Annual review of cell and developmental biology最新文献

In 1952, Alan Turing published the reaction-diffusion (RD) mathematical framework, laying the foundations of morphogenesis as a self-organized process emerging from physicochemical first principles. Regrettably, this approach has been widely doubted in the field of developmental biology. First, we summarize Turing's line of thoughts to alleviate the misconception that RD is an artificial mathematical construct. Second, we discuss why phenomenological RD models are particularly effective for understanding skin color patterning at the meso/macroscopic scales, without the need to parameterize the profusion of variables at lower scales. More specifically, we discuss how RD models (a) recapitulate the diversity of actual skin patterns, (b) capture the underlying dynamics of cellular interactions, (c) interact with tissue size and shape, (d) can lead to ordered sequential patterning, (e) generate cellular automaton dynamics in lizards and snakes, (f) predict actual patterns beyond their statistical features, and (g) are robust to model variations. Third, we discuss the utility of linear stability analysis and perform numerical simulations to demonstrate how deterministic RD emerges from the underlying chaotic microscopic agents.

Myriad mechanisms have evolved to adapt to changing environments. Environmental stimuli alter organisms' physiology to create memories of previous environments. Whether these environmental memories can cross the generational barrier has interested scientists for centuries. The logic of passing on information from generation to generation is not well understood. When is it useful to remember ancestral conditions, and when might it be deleterious to continue to respond to a context that may no longer exist? The key might be found in understanding the environmental conditions that trigger long-lasting adaptive responses. We discuss the logic that biological systems may use to remember environmental conditions. Responses spanning different generational timescales employ different molecular machineries and may result from differences in the duration or intensity of the exposure. Understanding the molecular components of multigenerational inheritance and the logic underlying beneficial and maladaptive adaptations is fundamental to understanding how organisms acquire and transmit environmental memories across generations.

Filopodia are dynamic cell surface protrusions used for cell motility, pathogen infection, and tissue development. The molecular mechanisms determining how and where filopodia grow and retract need to integrate mechanical forces and membrane curvature with extracellular signaling and the broader state of the cytoskeleton. The involved actin regulatory machinery nucleates, elongates, and bundles actin filaments separately from the underlying actin cortex. The refined membrane and actin geometry of filopodia, importance of tissue context, high spatiotemporal resolution required, and high degree of redundancy all limit current models. New technologies are improving opportunities for functional insight, with reconstitution of filopodia in vitro from purified components, endogenous genetic modification, inducible perturbation systems, and the study of filopodia in multicellular environments. In this review, we explore recent advances in conceptual models of how filopodia form, the molecules involved in this process, and our latest understanding of filopodia in vitro and in vivo.

During organismal development, organs and systems are built following a genetic blueprint that produces structures capable of performing specific physiological functions. Interestingly, we have learned that the physiological activities of developing tissues also contribute to their own morphogenesis. Specifically, physiological activities such as fluid secretion and cell contractility generate hydrostatic pressure that can act as a morphogenetic force. Here, we first review the role of hydrostatic pressure in tube formation during animal development and discuss mathematical models of lumen formation. We then illustrate specific roles of the notochord as a hydrostatic scaffold in anterior-posterior axis development in chordates. Finally, we cover some examples of how fluid flows influence morphogenetic processes in other developmental contexts. Understanding how fluid forces act during development will be key for uncovering the self-organizing principles that control morphogenesis.

Ciliates are a diverse group of unicellular eukaryotes that vary widely in size, shape, body plan, and ecological niche. Here, we review recent research advances achieved with ciliate models. Studies on patterning and regeneration have been revived in the giant ciliate Stentor, facilitated by modern omics methods. Cryo-electron microscopy and tomography have revolutionized the structural study of complex macromolecules such as telomerase, ribozymes, and axonemes. DNA elimination, gene scrambling, and mating type determination have been deciphered, revealing interesting adaptations of processes that have parallels in other kingdoms of life. Studies of common eukaryotic processes, such as intracellular trafficking, meiosis, and histone modification, reveal conservation as well as unique adaptations in these organisms that are evolutionarily distant from other models. Continual improvement of genetic and molecular tools makes ciliates accessible models for all levels of education and research. Such advances open new avenues of research and highlight the importance of ciliate research.

Cilia are ubiquitous microtubule-based eukaryotic organelles that project from the cell to generate motility or function in cellular signaling. Motile cilia or flagella contain axonemal dynein motors and other complexes to achieve beating. Primary cilia are immotile and act as signaling hubs, with receptors shuttling between the cytoplasm and ciliary compartment. In both cilia types, an intraflagellar transport (IFT) system powered by unique kinesin and dynein motors functions to deliver the molecules required to build cilia and maintain their functions. Cryo-electron tomography has helped to reveal the organization of protein complex arrangement along the axoneme and the structure of anterograde IFT trains as well as the structure of primary cilia. Only recently, single-particle analysis (SPA) cryo-electron microscopy has provided molecular details of the protein organization of ciliary components, helping us to understand how they bind to microtubule doublets and how mechanical force propagated by dynein conformational changes is converted into ciliary beating. Here we highlight recent structural advances that are leading to greater knowledge of ciliary function.

Since the proposal of the differential adhesion hypothesis, scientists have been fascinated by how cell adhesion mediates cellular self-organization to form spatial patterns during development. The search for molecular tool kits with homophilic binding specificity resulted in a diverse repertoire of adhesion molecules. Recent understanding of the dominant role of cortical tension over adhesion binding redirects the focus of differential adhesion studies to the signaling function of adhesion proteins to regulate actomyosin contractility. The broader framework of differential interfacial tension encompasses both adhesion and nonadhesion molecules, sharing the common function of modulating interfacial tension during cell sorting to generate diverse tissue patterns. Robust adhesion-based patterning requires close coordination between morphogen signaling, cell fate decisions, and changes in adhesion. Current advances in bridging theoretical and experimental approaches present exciting opportunities to understand molecular, cellular, and tissue dynamics during adhesion-based tissue patterning across multiple time and length scales.

Eukaryotic cells across the tree of life organize their subcellular components via intracellular transport mechanisms. In canonical transport, myosin, kinesin, and dynein motor proteins interact with cargos via adaptor proteins and move along filamentous actin or microtubule tracks. In contrast to this canonical mode, hitchhiking is a newly discovered mode of intracellular transport in which a cargo attaches itself to an already-motile cargo rather than directly associating with a motor protein itself. Many cargos including messenger RNAs, protein complexes, and organelles hitchhike on membrane-bound cargos. Hitchhiking-like behaviors have been shown to impact cellular processes including local protein translation, long-distance signaling, and organelle network reorganization. Here, we review instances of cargo hitchhiking in fungal, animal, and plant cells and discuss the potential cellular and evolutionary importance of hitchhiking in these different contexts.

Organoids are miniaturized and simplified versions of an organ produced in vitro from stem or progenitor cells. They are used as a model system consisting of multiple cell types forming an architecture relevant to the organ and carrying out the function of the organ. They are a useful tool to study development, homeostasis, regeneration, and disease. The imaging of organoids has become a pivotal method to visualize and understand their self-organization, symmetry breaking, growth, differentiation, and function. In this review, we discuss imaging methods, how to analyze these images, and challenges in organoid research.