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Thursday, March 30, 2023

To convention or to unconference… a little bit report of the Institut Pasteur/Qbio symposium MeMoDEvo (Mechanics Morphogenesis Growth and Evolution) and its experimental format

The range and complexity of form in uni- and multicellular organisms has lengthy been a supply of fascination and interrogation. Because the seminal work of D’Arcy Wentworth Thompson, the examine of the emergence of form, so referred to as morphogenesis, has been strongly influenced by the idea of emergence whereby advanced sample/form could be defined by comparatively easy mechanical and mathematical legal guidelines. In parallel, the fast progress of the biochemical characterisation of the regulators of cell signalling has opened the chance to match developmental applications and dissect the molecular foundation of evolution. But, how mechanics and mathematical legal guidelines might constrain the evolution of latest shapes and morphogenesis has solely come again to mild just lately. For 2 days (12 and thirteenth of December 2022), the symposium MeMoDEvo going down in Institut Pasteur in Paris tried to debate this concern by gathering interdisciplinary audio system and contributors on web site and on-line and organising two mornings of open discussions. The discussions and talks coated a wide range of approaches (arithmetic, fluid mechanics, mushy matter physics, genetics, evolution, developmental biology, epistemology…) showcasing a various set of organisms, from mammals, birds, reptiles, bugs,  choanoflagellates, crops, algae, yeasts, and micro organism.

This totally hybrid assembly gathered near 100 contributors on web site (principally from Europe) and 100 contributors on-line and its uncommon format led to very attention-grabbing discussions and interactions. The convention was attainable due to the help of a number of sponsors, together with The Firm of Biologists, the French Society of Developmental Biology, the Qbio initiative in Pasteur and the Pasteur Institute, in addition to the DIM Elicit initiative

“Unconference” morning periods and open discussions

The most effective components of conferences that we had been lacking over the previous two years is the free time and open discussions in between periods. We subsequently devoted a big period of time to open discussions and spherical tables throughout mornings with a subset of contributors and the audio system (roughly 40 folks). In keeping with the spirit of the assembly, we relied on a combination of programmed schedule and self-organization.This partaking time concerned first a fast introduction by every participant on their background and curiosity, adopted by open discussions on the primary day. This was adopted the following morning by three spherical desk discussions.

The primary spherical desk addressed constraints on the evolution of form and find out how to reveal them experimentally. How can an organ evolve from one form into one other? Are there any limitations concerning form innovation? The dialogue included the excellence between pure bodily/setting constraints and developmental hard-wired constraints associated to the evolution historical past of the organism. Exploring the distribution of organ form within the morphospace (utilizing landmarks and dimension discount) utilizing intra and inter-specific variability can reveal such constraints by non-occupied zones within the morphospace. The reason for these unoccupied areas could be both selective strain or funnelling of evolutionary change by developmental constraints. A mix of description of pure variation and exploration of form variability within the laboratory (together with direct perturbation of developmental processes by mutagenesis and experimental evolution) might assist to disentangle them. The dialogue ended (as anticipated) with extra questions than solutions concluding on the  mysterious instances of abrupt form evolution/innovation which need to bypass sturdy developmental constraints whereas sustaining correct adaptation.

The second dialogue was centred on the emergence of multicellularity evaluating a wide range of organisms which mix single cell and mixture life mode. By evaluating the mode of multicellularity (clonal/aggregative), the alerts/circumstances triggering aggregation or dissociation and the elements that may construction and organise the aggregates (adhesion, contractility, matrix), a really advanced footage emerge with all form of mixture of methods present in nature, outlining once more the range of evolutionary path resulting in multicellularity (see the desk under summarising the comparability).

Lastly, the final dialogue was centered on sharing expertise with varied methodologies for mechanical simulation of tissues, starting from steady mannequin, object based mostly modeling and finite aspect modeling.

Afternoon hybrid periods

The 2 afternoon periods had been following a extra traditional convention format alternating speak on web site and on-line with an hybrid crowd. You will discover hyperlinks linked to the printed works that had been mentioned throughout these periods (preprint and peer-reviewed articles). The assembly was launched by Thibaut Brunet (Institut Pasteur) who made a fast historic overview of the evolution of approaches to grasp growth and the varied phases that delivered to the entrance stage the position of mechanical constraints in form evolution and its current rejuvenation. The primary speak was then given by Bruno Vellutini from Max Planck CBG who illustrated how the looks of the cephallic furrow throughout evolution in Drosophila embryo might have helped to buffer mechanical constraints generated by ectoderm actions and cell division throughout gastrulation. Marie Monniaux, from the ENS RDP lab in Lyon, described the morphogenesis of petunia petals and sepals and how the comparability of mutants can assist to disentangle the regulation of progress and form by totally different epidermal layers. Jean-Léon Maître from Institut Curie then offered a quantitative comparability of the mechanisms of embryo compaction in several mammals, illustrating how qualitatively comparable mechanisms can but depend on fairly totally different absolute mechanical properties. Arghyadip Mukherjee from the ENS in Paris described how topological transition by means of totally different modes of epithelial fusion can assist to explain neuroepithelial organoid form evolution. This was adopted by Jose Bico, from the ESPCI, who illustrated how residing matter can be utilized as an inspiration for producing advanced inflatable form based mostly on native variations of inflation/progress (with a reside illustration on stage with cup, saddle or helix form producing gadgets). We then got here again to bugs with Steffen Lemke (from Heidelberg College) who in contrast gastrulation between totally different fly species (together with Drosophila) and recognized important genes enough to clarify a number of morphogenetic innovation in flies (together with the mode of mesoderm invagination, cell elongation and the requirement for cephalic furrow). We then completed the primary afternoon session with Annemiek Cornelissen from LMSC laboratory in Université Paris Cité,  who used cracking concept and differential mechanical properties of tissues to clarify the morphogenesis of jellyfish canal community.

The second afternoon session began with Arkhat Abzanof  from Imperial School London who illustrated the ability of morphospace evaluation for the understanding of craniofacial form evolution in vertebrates (from bats, Darwin finches and crocodiles). He was then adopted by Hélène de Maleprade from Sorbonne Université who described varied collective and single cell swimming methods in Chlamydomonas, Volvox and Gonium. We then had an internet speak from Lakshminarayanan Mahadevan from Harvard college describing fluid mechanics mannequin of multicellular actions occurring throughout chick gastrulation and how the variation of preliminary circumstances can recapitulate totally different modes of gastrulation throughout Vertebrates. This was adopted by conceptual and theoretical concerns from Ana Soto and Maël Montevil from the Centre Cavaillès on the idea of autonomy in residing methods and the definition of core ideas (default state, variation and organisation) permitting correct understanding of a residing system. We then got here again to crops with Etienne Couturier from the LMSC lab who utilized the Lockhart mannequin (describing cell progress as a perform of turgor strain and viscoelastic deformation of the wall) to explain the dynamics of maïze root progress in opposition to a bodily impediment. This was then adopted by an internet speak from Peter Yunker from Georgia Tech describing his work in collaboration with Will Ratcliff on the ‘long-term experimental evolution’ of multicellular growth in yeast. Remarkably, experimentally developed yeast colonies had been just lately reported to have acquired macroscopic sizes after years of choice within the lab. The speak dissected the mobile and bodily foundation of this transition, which turned out to depend on mutations selling elongated cell form and lowering the mechanical stress that may trigger colony fission. The assembly ended with a broad theoretical view of the evolution of multicellularity and morphogenetic innovation by Stuart Newman from New York Medical School, introducing the idea of dynamical sample modules (integrating gene regulatory community and related bodily/spatial constraints) and their contribution to developmental and morphological innovation throughout evolution.

Conclusion: a full of life and environmentally pleasant format selling discussions and connections

The assembly managed to assemble a various crowd resulting in a really refreshing and eclectic program. The relative “self-organisation” of the morning periods truly led to very vivid interactions and deepening of the questions associated to the assembly matter. All of the contributors got here to conclusion that we must be prepared for a MeMoDEvo#2 ! Of be aware, the symposium was the residing proof of the chance to organise a various, inclusive and really dynamics assembly whereas limiting environmental influence. Each audio system used the practice to commute to the assembly and we may but gathered a various crowd from Europe in addition to many on-line attendees and audio system from different continents. Regardless of the same old technical hiccup related to the hybrid format, we will solely advocate the applying of the identical recipe !

Romain Levayer, Thibaut Brunet, Katja Heuer and Roberto Toro, organisers of the MeMoDEvo symposium.

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