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Holland ND, Holland LZ. Serial block-face scanning electron microscopy of the tail tip of post-metamorphic amphioxus finds novel myomeres with odd shapes and unusually prominent sclerocoels. J Morphol 2024; 285:e21667. [PMID: 38100741 DOI: 10.1002/jmor.21667] [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: 11/09/2023] [Revised: 12/02/2023] [Accepted: 12/05/2023] [Indexed: 12/17/2023]
Abstract
Serial block-face scanning electron microscopy of the tail tip of post-metamorphic amphioxus (Branchiostoma floridae) revealed some terminal myomeres never been seen before with other techniques. The morphology of these myomeres differed markedly from the chevron shapes of their more anterior counterparts. Histologically, these odd-shaped myomeres ranged from empty vesicles bordered by undifferentiated cells to ventral sacs composed of well-developed myotome, dermatome, and sclerotome. Strikingly, several of these ventral sacs gave rise to a nipple-like dorsal projection composed either entirely of sclerotome or a mixture of sclerotome and myotome. Considered as a whole, from posterior to anterior, these odd-shaped posterior myomeres suggested that their more substantial ventral part may represent the ventral limb of a chevron, while the delicate projection represents a nascent dorsal limb. This scenario contrasts with formation of chevron-shaped myomeres along most of the antero-posterior axis. Although typical chevron formation in amphioxus is surprisingly poorly studied, it seems to be attained by a dorso-ventral extension of the myomere accompanied by the assumption of a V-shape; this is similar to what happens (at least superficially) in developing fishes. Another unusual feature of the odd-shaped posterior myomeres of amphioxus is their especially distended sclerocoels. One possible function for these might be to protect the posterior end of the central nervous system from trauma when the animals burrow into the substratum.
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Affiliation(s)
- Nicholas D Holland
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California, USA
| | - Linda Z Holland
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California, USA
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Holland ND, Holland LZ, Somorjai IML. Three-dimensional fine structure of fibroblasts and other mesodermally derived tissues in the dermis of adults of the Bahamas lancelet (Chordata, Cephalohordata), as seen by serial block-face scanning electron microscopy. J Morphol 2022; 283:1289-1298. [PMID: 35971624 DOI: 10.1002/jmor.21502] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 07/27/2022] [Accepted: 08/02/2022] [Indexed: 11/07/2022]
Abstract
Tissues of adult cephalochordates include sparsely distributed fibroblasts. Previous work on these cells has left unsettled such questions as their developmental origin, range of functions, and even their overall shape. Here, we describe fibroblasts of a cephalochordate, the Bahamas lancelet, Asymmetron lucayanum, by serial block-face scanning electron microscopy to demonstrate their three-dimensional (3D) distribution and fine structure in a 0.56-mm length of the tail. The technique reveals in detail their position, abundance, and morphology. In the region studied, we found only 20 fibroblasts, well separated from one another. Each was strikingly stellate with long cytoplasmic processes rather similar to those of a vertebrate telocyte, a possibly fortuitous resemblance that is considered in the discussion section. In the cephalochordate dermis, the fibroblasts were never linked with one another, although they occasionally formed close associations of unknown significance with other cell types. The fibroblasts, in spite of their name, showed no signs of directly synthesizing fibrillar collagen. Instead, they appeared to be involved in the production of nonfibrous components of the extracellular matrix-both by the release of coarsely granular dense material and by secretion of more finely granular material by the local breakdown of their cytoplasmic processes. For context, the 3D structures of two other mesoderm-derived tissues (the midline mesoderm and the posteriormost somite) are also described for the region studied.
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Affiliation(s)
- Nicholas D Holland
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California, USA
| | - Linda Z Holland
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California, USA
| | - Ildiko M L Somorjai
- School of Biology, University of Saint Andrews, St. Andrews, Fife, Scotland, UK
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The Evolution of Biomineralization through the Co-Option of Organic Scaffold Forming Networks. Cells 2022; 11:cells11040595. [PMID: 35203246 PMCID: PMC8870065 DOI: 10.3390/cells11040595] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2022] [Revised: 02/07/2022] [Accepted: 02/08/2022] [Indexed: 12/05/2022] Open
Abstract
Biomineralization is the process in which organisms use minerals to generate hard structures like teeth, skeletons and shells. Biomineralization is proposed to have evolved independently in different phyla through the co-option of pre-existing developmental programs. Comparing the gene regulatory networks (GRNs) that drive biomineralization in different species could illuminate the molecular evolution of biomineralization. Skeletogenesis in the sea urchin embryo was extensively studied and the underlying GRN shows high conservation within echinoderms, larval and adult skeletogenesis. The organic scaffold in which the calcite skeletal elements form in echinoderms is a tubular compartment generated by the syncytial skeletogenic cells. This is strictly different than the organic cartilaginous scaffold that vertebrates mineralize with hydroxyapatite to make their bones. Here I compare the GRNs that drive biomineralization and tubulogenesis in echinoderms and in vertebrates. The GRN that drives skeletogenesis in the sea urchin embryo shows little similarity to the GRN that drives bone formation and high resemblance to the GRN that drives vertebrates’ vascular tubulogenesis. On the other hand, vertebrates’ bone-GRNs show high similarity to the GRNs that operate in the cells that generate the cartilage-like tissues of basal chordate and invertebrates that do not produce mineralized tissue. These comparisons suggest that biomineralization in deuterostomes evolved through the phylum specific co-option of GRNs that control distinct organic scaffolds to mineralization.
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Yong LW, Lu TM, Tung CH, Chiou RJ, Li KL, Yu JK. Somite Compartments in Amphioxus and Its Implications on the Evolution of the Vertebrate Skeletal Tissues. Front Cell Dev Biol 2021; 9:607057. [PMID: 34041233 PMCID: PMC8141804 DOI: 10.3389/fcell.2021.607057] [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: 09/16/2020] [Accepted: 04/06/2021] [Indexed: 11/13/2022] Open
Abstract
Mineralized skeletal tissues of vertebrates are an evolutionary novelty within the chordate lineage. While the progenitor cells that contribute to vertebrate skeletal tissues are known to have two embryonic origins, the mesoderm and neural crest, the evolutionary origin of their developmental process remains unclear. Using cephalochordate amphioxus as our model, we found that cells at the lateral wall of the amphioxus somite express SPARC (a crucial gene for tissue mineralization) and various collagen genes. During development, some of these cells expand medially to surround the axial structures, including the neural tube, notochord and gut, while others expand laterally and ventrally to underlie the epidermis. Eventually these cell populations are found closely associated with the collagenous matrix around the neural tube, notochord, and dorsal aorta, and also with the dense collagen sheets underneath the epidermis. Using known genetic markers for distinct vertebrate somite compartments, we showed that the lateral wall of amphioxus somite likely corresponds to the vertebrate dermomyotome and lateral plate mesoderm. Furthermore, we demonstrated a conserved role for BMP signaling pathway in somite patterning of both amphioxus and vertebrates. These results suggest that compartmentalized somites and their contribution to primitive skeletal tissues are ancient traits that date back to the chordate common ancestor. The finding of SPARC-expressing skeletal scaffold in amphioxus further supports previous hypothesis regarding SPARC gene family expansion in the elaboration of the vertebrate mineralized skeleton.
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Affiliation(s)
- Luok Wen Yong
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
| | - Tsai-Ming Lu
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
| | - Che-Huang Tung
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
- Department of Aquatic Biology, Chia-Yi University, Chia-Yi, Taiwan
| | - Ruei-Jen Chiou
- Department of Anatomy and Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Kun-Lung Li
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
| | - Jr-Kai Yu
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
- Marine Research Station, Institute of Cellular and Organismic Biology, Academia Sinica, Yilan, Taiwan
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Murdock DJE. The ‘biomineralization toolkit’ and the origin of animal skeletons. Biol Rev Camb Philos Soc 2020; 95:1372-1392. [DOI: 10.1111/brv.12614] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 04/28/2020] [Accepted: 04/30/2020] [Indexed: 12/29/2022]
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HMGA Genes and Proteins in Development and Evolution. Int J Mol Sci 2020; 21:ijms21020654. [PMID: 31963852 PMCID: PMC7013770 DOI: 10.3390/ijms21020654] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 01/14/2020] [Accepted: 01/16/2020] [Indexed: 12/16/2022] Open
Abstract
HMGA (high mobility group A) (HMGA1 and HMGA2) are small non-histone proteins that can bind DNA and modify chromatin state, thus modulating the accessibility of regulatory factors to the DNA and contributing to the overall panorama of gene expression tuning. In general, they are abundantly expressed during embryogenesis, but are downregulated in the adult differentiated tissues. In the present review, we summarize some aspects of their role during development, also dealing with relevant studies that have shed light on their functioning in cell biology and with emerging possible involvement of HMGA1 and HMGA2 in evolutionary biology.
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Abstract
The BMP signaling pathway has been shown to be involved in different aspects of embryonic development across diverse metazoan phyla. Comparative studies on the roles of the BMP signaling pathway provide crucial insights into the evolution of the animal body plans. In this chapter, we present the general workflow on how to investigate the roles of BMP signaling pathway during amphioxus embryonic development. As amphioxus are basal invertebrate chordates, studies on the BMP signaling pathway in amphioxus could elucidate the functional evolution of BMP pathway in the chordate group. Here, we describe methods for animal husbandry, spawning induction, and manipulation of the BMP signaling pathway during embryonic development through drug inhibitors and recombinant proteins. We also introduce an efficient method of using mesh baskets to handle amphioxus embryos for fluorescence immunostaining and multicolor fluorescence in situ hybridization and to assay the effects of manipulating BMP signaling pathway during amphioxus embryogenesis.
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Trapani V, Bonaldo P, Corallo D. Role of the ECM in notochord formation, function and disease. J Cell Sci 2017; 130:3203-3211. [PMID: 28883093 DOI: 10.1242/jcs.175950] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The notochord is a midline structure common to all chordate animals; it provides mechanical and signaling cues for the developing embryo. In vertebrates, the notochord plays key functions during embryogenesis, being a source of developmental signals that pattern the surrounding tissues. It is composed of a core of vacuolated cells surrounded by an epithelial-like sheath of cells that secrete a thick peri-notochordal basement membrane made of different extracellular matrix (ECM) proteins. The correct deposition and organization of the ECM is essential for proper notochord morphogenesis and function. Work carried out in the past two decades has allowed researchers to dissect the contribution of different ECM components to this embryonic tissue. Here, we will provide an overview of these genetic and mechanistic studies. In particular, we highlight the specific functions of distinct matrix molecules in regulating notochord development and notochord-derived signals. Moreover, we also discuss the involvement of ECM synthesis and its remodeling in the pathogenesis of chordoma, a malignant bone cancer that originates from remnants of notochord remaining after embryogenesis.
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Affiliation(s)
- Valeria Trapani
- Department of Molecular Medicine, University of Padova, 35131 Padova, Italy
| | - Paolo Bonaldo
- Department of Molecular Medicine, University of Padova, 35131 Padova, Italy .,CRIBI Biotechnology Center, University of Padova, Padova, 35131, Italy
| | - Diana Corallo
- Department of Molecular Medicine, University of Padova, 35131 Padova, Italy .,Pediatric Research Institute, Città della Speranza, 35127 Padova, Italy
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The HMGA gene family in chordates: evolutionary perspectives from amphioxus. Dev Genes Evol 2017; 227:201-211. [DOI: 10.1007/s00427-017-0581-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Accepted: 04/24/2017] [Indexed: 02/07/2023]
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Evolutionary origin of endochondral ossification: the transdifferentiation hypothesis. Dev Genes Evol 2016; 227:121-127. [DOI: 10.1007/s00427-016-0567-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Accepted: 11/23/2016] [Indexed: 02/06/2023]
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