Mechanisms Of Morphogenesis Research Articles

Orientation of the Mitotic Spindle in Blood Vessel Development.

Angiogenesis requires coordinated endothelial cell specification, proliferation, and collective migration. The orientation of endothelial cell division is tightly regulated during the earliest stages of blood vessel formation in response to morphogenetic cues and the controlled orientation of the mitotic spindle. Consequently, oriented cell division is a vital mechanism in vessel morphogenesis, and defective spindle orientation can perturb the spatial arrangement of daughter cells and consequently contribute to several diseases related to vascular development. Many factors affect endothelial cell proliferation and orientation and therefore blood vessel formation, with the relationship between improper spindle orientation in endothelial cells and various diseases extensively studied. Here we review the molecular mechanisms driving the orientation of endothelial cell division, particularly with respect to the mitotic spindle, and how these processes affect vascular development, disease pathogenesis, and their potential as novel targets.

In Vitro Modeling of the Early Development of Mouse and Human Embryos

Mammalian embryonic development includes preimplantation, implantation and post-implantation development, during which the embryo is attached to the uterus wall. The modeling of embryo development in culture allows to study the process of ontogenesis in its dynamic development, which is especially valuable for studying early post-implantation development. We reviewed existing cultivation systems for mouse and human embryos. Also we considered a new experimental approach for studying early mammalian embryogenesis—embryo-like cell constructs. Using these methods, the most important results were obtained about the formation of embryonic germ layers, which provided insights into the molecular and cellular mechanisms of morphogenesis of the mouse and human embryos. The purpose of this review is to generalize the possibilities and limitations of such systems for studying mammalian embryogenesis and to find directions for further development of this approach.

An intimate view into the silica deposition vesicles of diatoms

Diatoms are single-celled microalgae that produce silica-based cell walls with intricate nano- and micropatterns. Biogenesis of diatom biosilica is a bottom-up process that occurs in large intracellular compartments termed silica deposition vesicles (SDVs). Investigating the mechanisms of silica morphogenesis has so far been severely limited by the lack of methods for imaging the entire volume of an SDV with high spatial resolution during all stages of development. Here we have developed a method that allows for rapid identification and electron microscopy imaging of many different, full sized SDVs that are in the process of producing biosilica valves. This enabled visualizing the development of characteristic morphological biosilica features with unprecedented spatio-temporal resolution. During early to mid-term development, valve SDVs contained ~ 20 nm sized particles that were primarily associated with the radially expanding rib-like biosilica structures. The results from electron dispersive X-ray analysis suggests that the immature biosilica patterns are silica-organic composites. This supports the hypothesis that silica morphogenesis is dependent on organic biomolecules inside the SDV lumen.

Spatial Statistics-Based Image Analysis Methods for the Study of Vascular Morphogenesis.

Several studies are available addressing the mechanisms of vascular morphogenesis in order to unravel how cooperative cell behavior can follow from the underlying, genetically regulated behavior of endothelial cells and from cell-to-cell and cell-to-extracellular matrix interactions. From the morphological standpoint several aspects of the process are of interest. They include the way the pattern of vessels fills the available tissue space and how the network grows during the angiogenic process, namely how a main trunk divides into smaller branches, and how branching occurs at different distances from the root point of a vascular tree. A third morphological aspect of interest concerns the spatial relationship between vessels and tissue cells able to secrete factors modulating endothelial cells self-organization, thus influencing vascular rearrangement.In the present chapter image analysis methods allowing for a quantitative characterization of these morphological aspects will be detailed and discussed. They are almost based on concepts derived from the theoretical framework represented by spatial statistics.

Action of Actomyosin Contraction With Shh Modulation Drive Epithelial Folding in the Circumvallate Papilla.

The mouse tongue possesses three types of gustatory papillae: large circumvallate papillae (CVP), foliate papillae (FOP) and fungiform papillae (FFP). Although CVP is the largest papilla and contain a high density of taste buds, little is known about CVP development. Their transition from placode to dome-shape is particularly ambiguous. Understanding this phase is crucial since dome-shaped morphology is essential for proper localization of the imminent nerve fibers and taste buds. Here, we report actomyosin-dependent apical and basal constriction of epithelial cells during dynamic epithelial folding. Furthermore, actomyosin-dependent basal constriction requires focal adhesion kinase to guide dome-shape formation. Sonic hedgehog (Shh) is closely associated with the differentiation or survival of the neurons in CVP ganglion and cytoskeletal alteration in trench epithelial cells which regulate CVP morphogenesis. Our results demonstrate the CVP morphogenesis mechanism from placode to dome-shape by actomyosin-dependent cell shape change and suggest roles that Shh may play in trench and stromal core formation during CVP development.

Competitive and Coordinative Interactions between Body Parts Produce Adaptive Developmental Outcomes.

Large-scale patterns of correlated growth in development are partially driven by competition for metabolic and informational resources. It is argued that competition between organs for limited resources is an important mesoscale morphogenetic mechanism that produces fitness-enhancing correlated growth. At the genetic level, the growth of individual characters appears independent, or "modular," because patterns of expression and transcription are often highly localized, mutations have trait-specific effects, and gene complexes can be co-opted as a unit to produce novel traits. However, body parts are known to interact over the course of ontogeny, and these reciprocal exchanges can be an important determinant of developmental outcomes. Genetic mechanisms underlie cell and tissue behaviors that allow organs to communicate with one another, but they also create evolutionarily adaptive competitive dynamics that are driven by physiological and biophysical processes. Advances in the understanding of competitive and closely related coordinative interactions across scales will complement existing research programs that emphasize the role of cellular mechanisms in morphogenesis. Study of the large-scale order produced by competitive dynamics promises to facilitate advances in basic evolutionary and developmental biology, as well as applied research in fields such as bioengineering and regenerative medicine that aim to regulate patterning outcomes.

Intrinsic and extrinsic mechanisms regulating neuronal dendrite morphogenesis

Neurons are the structural and functional unit of the nervous system. Precisely regulated dendrite morphogenesis is the basis of neural circuit assembly. Numerous studies have been conducted to explore the regulatory mechanisms of dendritic morphogenesis. According to their action regions, we divide them into two categories: the intrinsic and extrinsic regulators of neuronal dendritic morphogenesis. Intrinsic factors are cell type-specific transcription factors, actin polymerization or depolymerization regulators and regulators of the secretion or endocytic pathways. These intrinsic factors are produced by neuron itself and play an important role in regulating the development of dendrites. The extrinsic regulators are either secreted proteins or transmembrane domain containing cell adhesion molecules. They often form receptor-ligand pairs to mediate attractive or repulsive dendritic guidance. In this review, we summarize recent findings on the intrinsic and external molecular mechanisms of dendrite morphogenesis from multiple model organisms, including Caenorhabditis elegans, Drosophila and mice. These studies will provide a better understanding on how defective dendrite development and maintenance are associated with neurological diseases.

Polyhedral Water Droplets: Shape Transitions and Mechanism.

While classical liquid droplets are rounded, transitions have recently been discovered which render polyhedral water-suspended droplets of several oils. Yet, the mechanism of these transitions and the role of the droplets' interfacial curvature in inducing these transitions remain controversial. In particular, one of the two mechanisms suggested mandates a convex interface, in a view from the oil side. Here we show that oil-suspended water droplets can spontaneously assume polyhedral shapes, in spite of their concave interface. These results strongly support the alternative mechanism, where the faceting in both oil and water droplets is driven by the elasticity of a crystalline monolayer, known to self-assemble at the oil-water interface, independent of its curvature. The faceting transitions in the water droplets allow the fundamental elastic properties of two-dimensional matter to be probed, enable new strategies in faceted nanoparticle and nanoshell synthesis, and provide insight into the molecular mechanisms of morphogenesis.

Morphogenesis of a late Pleistocene delta off the south-western Hainan Island unraveled by numerical modeling

A paleo-river delta off the south-western (SW) Hainan Island has been identified based on seismic and core evidence. Dating results suggest its initial development in ~65 kyr BP during a global sea level lowstand (~85 m below modern level) and termination in ~56 kyr BP during a sea level highstand (~50 m below modern level). Analysis of the delta internal architecture indicated a dominant offshore transport pathway from the SW Hainan Island. In order to unravel possible driving mechanisms for morphogenesis of the delta, 3-Dimensional numerical modeling was applied to investigate oceanographic and morphodynamic scenarios corresponding to the initial delta development. Results indicate that sediment dynamics in the study area is controlled by a compound effect of monsoon-driven circulation, river plumes, tides and typhoons. Contribution of the Red River to the delta development is smaller than local rivers in SW Hainan due to a combined effect by regional circulation and tides which causes a detour of the buoyancy-driven plume around the delta, despite of its larger runoff and sediment discharge compared to those from the local rivers of Hainan. On the other hand, simulation results suggest at least ten-times higher sediment supply rate from SW Hainan during the developing phase of the river delta than the modern condition. Such enhanced sediment supply might be caused jointly by 1) increased local river runoff from SW Hainan, and 2) alongshore transport from eastern Hainan which was connected to the main land during the sea level lowstand.

A rare practice case — a diminutive sessile serrated adenoma of the colon

Aim. An illustration of a case of diminutive sessile serrated adenoma (SSA) as a variant of the development of the normal colon mucosa.Materials and methods. In 2017 a diminutive SSA was identified in the case of a 77 year-old patient. During endoscopic examination, which included white light endoscopy examination, narrow band imaging (NBI) and near focus, the main endoscopic signs of SSA were determined. Endoscopic removal of the lesion with subsequent confirmation of its histological structure was performed.Results. The colonoscopy revealed a diminutive SSA of up to 3mm in size with typical endoscopic signs: a flat-elevated type 0-IIA, a “mucinous cap”, the same color to the surrounding mucosa, pit pattern type II-О, absence of meshed capillary vessels, but with isolated dilated capillaries. Histological examination revealed the crypts to have a cytoplasmic-type serration, drop-like expansion and horizontal growth of the basal parts, without epithelial dysplasia.Conclusion. The presented clinical case shows a rare observation of a diminutive SSA, and the complexity of endoscopic diagnosis due to its small size. The above observation demonstrates one of the pathways — developing directly from the normal mucosa, bypassing the stage of hyperplastic polyp. Thus indicating the need for further study of serrated polyps, morphogenesis mechanisms and precancerous potential.

40th Annual David W Smith Workshop on Malformations and Morphogenesis: Abstracts of the 2019 Annual Meeting.

The 40th Annual David W. Smith Workshop on Malformations and Morphogenesis occurred August 23rd -28th, 2019 at the Snowbird Resort in Snowbird, Utah. The Workshop, which honors the legacy of David W. Smith, brought together clinicians and researchers interested in congenital malformations and their underlying mechanisms of morphogenesis from around the world. In addition to mechanisms of morphogenesis and delineation of new syndromes, the Workshop highlighted five themes: deformations, disruptions and fetal dysmorphology; orofacial clefting; central nervous system malformations; ciliopathies; and X-linked intellectual disabilities. This Conference Report includes the abstracts presented at the 2019 Workshop.

Catastrophic Recombination/Reaction of Aluminum Atoms in Cryogenic Parahydrogen Solids.

We report the results from experiments testing the limits of chemical energy storage in Al-atom-doped cryogenic parahydrogen (pH2) solids produced by codeposition of Al vapor and pH2 gas. These results map out three regimes of behavior. As described in the immediately preceding companion manuscript, for target Al atom concentrations, [Al]target ≲ 200 parts-per-million (ppm), the Al/pH2 solids are optically transparent and primarily contain isolated Al atoms, with a small admixture of AlxHy molecules formed by Al atom recombination/reaction. For [Al]target ≳ 500 ppm, the depositions fail immediately, producing highly optically scattering solids with evidence of extensive Al atom recombination/reaction. For intermediate [Al]target concentrations, near-threshold metastable transparent solids are formed which suffer catastrophic recombination/reaction as they grow past some critical thickness. Analysis of these catastrophic events using a minimal two parameter model [Jackson. J. Chem. Phys. 1959, 31, 722-729] yields a critical Al atom concentration near [Al] ≈ 280 ppm and an Al atom diffusion length ≈ 100 μm. While this diffusion length appears unphysically large, it is roughly compatible with even larger 300-900 μm wavelengths of spatial inhomogeneities visible in images of a remnant postrecombination sample. This spatial pattern is evocative of Turing structures or perhaps the structures sometimes formed upon phase separation; however, the actual mechanism for morphogenesis remains undetermined. The largest achieved Al atom concentrations of [Al] ≈ 300 ppm are roughly two orders-of-magnitude lower than those required for advanced chemical propulsion applications.

The mechanism of plant gall induction by insects: revealing clues, facts, and consequences in a cross-kingdom complex interaction

Galls are defined as modifications of the normal developmental design of plants, produced by a specific reaction to the presence and activity of a foreign organism. Although different organisms have the ability to induce galls in plants, insect-induced galls are the most elaborate and diverse. Some hypotheses have been proposed to explain the induction mechanism of plant galls by insects. The most general hypothesis suggests that gall formation is triggered by the action of chemical substances secreted by the gall inducer, including plant growth regulators such as auxins, cytokinins, indole-3-acetic acid (IAA), and other types of compounds. However, the mode of action of these chemical substances and the general mechanism by which the insect could control and manipulate plant development and physiology is still not known. Moreover, resulting from the complexity of the induction process and development of insect galls, the chemical hypothesis is very unlikely a complete explanation of the mechanism of induction and morphogenesis of these structures. Previous and new highlights of insect gall systems with emphasis on the induction process were analyzed on the basis of the author’s integrated point of view to propose a different perspective of gall induction, which is provided in this article. Due to the extraordinary diversity of shapes, colors, and complex structures present in insect galls, they are useful models for studying how form and structure are determined at the molecular level in plant systems. Furthermore, plant galls constitute an important source of material for the study and exploration of new chemical substances of interest to humans, due to their physiological and adaptive characteristics. Considering the finely tuned control of morphogenesis, structural complexity, and biochemical regulation of plant galls induced by insects, it is proposed that an induction mechanism mediated by the insertion of exogenous genetic elements into the genome of plant gall cells could be involved in the formation of this kind of structure through an endosymbiotic bacterium.

Auxin regulation involved in gynoecium morphogenesis of papaya flowers

The morphogenesis of gynoecium is crucial for propagation and productivity of fruit crops. For trioecious papaya (Carica papaya), highly differentiated morphology of gynoecium in flowers of different sex types is controlled by gene networks and influenced by environmental factors, but the regulatory mechanism in gynoecium morphogenesis is unclear. Gynodioecious and dioecious papaya varieties were used for analysis of differentially expressed genes followed by experiments using auxin and an auxin transporter inhibitor. We first compared differential gene expression in functional and rudimentary gynoecium at early stage of their development and detected significant difference in phytohormone modulating and transduction processes, particularly auxin. Enhanced auxin signal transduction in rudimentary gynoecium was observed. To determine the role auxin plays in the papaya gynoecium, auxin transport inhibitor (N-1-Naphthylphthalamic acid, NPA) and synthetic auxin analogs with different concentrations gradient were sprayed to the trunk apex of male and female plants of dioecious papaya. Weakening of auxin transport by 10 mg/L NPA treatment resulted in female fertility restoration in male flowers, while female flowers did not show changes. NPA treatment with higher concentration (30 and 50 mg/L) caused deformed flowers in both male and female plants. We hypothesize that the occurrence of rudimentary gynoecium patterning might associate with auxin homeostasis alteration. Proper auxin concentration and auxin homeostasis might be crucial for functional gynoecium morphogenesis in papaya flowers. These results will lead to further investigation on the auxin homeostasis and gynoecium morphogenesis in papaya.

Design Principles of Branching Morphogenesis in Filamentous Organisms.

The radiation of life on Earth was accompanied by the diversification of multicellular body plans in the eukaryotic kingdoms Animalia, Plantae, Fungi and Chromista. Branching forms are ubiquitous in nature and evolved repeatedly in the above lineages. The developmental and genetic basis of branch formation is well studied in the three-dimensional shoot and root systems of land plants, and in animal organs such as the lung, kidney, mammary gland, vasculature, etc. Notably, recent thought-provoking studies combining experimental analysis and computational modeling of branching patterns in whole animal organs have identified global patterning rules and proposed unifying principles of branching morphogenesis. Filamentous branching forms represent one of the simplest expressions of the multicellular body plan and constitute a key step in the evolution of morphological complexity. Similarities between simple and complex branching forms distantly related in evolution are compelling, raising the question whether shared mechanisms underlie their development. Here, we focus on filamentous branching organisms that represent major study models from three distinct eukaryotic kingdoms, including the moss Physcomitrella patens (Plantae), the brown alga Ectocarpus sp. (Chromista), and the ascomycetes Neurospora crassa and Aspergillus nidulans (Fungi), and bring to light developmental regulatory mechanisms and design principles common to these lineages. Throughout the review we explore how the regulatory mechanisms of branching morphogenesis identified in other models, and in particular animal organs, may inform our thinking on filamentous systems and thereby advance our understanding of the diverse strategies deployed across the eukaryotic tree of life to evolve similar forms.

Generation of complex human organoid models including vascular networks by incorporation of mesodermal progenitor cells

Organoids derived from human pluripotent stem cells are interesting models to study mechanisms of morphogenesis and promising platforms for disease modeling and drug screening. However, they mostly remain incomplete as they lack stroma, tissue resident immune cells and in particular vasculature, which create important niches during development and disease. We propose, that the directed incorporation of mesodermal progenitor cells (MPCs) into organoids will overcome the aforementioned limitations. In order to demonstrate the feasibility of the method, we generated complex human tumor as well as neural organoids. We show that the formed blood vessels display a hierarchic organization and mural cells are assembled into the vessel wall. Moreover, we demonstrate a typical blood vessel ultrastructure including endothelial cell-cell junctions, a basement membrane as well as luminal caveolae and microvesicles. We observe a high plasticity in the endothelial network, which expands, while the organoids grow and is responsive to anti-angiogenic compounds and pro-angiogenic conditions such as hypoxia. We show that vessels within tumor organoids connect to host vessels following transplantation. Remarkably, MPCs also deliver Iba1+ cells that infiltrate the neural tissue in a microglia-like manner.

Mechanosensitive Junction Remodeling Promotes Robust Epithelial Morphogenesis

Morphogenesis of epithelial tissues requires tight spatiotemporal coordination of cell shape changes. In vivo, many tissue-scale shape changes are driven by pulsatile contractions of intercellular junctions, which are rectified to produce irreversible deformations. The functional role of this pulsatory ratchet and its mechanistic basis remain unknown. Here we combine theory and biophysical experiments to show that mechanosensitive tension remodeling of epithelial cell junctions promotes robust epithelial shape changes via ratcheting. Using optogenetic control of actomyosin contractility, we find that epithelial junctions show elastic behavior under low contractile stress, returning to their original lengths after contraction, but undergo irreversible deformation under higher magnitudes of contractile stress. Existing vertex-based models for the epithelium are unable to capture these results, with cell junctions displaying purely elastic or fluid-like behaviors, depending on the choice of model parameters. To describe the experimental results, we propose a modified vertex model with two essential ingredients for junction mechanics: thresholded tension remodeling and continuous strain relaxation. First, junctions must overcome a critical strain threshold to trigger tension remodeling, resulting in irreversible junction length changes. Second, there is a continuous relaxation of junctional strain that removes mechanical memory from the system. This enables pulsatile contractions to further remodel cell shape via mechanical ratcheting. Taken together, the combination of mechanosensitive tension remodeling and junctional strain relaxation provides a robust mechanism for large-scale morphogenesis.

Establishment of a high-resolution 3D modeling system for studying pancreatic epithelial cell biology in vitro

ObjectiveTranslation of basic research from bench-to-bedside relies on a better understanding of similarities and differences between mouse and human cell biology, tissue formation, and organogenesis. Thus, establishing ex vivo modeling systems of mouse and human pancreas development will help not only to understand evolutionary conserved mechanisms of differentiation and morphogenesis but also to understand pathomechanisms of disease and design strategies for tissue engineering. MethodsHere, we established a simple and reproducible Matrigel-based three-dimensional (3D) cyst culture model system of mouse and human pancreatic progenitors (PPs) to study pancreatic epithelialization and endocrinogenesis ex vivo. In addition, we reanalyzed previously reported single-cell RNA sequencing (scRNA-seq) of mouse and human pancreatic lineages to obtain a comprehensive picture of differential expression of key transcription factors (TFs), cell–cell adhesion molecules and cell polarity components in PPs during endocrinogenesis. ResultsWe generated mouse and human polarized pancreatic epithelial cysts derived from PPs. This system allowed to monitor establishment of pancreatic epithelial polarity and lumen formation in cellular and sub-cellular resolution in a dynamic time-resolved fashion. Furthermore, both mouse and human pancreatic cysts were able to differentiate towards the endocrine fate. This differentiation system together with scRNA-seq analysis revealed how apical-basal polarity and tight and adherens junctions change during endocrine differentiation. ConclusionsWe have established a simple 3D pancreatic cyst culture system that allows to tempo-spatial resolve cellular and subcellular processes on the mechanistical level, which is otherwise not possible in vivo.

Novel computational model of gastrula morphogenesis to identify spatial discriminator genes by self-organizing map (SOM) clustering

Deciphering the key mechanisms of morphogenesis during embryonic development is crucial to understanding the guiding principles of the body plan and promote applications in biomedical research fields. Although several computational tissue reconstruction methods using cellular gene expression data have been proposed, those methods are insufficient with regard to arranging cells in their correct positions in tissues or organs unless spatial information is explicitly provided. Here, we report SPRESSO, a new in silico three-dimensional (3D) tissue reconstruction method using stochastic self-organizing map (stochastic-SOM) clustering, to estimate the spatial domains of cells in tissues or organs from only their gene expression profiles. With only five gene sets defined by Gene Ontology (GO), we successfully demonstrated the reconstruction of a four-domain structure of mid-gastrula mouse embryo (E7.0) with high reproducibility (success rate = 99%). Interestingly, the five GOs contain 20 genes, most of which are related to differentiation and morphogenesis, such as activin A receptor and Wnt family member genes. Further analysis indicated that Id2 is the most influential gene contributing to the reconstruction. SPRESSO may provide novel and better insights on the mechanisms of 3D structure formation of living tissues via informative genes playing a role as spatial discriminators.

The role of transposable elements in the ecological morphogenesis under the influence of stress

In natural selection, insertional mutagenesis is an important source of genome variability. Transposons are sensors of environmental stress effects, which contribute to adaptation and speciation. These effects are due to changes in the mechanisms of morphogenesis, since transposons contain regulatory sequences that have cis and trans effects on specific protein-coding genes. In variability of genomes, the horizontal transfer of transposons plays an important role, because it contributes to changing the composition of transposons and the acquisition of new properties. Transposons are capable of site-specific transpositions, which lead to the activation of stress response genes. Transposons are sources of non-coding RNA, transcription factors binding sites and protein-coding genes due to domestication, exonization, and duplication. These genes contain nucleotide sequences that interact with non-coding RNAs processed from transposons transcripts, and therefore they are under the control of epigenetic regulatory networks involving transposons. Therefore, inherited features of the location and composition of transposons, along with a change in the phenotype, play an important role in the characteristics of responding to a variety of environmental stressors. This is the basis for the selection and survival of organisms with a specific composition and arrangement of transposons that contribute to adaptation under certain environmental conditions. In evolution, the capability to transpose into specific genome sites, regulate gene expression, and interact with transcription factors, along with the ability to respond to stressors, is the basis for rapid variability and speciation by altering the regulation of ontogenesis. The review presents evidence of tissue-specific and stage-specific features of transposon activation and their role in the regulation of cell differentiation to confirm their role in ecological morphogenesis.