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Fetal development seen as work the work of an intelligent artisan

structure of an animal cell/royroydeb (CC BY-SA 4.0)

The balance of physical forces that shape developing embryos, moving not quite like liquids or solids but somewhere in between, is compared by a researcher to an artist at work:

Far more than expected, according to results published in Nature earlier this month. For the first time, using a series of clever, state-of-the-art techniques, scientists have uncovered the balance of physical forces that shapes tissues in developing embryos. And the process they’ve identified has turned out to be surprisingly familiar — not for its role in biology, but for its part in revolutionizing how physicists understand a slew of materials ranging from toothpaste to glass…

Campàs and his colleagues measured all three properties in different regions of the developing zebra fish embryo, from head to tail, and showed that the way the cells get packed and change their behavior also fits the theory of jamming. Before, scientists had thought that cells essentially fine-tuned forces, applying more stress here, less there, to guide everything into place like a sculptor molding clay. “Instead,” Campàs said, “it’s more like blowing glass,” like liquefying a part that needs sculpting and then letting its new form set.Jordana Cepelewicz, “‘Traffic Jams’ of Cells Help to Sculpt Embryos” at Quanta

Like blowing glass? Biology’s language is poorly adapted to Darwinism.

Technically, the researcher means “blowing glass but there is no glassblower.” But most people can’t say that and still feel that they are making sense. And maybe they aren’t. But they can certainly make life difficult for any who challenge them.

See also: Fish turn into fluids, which aids embryo development

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Pleiotropic signaling pathways must somehow engender specific cellular responses. for the circular visceral muscles, despite superficial similarities, a significantly different specification mechanism is at work. Our findings fit with a growing body of data that point to a complex interplay between the Ras pathway, ETS transcription factors, and enhancer binding as a crucial mechanism for determining unique responses to Ras signaling. Distinct roles and requirements for Ras pathway signaling in visceral versus somatic muscle founder specification Yiyun Zhou, Sarah E. Popadowski, Emily Deutschman, Marc S. Halfon Development 2019 146: dev169003 doi: 10.1242/dev.169003 PeterA
The acquisition of cellular identity during development depends on precise spatiotemporal regulation of gene expression, with combinatorial interactions between transcription factors, accessory proteins and the basal transcription machinery together translating complex signaling inputs into appropriate gene expression outputs. Genetic and epigenetic mechanisms together produce the spatiotemporal gene expression dynamics that drive accurate and robust developmental transitions. Although it is known that chromatin looping can physically coordinate the transcriptional complexes assembled at enhancers across a locus with the promoter-proximal complexes that orchestrate RNA pol II pause and release, the mechanisms by which these two layers of regulation are actually integrated to fine-tune gene expression dynamics during development are just beginning to be elucidated the collaborative action of an opposing activator-repressor pair establishes repressive complexes that collaborate with the pol II pausing machinery to create a locus-wide poised state that both prevents spurious gene activation and ensures timely induction of expression following signaling cues. analogous to the use of conflicting epigenetic marks to poise RNA pol II, the inherent conflict of co-occupancy by an activator-repressor pair such as Pnt-Yan establishes an exquisitely sensitive and dynamic repressive mechanism that confers robustness to developmental gene expression regulation. Collaborative repressive action of the antagonistic ETS transcription factors Pointed and Yan fine-tunes gene expression to confer robustness in Drosophila Jemma L. Webber, Jie Zhang, Alex Massey, Nicelio Sanchez-Luege, Ilaria Rebay Development 2018 145: dev165985 doi: 10.1242/dev.165985 PeterA
The more we know about developmental biology, more is there for us to learn. Do we see the light at the end of the tunnel or it’s a train coming our way? How long would it take for us to realize that we’re dealing with complex functionality and functional complexity at the same time? Developmental biology should remain at the top of research priority. Evo-devo beyond microevolutionary adaptations is just a fantasy. That’s why most evo-devo papers will remain just devo papers, sprinkled with ocasional “politically correct” neodarwinian jargon. Time to wake up and smell the flowers. PeterA
“important unanswered questions related to multiple aspects of ERK dynamics and function. There are a number of issues that need to be resolved to explain how a single pathway, like the ERK pathway, can have such diverse effects during embryogenesis. We need a quantitative understanding of signal initiation, as there may be important ligand-receptor dynamics that shape the inputs to signaling pathways. The interpretation of incoming signals ultimately determines the downstream transcriptional responses. In many cases, it is still not known how active ERK interacts with downstream targets and ultimately alters their functions. Moreover, we must now quantify the context-dependent limits on signaling parameters such as spatial extent, duration and signaling strength to understand the origins of the remarkable robustness observed in differentiating tissues. Accomplishing these tasks is crucial for laying down the foundation for a quantitative picture of developmental ERK signaling and is impossible without well-studied experimental systems” Outstanding questions in developmental ERK signaling Aleena L. Patel, Stanislav Y. Shvartsman Development 2018 145: dev143818 doi: 10.1242/dev.143818 PeterA
“When presented with the large and steadily growing number of publications about ERK signaling, one may wonder whether we have already reached saturation and satisfied our curiosity about this highly conserved signaling system. After all, the majority of publications revolve around the same set of components and frequently pose very similar questions about the specificity, dynamics and robustness of ERK regulation and function. “ “we are still far from answering these questions” “the field is in crucial need of new techniques for visualizing and manipulating ERK signaling in vivo.” “ new tools to manipulate ERK signaling inputs in vivo are much needed ” “we might have to revisit the current models of cell fate specification in this extensively studied model of inductive ERK signaling.” “Many of the unanswered questions that we highlight with examples of inductive ERK signaling must be asked for the handful of other signaling systems that together generate complexity during development” “This system may be an ideal application of dual-input optogenetics to study how the combinatorial actions of signaling systems control multiple aspects of tissue patterning and morphogenesis ” Outstanding questions in developmental ERK signaling Aleena L. Patel, Stanislav Y. Shvartsman Development 2018 145: dev143818 doi: 10.1242/dev.143818 PeterA
“Animal development relies on a small set of signaling systems acting in combination to guide pattern formation and tissue morphogenesis (Martinez-Arias and Stewart, 2002). By now we have a nearly complete parts lists of at least the core elements of these systems and are studying them at multiple levels of biological organization. However, we are still far from understanding what makes signaling systems robust and how a single pathway can have such diverse outputs, and also from being able to explain how relatively subtle perturbations to signaling transduction can cause developmental abnormalities (Tidyman and Rauen, 2012; Rauen, 2013).“ Outstanding questions in developmental ERK signaling Aleena L. Patel, Stanislav Y. Shvartsman Development 2018 145: dev143818 doi: 10.1242/dev.143818 PeterA
The modern synthesis (neo-Darwinian theory) is visibly bankrupt, but still pretending to have some assets to hang on for awhile. PeterA
At the end of the day evo-devo is just a “wishful thinking” way of approaching developmental biology from a convoluted angle. Perhaps valid up to certain point regarding microevolutionary adaptations, but empty-handed for delivering macroevolutionary promises that make sense. Simply pathetic. What we really need is more research in developmental biology. Why? Well, because... we’re far from understanding it well. Outstanding questions in developmental ERK signaling Aleena L. Patel, Stanislav Y. Shvartsman Development 2018 145: dev143818 doi: 10.1242/dev.143818 “The extracellular signal-regulated kinase (ERK) pathway leads to activation of the effector molecule ERK, which controls downstream responses by phosphorylating a variety of substrates, including transcription factors. Crucial insights into the regulation and function of this pathway came from studying embryos in which specific phenotypes arise from aberrant ERK activation. Despite decades of research, several important questions remain to be addressed for deeper understanding of this highly conserved signaling system and its function. Answering these questions will require quantifying the first steps of pathway activation, elucidating the mechanisms of transcriptional interpretation and measuring the quantitative limits of ERK signaling within which the system must operate to avoid developmental defects.” PeterA
Where’s (macro) evo in evo-devo? Seriously. Hand-waving incoherent just-so fairytales doesn’t seem to do the trick. “Based on our findings, we suggest that travelling waves may have evolved in response to shallow morphogen gradients and gene expression noise. These two factors may thus also be responsible for the observed differences between different species within both the arthropod and chordate phyla.“ Around the clock: gradient shape and noise impact the evolution of oscillatory segmentation dynamics Renske M. A. VroomansEmail authorView ORCID ID profile, Paulien Hogeweg and Kirsten H. W. J. ten Tusscher EvoDevo20189:24 https://doi.org/10.1186/s13227-018-0113-2 PeterA
Where’s the evo in evo-devo? Where’s the “how” besides the interesting “what”? “Morphogen signalling represents a key mechanism of developmental processes during animal development. Previously, several evolutionary conserved morphogen signalling pathways have been identified, and their players such as the morphogen receptors, morphogen modulating factors (MMFs) and the morphogens themselves have been studied. MMFs are factors that regulate morphogen distribution and activity. The interactions of MMFs with different morphogen signalling pathways such as Wnt signalling, Hedgehog (Hh) signalling and Decapentaplegic (Dpp) signalling are complex because some of the MMFs have been shown to interact with more than one signalling pathway, and depending on genetic context, to have different, biphasic or even opposing function.” “Expression profiles reveal a high degree of diversity, suggesting that MMFs may represent highly evolvable nodes in otherwise conserved gene regulatory networks. Conserved aspects of MMF expression, however, appear to concern function in segmentation and limb development, two of the key topics of evolutionary developmental research.” “most of the MMFs are expressed in diverse patterns suggesting that they may represent a group of genetic factors that have been free to evolve and thus may contribute to species- and clade-specific morphological features.” “Regulation of morphogen function is complex and relies on the interaction of multiple factors, many of which, like the MMFs investigated here, have multiple functions, can interact with multiple different morphogens, and can have opposing effects based on genetic context and morphogen concentration. Differences in morphogen function have been reported based on genetic context between species, but also in a given species. This high degree of regulatory flexibility of morphogen function is reflected by the expression patterns of the MMFs. The level of conservation is relatively low as suggested by divergent expression patterns in the different species. Therefore, this study cannot serve as anything other than a first step into investigating MMFs in these emerging panarthropod model species. Subsequent studies are needed to investigate gene function by means of knock-down experiments. Such experiments are currently not possible for any onychophoran or myriapod species, but can be conducted in the spider Parasteatoda and the beetle Tribolium (e.g. [104, 105]).” “Despite the above caveats, our data clearly indicate involvement of MMFs in morphogen signalling, and that these factors partly play roles in limb development and body segmentation, two of the main research field of (pan)arthropod evolutionary developmental research (EvoDevo).“ Gene expression analysis of potential morphogen signalling modifying factors in Panarthropoda Mattias Hogvall, Graham E. Budd, and Ralf Janssen EvoDevo. 2018; 9: 20. doi: 10.1186/s13227-018-0109-y https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6162966/pdf/13227_2018_Article_109.pdf PeterA
“Fetal Development Seen As Work The Work Of An Intelligent Artisan“ “Fetal Development Seen As The Work Of An Intelligent Artisan“ “As Work The Work “ ? PeterA
Oh, no. Random atoms at work. They're cunning, you know. Only the A/Mats can recognise their machinations. Axel

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