Topic: primary cilia

Primary cilia protein IFT88 governs smooth muscle phenotype and vascular remodeling

Project Summary/Abstract Cardiovascular disease remains the leading cause of death in the United States, accounting for nearly 1 million deaths in 2022. Vascular diseases such as atherosclerosis, aneurysm, and coronary artery disease are regulated largely by smooth muscle cells (SMCs) residing in the blood vessel wall. The central dogma of vascular SMC biology is that differentiated cells can de-differentiate and give rise to a spectrum of alternative phenotypes promoting invasion, proliferation, fibrosis, and inflammation, but the mechanisms regulating SMC phenotypic transitions are poorly understood. Intraflagellar transport 88 (IFT88) is an essential protein for the formation of primary cilia, centriole-associated plasma membrane organelles that project into the extracellular milieu and regulate cell cycle reentry and responses to stimuli like growth factors and mechanical strain. Non- ciliary functions of IFT88 also include progression of the cell cycle checkpoint and polarized motility, both of which are functionally critical for SMC-mediated vascular remodeling. Little is known about the functional role of the primary cilia in SMCs and the role of the essential cilia protein IFT88 in regulating SMC phenotype. To address this gap in knowledge, my postdoctoral studies focus on the role of IFT88 in the context of intimal hyperplasia (K99). During the independent phase (R00), I will apply these findings to arteriovenous fistula (AVF) maturation, a surgical intervention often required for dialysis individuals with polycystic kidney disease (PKD), an IFT88 loss-of-function disease. I will test my central hypothesis that cilia are key regulators of SMC phenotype in three Specific Aims: 1) determine the role of IFT88-dependent SMC primary cilia in mechanotransduction of extracellular matrix (ECM) stiffness (K99), 2) determine the role of IFT88 in pathological intimal hyperplasia (K99), and 3) test whether SMC IFT88 expression is required for adaptive remodeling of grafted veins following AVF placement (R00). Overall, we propose that IFT88+ ciliated SMC represent an unidentified subclass of the SMC phenotype spectrum that is primarily responsible for vascular remodeling and is an attractive potential target for treatment of vascular diseases. Building on strong existing collaborations, we have formed a research and mentoring team with expertise in SMC pathophysiology, primary cilia biology, mechanobiology, AVF surgery, and PKD to complete the proposed aims. The additional training in cell-ECM interactions (Aim 1, K99), in vivo murine ligation injury and in vivo cilia imaging (Aim 2, K99), and AVF surgery and PKD pathology (Aim 3, R00) will be indispensable for preparing the PI, Dr. O’Brien, for his career as an independent investigator. Completion of the proposed aims will also contribute directly to an understanding of the function of IFT88-dependent primary cilia in SMCs and may likely identify novel therapeutic targets for treatment of vascular diseases.

The multiciliation cycle: a variant cell cycle coordinating centriole biogenesis and ciliogenesis

Project summary/Abstract Differentiating multiciliated cells line the mammalian airway and are critical for protecting the lungs from inhaled pathogens and particulates. Multiciliated cells have a distinct architecture from other cell types, having hundreds of centrioles, each of which matures into a basal body and nucleates a motile cilium. Defects in multiciliation cause a form of Primary Ciliary Dyskinesia (PCD), a lung disease. Most cells generate two centrioles and one cilium per cell cycle. We found that differentiating multiciliated cells redeploy cell cycle regulators into a novel cell cycle variant, which we refer to as the multiciliation cycle, to break these rules, generate hundreds of centrioles and cilia, and coordinate their differentiation. The multiciliation cycle redeploys many mitotic cell cycle regulators, including cyclin-dependent kinases (CDKs) and their cognate cyclins. For example, Cyclin D1-CDK4/6, regulators of mitotic G1 to S progression, is required for multiciliated cell fate initiation and entry into the multiciliation cycle. While we have focused on lung multiciliated cells, others have found that cell cycle regulators similarly participate in multiciliation of ependymal cells of the brain. Some cells, such as mammalian trophoblast giant cells, employ cell cycle variants like the endocycle to bypass mitosis. We propose that the multiciliation cycle is another cell cycle variant that augments some aspects of the canonical cell cycle, such as centriole synthesis, and blocks others, such as DNA replication. During the multiciliation cycle, E2F7, a transcriptional regulator of canonical S to G2 progression, is expressed at high levels. During multiciliated cell differentiation, E2F7 directly dampens expression of genes encoding DNA replication machinery and terminates the S phase-like gene expression program. Loss of E2F7 causes a reacquisition of DNA synthesis in multiciliated cells and dysregulation of multiciliation cycle progression, disrupting centriole maturation and ciliogenesis. We propose that multiciliated cell differentiation is coordinated by an alternative cell cycle that organizes, instead of cell proliferation, the steps of cell differentiation. In this project, we investigate how the multiciliation cycle redeploys the mitotic cell cycle regulatory framework to generate many centrioles without undergoing DNA synthesis or cytokinesis. More specifically, we seek to uncover how CDKs and cyclins are regulated to control the amount and timing of basal body synthesis, how Retinoblastoma (RB) protein controls the transcriptional program of multiciliation, and how E2Fs advance the multiciliation cycle. This work will test the hypothesis that multiciliation is organized by a variant cell cycle that uncouples centriole synthesis from DNA replication and mitosis. We propose that his variant cell cycle orchestrates progression through sequential phases required to construct the multiciliated cells that protect the lungs.

The cell biology of Parkinson’s disease: a role for primary cilia and synaptic vesicle pleomorphism in dopaminergic neurons

Modeling human brain development and disease: the role of primary cilia

Neurodevelopmental disorders (NDDs) impose a global burden, affecting an increasing number of individuals. While some causative genes have been identified, understanding the human-specific mechanisms involved in these disorders remains limited. Traditional gene-driven approaches for modeling brain diseases have failed to capture the diverse and convergent mechanisms at play. Centrosomes and cilia act as intermediaries between environmental and intrinsic signals, regulating cellular behavior. Mutations or dosage variations disrupting their function have been linked to brain formation deficits, highlighting their importance, yet their precise contributions remain largely unknown. Hence, we aim to investigate whether the centrosome/cilia axis is crucial for brain development and serves as a hub for human-specific mechanisms disrupted in NDDs. Towards this direction, we first demonstrated species-specific and cell-type-specific differences in the cilia-genes expression during mouse and human corticogenesis. Then, to dissect their role, we provoked their ectopic overexpression or silencing in the developing mouse cortex or in human brain organoids. Our findings suggest that cilia genes manipulation alters both the numbers and the position of NPCs and neurons in the developing cortex. Interestingly, primary cilium morphology is disrupted, as we find changes in their length, orientation and number that lead to disruption of the apical belt and altered delamination profiles during development. Our results give insight into the role of primary cilia in human cortical development and address fundamental questions regarding the diversity and convergence of gene function in development and disease manifestation. It has the potential to uncover novel pharmacological targets, facilitate personalized medicine, and improve the lives of individuals affected by NDDs through targeted cilia-based therapies.

Braincils: Exploring the missing link between neuronal primary cilia dysfunction and neurodevelopmental disorders - hints from dental stem cell-derived brain organoids

A cell-autonomous role for primary cilia in long-range commissural axon guidance

The connection between primary cilia and the hypoxia-inducible factor-2alpha promotes the MEK/ERK signaling pathway

Growth/differentiation factor 15 influences primary cilia in neural stem cells in the ventricular-subventricular zone but not in the subgranular zone

Knockdown of Primary Ciliary Component Gene in Hypothalamic Paraventricular Nucleus Oxytocin Neurons Impairs Social Behavior

Role of the neuronal primary cilia-autophagy axis in the regulation of cognition during aging