The veins are cuticular structures that differentiate in precise patterns in insect wings. The genetic and molecular basis of vein pattern formation in Drosophila melanogaster is beginning to be unravelled with the identification and characterisation of the gene products that position the veins and direct their differentiation. Genes affecting the veins fall into two groups: transcriptional regulators that specify individual veins, and members of signalling pathways involved in patterning and differentiation of the veins. The elaboration of the vein (...) pattern is progressive in time and requires the coordinated activities of these signalling pathways and the transcription factors regulated by them. Although the network of genetic interactions that determine vein cell fate is well understood, very little is known about the cellular biology underlying the acquisition of vein histotype. BioEssays 25:443–451, 2003. © 2003 Wiley Periodicals, Inc. (shrink)

In three recent articles it was shown that β‐catenin is crucial for the establishment and the maintenance of the overall polarity and especially for the character ‘posterior’ in planarians. If the transcription of the β‐catenin gene was silenced by RNA interference, the overall polarity is lost, and in regenerating fragments a posterior blastema displays anterior characters by forming eyes and anterior ganglia. An attempt is made to integrate these new data, well‐known older observations, and observations from other regenerating systems into (...) an outline of a model that will clarify our current understanding as well as highlight areas still to be developed. (shrink)

The spontaneous organization of collective activities in animal groups and societies has attracted a considerable amount of attention over the last decade. This kind of coordination often permits group‐living species to achieve collective tasks that are far beyond single individuals' capabilities. In particular, a key benefit lies in the integration of partial knowledge of the environment at the collective level. In this contribution, we discuss various self‐organization phenomena in animal swarms and human crowds from the point of view of information (...) exchange among individuals. In particular, we provide a general description of collective dynamics across species and introduce a classification of these dynamics not only with respect to the way information is transferred among individuals but also with regard to the knowledge processing at the collective level. Finally, we highlight the fact that the individual’s ability to learn from past experiences can have a feedback effect on the collective dynamics, as experienced with the development of behavioral conventions in pedestrian crowds. (shrink)

Endosperm is emerging as a system for investigating the genetic control of wall placement and deposition in plant development. Development of endosperm progresses in distinct stages from a wall‐less syncytial stage to a cellular stage that is entirely typical of plant meristems where the division plane is predicted by a preprophase band of microtubules (PPB) and cytokinesis is completed by formation of a cell plate in association with a phragmoplast. Four developmentally different types of walls, each associated with a (...) different microtubule system, are sequentially produced: (1) free growing walls deposited in the absence of mitosis and phragmoplasts; (2) walls guided by cytoplasmic phragmoplasts formed adventitiously in the absence of mitosis; (3) walls formed by interzonal phragmoplasts in a cell cycle that lacks PPBs; and (4) wall deposition driven by interzonal phragmoplasts in a cycle that includes PPBs. We are using methods of differential screening to isolate cDNA clones corresponding in temporal and spatial pattern to the types of wall development, and are studying mutants for clues to the genetic controls of wall development. (shrink)

New research demonstrates that mechanics can serve as a means of information propagation in developing embryos. Historically, the study of embryonic development has had a dichotomy between morphogens and pattern formation on the one hand and morphogenesis and mechanics on the other. Secreted signals are the preeminent means of information propagation between cells and used to control cell fate, while physical forces act downstream or in parallel to shape tissue morphogenesis. However, recent work has blurred this division (...) of function by demonstrating that mechanics can serve as a means of information propagation. Adhesive or repulsive interactions can propagate through a tissue as a wave. These waves are rapid and directional and can be used to control the flux of cells through a developmental trajectory. Here, two examples are reviewed in which mechanics both guides and mediates morphogenesis and two examples in which mechanics intertwines with morphogens to regulate cell fate. (shrink)

Recent findings suggest that C. elegans, albeit displaying an invariant cell lineage for embryonic development, uses the same basic strategy for embryogenesis as other organisms. The early embryo is regionalised by cell‐cell interactions.

In 1972, we proposed a theory of biological pattern formation in which concentration maxima of pattern forming substances are generated through local self- enhancement in conjunction with long range inhibition. Since then, much evidence in various developmental systems has confirmed the importance of autocatalytic feedback loops combined with inhibitory interaction. Examples are found in the formation of embryonal organizing regions, in segmentation, in the polarization of individual cells, and in gene activation. By computer simulations, we have (...) shown that the theory accounts for much of the regulatory phenomena observed, including signalling to regenerate removed parts. These self- regulatory features contribute to making development robust and error-tolerant. Furthermore, the resulting pattern is, to a large extent, independent of the details provided by initial conditions and inducing signals. (shrink)

Almost all admit that there is beauty in the natural world. Many suspect that such beauty is more than an adornment of nature. Few in our contemporary world suggest that this beauty is an empirical principle of the natural world itself and instead relegate beauty to the eye and mind of the beholder. Guided by theological and scientific insight, the authors propose that such exclusion is no longer tenable, at least in the data of modern biology and in our view (...) of the natural world in general. More important, we believe an empirical aesthetics exists that can help guide experimental design and development of computational models in biology. Moreover, because theology and science can both contribute toward and equally profit from such an aesthetics, we propose that this empirical aesthetics provides the foundation for a living synergy between theology and science. (shrink)

The specification of specific and often unique fates to individual cells as a function of their position within a developing organism is a fundamental process during the development of multicellular organisms. The development of the Drosophila embryonic central nervous system serves as an excellent model system in which to clarify the developmental mechanisms that link pattern formation to cell-type specification. The Drosophila embryonic central nervous system develops from a set of neural stem cells termed neuroblasts. Neuroblasts arise (...) from the ectoderm in an invariant pattern, and each neuroblast acquires a unique fate based on its position within this pattern. Two groups of genes recently have been demonstrated to govern the individual fate specification of neuroblasts. One group, the segment polarity genes, enables neuroblasts that develop in different anteroposterior positions to acquire different fates. The second group, referred to as the columnar genes, ensures that neuroblasts that develop in different dorsoventral domains assume different fates. When integrated, the activities of the segment polarity and columnar genes create a Cartesian coordinate system that bestows unique fates to individual neuroblasts as a function of their position of formation within the ectoderm. BioEssays 1999;21:922–931. © 1999 John Wiley & Sons, Inc. (shrink)

The specification of specific and often unique fates to individual cells as a function of their position within a developing organism is a fundamental process during the development of multicellular organisms. The development of the Drosophila embryonic central nervous system serves as an excellent model system in which to clarify the developmental mechanisms that link pattern formation to cell-type specification. The Drosophila embryonic central nervous system develops from a set of neural stem cells termed neuroblasts. Neuroblasts arise (...) from the ectoderm in an invariant pattern, and each neuroblast acquires a unique fate based on its position within this pattern. Two groups of genes recently have been demonstrated to govern the individual fate specification of neuroblasts. One group, the segment polarity genes, enables neuroblasts that develop in different anteroposterior positions to acquire different fates. The second group, referred to as the columnar genes, ensures that neuroblasts that develop in different dorsoventral domains assume different fates. When integrated, the activities of the segment polarity and columnar genes create a Cartesian coordinate system that bestows unique fates to individual neuroblasts as a function of their position of formation within the ectoderm. BioEssays 1999;21:922–931. © 1999 John Wiley & Sons, Inc. (shrink)

One of the earliest and most‐fundamental pattern‐ formation events in embryonic development is endoderm and mesoderm specification. In sea urchin embryos, this process begins with blimp1 and wnt8 gene expression at the vegetal pole as soon as embryonic transcription begins. Shortly afterwards, wnt8/blimp1 expression spreads to the adjacent ring of mesoderm progenitor cells and is extinguished in the vegetal‐most cells. A little later, the ring of wnt8/blimp1 activity moves out of the mesoderm progenitors and into the neighboring endoderm (...) cells. Remarkably, this moving ring of gene expression has now been shown to be controlled entirely by transcriptional cis‐regulatory logic.1. BioEssays 30:412–417, 2008. © 2008 Wiley Periodicals, Inc. (shrink)

Although the segregation of mesenchyme into distinct aggregates is the first step in the development of a range of tissues that includes bones, somites, feathers and nephrons, we still know very little about the mechanisms by which this happens. There are two obvious types of explanation: first, that there are global pre‐patterns within the mesenchyme whose molecular expression leads to tissue fragmentation and, second, that the condensations arise spontaneously through the local morphogenetic abilities of the cells. The only known (...) mechanism for the latter possibility is cell traction and this paper suggests that current studies are compatible with traction playing a primary role in the formation of nephrogenic condensations in the developing kidney and the separation of somites, but not for the generation of feather rudiments where there is evidence of a prepattern of adhesivity. (shrink)

The paper addresses the formation of striking patterns within originally near-homogenous tissue, the process prototypical for embryology, and represented in particularly purist form by cut sections of hydra regenerating, by internal reorganisation of the pre-existing tissue, a complete animal with head and foot. The essential requirements are autocatalytic, self-enhancing activation, combined with inhibitory or depletion effects of wider range – “lateral inhibition”. Not only de-novo-pattern formation, but also well known, striking features of developmental regulation such as induction, (...) inhibition, and proportion regulation can be explained on this basis. The theory provides a mathematical recipe for the construction of molecular models with criteria for the necessary non-linear interactions. It has since been widely applied to different developmental processes. (shrink)

Significant progress in the molecular investigation of endogenous bioelectric signals during pattern formation in growing tissues has been enabled by recently developed techniques. Ion flows and voltage gradients produced by ion channels and pumps are key regulators of cell proliferation, migration, and differentiation. Now, instructive roles for bioelectrical gradients in embryogenesis, regeneration, and neoplasm are being revealed through the use of fluorescent voltage reporters and functional experiments using well‐characterized channel mutants. Transmembrane voltage gradients (Vmem) determine anatomical polarity (...) and function as master regulators during appendage regeneration and embryonic left‐right patterning. A state‐of‐the‐art recent study reveals that they can also serve as prepatterns for gene expression domains during craniofacial patterning. Continued development of novel tools and better ways to think about physical controls of cell‐cell interactions will lead to mastery of the morphogenetic information stored in physiological networks. This will enable fundamental advances in basic understanding of growth and form, as well as transformative biomedical applications in regenerative medicine. (shrink)

While many different mechanisms contribute to the generation of spatial order in biological development, the formation of morphogenetic fields which in turn direct cell responses giving rise to pattern and form are of major importance and essential for embryogenesis and regeneration. Most likely the fields represent concentration patterns of substances produced by molecular kinetics. Short range autocatalytic activation in conjunction with longer range “lateral” inhibition or depletion effects is capable of generating such patterns (Gierer and Meinhardt, 1972). Non-linear (...) reactions are required, and mathematical criteria were derived to design molecular models capable of pattern generation. The classical embryological feature of proportion regulation can be incorporated into the models. The conditions are mathematically necessary for the simplest two-factor case, and are likely to be a fair approximation in multi-component systems in which activation and inhibition are systems parameters subsuming the action of several agents. Gradients, symmetric and periodic patterns, in one or two dimensions, stable or pulsing in time, can be generated on this basis. Our basic concept of autocatalysis in conjunction with lateral inhibition accounts for self-regulatory biological features, including the reproducible formation of structures from near-uniform initial conditions as required by the logic of the generation cycle. Real tissue form, for instance that of budding Hydra, may often be traced back to local curvature arising within an initially relatively flat cell sheet, the position of evagination being determined by morphogenetic fields. Shell theory developed for architecture may also be applied to such biological processes. (shrink)

The control of pattern formation and the significance of gradients is reconsidered on the basis of the concept of cell sociology (which takes into account continuous exchange of information between cells and the possibility of autonomous progression in differentiation). Not all traits of a pattern are imposed by a single prepattern, which would be an organized molecular framework or a gradient. Patterns are unfolded in steps; these are readjustments of a cell population to intrinsic and extrinsic changes (...) in cell activities. Prepatterns are the various components of the programme of every readjustment and are established by information of various origins, which can be dissociated experimentally: determination (elementary social prepattern), pre-existing organization (antecedent pp.), surrounding cell populations (environmental pp.), position among other tissues (positional pp.) and the organization of inducers (imprinting pp.). Every transitory pattern formed during a readjustment serves as antecedent pp. during the next readjustment. Covert graded patterns result from various aspects of the social behaviour of cells (growth, aggregation, induction, cell renewal) and may serve as antecedent or imprinting prepatterns. They appear as water marks in the final patterns, or generate overt graded patterns. They also manifest themselves in temporal patterns, particularly in gradients of relative growth. (shrink)

The introductory personal remarks refer to my motivations for choosing research projects, and for moving from physics to molecular biology and then to development, with Hydra as a model system. Historically, Trembley’s discovery of Hydra regeneration in 1744 was the begin¬ning of developmental biology as we understand it, with passionate debates about preformation versus de novo generation, mechanisms versus organisms. In fact, seemingly conflicting bottom-up and top-down concepts are both required in combination to understand development. In modern terms, this means (...) analysing the molecules involved, as well as searching for physical principles underlying development within systems of molecules, cells and tissues. During the last decade, molecular biology has provided surprising and impressive evidence that the same types of mol¬ecules and molecular systems are involved in pattern formation in a wide range of organisms, including coelenterates like Hydra, and thus appear to have been “invented” early in evolution. Likewise, the features of certain systems, especially those of developmental regulation, are found in many different organisms. This includes the generation of spatial structures by the interplay of self-enhancing activation and “lateral” inhibitory effects of wider range, which is a main topic of my essay. Hydra regeneration is a particularly clear model for the formation of defined patterns within initially near-uniform tissues. In conclusion, this essay emphasizes the analysis of development in terms of physical laws, including the application of mathematics, and insists that Hydra was, and will continue to be, a rewarding model for understanding general features of embryogenesis and regeneration. -/- -/- . (shrink)

The Drosophila embryo provides a useful model system to study the mechanisms that lead to pattern and cell diversity in the central nervous system (CNS). The Drosophila CNS, which encompasses the brain and the ventral nerve cord, develops from a bilaterally symmetrical neuroectoderm, which gives rise to neural stem cells, called neuroblasts. The structure of the embryonic ventral nerve cord is relatively simple, consisting of a sequence of repeated segmental units (neuromeres), and the mechanisms controlling the formation and (...) specification of the neuroblasts that form these neuromeres are quite well understood. Owing to the much higher complexity and hidden segmental organization of the brain, our understanding of its development is still rudimentary. Recent investigations on the expression and function of proneural genes, segmentation genes, dorsoventral‐patterning genes and a number of other genes have provided new insight into the principles of neuroblast formation and patterning during embryonic development of the fly brain. Comparisons with the same processes in the trunk help us to understand what makes the brain different from the ventral nerve cord. Several parallels in early brain patterning between the fly and the vertebrate systems have become evident. BioEssays 26:739–751, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

Classical embryological studies have led to the suggestion that cells in developing tissues may be directed to differentiate along a particular pathway by the concentrations of molecules called morphogens. Studies of the slime mould Dictyostelium discoideum, which has a simple tissue pattern consisting of only two cell types, have revealed several molecules which may act as morphogens. Cyclic AMP and ammonia promote the formation of spores, while adenosine and a novel class of compounds called DIFs promote (...) the formation of stalk cells, the alternative cell fate. The constant proportions of the two differentiated cell types observed in this organism may result from a balance among the influences of these compounds. (shrink)

Early development of animal embryos begins from spatially distributed products of gene expression, i.e., gradients. While maternal and early zygotic genes form broad and/or terminal gradients, their direct targets appear later on as relatively narrow stripes, which foreshadow presumptive germ layers or future segments. Evidently, stripe expression of the zygotic genes is among the key mechanisms of embryo patterning. In this paper, known qualitative and quantitative models for the stripe formation are considered on the example of early embryogenesis of (...) Drosophila. The current model analysis emphasizes the role of spatial information flow in development. Discussion is given on frequent network motifs, pointing to spatial stripe formation solutions. (shrink)

The secondary vascular tissues (xylem and phloem) of woody plants originate from a vascular cambium and develop as radially oriented files of cells. The secondary phloem is composed of three or four cell types, which are organised into characteristic recurrent cellular sequences within the radial cell files of this tissue. There is a gradient of auxin (indole acetic acid) across both the cambium and the immediately postmitotic cells within the xylem and phloem domains, and it is believed that this (...) morphogen, probably in concert with other morphogenic factors, is closely associated with the determination and differentiation of the different cells types in each tissue. A hypothesis is developed that, in conjunction with the positional values conferred by the graded radial distribution of morphogen, cell divisions at particular positions within the cambium are sufficient to determine not only each of the phloem cell types but also their recurrent pattern of differentiation within each radial cell file. BioEssays 27: 533–541, 2005. © 2005 Wiley periodicals, Inc. (shrink)

Members of the astacin family of metalloproteinases such as human bone morphogenetic protein 1 (BMP‐1) have previously been linked to cell differentiation and pattern formation during development through a proposed role in the activation of latent growth factors of the TGF‐β superfamily. Recent finding(1) indicate that BMP‐1 is identical to pro‐collagen C‐proteinase, which is a metalloproteinase involved in extracellular matrix (ECM) formation. This observation suggests that a functional link may exist between astacin metalloproteinases, growth factors and cell (...) differentiation and pattern formation during development. Taken together, current studies indicate that BMP‐1 and possibly other astacin metalloproteinases are multifunctional enzymes that act directly on growth factors and the ECM. In combination, these dual actions would have profound effects on developmental processes. (shrink)

It has been convincingly shown that peptides play important roles in the regulation and maintenance of a variety of tissues and organs in living animals. However, little is known concerning the potential role of peptides as signaling molecules in developmental processes. In Hydra, there is circumstantial evidence that small diffusible molecules act as morphogens in the regulation of patterning processes. In order to view the entire spectrum of peptide signaling molecules, we initiated a project aiming at the systematic identification (...) of peptide signaling molecules in Hydra. In this review, we describe three peptide signaling molecules and one family of peptides that function as signaling molecules in the processes of axial pattern formation and neuron differentiation in Hydra. These peptides are produced by epithelial cells and are therefore termed “epitheliopeptides”. We discuss the importance of epitheliopeptides in developmental processes within a subset of hydrozoans. (shrink)

One of the major problems (or sometimes pseudo-problems) that archaeologists and historians encounter in the study of ancient cultures is the need to differentiate and to identify the sources of the various concepts, techniques, institutions, forms, designs, motifs, etc., that, at any given moment of time, form the constituent elements of the culture or cultural product to which they have turned their attention; or—to pose the question in its proper framework—to analyse the process of cultural formation inherent in the (...) subject of their study. Such considerations have a special significance for archaeologists, whose essential concern is with the often incomplete assemblages of material remains left behind by the cultures and civilizations of the past, and whose central task is to enumerate and reconstitute the structures and processes that were operative in the societies in question. The study of acculturation—culture change, cultural diffusion, “stimulus diffusion,” culture contact, etc.—has been part of the theoretical and empirical concerns of anthropologists and sociologists since some decades ago, and the subject of an old and now almost abandoned debate. While the terminology of the social sciences concerned with living societies can also be found in archaeological and historical discussion, such concerns have had inadequate application in the fields of archaeological and historical practice. What has dominated and, to a great extent, continues to dominate historical studies is what we might call “the ‘theory’ of influence” and its corollary, “the migration hypothesis.” Thus, it would not be an exaggeration to say that one of the leading aspects of the study of a past society or culture is the concern with the “parent” culture(s) which influenced it, or the search for the location of its “migratory origins.” While this is especially true of studies relating to the societies of the Third World, it is not exclusively so—as we see, for instance, in the case of European prehistory. The immediate epistemological sources of such approaches are not difficult to identify, being principally located in 19th century diffusionism and, as we shall see shortly, in colonial ideology. (shrink)

Retinoids are low molecular weight, lipophilic derivatives of vitamin A which have a profound effect upon the development of a diverse array of animals. Here, I review these effects on Invertebrates: a colonial hydroid, a colonial ascidian, and Vertebrates: the regenerating amphibian limb, the developing chick limb bud, the regenerating amphibian tail, the anteroposterior axis of the early embryo, the developing chick embryo skin. There is a striking uniformity of effect of retinoids on pattern formation when (...) applied to these diverse organisms. The majority react by being posteriorized in their development, although additional effects can also be seen. Several hypotheses which can explain these results are discussed along with the deduction that they lead to: retinoids may be components of a universal developmental mechanism or they may simply act in a similar way to alter a universal developmental mechanism. In either case the experimental analysis of retinoid effects on development has important implications for the evolution of developmental mechanisms. (shrink)

Claudins serve essential roles in regulating paracellular permeability properties within occluding junctions. Recent studies have begun to elucidate developmental roles of claudins within immature tissues. This work has uncovered an involvement of several claudins in determining tight junction properties that have an effect on embryonic morphogenesis and physiology. During zebrafish brain morphogenesis, Claudin‐5a determines the paracellular permeability of tight junctions within a transient neuroepithelial‐ventricular barrier that maintains the hydrostatic fluid pressure required for brain ventricular lumen expansion. However, the roles (...) of Claudins in development may well extend beyond being mere junctional components. Several post‐translational modifications of Claudins have been characterized that indicate a direct regulation by developmental signals. This review focuses on the involvement of Claudin‐5a in cerebral barrier formation in the zebrafish embryo and includes some speculations about possible modes of regulation. (shrink)

Morphogen gradient theories have enjoyed considerable popularity since the beginning of this century, but conclusive evidence for a role of morphogens in controlling multicellular development has been elusive. Recently, work on three secreted signalling proteins, Activin in Xenopus, and Wingless and Dpp in Drosophila, has stongly suggested that these proteins function as morphogens. In order to define a factor as a morphogen, it is necessary to show firstly, that it has a direct effect on target cells and secondly, that it (...) affects the development of target cells in a concentration‐dependent manner. With these criteria in mind, the evidence available for a variety of proposed morphogens is discussed. While the evidence is not conclusive in most of the cases considered, there is a strong case in favour of the three proteins mentioned above, which suggests that morphogens are potentially of general importance in controlling the development of multicellular organisms. (shrink)

In many animal species, the early development of the embryo follows a stereotypic pattern of cell cleavage, lineage allocation and generation of tissue asymmetry leading to delineation of the body plan with three primary embryonic axes. The mammalian embryo has been regarded as an exception and primary body axes of the mouse embryo were thought to develop after implantation. However, recent findings have challenged this view. Asymmetry in the fertilised oocyte, as defined by the position of the second polar (...) body and the sperm entry point, can be correlated with the orientation of the animal–vegetal and the embryonic–abembryonic axes in the preimplantation blastocyst. Studies of the pattern of morphogenetic movement of cells and genetic activity in the peri‐implantation embryo suggest that the animal–vegetal axis of the blastocyst might presage the orientation of the anterior–posterior axis of the gastrula. This suggests that the asymmetry of the zygote that is established at fertilisation and early cleavage has a lasting impact on the delineation of body axes during embryogenesis. BioEssays 23:508–517, 2001. © 2001 John Wiley & Sons, Inc. (shrink)

During mouse early development cell adhesion molecules are indispensable for the embryo organisation. A family of molecules probably involved in development is the transmembrane glycoprotein CD44 family, which exists in multiple isoforms. These are generated by alternative splicing of the pre‐mRNA, resulting in the enlargement of the extracellular part of the molecule. The standard form of CD44 is widely expressed in adult tissues and in embryos from day 9.5 post coitum onwards, while the numerous variant isoforms exhibit highly specialised (...) patterns of expression that are already in the egg cylinder at day 6.5 of development. In lymphohemopoiesis, specific variant isoforms also emerge at decisive differentiation stages. Although specific ligands for the variant region still await isolation, the highly organised expression of CD44 variant isoforms suggests they have a pivotal role in cellular interactions during early development, pattern formation and hemopoiesis. (shrink)

While evidence for the role of gap functions, particularly during development, has been mounting, it has remained largely correlative, linking structure with presumed functions. With the recent advent of functional antibodies raised to the junctional protein, however, it has become possible to study the role of gap junctions more directly. There is now considerable evidence indicating that they play a vital role in tissue pattern formation and differentiation by allowing direct cell‐to‐cell transfer of developmental signals or morphogens.

A theoretical model is presented for pattern formation in an epithelium. The epithelial model consists of a thin, incompressible, viscoelastic membrane on an elastic foundation (substrate), with the component cells assumed to have active contractile properties similar to those of smooth muscle. The analysis includes the effects of large strains and material nonlinearity, and the governing equations were solved using finite differences. Deformation patterns form when the cells activate while lying on the descending limb of their total (active (...) + passive) stress-stretch curve. Various one-dimensional and two-dimensional simulations illustrate the effects of spatial and temporal variations in passive stiffness, as well as the effects of foundation stiffness and stretch activation. The model can be used to examine the mechanical aspects of pattern formation in morphogenetic processes such as angiogenesis and myocardial trabeculation. (shrink)

Economist-philosopher Amartya Sen's writings on social and political issues have attracted wide audiences. Section 2 introduces his contributions on: how people reason as agents within society; social determinants of people's (lack of) access to goods and of the effective freedoms and agency they enjoy or lack; and associated advocacy of self-specification of identity and high expectations for ‘voice’ and reasoning democracy. Section 3 considers his relation to social theory, his tools for theorizing action in society, and his limited degree of (...) attention to work by sociologists and to capitalism and power structures. Section 4 characterizes a style marked by conceptual refinement, emphases on complexity and individuality, including personal individuality, and reformist optimism. Section 5 shows the features from Sections 3 and 4 at work in his conception of personhood that advocates freedom to make a reasoned composition of personal identity. Similarly, Section 6 addresses his conception of public reasoning and neglect of the sociology of democracy. It contrasts the ideal of a reasoning polity with features in many countries. Sen's programmes for critical autonomy in personhood and for reasoned politics play, nevertheless, a normic role, while his analytical formats help investigation of obstacles to more widespread agency, voice, and democratic participation. (shrink)

In this article the author argues that we need not just to ‘decolonize’ the Anthropocene but also to ‘desecularize’ it – to be aware that in the new age of the Earth we may be coeval with gods and spirits. Drawing particularly on the work of Gilles Deleuze, Félix Guattari and Georges Bataille, and using concepts from both thermodynamics and fluid dynamics, the author starts to develop an interdisciplinary theory of planetary spirit and use this to speak of both the (...) ‘laminar’ high gods of time that are being invoked to summon the story of Earth’s ongoing transformation into a canonical mythos, and the turbulent lower spirits of place which manifest particular, situated dynamics on an Earth crossed by interlocking gradients and flows of energy, value, power and entropy. He suggests that what might once have been distinct territorialized ‘cultures’ or ‘natures’ in which humans engaged in particular situated patterns of interaction with animals, spirits and other beings are increasingly being convened into a global multinatural system. (shrink)

Hydractinia echinata is a marine colonial hydroid, a relative of the more widely known Hydra. In contrast to Hydra, embryogenesis, metamorphosis and colony growth in Hydractinia are experimentally accessible and therefore, provide an ideal model system for investigating the biochemical basis of pattern formation. In particular, the processes involved in the transformation of the drop‐shaped freely swimming larva into a sessile tube‐shaped polyp are easily monitored, because this transfomation can be induced by application of various substances. Our results (...) indicate that the internal level of S‐adenosylmethionine (SAM), potentially the most important methyl donor in transmethylation processes, plays a key role in the onset of metamorphosis. It is also proposed that the internal level of SAM plays a pivotal role in the proportioning and spacing of polyps within the colony. (shrink)

Recent studies uncovered critical roles of the adhesion protein E‐cadherin in health and disease. Global inactivation of Cdh1, the gene encoding E‐cadherin in mice, results in early embryonic lethality due to an inability to form the trophectodermal epithelium. To unravel E‐cadherin's functions beyond development, numerous mouse lines with tissue‐specific disruption of Cdh1 have been generated. The consequences of E‐cadherin loss showed great variability depending on the tissue in question, ranging from nearly undetectable changes to a complete loss of tissue structure (...) and function. This review focuses on these studies and discusses how they provided important insights into E‐cadherin's role in cell adhesion, proliferation and differentiation, and its consequences for biological processes as epithelial‐to‐mesenchymal transition, vascularization, and carcinogenesis. Lastly, we present some perspectives and possible approaches for future research. (shrink)

Unraveling molecular and functional heterogeneity of niche cells within the developing endoderm could resolve mechanisms of tissue formation and maturation. Here, we discuss current unknowns in molecular mechanisms underlying key developmental events in pancreatic islet and intestinal epithelial formation. Recent breakthroughs in single‐cell and spatial transcriptomics, paralleled with functional studies in vitro, reveal that specialized mesenchymal subtypes drive the formation and maturation of pancreatic endocrine cells and islets via local interactions with epithelium, neurons, and microvessels. Analogous (...) to this, distinct intestinal niche cells regulate both epithelial development and homeostasis throughout life. We propose how this knowledge can be used to progress research in the human context using pluripotent stem cell‐derived multilineage organoids. Overall, understanding the interactions between the multitude of microenvironmental cells and how they drive tissue development and function could help us make more therapeutically relevant in vitro models. (shrink)

Megaprojects are implemented by different organisations, such as owners, consultants, and contractors. Gradually, these organisations and their connections can form business networks that influence both the market position of individual organisations and project performance. Previous research on large-scale projects mainly focused on static and homogeneous networks that were constructed by one individual project and/or carried out over one-off collaboration. However, this neglected the consideration of project network diversity, as well as repetitive, dynamic, cross-project coopetition relationship and long-term business networks formed (...) by key actors. Here, we chose Chinese skyscrapers over 300 meters that were built from 1996 to 2015 as typical megaproject cases and analysed the formation and evolution of megaproject business networks from the perspective of interorganisational coopetition. We identified the key actors involved and empirically studied their dynamic network positions over time. The main contributions of this study are threefold. First, we found that past collaboration experience has direct and dynamic impacts on the formation of megaproject business networks. Second, we identified key actors in the interorganisational business network and unveiled their dynamic positions with clear patterns. Third, we highlighted the temporal-spatial effect on the formation and development of business networks, alongside developments in the megaproject market. The findings of this study also provide practical applications for owners to choose collaboration partners and to build high-performance teams and for suppliers to enter and sustain the business in the megaprojects networks. (shrink)

In this work, I attempt to develop what I call a co-evolutionary model of scientific change, which I expect to afford a more balanced view on both the continuous and discontinuous aspects of scientific change. Supposing that scientific goals, methods and theories constitute the main components of scientific inquiry, I focus on the relationships among these components and their changing patterns. First of all, I identify explanatory power and empirical adequacy as primary goals of science and explore the possibility of (...) evaluating scientific goals. Then I try to bring out the major features of how the main components of science are related to each other. One major feature is that they mutually constrain each other, and as such each main component operates as a selective force on the other components. Another major feature is that the main components of science induce changes reciprocally, but with certain intervals. Other important features are the modes and tempos of changes in the main components of scientific inquiry. All these features together, I conclude, suggest that scientific change is evolutionary, as well as co-evolutionary. Finally I argue that this co-evolutionary model of scientific change does not yield to what I call the problems of circularity and scientific progress. (shrink)

Ensemble rehearsal in the European classical music tradition has a relatively homogenised format in which play-through, discussion, and practice of excerpts are employed to establish and agree on performance parameters of notated music. This research analyses patterns in such verbal communication during rehearsals and their development over time. Analysing two newly established ensembles that work over several months to a performance, it investigates the interaction dynamics of two closely collaborating groups and adaptation depending on task demands, familiarity with each other (...) and an upcoming deadline. A case study approach with two groups of five singers allowed in-depth exploration of individual behaviours and contributions; results are reported descriptively and supported by qualitative data. The results highlight changes over time that reflect the development of implicit interactions from explicit. They show a trajectory of opening up and closing down in terms of interactional flexibility, enabling members to significantly contribute to the group, followed by tightening the interaction to establish stability for performance. These findings and novel employment of T-pattern analysis contribute to the understanding of human group behaviour and interaction patterns leading to expert team performance. (shrink)

Knowledge of the patterns of location of retail stores in urban areas supports the development of effective urban planning and the reasonable allocation of commercial facilities. Using point of interest data and consumer survey data in three main commercial districts in Changchun, China, this study investigates the spatial structures of commercial districts and the patterns of distribution of retail stores to assess the determinants of the development of retail stores in commercial districts. Kernel density estimation, nearest neighbor index, and Pearson’s (...) correlation analysis were used for this study. The following conclusions are drawn. The spatial distribution of retail stores in Changchun commercial districts generates the coexistence of a concentration in the core area and diffusion in the peripheral area. The emergence of shopping malls has challenged the traditional single-center structure, resulting in the transformation of commercial districts from single-center to multicenter layouts, while also producing a hierarchical trend in development. The Chongqing Road and Hongqi Street commercial districts have a relatively high spatial concentration of retail stores. Retail stores in Guilin Road exhibit distinct characteristics, namely, stores selling textiles, clothing, and daily necessities show the highest concentration, and food, beverage, and tobacco outlets as well as integrated stores show the lowest concentration. The selected locations of the differing categories of stores on Chongqing Road strongly correlate, and textile, clothing, and daily necessity stores show a high correlation with other retail categories. Four main factors affect the development and spatial layout of retail in the commercial districts. First, the interaction between consumer behavior and location choice in retail stores promotes the evolution of retail formats and trends in the development of comprehensive, specialized, and hierarchical retail commercial spaces. Second, the retail format determines the spatial layouts and the historical inheritance of the format. Third, governmental planning and policies lead to the agglomeration and diffusion of commercial activities in different areas. Fourth, such spatial clustering effects are an external driving factor for integration and aggregation among retail formats. (shrink)

This paper articulates an account of causation as a collection of information-theoretic relationships between patterns instantiated in the causal nexus. I draw on Dennett’s account of real patterns to characterize potential causal relata as patterns with specific identification criteria and noise tolerance levels, and actual causal relata as those patterns instantiated at some spatiotemporal location in the rich causal nexus as originally developed by Salmon. I develop a representation framework using phase space to precisely characterize causal relata, including their degree (...) of counterfactual robustness, causal profiles, causal connectivity, and privileged grain size. By doing so, I show how the philosophical notion of causation can be rendered in a format that is amenable for direct application of mathematical techniques from information theory such that the resulting informational measures are causal informational measures. This account provides a metaphysics of causation that supports interventionist semantics and causal modeling and discovery techniques. (shrink)

The cuticular surface of Drosophila is decorated by parallel arrays of polarized structures such as hairs and sensory bristles; for example, on the wing each cell produces a distally pointing hair. These patterns are termed [tissue polarity]. Several genes are known whose activity is essential for the development of normal tissue polarity. Mutations in these genes alter the orientation of the hair or bristle with respect to neighboring cells and the body as a whole. The phenotypes of mutations in these (...) genes allows them to be placed in three phenotypic groups. Based on their behavior in genetic mosaics, it has proved possible to determine that individual genes are required either for the generation of an intercellular polarity signal and/or the transduction of that signal to the cytoskeleton. (shrink)

Despite the extensive literature describing the somatic genetic alterations in cancer cells, the precise origins of cancer cells remain controversial. In this article, I suggest that the etiology of cancer and the generation of genetic instability in cancer cells should be considered in the light of recent findings on both the stochastic nature of gene expression and its regulation at tissue level. By postulating that gene expression is intrinsically probabilistic and that stabilization of gene expression arises by cellular interactions in (...) “morphogenetic fields”, development and cellular differentiation can be rethought in an evolutionary perspective. In particular, this article proposes that disruptions of cellular interactions are the initial source of abnormal gene expression in cancer cells. Consequently, cancer phenotypes such as genetic and epigenetic instabilities, and also the presence of cells with stem cell‐like properties, may result from inaccurate and aberrant patterns of gene expression generated by microenvironmental alterations. Finally, the therapeutic implications of this view are discussed. BioEssays 27:1277–1285, 2005. © 2005 Wiley Periodicals, Inc. (shrink)

: In this paper I will focus on the notion of “dominant patterns”, as revealed by the recently discovered typescript of what we can assume to be Dewey’s fragmentary and incomplete preliminary lecture notes for the Lecture Series on Social and Political Philosophy. I will show that the way the notion of “dominant patterns” is dealt with in the text of the lecture notes is not only consistent with the conceptual content of the whole series of the Lectures in China (...) as published by R. W. Clopton and Tsuin-Chen, but also gives us further arguments to appreciate the centrality of this question to the development of Dewey’s philosophical project during this period. In particular, I will argue that a comparative reading of the lecture notes and of the Lectures in China allows us to appreciate the central role dominant patterns play for Dewey’s understanding of social groupings as embodying habitual patterns of action and the way habit formation shapes and gives content to the interests that groups identify with and are identified by in social practices. Secondly, I will argue that such a comparative reading allows us to appreciate how in the lecture series Dewey has developed the notion of dominant patterns into a theory of social domination which is basically described in terms of habitualized recognitive relations. Hence, the discovery of the lecture notes is also very helpful in deepening our understanding of the Deweyan approach to the question of social recognition – and in particular of the dynamics of institutional recognition and its ideological function – and how it relates to habitualized patterns of dominant-subservient relations. -/- domination, habits, social philosophy, struggle for recognition, conflict, groups, hegemony, power, institutionalization. (shrink)