Regulation Of Cell Shape Research Articles

First person – Jean Castillo

ABSTRACT First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Jean Castillo is first author on ‘ An optogenetic model reveals cell shape regulation through FAK and fascin’, published in JCS. Jean is a postdoctoral research associate in the lab of N. Gautam at Washington University in St Louis, MO, USA, investigating signal transduction, optogenetics and cell behavior.

Solving the Puzzle of Shape Regulation in Plant Epidermal Pavement Cells.

The plant epidermis serves many essential functions, including interactions with the environment, protection, mechanical strength, and regulation of tissue and organ growth. To achieve these functions, specialized epidermal cells develop into particular shapes. These include the intriguing interdigitated jigsaw puzzle shape of cotyledon and leaf pavement cells seen in many species, the precise functions of which remain rather obscure. Although pavement cell shape regulation is complex and still a long way from being fully understood, the roles of the cell wall, mechanical stresses, cytoskeleton, cytoskeletal regulatory proteins, and phytohormones are becoming clearer. Here, we provide a review of this current knowledge of pavement cell morphogenesis, generated from a wealth of experimental evidence and assisted by computational modeling approaches. We also discuss the evolution and potential functions of pavement cell interdigitation. Throughout the review, we highlight some of the thought-provoking controversies and creative theories surrounding the formation of the curious puzzle shape of these cells.

Nephron progenitor cell organization and nephrogenesis is dependent on Shroom3

The functional unit of the kidney, termed the nephron, develops from specialized mesenchyme cells known as the nephron progenitors. Nephron progenitors must undergo significant cell shape changes to regulate cell migration, cell movements, and cell projection formation during nephrogenesis. These dynamic cellular changes are essential for orientating and organizing the cells for progression through various stages of nephrogenesis to form a proper functioning nephron. The actin cytoskeleton regulates these dynamic morphological changes by interacting with intracellular proteins and their extracellular environment. Shroom3 is an actin-binding protein that regulates cell shape changes by modulating the actin cytoskeleton. In mice and humans, mutations in Shroom3 are strongly associated with poor nephron function and chronic kidney disease. Our previous work demonstrated unique Shroom3 expression patterns in nephron progenitor cells, yet the function of Shroom3 during nephrogenesis is not known. Here, we investigated functional roles for Shroom3 in nephron progenitor organization during nephrogenesis. Analysis of E13.5 and E18.5 kidney sections from Wildtype and Shroom3-/- null mutants demonstrated clustering abnormalities of nephron progenitor cells characterized by large abnormal gaps between cells in Shroom3 mutants. Analysis of Wildtype and Shroom3-/- nephron progenitor cell orientation by GM130 and Integrin-α8 immunofluorescence, markers of cell polarization, displayed altered cell orientation in some but not all cells. Transmission electron microscopy (TEM) confirmed that nephron progenitors of Shroom3-/- were irregularly shaped, abnormally clustered, and found at large distances from the neighboring epithelium. TEM analysis also revealed several filopodia-like long and thin actin-based membrane protrusions from both Wildtype and Shroom3-/- nephron progenitors. However, the broad, thick lamellipodia-like protrusions, found at the leading edge of the cells, were virtually absent from Shroom3-/- nephron progenitors. As nephrogenesis proceeds, Wildtype nephron progenitors develop into renal vesicles that consist of a central lumen surrounded by polarized wedge-shaped epithelial cells, which was not observed in Shroom3-/- renal vesicles. These alterations in the early stages of nephrogenesis in Shroom3-/- kidneys were also associated with a disruption in the epithelial polarization of mature nephrons demonstrated by irregular Sglt2 and Slc12a3 expression, key ion channels localized to the apical aspect in Wildtype epithelia. Our results demonstrate that Shroom3 is an important regulator of nephron progenitor organization and cell morphology in the earliest stages of nephron formation. It also suggests these abnormalities translate to a poorly polarized nephron epithelium and likely poor nephron function. These studies could explain why mutations in Shroom3 are so highly associated with poor nephron function and chronic kidney disease.

VINCULIN GENE EXPRESSION IN A COHORT OF EGYPTIAN PATIENTS WITH HEART FAILURE INDUCED BY ACUTE CORONARY SYNDROME

Heart failure (HF) remains a rising global epidemic with an estimated prevalence of >37.7 million individuals globally. Coronary artery disease is the most common form of heart disease and the most common cause of heart failure.Studying gene expression profile in heart failure could serve as a convenient tool contributing to identifying diagnostic and prognostic markers as well as targets for therapeutic intervention It was suggested that vinculin (VCL), a member of the family of membrane-associated proteins, may affect cardiac repair in heart failure.Vinculin is a force-sensitive protein, regulates cell shape and intracellular signaling. During cardiac stress and failure, there are significant alterations in the expression of cardiomyocyte cytoskeletal proteins, including vinculin.Studies addressing the role of VCL in remodeling after cardiac injury are limited. However, in this study we present an evidence that VCL may be a key player during hypertrophic and ischemic cardiac remodeling. Aim of the workThe aim of the work was to evaluate Vinculin gene and protein expression in heart failure induced by Acute Coronary Syndrome (ACS).

Regulation of Three-Dimensional Epithelial Cell Shape in a Two-Dimensional Tissue

Three-dimensional force distribution within the actin cytoskeleton of epithelial tissue regulates cell shape. While two-dimensional cell shape has been well characterized and heavily studied, three-dimensional cell shape regulation is less well understood despite its critical role in large scale epithelial processes such as invagination. By examining the relationship between cell height, density and biological components of the actin cytoskeleton, we explore the mechanisms by which the epithelial tissue regulates shape and volume. We observe that while cell density is not a strong indicator of epithelial height, osmotic shock drastically decreases both tissue height and cell volume while leaving the lateral shape of cells in the tissue undisturbed. In addition, we examine how the maturity of the tight junction regulates local volume and height correlation in the tissue.

Growth Phase Dependent Cell Shape of Haloarcula.

Several haloarchaea are reported to be pleomorphic, while others exhibit remarkable shapes, such as squares. Recently, Haloferax volcanii was found to alter its morphology during growth. Cells are motile rods in early exponential phase, and immotile plates in stationary phase. It is unknown if this growth phase dependent cell shape alteration is a specific feature of Hfx. volcanii, or conserved amongst haloarchaea. Here, we studied the cell shape and motility of two haloarchaea species Haloarcula hispanica and Haloarcula californiae. With a combination of light and electron microscopy, we observed that both strains undergo a growth phase dependent morphological development, albeit in a slightly different fashion as Hfx. volcanii. For both Haloarcula strains, the cell size is changing throughout growth. Cell shape seems to be related with motility, as highly motile cells on semi-solid agar plates are predominantly rod-shaped. We conclude that the growth phase dependent cell morphology alteration might be a common feature amongst haloarchaea, and that cell shape is generally linked with a motile life style. The conservation of this phenomenon underscores the importance of studies of the molecular mechanisms regulating cell shape in archaea.

Multiplexed Quantitative Screens of Single Cell Shape and YAP/TAZ Localisation Identify DOCK5 as a Coincident Detector of Polarity and Adhesion During Migration

YAP and TAZ are transcriptional co-activators that are often constitutively active in triple negative breast cancer (TNBC) cells driving proliferation, invasion, and drug resistance. Through multiplexed quantitative genetic screens for YAP/TAZ localisation and cell shape, we found that the RhoGEF DOCK5 is essential for YAP/TAZ activation in metastatic cells and is required for the maintenance of polarity during migration. DOCK5 regulates cell shape and thus YAP/TAZ through different genetic interactions with CDC42, RAC, and RHOA GTPases. DOCK5 regulates focal adhesion (FA) morphogenesis in RAC-dependent fashions that promote RHOA mediated actomyosin engagement of FA. Using unbiased systems-level quantification of protein levels by mass spectrometry we show that DOCK5 maintains polarity by stabilising protein levels of the CDC42 effector GSK3b. We conclude DOCK5 acts as a coincidence detector to promote leading edge persistence in subcellular locations where there is both RAC and RHOA dependent FA morphogenesis and active CDC42 mediated cell polarisation.

Structural features conserved in subclass of type II arabinogalactan.

Arabinogalactan-proteins (AGPs) are extracellular proteoglycans, which are presumed to participate in the regulation of cell shape, thus contributing to the excellent mechanical properties of plants. AGPs consist of a hydroxyproline-rich core-protein and large arabinogalactan (AG) sugar chains, called type II AGs. These AGs have a β-1,3-galactan backbone and β-1,6-galactan side chains, to which other sugars are attached. The structure of type II AG differs depending on source plant, tissue, and age. Type II AGs obtained from woody plants in large quantity as represented by gum arabic and larch AG, here designated gum arabic-subclass, have a β-1,3;1,6-galactan structure in which the β-1,3-galactan backbone is highly substituted with short β-1,6-galactan side chains. On the other hand, it is unclear whether type II AGs found as the glycan part of AGPs from herbaceous plants, here designated AGP-subclass, also have conserved β-1,3:1,6-galactan structural features. In the present study we explore similarities of type II AG structures in the AGP-subclass. Type II AGs in fractions obtained from spinach, broccoli, bok choy, komatsuna, and cucumber were hydrolyzed into galactose and β-1,6-galactooligosaccharides by specific enzymes. Based on the proportion of these sugars, the substitution ratio of the β-1,3-galactan backbone was calculated as 46-58% in the five vegetables, which is consistently lower than what is seen in gum arabic and larch AG. Although most side chains were short, long chains such as β-1,6-galactohexaose chains were also observed in these vegetables. The results suggest a conserved β-1,3;1,6-galactan structure in the AGP-subclass that distinguishes it from the gum arabic-subclass.

Bridging from single to collective cell migration: A review of models and links to experiments.

Mathematical and computational models can assist in gaining an understanding of cell behavior at many levels of organization. Here, we review models in the literature that focus on eukaryotic cell motility at 3 size scales: intracellular signaling that regulates cell shape and movement, single cell motility, and collective cell behavior from a few cells to tissues. We survey recent literature to summarize distinct computational methods (phase-field, polygonal, Cellular Potts, and spherical cells). We discuss models that bridge between levels of organization, and describe levels of detail, both biochemical and geometric, included in the models. We also highlight links between models and experiments. We find that models that span the 3 levels are still in the minority.

AMPK regulates cell shape of cardiomyocytes by modulating turnover of microtubules through CLIP-170

AMP-activated protein kinase (AMPK) is a multifunctional kinase that regulates microtubule (MT) dynamic instability through CLIP-170 phosphorylation; however, its physiological relevance in vivo remains to be elucidated. In this study, we identified an active form of AMPK localized at the intercalated disks in the heart, a specific cell–cell junction present between cardiomyocytes. A contractile inhibitor, MYK-461, prevented the localization of AMPK at the intercalated disks, and the effect was reversed by the removal of MYK-461, suggesting that the localization of AMPK is regulated by mechanical stress. Time-lapse imaging analysis revealed that the inhibition of CLIP-170 Ser-311 phosphorylation by AMPK leads to the accumulation of MTs at the intercalated disks. Interestingly, MYK-461 increased the individual cell area of cardiomyocytes in CLIP-170 phosphorylation-dependent manner. Moreover, heart-specific CLIP-170 S311A transgenic mice demonstrated elongation of cardiomyocytes along with accumulated MTs, leading to progressive decline in cardiac contraction. In conclusion, these findings suggest that AMPK regulates the cell shape and aspect ratio of cardiomyocytes by modulating the turnover of MTs through homeostatic phosphorylation of CLIP-170 at the intercalated disks.

Vibrio cholerae adapts to sessile and motile lifestyles by cyclic di-GMP regulation of cell shape

The cell morphology of rod-shaped bacteria is determined by the rigid net of peptidoglycan forming the cell wall. Alterations to the rod shape, such as the curved rod, occur through manipulating the process of cell wall synthesis. The human pathogen Vibrio cholerae typically exists as a curved rod, but straight rods have been observed under certain conditions. While this appears to be a regulated process, the regulatory pathways controlling cell shape transitions in V. cholerae and the benefits of switching between rod and curved shape have not been determined. We demonstrate that cell shape in V. cholerae is regulated by the bacterial second messenger cyclic dimeric guanosine monophosphate (c-di-GMP) by posttranscriptionally repressing expression of crvA, a gene encoding an intermediate filament-like protein necessary for curvature formation in V. cholerae. This regulation is mediated by the transcriptional cascade that also induces production of biofilm matrix components, indicating that cell shape is coregulated with V. cholerae's induction of sessility. During microcolony formation, wild-type V. cholerae cells tended to exist as straight rods, while genetically engineering cells to maintain high curvature reduced microcolony formation and biofilm density. Conversely, straight V. cholerae mutants have reduced swimming speed when using flagellar motility in liquid. Our results demonstrate regulation of cell shape in bacteria is a mechanism to increase fitness in planktonic and biofilm lifestyles.

Marcksl1 modulates endothelial cell mechanoresponse to haemodynamic forces to control blood vessel shape and size

The formation of vascular tubes is driven by extensive changes in endothelial cell (EC) shape. Here, we have identified a role of the actin-binding protein, Marcksl1, in modulating the mechanical properties of EC cortex to regulate cell shape and vessel structure during angiogenesis. Increasing and depleting Marcksl1 expression level in vivo results in an increase and decrease, respectively, in EC size and the diameter of microvessels. Furthermore, endothelial overexpression of Marcksl1 induces ectopic blebbing on both apical and basal membranes, during and after lumen formation, that is suppressed by reduced blood flow. High resolution imaging reveals that Marcksl1 promotes the formation of linear actin bundles and decreases actin density at the EC cortex. Our findings demonstrate that a balanced network of linear and branched actin at the EC cortex is essential in conferring cortical integrity to resist the deforming forces of blood flow to regulate vessel structure.

Molecular Logic of Prokaryotic Surface Layer Structures.

Most prokaryotic cells are encased in a surface layer (S-layer) consisting of a paracrystalline array of repeating lattice-forming proteins. S-layer proteins populate a vast and diverse sequence space, performing disparate functions in prokaryotic cells, including cellular defense, cell-shape maintenance, and regulation of import and export of materials. This article highlights recent advances in the understanding of S-layer structure and assembly, made possible by rapidly evolving structural and cell biology methods. We underscore shared assembly principles revealed by recent work and discuss a common molecular framework that may be used to understand the structural organization of S-layer proteins across bacteria and archaea.

Interplay between actomyosin and E-cadherin dynamics regulates cell shape in the Drosophila embryonic epidermis.

Precise regulation of cell shape is vital for building functional tissues. Here, we study the mechanisms that lead to the formation of highly elongated anisotropic epithelial cells in the Drosophila epidermis. We demonstrate that this cell shape is the result of two counteracting mechanisms at the cell surface that regulate the degree of elongation: actomyosin, which inhibits cell elongation downstream of RhoA (Rho1 in Drosophila) and intercellular adhesion, modulated via clathrin-mediated endocytosis of E-cadherin (encoded by shotgun in flies), which promotes cell elongation downstream of the GTPase Arf1 (Arf79F in Drosophila). We show that these two mechanisms do not act independently but are interconnected, with RhoA signalling reducing Arf1 recruitment to the plasma membrane. Additionally, cell adhesion itself regulates both mechanisms - p120-catenin, a regulator of intercellular adhesion, promotes the activity of both Arf1 and RhoA. Altogether, we uncover a complex network of interactions between cell-cell adhesion, the endocytic machinery and the actomyosin cortex, and demonstrate how this network regulates cell shape in an epithelial tissue in vivo.

Control of fibroblast shape in sequentially formed 3D hybrid hydrogels regulates cellular responses to microenvironmental cues

Cell shape plays important roles in regulating cell behavior; however, independently controlling cell shape in three dimensions is a challenging undertaking, and how cell shape affects cellular responses to mechanical and biochemical cues in three dimensions remains unclear. Here, we present a hydrogel-based platform to control cell shape in three dimensions by using sequentially formed hybrid hydrogels consisting of collagen and alginate. By adjusting the cross-linking time of the alginate, we fixed the shape of NIH 3T3 fibroblasts at different spreading states. Then, we explored the influence of cell shape on the cell responses to microenvironmental cues by using cardiac fibroblasts (CFs) as model cells. We found that the spreading state of the CFs influences their responses to both mechanical (i.e., matrix stiffness) and biochemical (i.e., transforming growth factor-β1 (TGF-β1)) cues in three dimensions. Additional experiments revealed that integrin β1 in focal adhesions and Smad2/3 are involved in mediating the cell shape-dependent responses of CFs to matrix stiffness and TGF-β1 cues, respectively. This work represents the first step in understanding how cell shape influences cell responses to mechanical and biochemical cues in three dimensions and can be instructive for developing novel approaches to target cell shape regulation for treating fibrosis and other diseases.

Phosphatidylinositol 4-kinase III beta regulates cell shape, migration, and focal adhesion number.

Cell shape is regulated by cell adhesion and cytoskeletal and membrane dynamics. Cell shape, adhesion, and motility have a complex relationship and understanding them is important in understanding developmental patterning and embryogenesis. Here we show that the lipid kinase phosphatidylinositol 4-kinase III beta (PI4KIIIβ) regulates cell shape, migration, and focal adhesion (FA) number. PI4KIIIβ generates phosphatidylinositol 4-phosphate (PI4P) from phosphatidylinositol and is highly expressed in a subset of human breast cancers. PI4KIIIβ and the PI4P it generates regulate a variety of cellular functions, ranging from control of Golgi structure, fly fertility, and Akt signaling. Here, we show that loss of PI4KIIIβ expression decreases cell migration and alters cell shape in NIH3T3 fibroblasts. The changes are accompanied by an increase in the number of FA in cells lacking PI4KIIIβ. Furthermore, we find that PI4P-containing vesicles move to the migratory leading edge during migration and that some of these vesicles tether to and fuse with FA. Fusion is associated with FA disassembly. This suggests a novel regulatory role for PI4KIIIβ and PI4P in cell adhesion and cell shape maintenance.

127 ROCK inhibition reduces Ras-induced senescence in primary mouse keratinocytes

The Rho-associated protein kinase (ROCK) is responsible for the regulation of cell adhesion, shape and migration by altering cytoskeletal structure. The ROCK inhibitor, Y27632, protects cells from anoikis and enhances embryonic stem cell viability in culture and cryopreservation. Y27632 prolongs the life span of cultured primary mouse keratinocytes. Oncogenic RAS transduced primary mouse keratinocytes (RAS-keratinocytes) become senescent in vitro. Here, we show that chronic treatment of Ras transduced primary mouse keratinocytes (RAS-keratinocytes) with Y27632 reduces the number of senescence associated β-galactosidase positive cells which are flat and enlarged.

Functional Properties of the MAP Kinase UeKpp2 in Ustilago esculenta.

Ustilago esculenta undergoes an endophytic life cycle in Zizania latifolia. It induces the stem of its host to swell, forming the edible galls called jiaobai in China, which are the second most commonly cultivated aquatic vegetable in China. Z. latifolia raised for jiaobai can only reproduce asexually because the U. esculenta infection completely inhibits flowering. The infection and proliferation in the host plants during the formation of edible gall differ from those of conventional pathogens. Previous studies have shown a close relationship between mitogen-activated protein kinase (MAPK) and fungal pathogenesis. In this study, we explored the functional properties of the MAPK UeKpp2. Cross-species complementation assays were carried out, which indicated a functional complementation between the UeKpp2 of U. esculenta and the Kpp2 of Ustilago maydis. Next, UeKpp2 mutants of the UeT14 and the UeT55 sporidia background were generated; these showed an aberrant morphology of budding cells, and attenuated mating and filamentous growth in vitro, in the context of normal pathogenicity. Interestingly, we identified another protein kinase, UeUkc1, which acted downstream of UeKpp2 and may participate in the regulation of cell shape. We also found a defect of filamentous growth in UeKpp2 mutants that was not related to a defect of the induction of mating-type genes but was directly related to a defect in UeRbf1 induction. Overall, our results indicate an important role for UeKpp2 in U. esculenta that is slightly different from those reported for other smut fungi.

1327-P: Maternal Diabetes Suppresses Neural Tube Closure Gene Shroom3 through DNA Hypermethylation and Thus Disrupts Planar Cell Polarity

Neural Tube Defects (NTDs) are among the most frequent and severe malformations associated with maternal diabetes. DNA hypermethylation inhibits gene expression. Our recent studies have revealed a group of neural tube closure-related genes are downregulated by maternal diabetes. Planar cell polarity (PCP) is conserved in metazoans and is essential for development, deficiencies of PCP genes result in NTDs. Shroom3 encodes a PDZ-domain-containing protein that regulates cell shape in epithelium. Shroom3 interacts with PCP genes, loss of function of Shroom3 leads to NTDs. We hypothesize that DNA hypermethylation induced by maternal diabetes is responsible for the downregulation of Shroom3, which disrupts the PCP pathway leading to NTD formation. We found global DNA methylation levels were increased about 3 times and all 3 DNA methyltransferase levels were increased in the embryos from diabetic dams compared to the nondiabetic control group. Conditional double knockout of Dnmt3a/Dnmt3b gene in the developing neuroepithelium ameliorated maternal diabetes-induced NTDs, while overexpression Dnmt3b in the neuroepithelium induced NTDs in a dose dependent manner. Expression levels of PCP genes and Shroom3 were reduced by maternal diabetes and Dnmt3b transgenic overexpression. Similarly, PCP protein subcellular expression patterns were also disrupted. DNA methyl-sequencing revealed maternal diabetes-induced hypermethylation in the Shromm3 gene promoter. De-methylation rescued Shroom3 promoter activity suppressed by high glucose. Our study reveals that diabetes-induced DNA hypermethylation inhibits Shroom3 gene expression and Shroom3 deficiency mediates the teratogenic effect of maternal diabetes by disrupting PCP and resulting in NTDs. Since de-methylation can rescue Shroom3 activity, our findings suggest that targeting DNA hypermethylation could be therapeutically effective in treating maternal diabetes-induced NTDs. Disclosure C. Xu: None. P. Yang: None. Funding National Institutes of Health (R01DK083243, R01DK101972, R01HL131737, R01HL134368, R01DK103024)

Expression of a fungal exo-β-1,3-galactanase in Arabidopsis reveals a role of type II arabinogalactans in the regulation of cell shape.

Arabinogalactan-proteins (AGPs) are a family of plant extracellular proteoglycans implicated in many physiological events. AGP is decorated with type II arabinogalactans (AGs) consisting of a β-1,3-galactan backbone and β-1,6-galactan side chains, to which other sugars are attached. Based on the fact that a type II AG-specific inhibitor, β-Yariv reagent, perturbs growth and development, it has been proposed that type II AGs participate in the regulation of cell shape and tissue organization. However, the mechanisms by which type II AGs participate have not yet been established. Here, we describe a novel system that causes specific degradation of type II AGs in Arabidopsis, by which a gene encoding a fungal exo-β-1,3-galactanase that specifically hydrolyzes β-1,3-galactan backbones of type II AGs is expressed under the control of a dexamethasone-inducible promoter. Dexamethasone treatment increased the galactanase activity, leading to a decrease in Yariv reagent-reactive AGPs in transgenic Arabidopsis. We detected the typical oligosaccharides released from type II AGs by Il3GAL in the soluble fraction, demonstrating that Il3GAL acted on type II AG in the transgenic plants. Additionally, this resulted in severe tissue disorganization in the hypocotyl and cotyledons, suggesting that the degradation of type II AGs affected the regulation of cell shape.