Apicobasal Polarity Research Articles

Adherens Junctions: Guardians of Cortical Development.

Apical radial glia comprise the pseudostratified neuroepithelium lining the embryonic lateral ventricles and give rise to the extensive repertoire of pyramidal neuronal subtypes of the neocortex. The establishment of a highly apicobasally polarized radial glial morphology is a mandatory prerequisite for cortical development as it governs neurogenesis, neural migration and the integrity of the ventricular wall. As in all epithelia, cadherin-based adherens junctions (AJs) play an obligate role in the maintenance of radial glial apicobasal polarity and neuroepithelial cohesion. In addition, the assembly of resilient AJs is critical to the integrity of the neuroepithelium which must resist the tensile forces arising from increasing CSF volume and other mechanical stresses associated with the expansion of the ventricles in the embryo and neonate. Junctional instability leads to the collapse of radial glial morphology, disruption of the ventricular surface and cortical lamination defects due to failed neuronal migration. The fidelity of cortical development is therefore dependent on AJ assembly and stability. Mutations in genes known to control radial glial junction formation are causative for a subset of inherited cortical malformations (neuronal heterotopias) as well as perinatal hydrocephalus, reinforcing the concept that radial glial junctions are pivotal determinants of successful corticogenesis. In this review we explore the key animal studies that have revealed important insights into the role of AJs in maintaining apical radial glial morphology and function, and as such, have provided a deeper understanding of the aberrant molecular and cellular processes contributing to debilitating cortical malformations. We highlight the reciprocal interactions between AJs and the epithelial polarity complexes that impose radial glial apicobasal polarity. We also discuss the critical molecular networks promoting AJ assembly in apical radial glia and emphasize the role of the actin cytoskeleton in the stabilization of cadherin adhesion – a crucial factor in buffering the mechanical forces exerted as a consequence of cortical expansion.

Stepwise polarisation of developing bilayered epidermis is mediated by aPKC and E-cadherin in zebrafish.

The epidermis, a multilayered epithelium, surrounds and protects the vertebrate body. It develops from a bilayered epithelium formed of the outer periderm and underlying basal epidermis. How apicobasal polarity is established in the developing epidermis has remained poorly understood. We show that both the periderm and the basal epidermis exhibit polarised distribution of adherens junctions in zebrafish. aPKC, an apical polarity regulator, maintains the robustness of polarisation of E-cadherin- an adherens junction component- in the periderm. E-cadherin in one layer controls the localisation of E-cadherin in the second layer in a layer non-autonomous manner. Importantly, E-cadherin controls the localisation and levels of Lgl, a basolateral polarity regulator, in a layer autonomous as well non-autonomous manner. Since periderm formation from the enveloping layer precedes the formation of the basal epidermis, our analyses suggest that peridermal polarity, initiated by aPKC, is transduced in a stepwise manner by E-cadherin to the basal layer.

Enteropathogenic Escherichia coli (EPEC) Recruitment of PAR Polarity Protein Atypical PKCζ to Pedestals and Cell-Cell Contacts Precedes Disruption of Tight Junctions in Intestinal Epithelial Cells.

Enteropathogenic Escherichia coli (EPEC) uses a type three secretion system to inject effector proteins into host intestinal epithelial cells, causing diarrhea. EPEC induces the formation of pedestals underlying attached bacteria, disrupts tight junction (TJ) structure and function, and alters apico-basal polarity by redistributing the polarity proteins Crb3 and Pals1, although the mechanisms are unknown. Here we investigate the temporal relationship of PAR polarity complex and TJ disruption following EPEC infection. EPEC recruits active aPKCζ, a PAR polarity protein, to actin within pedestals and at the plasma membrane prior to disrupting TJ. The EPEC effector EspF binds the endocytic protein sorting nexin 9 (SNX9). This interaction impacts actin pedestal organization, recruitment of active aPKCζ to actin at cell–cell borders, endocytosis of JAM-A S285 and occludin, and TJ barrier function. Collectively, data presented herein support the hypothesis that EPEC-induced perturbation of TJ is a downstream effect of disruption of the PAR complex and that EspF binding to SNX9 contributes to this phenotype. aPKCζ phosphorylates polarity and TJ proteins and participates in actin dynamics. Therefore, the early recruitment of aPKCζ to EPEC pedestals and increased interaction with actin at the membrane may destabilize polarity complexes ultimately resulting in perturbation of TJ.

The Physics of Cellular Decision Making During Epithelial-Mesenchymal Transition.

The epithelial-mesenchymal transition (EMT) is a process by which cells lose epithelial traits, such as cell-cell adhesion and apico-basal polarity, and acquire migratory and invasive traits. EMT is crucial to embryonic development and wound healing. Misregulated EMT has been implicated in processes associated with cancer aggressiveness, including metastasis. Recent experimental advances such as single-cell analysis and temporal phenotypic characterization have established that EMT is a multistable process wherein cells exhibit and switch among multiple phenotypic states. This is in contrast to the classical perception of EMT as leading to a binary choice. Mathematical modeling has been at the forefront of this transformation for the field, not only providing a conceptual framework to integrate and analyze experimental data, but also making testable predictions. In this article, we review the key features and characteristics of EMT dynamics, with a focus on the mathematical modeling approaches that have been instrumental to obtaining various useful insights.

Pluripotent stem cell-derived cholangiocytes and cholangiocyte organoids.

The development of protocols for pluripotent stem cell (PSC) differentiation into cholangiocytes and cholangiocyte organoids in three-dimensional structures represent a huge advance in both research and medical fields because of the limited access to primary human cholangiocytes and the potential bias induced by animal models used to study cholangiopathies in vivo. PSC-derived cholangiocyte organoids consisting of either cysts with luminal space or branching tubular structures are composed of cells with apico-basal polarity that can fulfill cholangiocyte functions like the transport of bile salts. Several protocols of PSC differentiation have already been published but we added to the detailed protocol we describe here some notes or advice to facilitate its handling by new users. We also propose detailed protocols to carry out some of the characterization analyses using immunofluorescence to study the expression of specific markers and a functionality test to visualize bile acid transport using cholyl-lysyl-fluorescein (CLF).

Establishment of a relationship between blastomere geometry and YAP localisation during compaction.

ABSTRACTPrecise patterning within the three-dimensional context of tissues, organs and embryos implies that cells can sense their relative position. During preimplantation development, outside and inside cells rely on apicobasal polarity and the Hippo pathway to choose their fate. Despite recent findings suggesting that mechanosensing might be central to this process, the relationship between blastomere geometry (i.e. shape and position) and the Hippo pathway effector YAP remains unknown. We used a highly quantitative approach to analyse information on the geometry and YAP localisation of individual blastomeres of mouse and human embryos. We identified the proportion of exposed cell surface area as most closely correlating with the nuclear localisation of YAP. To test this relationship, we developed several hydrogel-based approaches to alter blastomere geometry in cultured embryos. Unbiased clustering analyses of blastomeres from such embryos revealed that this relationship emerged during compaction. Our results therefore pinpoint the time during early embryogenesis when cells acquire the ability to sense changes in geometry and provide a new framework for how cells might integrate signals from different membrane domains to assess their relative position within the embryo.

A putative stem-loop structure in Drosophila crumbs is required for mRNA localisation in epithelia and germline cells.

Crumbs (Crb) is an evolutionarily conserved transmembrane protein localised to the apical membrane of epithelial cells. Loss or mislocalisation of Crb is often associated with disruption of apicobasal cell polarity. crb mRNA is also apically enriched in epithelial cells, and, as shown here, accumulates in the oocyte of developing egg chambers. We narrowed down the localisation element (LE) of crb mRNA to 47 nucleotides, which form a putative stem-loop structure that may be recognised by Egalitarian (Egl). Mutations in conserved nucleotides abrogate apical transport. crb mRNA enrichment in the oocyte is affected in egl mutant egg chambers. A CRISPR-based genomic deletion of the crb locus that includes the LE disrupts asymmetric crb mRNA localisation in epithelia and prevents its accumulation in the oocyte during early stages of oogenesis, but does not affect Crb protein localisation in embryonic and follicular epithelia. However, flies lacking the LE show ectopic Crb protein expression in the nurse cells. These data suggest an additional role for the Drosophila 3'-UTR in regulating translation in a tissue-specific manner.This article has an associated First Person interview with the first author of the paper.

Loss of Crb2b-lf leads to anterior segment defects in old zebrafish.

ABSTRACTDefects in the retina or the anterior segment of the eye lead to compromised vision and affect millions of people. Understanding how these ocular structures develop and are maintained is therefore of paramount importance. The maintenance of proper vision depends, among other factors, on the function of genes controlling apico-basal polarity. In fact, mutations in polarity genes are linked to retinal degeneration in several species, including human. Here we describe a novel zebrafish crb2b allele (crb2be40), which specifically affects the crb2b long isoform. crb2be40 mutants are viable and display normal ocular development. However, old crb2be40 mutant fish develop multiple defects in structures of the anterior segment, which includes the cornea, the iris and the lens. Phenotypes are characterised by smaller pupils due to expansion of the iris and tissues of the iridocorneal angle, an increased number of corneal stromal keratocytes, an abnormal corneal endothelium and an expanded lens capsule. These findings illustrate a novel role for crb2b in the maintenance of the anterior segment and hence add an important function to this polarity regulator, which may be conserved in other vertebrates including humans.

Class III PI3K Vps34 Controls Thyroid Hormone Production by Regulating Thyroglobulin Iodination, Lysosomal Proteolysis, and Tissue Homeostasis.

Background: The production of thyroid hormones [triiodothyronine (T3), thyroxine (T4)] depends on the organization of the thyroid in follicles, which are lined by a monolayer of thyrocytes with strict apicobasal polarity. This polarization supports vectorial transport of thyroglobulin (Tg) for storage into, and recapture from, the colloid. It also allows selective addressing of channels, transporters, ion pumps, and enzymes to their appropriate basolateral [Na+/I- symporter (NIS), SLC26A7, and Na+/K+-ATPase] or apical membrane domain (anoctamin, SLC26A4, DUOX2, DUOXA2, and thyroperoxidase). How these actors of T3/T4 synthesis reach their final destination remains poorly understood. The PI 3-kinase isoform Vps34/PIK3C3 is now recognized as a main component in the general control of vesicular trafficking and of cell homeostasis through the regulation of endosomal trafficking and autophagy. We recently reported that conditional Vps34 inactivation in proximal tubular cells in the kidney prevents normal addressing of apical membrane proteins and causes abortive macroautophagy. Methods:Vps34 was inactivated using a Pax8-driven Cre recombinase system. The impact of Vps34 inactivation in thyrocytes was analyzed by histological, immunolocalization, and messenger RNA expression profiling. Thyroid hormone synthesis was assayed by 125I injection and plasma analysis. Results:Vps34 conditional knockout (Vps34cKO) mice were born at the expected Mendelian ratio and showed normal growth until postnatal day 14 (P14), then stopped growing and died at ∼1 month of age. We therefore analyzed thyroid Vps34cKO at P14. We found that loss of Vps34 in thyrocytes causes (i) disorganization of thyroid parenchyma, with abnormal thyrocyte and follicular shape and reduced PAS+ colloidal spaces; (ii) severe noncompensated hypothyroidism with extremely low T4 levels (0.75 ± 0.62 μg/dL) and huge thyrotropin plasma levels (19,300 ± 10,500 mU/L); (iii) impaired 125I organification at comparable uptake and frequent occurrence of follicles with luminal Tg but nondetectable T4-bearing Tg; (iv) intense signal in thyrocytes for the lysosomal membrane marker, LAMP-1, as well as Tg and the autophagy marker, p62, indicating defective lysosomal proteolysis; and (v) presence of macrophages in the colloidal space. Conclusions: We conclude that Vps34 is crucial for thyroid hormonogenesis, at least by controlling epithelial organization, Tg iodination as well as proteolytic T3/T4 excision in lysosomes.

Reciprocal Association between the Apical Junctional Complex and AMPK: A Promising Therapeutic Target for Epithelial/Endothelial Barrier Function?

Epithelial/endothelial cells adhere to each other via cell–cell junctions including tight junctions (TJs) and adherens junctions (AJs). TJs and AJs are spatiotemporally and functionally integrated, and are thus often collectively defined as apical junctional complexes (AJCs), regulating a number of spatiotemporal events including paracellular barrier, selective permeability, apicobasal cell polarity, mechano-sensing, intracellular signaling cascades, and epithelial morphogenesis. Over the past 15 years, it has been acknowledged that adenosine monophosphate (AMP)-activated protein kinase (AMPK), a well-known central regulator of energy metabolism, has a reciprocal association with AJCs. Here, we review the current knowledge of this association and show the following evidences: (1) as an upstream regulator, AJs activate the liver kinase B1 (LKB1)–AMPK axis particularly in response to applied junctional tension, and (2) TJ function and apicobasal cell polarization are downstream targets of AMPK and are promoted by AMPK activation. Although molecular mechanisms underlying these phenomena have not yet been completely elucidated, identifications of novel AMPK effectors in AJCs and AMPK-driven epithelial transcription factors have enhanced our knowledge. More intensive studies along this line would eventually lead to the development of AMPK-based therapies, enabling us to manipulate epithelial/endothelial barrier function.

Position-Sensing Established During Compaction Dictates Cell Fate in the Mammalian Embryo

Precise patterning within the 3-dimensional context of tissues, organs and embryos implies that cells can sense their relative position. We still understand relatively little about how cells sense their relative position within small groups of cells. During preimplantation development, outside and inside cells rely on apicobasal polarity and the Hippo pathway to choose their fate. Despite recent findings suggesting that mechanosensing may be central to this process, the relationship between blastomere geometry (i.e. shape and position) and the Hippo pathway effector YAP remains unknown. To address this, we used a highly quantitative approach to collect and analyse information on the geometry and YAP localisation of individual blastomeres of mouse and human embryos. We find that the fraction of YAP in the nucleus responds to the proportion of exposed cell surface area rather than blastomere shape. To directly test the influence of blastomere position on YAP localisation we developed an approach using hydrogel based cylindrical cavities to alter blastomere arrangement in cultured embryos. Unbiased clustering analyses of blastomeres from such embryos reveal that the ability to respond to position emerges as early as the 8-cell stage during compaction and that altering the relative position of a blastomere within an embryo can alter its fate. Finally, we demonstrate that this response is lost upon inhibiting PKC signalling, linking it to the cell polarity. Our results pinpoint when during early embryogenesis cell specification decisions are initiated and show how blastomeres can sense their position in a polarity dependent manner to alter YAP localisation.

Crumbs proteins regulate layered retinal vascular development required for vision

Crumbs proteins are transmembrane proteins that regulate cellular apico-basal polarity. Animals carrying mutated crb1 present retinal vascular abnormalities; this mutation is associated with progressive retinal degeneration with intraretinal cystoid fluid collection in humans. This study aimed to evaluate a potential role of crumbs proteins in retinal vascular development and maintenance. We demonstrated that crumbs homologues (CRBs) were differentially expressed and changed dramatically during mouse retinal vascular development. Intravitreal injection of CRB1 and CRB2 siRNA induced delayed development of the deep capillary plexus and premature development of the intermediate capillary plexus, resulting in disrupted vascular integrity. However, microfluidic chip assay using human retinal endothelial cells revealed that CRBs do not directly affect in vitro retinal angiogenesis. CRBs control retinal angiogenesis by regulating neuroglial vascular endothelial growth factor-A (VEGFA) and matrix metalloproteinase-3 expression. These findings demonstrate a pivotal role of CRBs in providing critical neurotrophic support through normal layered vascular network development and maintenance. This implies that preserving CRBs and restoring layered retinal vascular networks could be novel targets for preventing vision-threatening retinal diseases.

Crumbs organizes the transport machinery by regulating apical levels of PI(4,5)P2 in Drosophila.

An efficient vectorial intracellular transport machinery depends on a well-established apico-basal polarity and is a prerequisite for the function of secretory epithelia. Despite extensive knowledge on individual trafficking pathways, little is known about the mechanisms coordinating their temporal and spatial regulation. Here, we report that the polarity protein Crumbs is essential for apical plasma membrane phospholipid-homeostasis and efficient apical secretion. Through recruiting βHeavy-Spectrin and MyosinV to the apical membrane, Crumbs maintains the Rab6-, Rab11- and Rab30-dependent trafficking and regulates the lipid phosphatases Pten and Ocrl. Crumbs knock-down results in increased apical levels of PI(4,5)P2 and formation of a novel, Moesin- and PI(4,5)P2-enriched apical membrane sac containing microvilli-like structures. Our results identify Crumbs as an essential hub required to maintain the organization of the apical membrane and the physiological activity of the larval salivary gland.

The Hippo Pathway Is Essential for Maintenance of Apicobasal Polarity in the Growing Intestine of Caenorhabditis elegans.

Although multiple determinants for establishing polarity in membranes of epithelial cells have been identified, the mechanism for maintaining apicobasal polarity is not fully understood. Here, we show that the conserved Hippo kinase pathway plays a role in the maintenance of apicobasal polarity in the developing intestine of Caenorhabditis elegans We screened suppressors of the mutation in wts-1-the gene that encodes the LATS kinase homolog, deficiency of which leads to disturbance of the apicobasal polarity of the intestinal cells and to eventual death of the organism. We identified several alleles of yap-1 and egl-44 that suppress the effects of this mutation. yap-1 encodes a homolog of YAP/Yki, and egl-44 encodes a homolog of TEAD/Sd. WTS-1 bound directly to YAP-1 and inhibited its nuclear accumulation in intestinal cells. We also found that NFM-1, which is a homolog of NF2/Merlin, functioned in the same genetic pathway as WTS-1 to regulate YAP-1 to maintain cellular polarity. Transcriptome analysis identified several target candidates of the YAP-1-EGL-44 complex including TAT-2, which encodes a putative P-type ATPase. In summary, we have delineated the conserved Hippo pathway in C. elegans consisting of NFM-1-WTS-1-YAP-1-EGL-44 and proved that the proper regulation of YAP-1 by upstream NFM-1 and WTS-1 is essential for maintenance of apicobasal membrane identities of the growing intestine.

Constitutive Active Mutant TIE2 Induces Enlarged Vascular Lumen Formation with Loss of Apico-basal Polarity and Pericyte Recruitment

Abnormalities in controlling key aspects of angiogenesis including vascular cell migration, lumen formation and vessel maturation are hallmarks of vascular anomalies including venous malformation (VM). Gain-of-function mutations in the tyrosine kinase receptor TIE2 can cause VM and induce a ligand-independent hyperactivation of TIE2. Despite these important findings, the TIE2-dependent mechanisms triggering enlarged vascular lesions are not well understood. Herein we studied TIE2 p.L914F, the most frequent mutation identified in VM patients. We report that endothelial cells harboring a TIE2-L914F mutation display abnormal cell migration due to a loss of front-rear polarity as demonstrated by a non-polarized Golgi apparatus. Utilizing a three-dimensional fibrin-matrix based model we show that TIE2-L914F mutant cells form enlarged lumens mimicking vascular lesions present in VM patients, independently of exogenous growth factors. Moreover, these abnormal vascular channels demonstrate a dysregulated expression pattern of apico-basal polarity markers Podocalyxin and Collagen IV. Furthermore, in this system we recapitulated another pathological feature of VM, the paucity of pericytes around ectatic veins. The presented data emphasize the value of this in vitro model as a powerful tool for the discovery of cellular and molecular signals contributing to abnormal vascular development and subsequent identification of novel therapeutic approaches.

Rgma-Induced Neo1 Proteolysis Promotes Neural Tube Morphogenesis.

Neuroepithelial cell (NEC) elongation is one of several key cell behaviors that mediate the tissue-level morphogenetic movements that shape the neural tube (NT), the precursor of the brain and spinal cord. However, the upstream signals that promote NEC elongation have been difficult to tease apart from those regulating apico-basal polarity and hingepoint formation, due to their confounding interdependence. The Repulsive Guidance Molecule a (Rgma)/Neogenin 1 (Neo1) signaling pathway plays a conserved role in NT formation (neurulation) and is reported to regulate both NEC elongation and apico-basal polarity, through signal transduction events that have not been identified. We examine here the role of Rgma/Neo1 signaling in zebrafish (sex unknown), an organism that does not use hingepoints to shape its hindbrain, thereby enabling a direct assessment of the role of this pathway in NEC elongation. We confirm that Rgma/Neo1 signaling is required for microtubule-mediated NEC elongation, and demonstrate via cell transplantation that Neo1 functions cell autonomously to promote elongation. However, in contrast to previous findings, our data do not support a role for this pathway in establishing apical junctional complexes. Last, we provide evidence that Rgma promotes Neo1 glycosylation and intramembrane proteolysis, resulting in the production of a transient, nuclear intracellular fragment (NeoICD). Partial rescue of Neo1a and Rgma knockdown embryos by overexpressing neoICD suggests that this proteolytic cleavage is essential for neurulation. Based on these observations, we propose that RGMA-induced NEO1 proteolysis orchestrates NT morphogenesis by promoting NEC elongation independently of the establishment of apical junctional complexes.SIGNIFICANCE STATEMENT The neural tube, the CNS precursor, is shaped during neurulation. Neural tube defects occur frequently, yet underlying genetic risk factors are poorly understood. Neuroepithelial cell (NEC) elongation is essential for proper completion of neurulation. Thus, connecting NEC elongation with the molecular pathways that control this process is expected to reveal novel neural tube defect risk factors and increase our understanding of NT development. Effectors of cell elongation include microtubules and microtubule-associated proteins; however, upstream regulators remain controversial due to the confounding interdependence of cell elongation and establishment of apico-basal polarity. Here, we reveal that Rgma-Neo1 signaling controls NEC elongation independently of the establishment of apical junctional complexes and identify Rgma-induced Neo1 proteolytic cleavage as a key upstream signaling event.

Cytocortex-dependent dynamics of Drosophila Crumbs controls junctional stability and tension during germ band retraction.

During morphogenesis, epithelia undergo dynamic rearrangements, which requires continuous remodelling of junctions and cell shape, but at the same time mechanisms preserving cell polarity and tissue integrity. Apico-basal polarity is key for the localisation of the machinery that enables cell shape changes. The evolutionarily conserved Drosophila Crumbs protein is critical for maintaining apico-basal polarity and epithelial integrity. How Crumbs is maintained in a dynamically developing embryo remains largely unknown. Here, we applied quantitative fluorescence techniques to show that, during germ band retraction, Crumbs dynamics correlates with the morphogenetic activity of the epithelium. Genetic and pharmacological perturbations revealed that the mobile pool of Crumbs is fine-tuned by the actomyosin cortex in a stage-dependent manner. Stabilisation of Crumbs at the plasma membrane depends on a proper link to the actomyosin cortex via an intact FERM-domain-binding site in its intracellular domain, loss of which leads to increased junctional tension and higher DE-cadherin (also known as Shotgun) turnover, resulting in impaired junctional rearrangements. These data define Crumbs as a mediator between polarity and junctional regulation to orchestrate epithelial remodelling in response to changes in actomyosin activity.This article has an associated First Person interview with the first author of the paper.

Dynamic MAPK signaling activity underlies a transition from growth arrest to proliferation in Drosophila scribble mutant tumors.

ABSTRACTHuman tumors exhibit plasticity and evolving capacity over time. It is difficult to study the mechanisms of how tumors change over time in human patients, in particular during the early stages when a few oncogenic cells are barely detectable. Here, we used a Drosophila tumor model caused by loss of scribble (scrib), a highly conserved apicobasal cell polarity gene, to investigate the spatial-temporal dynamics of early tumorigenesis events. The fly scrib mutant tumors have been successfully used to model many aspects of tumorigenesis processes. However, it is still unknown whether Drosophila scrib mutant tumors exhibit plasticity and evolvability along the temporal axis. We found that scrib mutant tumors displayed different growth rates and cell cycle profiles over time, indicative of a growth arrest-to-proliferation transition as the scrib mutant tumors progress. Longitudinal bulk and single-cell transcriptomic analysis of scrib mutant tumors revealed that the MAPK pathway, including JNK and ERK signaling activities, showed quantitative changes over time. We found that high JNK signaling activity caused G2/M cell cycle arrest in early scrib mutant tumors. In addition, JNK signaling activity displayed a radial polarity with the JNKhigh cells located at the periphery of scrib mutant tumors, providing an inherent mechanism that leads to an overall decrease in JNK signaling activity over time. We also found that ERK signaling activity, in contrast to JNK activity, increased over time and promoted growth in late-stage scrib mutant tumors. Furthermore, high JNK signaling activity repressed ERK signaling activity in early scrib mutant tumors. Together, these data demonstrate that dynamic MAPK signaling activity, fueled by intratumor heterogeneity derived from tissue topological differences, drives a growth arrest-to-proliferation transition in scrib mutant tumors.This article has an associated First Person interview with the joint first authors of the paper.

Apico-basal Polarity Determinants Encoded by crumbs Genes Affect Ciliary Shaft Protein Composition, IFT Movement Dynamics, and Cilia Length.

Apico-basal Polarity Determinants Encoded by crumbs Genes Affect Ciliary Shaft Protein Composition, IFT Movement Dynamics, and Cilia Length.

Micropattern-based platform as a physiologically relevant model to study epithelial morphogenesis and nephrotoxicity

Tubulogenesis in epithelial organs often initiates with the acquisition of apicobasal polarity, giving rise to the formation of small lumens that expand and fuse to generate a single opened cavity. In this study, we present a micropattern-based device engineered to generate epithelial tubes through a process that recapitulates in vivo tubule morphogenesis. Interestingly, tubulogenesis in this device is dependent on microenvironmental cues such as cell confinement, extracellular matrix composition, and substrate stiffness, and our set-up specifically allows the control of these extracellular conditions. Additionally, proximal tubule cell lines growing on micropatterns express higher levels of drug transporters and are more sensitive to nephrotoxicity. These tubes display specific morphological defects that can be linked to nephrotoxicity, which would be helpful to predict potential toxicity when developing new compounds. This device, with the ability to recapitulate tube formation in vitro, has emerged as a powerful tool to study the molecular mechanisms involved in organogenesis and, by being more physiologically relevant than existing cellular models, becomes an innovative platform to conduct drug discovery assays.