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The International Journal of... 2017The vertebrate head characteristically exhibits a complex pattern with sense organs, brain, paired eyes and jaw muscles, and the brain case is not found in other... (Review)
Review
The vertebrate head characteristically exhibits a complex pattern with sense organs, brain, paired eyes and jaw muscles, and the brain case is not found in other chordates. How the extant vertebrate head has evolved remains enigmatic. Historically, there have been two conflicting views on the origin of the vertebrate head, segmental and non-segmental views. According to the segmentalists, the vertebrate head is organized as a metameric structure composed of segments equivalent to those in the trunk; a metamere in the vertebrate head was assumed to consist of a somite, a branchial arch and a set of cranial nerves, considering that the head evolved from rostral segments of amphioxus-like ancestral vertebrates. Non-segmentalists, however, considered that the vertebrate head was not segmental. In that case, the ancestral state of the vertebrate head may be non-segmented, and rostral segments in amphioxus might have been secondarily gained, or extant vertebrates might have evolved through radical modifications of amphioxus-like ancestral vertebrate head. Comparative studies of mesodermal development in amphioxus and vertebrate gastrula embryos have revealed that mesodermal gene expressions become segregated into two domains anteroposteriorly to specify the head mesoderm and trunk mesoderm only in vertebrates; in this segregation, key genes such as delta and hairy, involved in segment formation, are expressed in the trunk mesoderm, but not in the head mesoderm, strongly suggesting that the head mesoderm of extant vertebrates is not segmented. Taken together, the above finding possibly adds a new insight into the origin of the vertebrate head; the vertebrate head mesoderm would have evolved through an anteroposterior polarization of the paraxial mesoderm if the ancestral vertebrate had been amphioxus-like.
Topics: Animals; Body Patterning; Cephalochordata; Gene Expression Regulation, Developmental; Head; Lancelets; Models, Biological; Somites; Vertebrates
PubMed: 29319111
DOI: 10.1387/ijdb.170121to -
Nature Communications Jun 2021Positional information driving limb muscle patterning is contained in connective tissue fibroblasts but not in myogenic cells. Limb muscles originate from somites, while...
Positional information driving limb muscle patterning is contained in connective tissue fibroblasts but not in myogenic cells. Limb muscles originate from somites, while connective tissues originate from lateral plate mesoderm. With cell and genetic lineage tracing we challenge this model and identify an unexpected contribution of lateral plate-derived fibroblasts to the myogenic lineage, preferentially at the myotendinous junction. Analysis of single-cell RNA-sequencing data from whole limbs at successive developmental stages identifies a population displaying a dual muscle and connective tissue signature. BMP signalling is active in this dual population and at the tendon/muscle interface. In vivo and in vitro gain- and loss-of-function experiments show that BMP signalling regulates a fibroblast-to-myoblast conversion. These results suggest a scenario in which BMP signalling converts a subset of lateral plate mesoderm-derived cells to a myogenic fate in order to create a boundary of fibroblast-derived myonuclei at the myotendinous junction that controls limb muscle patterning.
Topics: Animals; Body Patterning; Cell Lineage; Cells, Cultured; Chick Embryo; Extremities; Fibroblasts; Gene Expression Regulation, Developmental; Mesoderm; Mice, Inbred C57BL; Mice, Inbred DBA; Mice, Transgenic; Muscle Development; Muscle, Skeletal; Reverse Transcriptase Polymerase Chain Reaction; Somites; Mice
PubMed: 34158501
DOI: 10.1038/s41467-021-24157-x -
Seminars in Cell & Developmental Biology Jun 2015During development, vertebrate embryos produce serially repeated elements, the somites, on each side of the midline. These generate the vertebral column, skeletal... (Review)
Review
During development, vertebrate embryos produce serially repeated elements, the somites, on each side of the midline. These generate the vertebral column, skeletal musculature and dermis. They form sequentially, one pair at a time, from mesenchymal tissue near the tail. Somite development is a complex process. The embryo must control the number, size, and timing of somite formation, their subdivision into functional regions along three axes, regional identity such that somites develop in a region-specific way, and interactions with neighbouring tissues that coordinate them with nearby structures. Here we discuss many timing-related mechanisms that contribute to set up the spatial pattern.
Topics: Animals; Body Patterning; Gene Expression Regulation; Homeodomain Proteins; Signal Transduction; Somites; Vertebrates
PubMed: 26116228
DOI: 10.1016/j.semcdb.2015.06.002 -
Developmental Dynamics : An Official... Nov 2000Much of our understanding of early vertebrate embryogenesis derives from experimental work done with the chick embryo. Studies of the avian somite have played a key role... (Review)
Review
Much of our understanding of early vertebrate embryogenesis derives from experimental work done with the chick embryo. Studies of the avian somite have played a key role in elucidating the developmental history of this important structure, the source of most muscle and bone in the organism. Here we review the development of the avian somite including morphological and molecular data on the origin of paraxial mesoderm, maturation of the segmental plate, specification and formation of somite compartments, and somite cell differentiation into cartilage and skeletal muscle.
Topics: Animals; Body Patterning; Cartilage; Cell Differentiation; Cell Division; Chick Embryo; Gene Expression Regulation, Developmental; In Situ Hybridization; Mesoderm; Microscopy, Electron, Scanning; Molecular Biology; Muscle, Skeletal; Signal Transduction; Somites; Terminology as Topic
PubMed: 11066088
DOI: 10.1002/1097-0177(2000)9999:9999<::AID-DVDY1057>3.0.CO;2-5 -
Developmental Biology May 2022
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Development (Cambridge, England) Aug 2019Consistent asymmetries between the left and right sides of animal bodies are common. For example, the internal organs of vertebrates are left-right (L-R) asymmetric in a... (Review)
Review
Consistent asymmetries between the left and right sides of animal bodies are common. For example, the internal organs of vertebrates are left-right (L-R) asymmetric in a stereotyped fashion. Other structures, such as the skeleton and muscles, are largely symmetric. This Review considers how symmetries and asymmetries form alongside each other within the embryo, and how they are then maintained during growth. I describe how asymmetric signals are generated in the embryo. Using the limbs and somites as major examples, I then address mechanisms for protecting symmetrically forming tissues from asymmetrically acting signals. These examples reveal that symmetry should not be considered as an inherent background state, but instead must be actively maintained throughout multiple phases of embryonic patterning and organismal growth.
Topics: Animals; Body Patterning; Disease; Embryonic Development; Extremities; Humans; Mice; Somites
PubMed: 31416929
DOI: 10.1242/dev.170985 -
Developmental Dynamics : An Official... Sep 2007Somites are segments of paraxial mesoderm that give rise to a multitude of tissues in the vertebrate embryo. Many decades of intensive research have provided a wealth of... (Review)
Review
Somites are segments of paraxial mesoderm that give rise to a multitude of tissues in the vertebrate embryo. Many decades of intensive research have provided a wealth of data on the complex molecular interactions leading to the formation of various somitic derivatives. In this review, we focus on the crucial role of the somites in building the body wall and limbs of amniote embryos. We give an overview on the current knowledge on the specification and differentiation of somitic cell lineages leading to the development of the vertebral column, skeletal muscle, connective tissue, meninges, and vessel endothelium, and highlight the importance of the somites in establishing the metameric pattern of the vertebrate body.
Topics: Amnion; Animals; Cell Differentiation; Cell Lineage; Chick Embryo; Embryonic Development; Endothelium; Epithelium; Extremities; Microscopy, Electron, Scanning; Models, Anatomic; Models, Biological; Muscles; Somites; Spinal Cord
PubMed: 17557304
DOI: 10.1002/dvdy.21189 -
Current Topics in Developmental Biology 2008Somitogenesis is the process of division of the anterior-posterior vertebrate embryonic axis into similar morphological units known as somites. These segments generate... (Review)
Review
Somitogenesis is the process of division of the anterior-posterior vertebrate embryonic axis into similar morphological units known as somites. These segments generate the prepattern which guides formation of the vertebrae, ribs and other associated features of the body trunk. In this work, we review and discuss a series of mathematical models which account for different stages of somite formation. We begin by presenting current experimental information and mechanisms explaining somite formation, highlighting features which will be included in the models. For each model we outline the mathematical basis, show results of numerical simulations, discuss their successes and shortcomings and avenues for future exploration. We conclude with a brief discussion of the state of modeling in the field and current challenges which need to be overcome in order to further our understanding in this area.
Topics: Animals; Body Patterning; Cell Adhesion; Fibroblast Growth Factor 8; Gene Expression Regulation, Developmental; Mathematics; Models, Biological; Somites
PubMed: 18023728
DOI: 10.1016/S0070-2153(07)81006-4 -
Science Advances Jan 2024Spatiotemporal patterns widely occur in biological, chemical, and physical systems. Particularly, embryonic development displays a diverse gamut of repetitive patterns... (Review)
Review
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.
Topics: Animals; Body Patterning; Somites; Mesoderm; Vertebrates; Embryonic Development; Gene Expression Regulation, Developmental
PubMed: 38277458
DOI: 10.1126/sciadv.adk8937 -
ELife Jan 2022During the development of the vertebrate embryo, segmented structures called somites are periodically formed from the presomitic mesoderm (PSM) and give rise to the...
During the development of the vertebrate embryo, segmented structures called somites are periodically formed from the presomitic mesoderm (PSM) and give rise to the vertebral column. While somite formation has been studied in several animal models, it is less clear how well this process is conserved in humans. Recent progress has made it possible to study aspects of human paraxial mesoderm (PM) development such as the human segmentation clock using human pluripotent stem cells (hPSCs); however, somite formation has not been observed in these monolayer cultures. Here, we describe the generation of human PM organoids from hPSCs (termed Somitoids), which recapitulate the molecular, morphological, and functional features of PM development, including formation of somite-like structures . Using a quantitative image-based screen, we identify critical parameters such as initial cell number and signaling modulations that reproducibly yielded formation of somite-like structures in our organoid system. In addition, using single-cell RNA-sequencing and 3D imaging, we show that PM organoids both transcriptionally and morphologically resemble their counterparts and can be differentiated into somite derivatives. Our organoid system is reproducible and scalable, allowing for the systematic and quantitative analysis of human spine development and disease .
Topics: Animals; Cell Differentiation; Humans; Mesoderm; Organoids; Pluripotent Stem Cells; Somites
PubMed: 35088712
DOI: 10.7554/eLife.68925