Regulation of cell adhesion and collective cell migration by hindsight and its human homolog RREB1

A 3D model of ovarian cancer cell lines on peptide nanofiber scaffold to explore the cell-scaffold interaction and chemotherapeutic resistance of anticancer drugs

RADA16-I peptide hydrogel, a type of nanofiber scaffold derived from self-assembling peptide RADA16-I, has been extensively applied to regenerative medicine and tissue repair in order to develop novel nanomedicine systems. In this study, using RADA16-I peptide hydrogel, a three-dimensional (3D) cell culture model was fabricated for in vitro culture of three ovarian cancer cell lines. Firstly, the peptide nanofiber scaffold was evaluated by transmission electron microscopy and atom force microscopy. Using phase contrast microscopy, the appearance of the representative ovarian cancer cells encapsulated in RADA16-I peptide hydrogel on days 1, 3, and 7 in 24-well Petri dishes was illustrated. The cancer cell-nanofiber scaffold construct was cultured for 5 days, and the ovarian cancer cells had actively proliferative potential. The precultured ovarian cancer cells exhibited nearly similar adhesion properties and invasion potentials in vitro between RADA16-I peptide nanofiber and type I collagen, which suggested that RADA16-I peptide hydrogel had some similar characteristics to type I collagen. The precultured ovarian cancer cells had two-fold to five-fold higher anticancer drug resistance than the conventional two-dimensional Petri dish culture. So the 3D cell model on peptide nanofiber scaffold is an optimal type of cell pattern for anticancer drug screening and tumor biology.

Fluid shear stress-induced JNK activity leads to actin remodeling for cell alignment

Fluid shear stress (FSS) exerted on endothelial cell (EC) surfaces induces actin cytoskeleton remodeling through mechanotransduction. This study was designed to determine whether FSS activates Jun N-terminal kinase (JNK), to examine the spatial and temporal distribution of active JNK relative to the actin cytoskeleton in ECs exposed to different FSS conditions, and to evaluate the effects of active JNK on actin realignment. Exposure to 15 and 20 dyn/cm(2) FSS induced higher activity levels of JNK than the lower 2 and 4 dyn/cm(2) flow conditions. At the higher FSS treatments, JNK activity increased with increasing exposure time, peaking 30 min after flow onset with an eightfold activity increase compared to cells in static culture. FSS-induced phospho-JNK co-localized with actin filaments at cell peripheries, as well as with stress fibers. Pharmacologically blocking JNK activity altered FSS-induced actin structure and distribution as a response to FSS. Our results indicate that FSS-induced actin remodeling occurs in three phases, and that JNK plays a role in at least one, suggesting that this kinase activity is involved in mechanotransduction from the apical surface to the actin cytoskeleton in ECs.

The Ste20 kinase misshapen is essential for the invasive behaviour of ovarian epithelial cells in Drosophila

Stationary-to-migratory transitions of epithelial cells have a key role in development and tumour progression. Border cell migration is a powerful system in which to investigate this transition in living organisms. Here, we identify the Ste20-like kinase misshapen (msn) as a novel regulator of border-cell migration in Drosophila. Expression of msn in border cells is independent of the transcription factor slow border cells and of inputs from all pathways that are known to control border-cell migration. The msn gene functions to modulate the levels and/or distribution of Drosophila E-cadherin to promote the invasive migratory behaviour of border cells.

Molecular signatures of the primitive prostate stem cell niche reveal novel mesenchymal-epithelial signaling pathways

Background

Signals between stem cells and stroma are important in establishing the stem cell niche. However, very little is known about the regulation of any mammalian stem cell niche as pure isolates of stem cells and their adjacent mesenchyme are not readily available. The prostate offers a unique model to study signals between stem cells and their adjacent stroma as in the embryonic prostate stem cell niche, the urogenital sinus mesenchyme is easily separated from the epithelial stem cells. Here we investigate the distinctive molecular signals of these two stem cell compartments in a mammalian system.

Methodology/Principal Findings

We isolated fetal murine urogenital sinus epithelium and urogenital sinus mesenchyme and determined their differentially expressed genes. To distinguish transcripts that are shared by other developing epithelial/mesenchymal compartments from those that pertain to the prostate stem cell niche, we also determined the global gene expression of epidermis and dermis of the same embryos. Our analysis indicates that several of the key transcriptional components that are predicted to be active in the embryonic prostate stem cell niche regulate processes such as self-renewal (e.g., E2f and Ap2), lipid metabolism (e.g., Srebp1) and cell migration (e.g., Areb6 and Rreb1). Several of the enriched promoter binding motifs are shared between the prostate epithelial/mesenchymal compartments and their epidermis/dermis counterparts, indicating their likely relevance in epithelial/mesenchymal signaling in primitive cellular compartments. Based on differential gene expression we also defined ligand-receptor interactions that may be part of the molecular interplay of the embryonic prostate stem cell niche.

Conclusions/Significance

We provide a comprehensive description of the transcriptional program of the major regulators that are likely to control the cellular interactions in the embryonic prostatic stem cell niche, many of which may be common to mammalian niches in general. This study provides a comprehensive source for further studies of mesenchymal/epithelial interactions in the prostate stem cell niche. The elucidation of pathways in the normal primitive niche may provide greater insight into mechanisms subverted during abnormal proliferative and oncogenic processes. Understanding these events may result in the development of specific targeted therapies for prostatic diseases such as benign prostatic hypertrophy and carcinomas.

Spatial organization of adhesion: force-dependent regulation and function in tissue morphogenesis

Integrin- and cadherin-mediated adhesion is central for cell and tissue morphogenesis, allowing cells and tissues to change shape without loosing integrity. Studies predominantly in cell culture showed that mechanosensation through adhesion structures is achieved by force-mediated modulation of their molecular composition. The specific molecular composition of adhesion sites in turn determines their signalling activity and dynamic reorganization. Here, we will review how adhesion sites respond to mecanical stimuli, and how spatially and temporally regulated signalling from different adhesion sites controls cell migration and tissue morphogenesis.

Hypoxia response pathway in border cell migration

Cell invasion and metastasis mark the most lethal phase of cancer, but little is known about the key molecular events that initiate this crucial turning point. Low oxygen, or hypoxia, is thought to be one trigger for metastasis. Hypoxic conditions within the tumor mass are thought to activate signaling pathways that stimulate invasiveness of cancer cells spreading the disease. However, the molecular basis of this process is not well understood. A recent study used Drosophila ovarian border cell migration to model the type of cell migration that occurs in tumors in response to oxygen deprivation through the activation of the hypoxia response pathway (Doronkin et al. Oncogene. 2009). This model organism approach revealed a highly sophisticated mechanism of control of cell migration that is regulated by multiple genetic inputs tied to the hypoxic response. Genetic manipulations with the components of the HIF-1 (hypoxia-inducible factor 1) pathway were able to either inhibit or block the migration of border cells or cause unprecedented acceleration of their migration. The HIF-1-mediated transcriptional cascade appears to be the major regulator of border cell locomotion. Based on the similarity of the fly and human HIF-1 pathways, this model organism study might lead to improvements in understanding hypoxia-induced metastasizing of human cancers. This article discusses new findings in the context of their relevance to cancer metastasis and speculates on the potential regulatory mechanisms and future research directions.

Biology and physics of cell shape changes in development

Together with cell growth, division and death, changes in cell shape are of central importance for tissue morphogenesis during development. Cell shape is the product of a cell's material and active properties balanced by external forces. Control of cell shape, therefore, relies on both tight regulation of intracellular mechanics and the cell's physical interaction with its environment. In this review, we first discuss the biological and physical mechanisms of cell shape control. We next examine a number of developmental processes in which cell shape change - either individually or in a coordinated manner - drives embryonic morphogenesis and discuss how cell shape is controlled in these processes. Finally, we emphasize that cell shape control during tissue morphogenesis can only be fully understood by using a combination of cellular, molecular, developmental and biophysical approaches.

Movement directionality in collective migration of germ layer progenitors

Collective cell migration, the simultaneous movement of multiple cells that are connected by cell-cell adhesion, is ubiquitous in development, tissue repair, and tumor metastasis [1, 2]. It has been hypothesized that the directionality of cell movement during collective migration emerges as a collective property [3, 4]. Here we determine how movement directionality is established in collective mesendoderm migration during zebrafish gastrulation. By interfering with two key features of collective migration, (1) having neighboring cells and (2) adhering to them, we show that individual mesendoderm cells are capable of normal directed migration when moving as single cells but require cell-cell adhesion to participate in coordinated and directed migration when moving as part of a group. We conclude that movement directionality is not a de novo collective property of mesendoderm cells but rather a property of single mesendoderm cells that requires cell-cell adhesion during collective migration.

Collective cell migration in development

Collective cell migration is a key process during the development of most organisms. It can involve either the migration of closely packed mesenchymal cells that make dynamic contacts with frequently changing neighbour cells, or the migration of epithelial sheets that typically display more stable cell-cell interactions and less frequent changes in neighbours. These collective movements can be controlled by short- or long-range dynamic gradients of extracellular signalling molecules, depending on the number of cells involved and their distance of migration. These gradients are sensed by some or all of the migrating cells and translated into directed migration, which in many settings is further modulated by cell-contact-mediated attractive or repulsive interactions that result in contact-following or contact-inhibition of locomotion, respectively. Studies of collective migration of groups of epithelial cells during development indicate that, in some cases, only leader cells sense and migrate up an external signal gradient, and that adjacent cells follow through strong cell-cell contacts. In this Commentary, I review studies of collective cell migration of differently sized cell populations during the development of several model organisms, and discuss our current understanding of the molecular mechanisms that coordinate this migration.

Cell migration during morphogenesis

During development, functional structures must form with the correct three-dimensional geometry composed of the correct cell types. In many cases cell types are specified at locations distant to where they will ultimately reside for normal biological function. Although cell migration is crucial for normal development and morphogenesis of animal body plans and organ systems, abnormal cell migration during adult life underlies pathological states such as invasion and metastasis of cancer. In both contexts cells migrate either individually, as loosely associated sheets or as clusters of cells. In this review, we summarize, compare and integrate knowledge gained from several in vivo model systems that have yielded insights into the regulation of morphogenic cell migration, such as the zebrafish lateral line primordium and primordial germ cells, Drosophila border cell clusters, vertebrate neural crest migration and angiogenic sprouts in the post-natal mouse retina. Because of its broad multicontextual and multiphylletic distribution, understanding cell migration in its various manifestations in vivo is likely to provide new insights into both the function and malfunction of key embryonic and postembryonic events. In this review, we will provide a succinct phenotypic description of the many model systems utilized to study cell migration in vivo. More importantly, we will highlight, compare and integrate recent advances in our understanding of how cell migration is regulated in these varied model systems with special emphasis on individual and collective cell movements.

Interleukin-11 and leukemia inhibitory factor regulate the adhesion of endometrial epithelial cells: implications in fertility regulation

Embryo implantation requires the closely harmonized processes of apposition, attachment, and adhesion of the conceptus to the maternal endometrial epithelium. IL-11 and leukemia inhibitory factor (LIF), two IL-6 family cytokines, are produced by the endometrium and are absolutely required for implantation in mice. We examined the effect of IL-11 and LIF on human endometrial epithelial cell adhesion. Both cytokines increased adhesion of primary human endometrial epithelial cells to fibronectin and collagen IV. IL-11 stimulated, whereas LIF had no effect on the adhesion of trophoblast to endometrial epithelial cells. Focused oligogene arrays were used to identify extracellular matrix and adhesion molecules mRNAs regulated by endometrial epithelial cells. We demonstrated by real-time RT-PCR and antibody arrays that both cytokines increased integrin-alpha2 mRNA and protein by endometrial epithelial cells. Signal transducers and activators of transcription (STAT)-3 inhibition reduced IL-11- and LIF-mediated epithelial cell adhesion to fibronectin, suggesting both cytokines regulated adhesion via phosphorylation of STAT3. Addition of either IL-11 neutralizing antibody and IL-11 or LIF and LIF antagonist to endometrial epithelial cells abolished cytokine induced phosphorylated STAT3. LIF but not IL-11 induced adhesion to collagen IV was reduced by an integrin-alpha2beta1 neutralizing antibody. This study demonstrated that IL-11 and LIF regulated endometrial epithelial cell adhesion, suggesting that targeting IL-11 and LIF may be useful in regulating fertility by either enhancing or blocking implantation.

Morphogenetic cell movements: diversity from modular mechanical properties

Animal tissue and organ development requires the orchestration of cell movements, including those of interconnected cell groups, termed collective cell movements. Such movements are incredibly diverse. Recent work suggests that two core cellular properties, cell-cell adhesion and contractility, can largely determine geometry, packing, sorting, and rearrangement of epithelial cell layers. Two additional force-generating properties, the ability to generate cell protrusions and cell adhesion to the extracellular matrix, contribute to active motility. These mechanical properties can be regulated independently in cells, suggesting that they can be employed in a combinatorial manner. A small number of properties used in combination could, in principle, generate a diverse array of cell shapes and arrangements and thus orchestrate the varied morphogenetic events observed during metazoan organ development.

JNK-mediated phosphorylation of paxillin in adhesion assembly and tension-induced cell death by the adenovirus death factor E4orf4

The adenovirus type 2 Early Region 4 ORF4 (E4orf4) protein induces a caspase-independent death program in tumor cells involving changes in actin dynamics that are functionally linked to cell killing. Because an increase in myosin II-based contractility is needed for the death of E4orf4-expressing cells, we have proposed that alteration of cytoskeletal tension is part of the signals engaging the death pathway. Yet the mechanisms involved are poorly defined. Herein, we show that the Jun N-terminal kinase JNK is activated in part through a pathway involving Src, Rho, and ROCK (Rho kinase) and contributes to dysregulate adhesion dynamics and to kill cells in response to E4orf4. JNK supports the formation of atypically robust focal adhesions, which are bound to the assembly of the peculiar actomyosin network typifying E4orf4-induced cell death and which are required for driving nuclear condensation. Remarkably, the dramatic enlargement of focal adhesions, actin remodeling, and cell death all rely on paxillin phosphorylation at Ser-178, which is induced by E4orf4 in a JNK-dependent way. Furthermore, we found that Ser-178-paxillin phosphorylation is necessary to decrease adhesion turnover and to enhance the time residency of paxillin at focal adhesions, promoting its recruitment from an internal pool. Our results indicate that perturbation of tensional homeostasis by E4orf4 involves JNK-regulated changes in paxillin adhesion dynamics that are required to engage the death pathway. Moreover, our findings support a role for JNK-mediated paxillin phosphorylation in adhesion growth and stabilization during tension signaling.

JNK signaling controls border cell cluster integrity and collective cell migration

Collective cell movement is a mechanism for invasion identified in many developmental events. Examples include the movement of lateral-line neurons in Zebrafish, cells in the inner blastocyst, and metastasis of epithelial tumors [1]. One key model to study collective migration is the movement of border cell clusters in Drosophila. Drosophila egg chambers contain 15 nurse cells and a single oocyte surrounded by somatic follicle cells. At their anterior end, polar cells recruit several neighboring follicle cells to form the border cell cluster [2]. By stage 9, and over 6 hr, border cells migrate as a cohort between nurse cells toward the oocyte. The specification and directionality of border cell movement are regulated by hormonal and signaling mechanisms [3]. However, how border cells are held together while they migrate is not known. Here, we show that a negative-feedback loop controlling JNK activity regulates border cell cluster integrity. JNK signaling modulates contacts between border cells and between border cells and substratum to sustain collective migration by regulating several effectors including the polarity factor Bazooka and the cytoskeletal adaptor D-Paxillin. We anticipate a role for the JNK pathway in controlling collective cell movements in other morphogenetic and clinical models.