1
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Miao Y, Pourquié O. Cellular and molecular control of vertebrate somitogenesis. Nat Rev Mol Cell Biol 2024; 25:517-533. [PMID: 38418851 DOI: 10.1038/s41580-024-00709-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/30/2024] [Indexed: 03/02/2024]
Abstract
Segmentation is a fundamental feature of the vertebrate body plan. This metameric organization is first implemented by somitogenesis in the early embryo, when paired epithelial blocks called somites are rhythmically formed to flank the neural tube. Recent advances in in vitro models have offered new opportunities to elucidate the mechanisms that underlie somitogenesis. Notably, models derived from human pluripotent stem cells introduced an efficient proxy for studying this process during human development. In this Review, we summarize the current understanding of somitogenesis gained from both in vivo studies and in vitro studies. We deconstruct the spatiotemporal dynamics of somitogenesis into four distinct modules: dynamic events in the presomitic mesoderm, segmental determination, somite anteroposterior polarity patterning, and epithelial morphogenesis. We first focus on the segmentation clock, as well as signalling and metabolic gradients along the tissue, before discussing the clock and wavefront and other models that account for segmental determination. We then detail the molecular and cellular mechanisms of anteroposterior polarity patterning and somite epithelialization.
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Affiliation(s)
- Yuchuan Miao
- Department of Genetics, Harvard Medical School, Boston, MA, USA.
- Department of Pathology, Brigham and Women's Hospital, Boston, MA, USA.
| | - Olivier Pourquié
- Department of Genetics, Harvard Medical School, Boston, MA, USA.
- Department of Pathology, Brigham and Women's Hospital, Boston, MA, USA.
- Harvard Stem Cell Institute, Harvard University, Cambridge, MA, USA.
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2
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Merle M, Friedman L, Chureau C, Shoushtarizadeh A, Gregor T. Precise and scalable self-organization in mammalian pseudo-embryos. Nat Struct Mol Biol 2024; 31:896-902. [PMID: 38491138 DOI: 10.1038/s41594-024-01251-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2023] [Accepted: 02/08/2024] [Indexed: 03/18/2024]
Abstract
Gene expression is inherently noisy, posing a challenge to understanding how precise and reproducible patterns of gene expression emerge in mammals. Here we investigate this phenomenon using gastruloids, a three-dimensional in vitro model for early mammalian development. Our study reveals intrinsic reproducibility in the self-organization of gastruloids, encompassing growth dynamics and gene expression patterns. We observe a remarkable degree of control over gene expression along the main body axis, with pattern boundaries positioned with single-cell precision. Furthermore, as gastruloids grow, both their physical proportions and gene expression patterns scale proportionally with system size. Notably, these properties emerge spontaneously in self-organizing cell aggregates, distinct from many in vivo systems constrained by fixed boundary conditions. Our findings shed light on the intricacies of developmental precision, reproducibility and size scaling within a mammalian system, suggesting that these phenomena might constitute fundamental features of multicellularity.
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Affiliation(s)
- Mélody Merle
- Department of Developmental and Stem Cell Biology, CNRS UMR3738 Paris Cité, Institut Pasteur, Paris, France
| | - Leah Friedman
- Department of Developmental and Stem Cell Biology, CNRS UMR3738 Paris Cité, Institut Pasteur, Paris, France
| | - Corinne Chureau
- Department of Developmental and Stem Cell Biology, CNRS UMR3738 Paris Cité, Institut Pasteur, Paris, France
| | - Armin Shoushtarizadeh
- Department of Developmental and Stem Cell Biology, CNRS UMR3738 Paris Cité, Institut Pasteur, Paris, France
| | - Thomas Gregor
- Department of Developmental and Stem Cell Biology, CNRS UMR3738 Paris Cité, Institut Pasteur, Paris, France.
- Joseph Henry Laboratories of Physics & Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA.
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3
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Small CD, Benfey TJ, Crawford BD. Tissue-specific compensatory mechanisms maintain tissue architecture and body size independent of cell size in polyploid zebrafish. Dev Biol 2024; 509:85-96. [PMID: 38387487 DOI: 10.1016/j.ydbio.2024.02.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2022] [Revised: 01/01/2024] [Accepted: 02/13/2024] [Indexed: 02/24/2024]
Abstract
Genome duplications and ploidy transitions have occurred in nearly every major taxon of eukaryotes, but they are far more common in plants than in animals. Due to the conservation of the nuclear:cytoplasmic volume ratio increased DNA content results in larger cells. In plants, polyploid organisms are larger than diploids as cell number remains relatively constant. Conversely, vertebrate body size does not correlate with cell size and ploidy as vertebrates compensate for increased cell size to maintain tissue architecture and body size. This has historically been explained by a simple reduction in cell number that matches the increase in cell size maintaining body size as ploidy increases, but here we show that the compensatory mechanisms that maintain body size in triploid zebrafish are tissue-specific: A) erythrocytes respond in the classical pattern with a reduced number of larger erythrocytes in circulation, B) muscle, a tissue comprised of polynucleated muscle fibers, compensates by reducing the number of larger nuclei such that myofiber and myotome size in unaffected by ploidy, and C) vascular tissue compensates by thickening blood vessel walls, possibly at the expense of luminal diameter. Understanding the physiological implications of ploidy on tissue function requires a detailed description of the specific mechanisms of morphological compensation occurring in each tissue to understand how ploidy changes affect development and physiology.
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Affiliation(s)
- C D Small
- Center for Precision Environmental Health, Baylor College of Medicine, Houston, TX, USA
| | - T J Benfey
- Biology Department, University of New Brunswick, Fredericton, NB, Canada
| | - B D Crawford
- Biology Department, University of New Brunswick, Fredericton, NB, Canada.
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4
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Serra KM, Vyzas C, Shehreen S, Chipendo I, Clifford KM, Youngstrom DW, Devoto SH. Vertebral pattern and morphology is determined during embryonic segmentation. Dev Dyn 2024; 253:204-214. [PMID: 37688793 DOI: 10.1002/dvdy.649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 06/29/2023] [Accepted: 07/17/2023] [Indexed: 09/11/2023] Open
Abstract
BACKGROUND The segmented nature of the adult vertebral column is based on segmentation of the paraxial mesoderm during early embryogenesis. Disruptions to embryonic segmentation, whether caused by genetic lesions or environmental stress, result in adult vertebral pathologies. However, the mechanisms linking embryonic segmentation and the details of adult vertebral morphology are poorly understood. RESULTS We induced border defects using two approaches in zebrafish: heat stress and misregulation of embryonic segmentation genes tbx6, mesp-ba, and ripply1. We assayed vertebral length, regularity, and polarity using microscopic and radiological imaging. In population studies, we find a correlation between specific embryonic border defects and specific vertebral defects, and within individual fish, we trace specific adult vertebral defects to specific embryonic border defects. CONCLUSIONS Our data reveal that transient disruptions of embryonic segment border formation led to significant vertebral anomalies that persist through adulthood. The spacing of embryonic borders controls the length of the vertebra. The positions of embryonic borders control the positions of ribs and arches. Embryonic borders underlie fusions and divisions between adjacent spines and ribs. These data suggest that segment borders have a dominant role in vertebral development.
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Affiliation(s)
- Kevin M Serra
- Department of Biology, Wesleyan University, Middletown, Connecticut, USA
| | - Christina Vyzas
- Department of Biology, Wesleyan University, Middletown, Connecticut, USA
| | - Sarah Shehreen
- Department of Biology, Wesleyan University, Middletown, Connecticut, USA
| | - Iris Chipendo
- Department of Biology, Wesleyan University, Middletown, Connecticut, USA
| | - Katherine M Clifford
- Department of Biology, Wesleyan University, Middletown, Connecticut, USA
- Department of Neurology, Stanford University, Stanford, California, USA
| | - Daniel W Youngstrom
- Department of Orthopaedic Surgery, University of Connecticut School of Medicine, Farmington, Connecticut, USA
| | - Stephen H Devoto
- Department of Biology, Wesleyan University, Middletown, Connecticut, USA
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5
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Ramesh PS, Chu LF. Species-specific roles of the Notch ligands, receptors, and targets orchestrating the signaling landscape of the segmentation clock. Front Cell Dev Biol 2024; 11:1327227. [PMID: 38348091 PMCID: PMC10859470 DOI: 10.3389/fcell.2023.1327227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Accepted: 12/20/2023] [Indexed: 02/15/2024] Open
Abstract
Somitogenesis is a hallmark feature of all vertebrates and some invertebrate species that involves the periodic formation of block-like structures called somites. Somites are transient embryonic segments that eventually establish the entire vertebral column. A highly conserved molecular oscillator called the segmentation clock underlies this periodic event and the pace of this clock regulates the pace of somite formation. Although conserved signaling pathways govern the clock in most vertebrates, the mechanisms underlying the species-specific divergence in various clock characteristics remain elusive. For example, the segmentation clock in classical model species such as zebrafish, chick, and mouse embryos tick with a periodicity of ∼30, ∼90, and ∼120 min respectively. This enables them to form the species-specific number of vertebrae during their overall timespan of somitogenesis. Here, we perform a systematic review of the species-specific features of the segmentation clock with a keen focus on mouse embryos. We perform this review using three different perspectives: Notch-responsive clock genes, ligand-receptor dynamics, and synchronization between neighboring oscillators. We further review reports that use non-classical model organisms and in vitro model systems that complement our current understanding of the segmentation clock. Our review highlights the importance of comparative developmental biology to further our understanding of this essential developmental process.
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Affiliation(s)
- Pranav S. Ramesh
- Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
- Reproductive Biology and Regenerative Medicine Research Group, University of Calgary, Calgary, AB, Canada
- Alberta Children’s Hospital Research Institute, Calgary, AB, Canada
| | - Li-Fang Chu
- Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
- Reproductive Biology and Regenerative Medicine Research Group, University of Calgary, Calgary, AB, Canada
- Alberta Children’s Hospital Research Institute, Calgary, AB, Canada
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6
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McDaniel C, Simsek MF, Chandel AS, Özbudak EM. Spatiotemporal control of pattern formation during somitogenesis. SCIENCE ADVANCES 2024; 10:eadk8937. [PMID: 38277458 PMCID: PMC10816718 DOI: 10.1126/sciadv.adk8937] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2023] [Accepted: 12/27/2023] [Indexed: 01/28/2024]
Abstract
Spatiotemporal patterns widely occur in biological, chemical, and physical systems. Particularly, embryonic development displays a diverse gamut of repetitive patterns established in many tissues and organs. Branching treelike structures in lungs, kidneys, livers, pancreases, and mammary glands as well as digits and bones in appendages, teeth, and palates are just a few examples. A fascinating instance of repetitive patterning is the sequential segmentation of the primary body axis, which is conserved in all vertebrates and many arthropods and annelids. In these species, the body axis elongates at the posterior end of the embryo containing an unsegmented tissue. Meanwhile, segments sequentially bud off from the anterior end of the unsegmented tissue, laying down an exquisite repetitive pattern and creating a segmented body plan. In vertebrates, the paraxial mesoderm is sequentially divided into somites. In this review, we will discuss the most prominent models, the most puzzling experimental data, and outstanding questions in vertebrate somite segmentation.
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Affiliation(s)
- Cassandra McDaniel
- Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229, USA
- Systems Biology and Physiology Graduate Program, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA
| | - M. Fethullah Simsek
- Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Angad Singh Chandel
- Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229, USA
- Systems Biology and Physiology Graduate Program, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA
| | - Ertuğrul M. Özbudak
- Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229, USA
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA
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7
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Nikolić M, Antonetti V, Liu F, Muhaxheri G, Petkova MD, Scheeler M, Smith EM, Bialek W, Gregor T. Scale invariance in early embryonic development. ARXIV 2023:arXiv:2312.17684v1. [PMID: 38235065 PMCID: PMC10793483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
The body plan of the fruit fly is determined by the expression of just a handful of genes. We show that the spatial patterns of expression for several of these genes scale precisely with the size of the embryo. Concretely, discrete positional markers such as the peaks in striped patterns have absolute positions along the anterior-posterior axis that are proportional to embryo length, with better than 1% accuracy. Further, the information (in bits) that graded patterns of expression provide about position can be decomposed into information about fractional or scaled position and information about absolute position or embryo length; all of the available information is about scaled position, again with ~ 1% accuracy. These observations suggest that the underlying genetic network exhibits scale invariance in a deeper mathematical sense. Taking this mathematical statement seriously requires that the network dynamics have a zero mode, which connects to many other observations on this system.
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Affiliation(s)
- Miloš Nikolić
- Joseph Henry Laboratories of Physics and Princeton University, Princeton NJ 08544 USA
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton NJ 08544 USA
| | - Victoria Antonetti
- Joseph Henry Laboratories of Physics and Princeton University, Princeton NJ 08544 USA
- Center for Quantitative Biology and School of Physics, Peking University, Beijing 100871 China
| | - Feng Liu
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton NJ 08544 USA
- Center for Quantitative Biology and School of Physics, Peking University, Beijing 100871 China
| | - Gentian Muhaxheri
- Joseph Henry Laboratories of Physics and Princeton University, Princeton NJ 08544 USA
- Department of Physics, Lehman College, City University of New York, Bronx, NY 10468 USA
| | | | - Martin Scheeler
- Joseph Henry Laboratories of Physics and Princeton University, Princeton NJ 08544 USA
| | - Eric M Smith
- Joseph Henry Laboratories of Physics and Princeton University, Princeton NJ 08544 USA
| | - William Bialek
- Joseph Henry Laboratories of Physics and Princeton University, Princeton NJ 08544 USA
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton NJ 08544 USA
- Initiative for the Theoretical Sciences, The Graduate Center, City University of New York, 365 Fifth Ave., New York, NY 10016 USA
| | - Thomas Gregor
- Joseph Henry Laboratories of Physics and Princeton University, Princeton NJ 08544 USA
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton NJ 08544 USA
- Department of Developmental and Stem Cell Biology UMR3738, Institut Pasteur, 75015 Paris, France
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8
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Abstract
During gastrulation, early embryos specify and reorganise the topology of their germ layers. Surprisingly, this fundamental and early process does not appear to be rigidly constrained by evolutionary pressures; instead, the morphology of gastrulation is highly variable throughout the animal kingdom. Recent experimental results demonstrate that it is possible to generate different alternative gastrulation modes in single organisms, such as in early cnidarian, arthropod and vertebrate embryos. Here, we review the mechanisms that underlie the plasticity of vertebrate gastrulation both when experimentally manipulated and during evolution. Using the insights obtained from these experiments we discuss the effects of the increase in yolk volume on the morphology of gastrulation and provide new insights into two crucial innovations during amniote gastrulation: the transition from a ring-shaped mesoderm domain in anamniotes to a crescent-shaped domain in amniotes, and the evolution of the reptilian blastoporal plate/canal into the avian primitive streak.
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Affiliation(s)
| | - Cornelis J. Weijer
- School of Life Sciences Research Complex, University of Dundee, Dow Street, Dundee, DD1 5EH, UK
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9
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Yaman YI, Ramanathan S. Controlling human organoid symmetry breaking reveals signaling gradients drive segmentation clock waves. Cell 2023; 186:513-527.e19. [PMID: 36657441 PMCID: PMC10025047 DOI: 10.1016/j.cell.2022.12.042] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 09/29/2022] [Accepted: 12/21/2022] [Indexed: 01/19/2023]
Abstract
Axial development of mammals involves coordinated morphogenetic events, including axial elongation, somitogenesis, and neural tube formation. To gain insight into the signals controlling the dynamics of human axial morphogenesis, we generated axially elongating organoids by inducing anteroposterior symmetry breaking of spatially coupled epithelial cysts derived from human pluripotent stem cells. Each organoid was composed of a neural tube flanked by presomitic mesoderm sequentially segmented into somites. Periodic activation of the somite differentiation gene MESP2 coincided in space and time with anteriorly traveling segmentation clock waves in the presomitic mesoderm of the organoids, recapitulating critical aspects of somitogenesis. Timed perturbations demonstrated that FGF and WNT signaling play distinct roles in axial elongation and somitogenesis, and that FGF signaling gradients drive segmentation clock waves. By generating and perturbing organoids that robustly recapitulate the architecture of multiple axial tissues in human embryos, this work offers a means to dissect mechanisms underlying human embryogenesis.
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Affiliation(s)
- Yusuf Ilker Yaman
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA; Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 02138, USA.
| | - Sharad Ramanathan
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA; Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA; Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 02138, USA.
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10
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Fgf8 dynamics and critical slowing down may account for the temperature independence of somitogenesis. Commun Biol 2022; 5:113. [PMID: 35132142 PMCID: PMC8821593 DOI: 10.1038/s42003-022-03053-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Accepted: 12/29/2021] [Indexed: 12/17/2022] Open
Abstract
Somitogenesis, the segmentation of the antero-posterior axis in vertebrates, is thought to result from the interactions between a genetic oscillator and a posterior-moving determination wavefront. The segment (somite) size is set by the product of the oscillator period and the velocity of the determination wavefront. Surprisingly, while the segmentation period can vary by a factor three between 20 °C and 32 °C, the somite size is constant. How this temperature independence is achieved is a mystery that we address in this study. Using RT-qPCR we show that the endogenous fgf8 mRNA concentration decreases during somitogenesis and correlates with the exponent of the shrinking pre-somitic mesoderm (PSM) size. As the temperature decreases, the dynamics of fgf8 and many other gene transcripts, as well as the segmentation frequency and the PSM shortening and tail growth rates slows down as T-Tc (with Tc = 14.4 °C). This behavior characteristic of a system near a critical point may account for the temperature independence of somitogenesis in zebrafish.
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11
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Live imaging approach of dynamic multicellular responses in ERK signaling during vertebrate tissue development. Biochem J 2022; 479:129-143. [PMID: 35050327 PMCID: PMC8883488 DOI: 10.1042/bcj20210557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 12/28/2021] [Accepted: 01/05/2022] [Indexed: 11/17/2022]
Abstract
The chemical and mechanical responses of cells via the exchange of information during growth and development result in the formation of biological tissues. Information processing within the cells through the signaling pathways and networks inherent to the constituent cells has been well-studied. However, the cell signaling mechanisms responsible for generating dynamic multicellular responses in developing tissues remain unclear. Here, I review the dynamic multicellular response systems during the development and growth of vertebrate tissues based on the extracellular signal-regulated kinase (ERK) pathway. First, an overview of the function of the ERK signaling network in cells is provided, followed by descriptions of biosensors essential for live imaging of the quantification of ERK activity in tissues. Then adducing four examples, I highlight the contribution of live imaging techniques for studying the involvement of spatio-temporal patterns of ERK activity change in tissue development and growth. In addition, theoretical implications of ERK signaling are also discussed from the viewpoint of dynamic systems. This review might help in understanding ERK-mediated dynamic multicellular responses and tissue morphogenesis.
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12
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Linde-Medina M, Smit TH. Molecular and Mechanical Cues for Somite Periodicity. Front Cell Dev Biol 2021; 9:753446. [PMID: 34901002 PMCID: PMC8663771 DOI: 10.3389/fcell.2021.753446] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 10/14/2021] [Indexed: 11/13/2022] Open
Abstract
Somitogenesis refers to the segmentation of the paraxial mesoderm, a tissue located on the back of the embryo, into regularly spaced and sized pieces, i.e., the somites. This periodicity is important to assure, for example, the formation of a functional vertebral column. Prevailing models of somitogenesis are based on the existence of a gene regulatory network capable of generating a striped pattern of gene expression, which is subsequently translated into periodic tissue boundaries. An alternative view is that the pre-pattern that guides somitogenesis is not chemical, but of a mechanical origin. A striped pattern of mechanical strain can be formed in physically connected tissues expanding at different rates, as it occurs in the embryo. Here we argue that both molecular and mechanical cues could drive somite periodicity and suggest how they could be integrated.
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Affiliation(s)
| | - Theodoor H. Smit
- Department of Orthopaedic Surgery, Amsterdam Movement Sciences, Amsterdam University Medical Centres, Amsterdam, Netherlands
- Department of Medical Biology, Amsterdam University Medical Centres, Amsterdam, Netherlands
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13
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Nakamura A, Goto Y, Kondo Y, Aoki K. Shedding light on developmental ERK signaling with genetically encoded biosensors. Development 2021; 148:271153. [PMID: 34338283 DOI: 10.1242/dev.199767] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The extracellular signal-regulated kinase (ERK) pathway governs cell proliferation, differentiation and migration, and therefore plays key roles in various developmental and regenerative processes. Recent advances in genetically encoded fluorescent biosensors have unveiled hitherto unrecognized ERK activation dynamics in space and time and their functional importance mainly in cultured cells. However, ERK dynamics during embryonic development have still only been visualized in limited numbers of model organisms, and we are far from a sufficient understanding of the roles played by developmental ERK dynamics. In this Review, we first provide an overview of the biosensors used for visualization of ERK activity in live cells. Second, we highlight the applications of the biosensors to developmental studies of model organisms and discuss the current understanding of how ERK dynamics are encoded and decoded for cell fate decision-making.
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Affiliation(s)
- Akinobu Nakamura
- Division of Quantitative Biology, National Institute for Basic Biology, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji-cho, Okazaki, Aichi 444-8787, Japan.,Quantitative Biology Research Group, Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji-cho, Okazaki, Aichi 444-8787, Japan
| | - Yuhei Goto
- Division of Quantitative Biology, National Institute for Basic Biology, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji-cho, Okazaki, Aichi 444-8787, Japan.,Quantitative Biology Research Group, Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji-cho, Okazaki, Aichi 444-8787, Japan.,Department of Basic Biology, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), 5-1 Higashiyama, Myodaiji-cho, Okazaki, Aichi 444-8787, Japan
| | - Yohei Kondo
- Division of Quantitative Biology, National Institute for Basic Biology, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji-cho, Okazaki, Aichi 444-8787, Japan.,Quantitative Biology Research Group, Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji-cho, Okazaki, Aichi 444-8787, Japan.,Department of Basic Biology, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), 5-1 Higashiyama, Myodaiji-cho, Okazaki, Aichi 444-8787, Japan
| | - Kazuhiro Aoki
- Division of Quantitative Biology, National Institute for Basic Biology, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji-cho, Okazaki, Aichi 444-8787, Japan.,Quantitative Biology Research Group, Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji-cho, Okazaki, Aichi 444-8787, Japan.,Department of Basic Biology, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), 5-1 Higashiyama, Myodaiji-cho, Okazaki, Aichi 444-8787, Japan.,IRCC International Research Collaboration Center, National Institutes of Natural Sciences, 4-3-13 Toranomon, Minato-ku, Tokyo 105-0001, Japan
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14
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Abstract
Arthropod segmentation and vertebrate somitogenesis are leading fields in the experimental and theoretical interrogation of developmental patterning. However, despite the sophistication of current research, basic conceptual issues remain unresolved. These include: (i) the mechanistic origins of spatial organization within the segment addition zone (SAZ); (ii) the mechanistic origins of segment polarization; (iii) the mechanistic origins of axial variation; and (iv) the evolutionary origins of simultaneous patterning. Here, I explore these problems using coarse-grained models of cross-regulating dynamical processes. In the morphogenetic framework of a row of cells undergoing axial elongation, I simulate interactions between an 'oscillator', a 'switch' and up to three 'timers', successfully reproducing essential patterning behaviours of segmenting systems. By comparing the output of these largely cell-autonomous models to variants that incorporate positional information, I find that scaling relationships, wave patterns and patterning dynamics all depend on whether the SAZ is regulated by temporal or spatial information. I also identify three mechanisms for polarizing oscillator output, all of which functionally implicate the oscillator frequency profile. Finally, I demonstrate significant dynamical and regulatory continuity between sequential and simultaneous modes of segmentation. I discuss these results in the context of the experimental literature.
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Affiliation(s)
- Erik Clark
- Department of Systems Biology, Harvard Medical School, 210 Longwood Ave, Boston, MA 02115, USA
- Trinity College Cambridge, University of Cambridge, Trinity Street, Cambridge CB2 1TQ, UK
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15
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Uriu K, Liao BK, Oates AC, Morelli LG. From local resynchronization to global pattern recovery in the zebrafish segmentation clock. eLife 2021; 10:61358. [PMID: 33587039 PMCID: PMC7984840 DOI: 10.7554/elife.61358] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Accepted: 01/27/2021] [Indexed: 01/26/2023] Open
Abstract
Integrity of rhythmic spatial gene expression patterns in the vertebrate segmentation clock requires local synchronization between neighboring cells by Delta-Notch signaling and its inhibition causes defective segment boundaries. Whether deformation of the oscillating tissue complements local synchronization during patterning and segment formation is not understood. We combine theory and experiment to investigate this question in the zebrafish segmentation clock. We remove a Notch inhibitor, allowing resynchronization, and analyze embryonic segment recovery. We observe unexpected intermingling of normal and defective segments, and capture this with a new model combining coupled oscillators and tissue mechanics. Intermingled segments are explained in the theory by advection of persistent phase vortices of oscillators. Experimentally observed changes in recovery patterns are predicted in the theory by temporal changes in tissue length and cell advection pattern. Thus, segmental pattern recovery occurs at two length and time scales: rapid local synchronization between neighboring cells, and the slower transport of the resulting patterns across the tissue through morphogenesis.
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Affiliation(s)
- Koichiro Uriu
- Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, Japan
| | - Bo-Kai Liao
- Department of Aquaculture, National Taiwan Ocean University, Keelung, Taiwan.,Department of Cell and Developmental Biology, University College London, Gower Street, London, United Kingdom.,The Francis Crick Institute, London, United Kingdom.,Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Andrew C Oates
- Department of Cell and Developmental Biology, University College London, Gower Street, London, United Kingdom.,The Francis Crick Institute, London, United Kingdom.,Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Institute of Bioengineering, École polytechnique fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Luis G Morelli
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA) - CONICET - Partner Institute of the Max Planck Society, Polo Científico Tecnológico, Buenos Aires, Argentina.,Departamento de Física, FCEyN UBA, Ciudad Universitaria, Buenos Aires, Argentina.,Max Planck Institute for Molecular Physiology, Department of Systemic Cell Biology, Dortmund, Germany
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16
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Scaling a Dpp Morphogen Gradient through Feedback Control of Receptors and Co-receptors. Dev Cell 2021; 53:724-739.e14. [PMID: 32574592 DOI: 10.1016/j.devcel.2020.05.029] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 03/23/2020] [Accepted: 05/26/2020] [Indexed: 11/21/2022]
Abstract
Gradients of decapentaplegic (Dpp) pattern Drosophila wing imaginal discs, establishing gene expression boundaries at specific locations. As discs grow, Dpp gradients expand, keeping relative boundary positions approximately stationary. Such scaling fails in mutants for Pentagone (pent), a gene repressed by Dpp that encodes a diffusible protein that expands Dpp gradients. Although these properties fit a recent mathematical model of automatic gradient scaling, that model requires an expander that spreads with minimal loss throughout a morphogen field. Here, we show that Pent's actions are confined to within just a few cell diameters of its site of synthesis and can be phenocopied by manipulating non-diffusible Pent targets strictly within the Pent expression domain. Using genetics and mathematical modeling, we develop an alternative model of scaling driven by feedback downregulation of Dpp receptors and co-receptors. Among the model's predictions is a size beyond which scaling fails-something we observe directly in wing discs.
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17
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Chen H, Qian W, Good MC. Integrating cellular dimensions with cell differentiation during early development. Curr Opin Cell Biol 2020; 67:109-117. [PMID: 33152556 DOI: 10.1016/j.ceb.2020.08.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 07/14/2020] [Accepted: 08/03/2020] [Indexed: 11/25/2022]
Abstract
Early embryo development is characterized by alteration of cellular dimensions and fating of blastomeres. An emerging concept is that cell size and shape drive cellular differentiation during early embryogenesis in a variety of model organisms. In this review, we summarize recent advances that elucidate the contribution of the physical dimensions of a cell to major embryonic transitions and cell fate specification in vivo. We also highlight techniques and newly evolving methods for manipulating the sizes and shapes of cells and whole embryos in situ and ex vivo. Finally, we provide an outlook for addressing fundamental questions in the field and more broadly uncovering how changes to cell size control decision making in a variety of biological contexts.
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Affiliation(s)
- Hui Chen
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Wenchao Qian
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Matthew C Good
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA.
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18
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Brotzmann K, Wolterbeek A, Kroese D, Braunbeck T. Neurotoxic effects in zebrafish embryos by valproic acid and nine of its analogues: the fish-mouse connection? Arch Toxicol 2020; 95:641-657. [PMID: 33111190 PMCID: PMC7870776 DOI: 10.1007/s00204-020-02928-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 10/05/2020] [Indexed: 01/26/2023]
Abstract
Since teratogenicity testing in mammals is a particular challenge from an animal welfare perspective, there is a great need for the development of alternative test systems. In this context, the zebrafish (Danio rerio) embryo has received increasing attention as a non-protected embryonic vertebrate in vivo model. The predictive power of zebrafish embryos for general vertebrate teratogenicity strongly depends on the correlation between fish and mammals with respect to both overall general toxicity and more specific endpoints indicative of certain modes-of-action. The present study was designed to analyze the correlation between (1) effects of valproic acid and nine of its analogues in zebrafish embryos and (2) their known neurodevelopmental effects in mice. To this end, zebrafish embryos exposed for 120 h in an extended version of the acute fish embryo toxicity test (FET; OECD TG 236) were analyzed with respect to an extended list of sublethal endpoints. Particular care was given to endpoints putatively related to neurodevelopmental toxicity, namely jitter/tremor, deformation of sensory organs (eyes) and craniofacial deformation, which might correlate to neural tube defects caused by valproic acid in mammals. A standard evaluation of lethal (LC according to OECD TG 236) and sublethal toxicity (EC) merely indicated that four out of ten compounds tested in zebrafish correlate with positive results in mouse in vivo studies. A detailed assessment of more specific effects, however, namely, jitter/tremor, small eyes and craniofacial deformation, resulted in a correspondence of 75% with in vivo mouse data. A refinement of endpoint analysis from an integration of all observations into one LCx or ECx data (as foreseen by current ecotoxicology-driven OECD guidelines) to a differential evaluation of endpoints specific of selected modes-of-action thus increases significantly the predictive power of the zebrafish embryo model for mammalian teratogenicity. However, for some of the endpoints observed, e.g., scoliosis, lordosis, pectoral fin deformation and lack of movement, further experiments are required for the identification of underlying modes-of-action and an unambiguous interpretation of their predictive power for mammalian toxicity.
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Affiliation(s)
- Katharina Brotzmann
- Aquatic Ecology and Toxicology Group, Centre for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 504, 69120, Heidelberg, Germany.
| | - André Wolterbeek
- TNO Healthy Living Unit, Department of Risk Analysis for Products in Development, The Netherlands Organization for Applied Scientific Research, Princetonlaan 6, 3584 CB, Utrecht, The Netherlands
| | - Dinant Kroese
- TNO Healthy Living Unit, Department of Risk Analysis for Products in Development, The Netherlands Organization for Applied Scientific Research, Princetonlaan 6, 3584 CB, Utrecht, The Netherlands
| | - Thomas Braunbeck
- Aquatic Ecology and Toxicology Group, Centre for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 504, 69120, Heidelberg, Germany.
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19
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Saiz N, Hadjantonakis AK. Coordination between patterning and morphogenesis ensures robustness during mouse development. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190562. [PMID: 32829684 PMCID: PMC7482220 DOI: 10.1098/rstb.2019.0562] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/01/2020] [Indexed: 12/11/2022] Open
Abstract
The mammalian preimplantation embryo is a highly tractable, self-organizing developmental system in which three cell types are consistently specified without the need for maternal factors or external signals. Studies in the mouse over the past decades have greatly improved our understanding of the cues that trigger symmetry breaking in the embryo, the transcription factors that control lineage specification and commitment, and the mechanical forces that drive morphogenesis and inform cell fate decisions. These studies have also uncovered how these multiple inputs are integrated to allocate the right number of cells to each lineage despite inherent biological noise, and as a response to perturbations. In this review, we summarize our current understanding of how these processes are coordinated to ensure a robust and precise developmental outcome during early mouse development. This article is part of a discussion meeting issue 'Contemporary morphogenesis'.
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Affiliation(s)
- Néstor Saiz
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
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20
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Leibovich A, Edri T, Klein SL, Moody SA, Fainsod A. Natural size variation among embryos leads to the corresponding scaling in gene expression. Dev Biol 2020; 462:165-179. [PMID: 32259520 PMCID: PMC8073595 DOI: 10.1016/j.ydbio.2020.03.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Revised: 02/27/2020] [Accepted: 03/23/2020] [Indexed: 11/17/2022]
Abstract
Xenopus laevis frogs from laboratory stocks normally lay eggs exhibiting extensive size variability. We find that these initial size differences subsequently affect the size of the embryos prior to the onset of growth, and the size of tadpoles during the growth period. Even though these tadpoles differ in size, their tissues, organs, and structures always seem to be properly proportioned, i.e. they display static allometry. Initial axial patterning events in Xenopus occur in a spherical embryo, allowing easy documentation of their size-dependent features. We examined the size distribution of early Xenopus laevis embryos and measured diameters that differed by about 38% with a median of about 1.43 mm. This range of embryo sizes corresponds to about a 1.9-fold difference in surface area and a 2.6-fold difference in volume. We examined the relationship between embryo size and gene expression and observed a significant correlation between diameter and RNA content during gastrula stages. In addition, we investigated the expression levels of genes that pattern the mesoderm, induce the nervous system and mediate the progression of ectodermal cells to neural precursors in large and small embryos. We found that most of these factors were expressed at levels that scaled with the different embryo sizes and total embryo RNA content. In agreement with the changes in transcript levels, the expression domains in larger embryos increased proportionally with the increase in surface area, maintaining their relative expression domain size in relation to the total size of the embryo. Thus, our study identified a mechanism for adapting gene expression domains to embryo size by adjusting the transcript levels of the genes regulating mesoderm induction and patterning. In the neural plate, besides the scaling of the expression domains, we observed similar cell sizes and cell densities in small and large embryos suggesting that additional cell divisions took place in large embryos to compensate for the increased size. Our results show in detail the size variability among Xenopus laevis embryos and the transcriptional adaptation to scale gene expression with size. The observations further support the involvement of BMP/ADMP signaling in the scaling process.
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Affiliation(s)
- Avi Leibovich
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University of Jerusalem, Israel
| | - Tamir Edri
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University of Jerusalem, Israel
| | - Steven L Klein
- Department of Anatomy and Cell Biology, George Washington University School of Medicine and Health Sciences, USA
| | - Sally A Moody
- Department of Anatomy and Cell Biology, George Washington University School of Medicine and Health Sciences, USA
| | - Abraham Fainsod
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University of Jerusalem, Israel.
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21
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Naoki H, Matsui T. Somite boundary determination in normal and clock-less vertebrate embryos. Dev Growth Differ 2020; 62:177-187. [PMID: 32108939 DOI: 10.1111/dgd.12655] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2019] [Revised: 01/31/2020] [Accepted: 02/01/2020] [Indexed: 12/21/2022]
Abstract
Vertebrate segments called somites are generated by periodic segmentation of the presomitic mesoderm (PSM). In the most accepted theoretical model for somite segmentation, the clock and wavefront (CW) model, a clock that ticks to determine particular timings and a wavefront that moves posteriorly are presented in the PSM, and somite positions are determined when the clock meets the posteriorly moving wavefront somewhere in the PSM. Over the last two decades, it has been revealed that the molecular mechanism of the clock and wavefront in vertebrates is based on clock genes including Hes family transcription factors and Notch effectors that oscillate within the PSM to determine particular timings and fibroblast growth factor (FGF) gradients, acting as the posteriorly moving wavefront to determine the position of somite segmentation. A clock-less condition in the CW model was predicted to form no somites; however, irregularly sized somites were still formed in mice and zebrafish, suggesting that this was one of the limitations of the CW model. Recently, we performed interdisciplinary research of experimental and theoretical biological studies and revealed the mechanisms of somite boundary determination in normal and clock-less conditions by characterization of the FGF/extracellular signal-regulated kinase (ERK) activity dynamics. Since features of the molecular clock have already been described in-depth in several reviews, we summarized recent findings regarding the role of FGF/ERK signaling in somite boundary formation and described our current understanding of how FGF/ERK signaling contributes to somitogenesis in normal and clock-less conditions in this review.
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Affiliation(s)
- Honda Naoki
- Laboratory of Theoretical Biology, Research Center for Dynamic Living Systems, Graduate School of Biostudies, Kyoto University, Sakyo, Kyoto, Japan
| | - Takaaki Matsui
- Gene Regulation Research, Division of Biological Science, Nara Institute of Science and Technology, Takayama, Nara, Japan
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22
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Čapek D, Müller P. Positional information and tissue scaling during development and regeneration. Development 2019; 146:146/24/dev177709. [PMID: 31862792 DOI: 10.1242/dev.177709] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
In order to contribute to the appropriate tissues during development, cells need to know their position within the embryo. This positional information is conveyed by gradients of signaling molecules, termed morphogens, that are produced in specific regions of the embryo and induce concentration-dependent responses in target tissues. Positional information is remarkably robust, and embryos often develop with the correct proportions even if large parts of the embryo are removed. In this Review, we discuss classical embryological experiments and modern quantitative analyses that have led to mechanistic insights into how morphogen gradients adapt, scale and properly pattern differently sized domains. We analyze these experimental findings in the context of mathematical models and synthesize general principles that apply to multiple systems across species and developmental stages.
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Affiliation(s)
- Daniel Čapek
- Systems Biology of Development Group, Friedrich Miescher Laboratory of the Max Planck Society, Max-Planck-Ring 9, 72076 Tübingen Germany
| | - Patrick Müller
- Systems Biology of Development Group, Friedrich Miescher Laboratory of the Max Planck Society, Max-Planck-Ring 9, 72076 Tübingen Germany .,Modeling Tumorigenesis Group, Translational Oncology Division, Eberhard Karls University Tübingen, Otfried-Müller-Strasse 10, 72076 Tübingen Germany
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23
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Grall E, Tschopp P. A sense of place, many times over ‐ pattern formation and evolution of repetitive morphological structures. Dev Dyn 2019; 249:313-327. [DOI: 10.1002/dvdy.131] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 10/30/2019] [Accepted: 11/04/2019] [Indexed: 12/14/2022] Open
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24
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P J M, F A C, J K D. Cell cycle regulation of oscillations yields coupling of growth and form in a computational model of the presomitic mesoderm. J Theor Biol 2019; 481:75-83. [PMID: 31121170 DOI: 10.1016/j.jtbi.2019.05.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Revised: 05/06/2019] [Accepted: 05/08/2019] [Indexed: 11/27/2022]
Abstract
A striking example of coupling between growth and form occurs during the segmentation of the vertebrate embryo. During segmentation, pairs of segments, one on either side of the anterior-posterior axis, bud off from the presomitic mesoderm (PSM) at regular intervals in time. In the clock and wavefront model, a multicellular oscillator regulates the time at which the next pair of segments form whilst a wavefront regulates their spatial location. In most mathematical models of segmentation, it is assumed that cells in the PSM are oscillators that have a constant natural frequency. Based on recent experimental findings, here we propose a model in which the natural oscillation frequency of each PSM cell is a function of its position in the cell cycle. Given adequate oscillator coupling and that cells in the PSM are randomly distributed in the cell cycle, we find that the emergent oscillator frequency is a weighted average of the constituent oscillator frequencies with the weightings dependent on the fraction of cells in a given cell cycle state. Here, we show that such a model can allow for coupling between pattern formation and growth rate in PSM tissue.
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Affiliation(s)
- Murray P J
- Department of Mathematics, University of Dundee, Nethergate, Dundee, DD14HN Scotland, UK.
| | - Carrieri F A
- Division of Cell and Developmental Biology, School of Life Sciences, University of Dundee, Dow Street, Dundee, DD15EH Scotland, UK
| | - Dale J K
- Division of Cell and Developmental Biology, School of Life Sciences, University of Dundee, Dow Street, Dundee, DD15EH Scotland, UK
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25
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Abstract
Segment formation in vertebrate embryos is a stunning example of biological self-organization. Here, we present an idealized framework, in which we treat the presomitic mesoderm (PSM) as a one-dimensional line of oscillators. We use the framework to derive constraints that connect the size of somites, and the timing of their formation, to the growth of the PSM and the gradient of the somitogenesis clock period across the PSM. Our analysis recapitulates the observations made recently in ex vivo cultures of mouse PSM cells, and makes predictions for how perturbations, such as increased Wnt levels, would alter somite widths. Finally, our analysis makes testable predictions for the shape of the phase profile and somite widths at different stages of PSM growth. In particular, we show that the phase profile is robustly concave when the PSM length is steady and slightly convex in an important special case when it is decreasing exponentially. In both cases, the phase profile scales with the PSM length; in the latter case, it scales dynamically. This has important consequences for the velocity of the waves that traverse the PSM and trigger somite formation, as well as the effect of errors in phase measurement on somite widths.
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Affiliation(s)
- Jonas S Juul
- Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, Copenhagen 2100, Denmark
| | - Mogens H Jensen
- Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, Copenhagen 2100, Denmark
| | - Sandeep Krishna
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
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26
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Bergmann PJ, Morinaga G. The convergent evolution of snake‐like forms by divergent evolutionary pathways in squamate reptiles*. Evolution 2018; 73:481-496. [DOI: 10.1111/evo.13651] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Accepted: 11/08/2018] [Indexed: 12/15/2022]
Affiliation(s)
- Philip J. Bergmann
- Department of Biology Clark University 950 Main Street Worcester Massachusetts 01610
| | - Gen Morinaga
- Department of Biology Clark University 950 Main Street Worcester Massachusetts 01610
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