From heterogeneous morphogenetic fields to homogeneous regions as a step towards understanding complex tissue dynamics

ABSTRACT Within developing tissues, cell proliferation, cell motility and other cell behaviors vary spatially, and this variability gives a complexity to the morphogenesis. Recently, novel formalisms have been developed to quantify tissue deformation and underlying cellular processes. A major challenge for the study of morphogenesis now is to objectively define tissue sub-regions exhibiting different dynamics. Here, we propose a method to automatically divide a tissue into regions where the local deformation rate is homogeneous. This was achieved by several steps including image segmentation, clustering and region boundary smoothing. We illustrate the use of the pipeline using a large dataset obtained during the metamorphosis of the Drosophila pupal notum. We also adapt it to determine regions in which the time evolution of the local deformation rate is homogeneous. Finally, we generalize its use to find homogeneous regions for cellular processes such as cell division, cell rearrangement, or cell size and shape changes. We also illustrate it on wing blade morphogenesis. This pipeline will contribute substantially to the analysis of complex tissue shaping, and the biochemical and biomechanical regulations driving tissue morphogenesis.

Dynamic structures in evo-devo: From morphogenetic fields to evolving organisms

Evolution does not act on particular stages in the life of an organism. Instead, it alters developmental processes and life cycles in response to environmental conditions to bring about phenotypic change. The structure of these processes determines evolvability, the capacity of organisms to adapt. These structures are intrinsically dynamic. The organisational principles underlying organisms and the morphogenetic fields that constitute their ontogeny actively remodel themselves over time. How this occurs, and how it influences the rate and direction of evolutionary change, are central questions for biology. They lead us to fundamentally reconsider the active role of organisms in evolutionary change, which raises the possibility of a new agent-based theory of evolution in which organisms and their perceived environments co-construct each other in a radically innovative dialectic dynamic.

From heterogenous morphogenetic fields to homogeneous regions as a step towards understanding complex tissue dynamics

Within developing tissues, cell proliferation, cell motility, and other cell behaviors vary spatially, and this variability gives a complexity to the morphogenesis. Recently, novel formalisms have been developed to quantify tissue deformation and underlying cellular processes. A major challenge for the study of morphogenesis now is to objectively define tissue sub-regions exhibiting different dynamics. Here we propose a method to automatically divide a tissue into regions where the local deformation rate is homogeneous. This was achieved by several steps including image segmentation, clustering, and region boundary smoothing. We illustrate the use of the pipeline using a large dataset obtained during the metamorphosis of the Drosophila pupal notum. We also adapt it to determine regions where the time evolution of the local deformation rate is homogeneous. Finally, we generalize its use to find homogeneous regions for the cellular processes such as cell division, cell rearrangement, or cell size and shape changes. We also illustrate it on wing blade morphogenesis. This pipeline will contribute substantially to the analysis of complex tissue shaping and the biochemical and bio-mechanical regulations driving tissue morphogenesis.

White Sangomas: the manifestation of Bantu forms of shamanic calling among whites in South Africa

South Africa is one of some few countries where sizeable communities of black and white people live together which have preserved their distinct cultures. Other than in the Americas, South Africa has a black majority with the Bantu African languages and cultural institutions largely preserved – and it has the most marked history of segregation. Thus few elements of Bantu cultures have been adopted by white South Africans. Yet in recent years a core element of Bantu culture, the shamanism and mediumism of the “Sangomas”, has begun to manifest itself among whites in South Africa – in the characteristic forms of such “calling”. Interestingly this has not happened by “cultural learning” in significant cases. This requires a different model of explanation. In this essay Rupert Sheldrake’s theory of “morphogenetic fields” will be applied to this phenomenon and its implications considered.

Racial diferences in tooth crown size gradients within morphogenetic fields

Summary: Teeth are arranged in morphogenetic fields,which are anatomical locations in the jaws that regulate tooth types, namely incisors, canines,premolars, and molars in primates. Each field is composed of two or three teeth (except for theisolated canine), and there is a characteristic size gradient corresponding to directionality withineach field, generally with the mesial tooth being larger and more stable than the distal, variabletooth. Focus of the present study is on racial differences in the steepness of these mesial-distalcrown size gradients. Groups with “steep” gradients have appreciable size reduction from the stableto the variable tooth, while other groups, with “shallow” gradients, have more similar crowndimensions across a field. This worldwide survey of published studies (107 groups) assessedintergroup (rather than inter-individual) variation in size gradients calculated for the incisors,premolars, and molars in each arcade. Caucasians tend to have the steepest gradients; aboriginalAustralians tend to have the most shallow gradients. Correlations among the gradients of differenttooth types are significant statistically, but modest, suggesting that microevolutionary factorshave influenced the gradients of different groups differently. Of the seven geographic groupingsevaluated, Amerindians are the most distinctive. We briefly speculate on the nature of thedevelopmental molecular signaling that determines these gradients. Key words: Tooth size.Odontometrics. Morphogenetic fields. Human variation. humana.

Morphozoic, Cellular Automata with Nested Neighborhoods as a Metamorphic Representation of Morphogenesis

A cellular automaton model, Morphozoic, is presented. Morphozoic may be used to investigate the computational power of morphogenetic fields to foster the development of structures and cell differentiation. The term morphogenetic field is used here to describe a generalized abstraction: a cell signals information about its state to its environment and is able to sense and act on signals from nested neighborhood of cells that can represent local to global morphogenetic effects. Neighborhood signals are compacted into aggregated quantities, capping the amount of information exchanged: signals from smaller, more local neighborhoods are thus more finely discriminated, while those from larger, more global neighborhoods are less so. An assembly of cells can thus cooperate to generate spatial and temporal structure. Morphozoic was found to be robust and noise tolerant. Applications of Morphozoic presented here include: 1) Conway's Game of Life, 2) Cell regeneration, 3) Evolution of a gastrulation-like sequence, 4) Neuron pathfinding, and 5) Turing's reaction-diffusion morphogenesis.