of oligodendrocyte precursor cells in the early postnatal mouse optic nerve observed by serial block-face scanning electron microscopy

Oligodendrocyte precursor cells (OPC) arise from restricted regions of the central nervous system (CNS) and differentiate into myelin-forming cells after migration, but their ultrastructural characteristics have not been fully elucidated. This study examined the three-dimensional ultrastructure of OPCs in comparison with other glial cells in the early postnatal optic nerve by serial block-face scanning electron microscopy. We examined 70 putative OPCs (pOPC) that were distinct from other glial cells according to established morphological criteria. The pOPCs were unipolar in shape with relatively few processes, and their Golgi apparatus were localized in the perinuclear region with a single cisterna. Astrocytes abundant in the optic nerve were distinct from pOPCs and had a greater number of processes and more complicated Golgi apparatus morphology. All pOPCs and astrocytes contained a pair of centrioles (basal bodies). Among them, 45% of pOPCs extended a short cilium, and 20% of pOPCs had centrioles accompanied by vesicles, whereas all astrocytes with basal bodies had cilia with invaginated ciliary pockets. These results suggest that the fine structures of pOPCs during the developing and immature stages may account for their distinct behavior. Additionally, the vesicular transport of the centrioles, along with a short cilium length, suggests active ciliogenesis in pOPCs.

Oligodendroglial primary cilium heterogeneity during development and demyelination/remyelination

The primary cilium (PC) has emerged as an indispensable cellular antenna essential for signal transduction of important cell signaling pathways. The rapid acquisition of knowledge about PC biology has raised attention to PC as a therapeutic target in some neurological and psychiatric diseases. However, the role of PC in oligodendrocytes and its participation in myelination/remyelination remain poorly understood. Oligodendrocyte precursor cells (OPCs) give rise to oligodendrocytes during central nervous system (CNS) development. In adult, a small percentage of OPCs remains as undifferentiated cells located sparsely in the different regions of the CNS. These cells can regenerate oligodendrocytes and participate to certain extent in remyelination. This study aims characterize PC in oligodendrocyte lineage cells during post-natal development and in a mouse model of demyelination/remyelination. We show heterogeneity in the frequency of cilium presence on OPCs, depending on culture conditions in vitro and cerebral regions in vivo during development and demyelination/remyelination. In vitro, Lithium chloride (LiCl), Forskolin and Chloral Hydrate differentially affect cilium, depending on culture environment and PC length correlates with the cell differentiation state. Beside the role of PC as a keeper of cell proliferation, our results suggest its involvement in myelination/remyelination.

KIF3A inhibits nasopharyngeal carcinoma proliferation, migration and invasion by interacting with β-catenin to suppress its nuclear accumulation

Nasopharyngeal carcinoma (NPC) is a malignant epithelial tumor prevalent in southern China and Southeast Asia. Previous studies have shown that Kinesin Family Member 3A (KIF3A) plays a critical role in the oncogenesis of various cancer types. However, the role of KIF3A in NPC tumorigenesis and the mechanism underlying its function have not been reported. In this study, we found that KIF3A was significantly downregulated in NPC cells and tissues, and KIF3A expression in NPC patients was associated with tumor stage and was positively corrected with overall survival. In vitro and in vivo experiments indicated that overexpression of KIF3A inhibited NPC cell proliferation, migration, and invasion. Mechanistic studies found that KIF3A bound β-catenin and attenuated β-catenin aggregation in the nucleus. Moreover, rescue experiments demonstrated that the inhibitory effect of KIF3A on NPC proliferation, migration and invasion was partially dependent on β-catenin. Taken together, our data suggest that KIF3A interacts with β-catenin and attenuates NPC proliferation, migration, and invasion by suppressing the intranuclear aggregation of β-catenin. KIF3A may be a promising therapeutic target of patients with NPC.

Protocadherin 15 suppresses oligodendrocyte progenitor cell proliferation and promotes motility through distinct signalling pathways

Oligodendrocyte progenitor cells (OPCs) express protocadherin 15 (Pcdh15), a member of the cadherin superfamily of transmembrane proteins. Little is known about the function of Pcdh15 in the central nervous system (CNS), however, Pcdh15 expression can predict glioma aggression and promote the separation of embryonic human OPCs immediately following a cell division. Herein, we show that Pcdh15 knockdown significantly increases extracellular signal-related kinase (ERK) phosphorylation and activation to enhance OPC proliferation in vitro. Furthermore, Pcdh15 knockdown elevates Cdc42-Arp2/3 signalling and impairs actin kinetics, reducing the frequency of lamellipodial extrusion and slowing filopodial withdrawal. Pcdh15 knockdown also reduces the number of processes supported by each OPC and new process generation. Our data indicate that Pcdh15 is a critical regulator of OPC proliferation and process motility, behaviours that characterise the function of these cells in the healthy CNS, and provide mechanistic insight into the role that Pcdh15 might play in glioma progression.

Protocadherin 15 promotes lamellipodial and filopodial dynamics in oligodendrocyte progenitor cells by regulating Cdc42-Arp2/3 activity, but also suppresses ERK1/2 phosphorylation to reduce proliferation.

Primary Cilia in Glial Cells: An Oasis in the Journey to Overcoming Neurodegenerative Diseases

Many neurodegenerative diseases have been associated with defects in primary cilia, which are cellular organelles involved in diverse cellular processes and homeostasis. Several types of glial cells in both the central and peripheral nervous systems not only support the development and function of neurons but also play significant roles in the mechanisms of neurological disease. Nevertheless, most studies have focused on investigating the role of primary cilia in neurons. Accordingly, the interest of recent studies has expanded to elucidate the role of primary cilia in glial cells. Correspondingly, several reports have added to the growing evidence that most glial cells have primary cilia and that impairment of cilia leads to neurodegenerative diseases. In this review, we aimed to understand the regulatory mechanisms of cilia formation and the disease-related functions of cilia, which are common or specific to each glial cell. Moreover, we have paid close attention to the signal transduction and pathological mechanisms mediated by glia cilia in representative neurodegenerative diseases. Finally, we expect that this field of research will clarify the mechanisms involved in the formation and function of glial cilia to provide novel insights and ideas for the treatment of neurodegenerative diseases in the future.

Kif3a deletion prevents primary cilia assembly on oligodendrocyte progenitor cells, reduces oligodendrogenesis and impairs fine motor function

Primary cilia are small microtubule‐based organelles capable of transducing signals from growth factor receptors embedded in the cilia membrane. Developmentally, oligodendrocyte progenitor cells (OPCs) express genes associated with primary cilia assembly, disassembly, and signaling, however, the importance of primary cilia for adult myelination has not been explored. We show that OPCs are ciliated in vitro and in vivo, and that they disassemble their primary cilia as they progress through the cell cycle. OPC primary cilia are also disassembled as OPCs differentiate into oligodendrocytes. When kinesin family member 3a (Kif3a), a gene critical for primary cilium assembly, was conditionally deleted from adult OPCs in vivo (Pdgfrα‐CreER™:: Kif3a^fl/fl transgenic mice), OPCs failed to assemble primary cilia. Kif3a‐deletion was also associated with reduced OPC proliferation and oligodendrogenesis in the corpus callosum and motor cortex and a progressive impairment of fine motor coordination.