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Lovely AM, Duerr TJ, Qiu Q, Galvan S, Voss SR, Monaghan JR. Wnt Signaling Coordinates the Expression of Limb Patterning Genes During Axolotl Forelimb Development and Regeneration. Front Cell Dev Biol 2022; 10:814250. [PMID: 35531102 PMCID: PMC9068880 DOI: 10.3389/fcell.2022.814250] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2021] [Accepted: 03/21/2022] [Indexed: 11/13/2022] Open
Abstract
After amputation, axolotl salamanders can regenerate their limbs, but the degree to which limb regeneration recapitulates limb development remains unclear. One limitation in answering this question is our lack of knowledge about salamander limb development. Here, we address this question by studying expression patterns of genes important for limb patterning during axolotl salamander limb development and regeneration. We focus on the Wnt signaling pathway because it regulates multiple functions during tetrapod limb development, including limb bud initiation, outgrowth, patterning, and skeletal differentiation. We use fluorescence in situ hybridization to show the expression of Wnt ligands, Wnt receptors, and limb patterning genes in developing and regenerating limbs. Inhibition of Wnt ligand secretion permanently blocks limb bud outgrowth when treated early in limb development. Inhibiting Wnt signaling during limb outgrowth decreases the expression of critical signaling genes, including Fgf10, Fgf8, and Shh, leading to the reduced outgrowth of the limb. Patterns of gene expression are similar between developing and regenerating limbs. Inhibition of Wnt signaling during regeneration impacted patterning gene expression similarly. Overall, our findings suggest that limb development and regeneration utilize Wnt signaling similarly. It also provides new insights into the interaction of Wnt signaling with other signaling pathways during salamander limb development and regeneration.
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Affiliation(s)
| | - Timothy J. Duerr
- Department of Biology, Northeastern University, Boston, MA, United States
| | - Qingchao Qiu
- Department of Neuroscience, Spinal Cord and Brain Injury Research Center, and Ambystoma Genetic Stock Center, University of Kentucky, Lexington, KY, United States
| | | | - S. Randal Voss
- Department of Neuroscience, Spinal Cord and Brain Injury Research Center, and Ambystoma Genetic Stock Center, University of Kentucky, Lexington, KY, United States
| | - James R. Monaghan
- Department of Biology, Northeastern University, Boston, MA, United States
- Institute for Chemical Imaging of Living Systems, Northeastern University, Boston, MA, United States
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2
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Takeuchi T, Matsubara H, Minamitani F, Satoh Y, Tozawa S, Moriyama T, Maruyama K, Suzuki KIT, Shigenobu S, Inoue T, Tamura K, Agata K, Hayashi T. Newt Hoxa13 has an essential and predominant role in digit formation during development and regeneration. Development 2022; 149:274659. [DOI: 10.1242/dev.200282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Accepted: 01/21/2022] [Indexed: 11/20/2022]
Abstract
ABSTRACT
The 5′Hox genes play crucial roles in limb development and specify regions in the proximal-distal axis of limbs. However, there is no direct genetic evidence that Hox genes are essential for limb development in non-mammalian tetrapods or for limb regeneration. Here, we produced single to quadruple Hox13 paralog mutants using the CRISPR/Cas9 system in newts (Pleurodeles waltl), which have strong regenerative capacities, and also produced germline mutants. We show that Hox13 genes are essential for digit formation in development, as in mice. In addition, Hoxa13 has a predominant role in digit formation, unlike in mice. The predominance is probably due to the restricted expression pattern of Hoxd13 in limb buds and the strong dependence of Hoxd13 expression on Hoxa13. Finally, we demonstrate that Hox13 genes are also necessary for digit formation in limb regeneration. Our findings reveal that the general function of Hox13 genes is conserved between limb development and regeneration, and across taxa. The predominance of Hoxa13 function both in newt limbs and fish fins, but not in mouse limbs, suggests a potential contribution of Hoxa13 function in fin-to-limb transition.
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Affiliation(s)
- Takashi Takeuchi
- Division of Developmental Biology, School of Life Sciences, Faculty of Medicine, Tottori University, 86 Nishi-cho, Yonago, Tottori 683-8503, Japan
| | - Haruka Matsubara
- Division of Developmental Biology, School of Life Sciences, Faculty of Medicine, Tottori University, 86 Nishi-cho, Yonago, Tottori 683-8503, Japan
| | - Fumina Minamitani
- Division of Developmental Biology, School of Life Sciences, Faculty of Medicine, Tottori University, 86 Nishi-cho, Yonago, Tottori 683-8503, Japan
| | - Yukio Satoh
- Division of Developmental Biology, School of Life Sciences, Faculty of Medicine, Tottori University, 86 Nishi-cho, Yonago, Tottori 683-8503, Japan
| | - Sayo Tozawa
- Division of Developmental Biology, School of Life Sciences, Faculty of Medicine, Tottori University, 86 Nishi-cho, Yonago, Tottori 683-8503, Japan
| | - Tomoki Moriyama
- Division of Developmental Biology, School of Life Sciences, Faculty of Medicine, Tottori University, 86 Nishi-cho, Yonago, Tottori 683-8503, Japan
| | - Kohei Maruyama
- Division of Developmental Biology, School of Life Sciences, Faculty of Medicine, Tottori University, 86 Nishi-cho, Yonago, Tottori 683-8503, Japan
| | - Ken-ichi T. Suzuki
- Laboratory of Regeneration Biology, National Institute for Basic Biology, Nishigonaka 38, Myodaiji, Okazaki, Aichi 444-8585, Japan
| | - Shuji Shigenobu
- Laboratory of Regeneration Biology, National Institute for Basic Biology, Nishigonaka 38, Myodaiji, Okazaki, Aichi 444-8585, Japan
| | - Takeshi Inoue
- Department of Life Science, Faculty of Science, Gakushuin University, Toyoshima-Ku, Tokyo 171-8588, Japan
| | - Koji Tamura
- Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Aoba-ku, Sendai, 980-8578, Japan
| | - Kiyokazu Agata
- Laboratory of Regeneration Biology, National Institute for Basic Biology, Nishigonaka 38, Myodaiji, Okazaki, Aichi 444-8585, Japan
- Department of Life Science, Faculty of Science, Gakushuin University, Toyoshima-Ku, Tokyo 171-8588, Japan
| | - Toshinori Hayashi
- Division of Developmental Biology, School of Life Sciences, Faculty of Medicine, Tottori University, 86 Nishi-cho, Yonago, Tottori 683-8503, Japan
- Program of Biomedical Science, Graduate School of Integrated Sciences for Life, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
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3
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Royle SR, Young JJ. Developmental biology: A 5'Hoxd-Gli3 balance in tetrapod axial polarity. Curr Biol 2021; 31:R1487-R1490. [PMID: 34813756 DOI: 10.1016/j.cub.2021.10.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Almost all living tetrapods exhibit postaxial dominance in digit formation, apart from urodele amphibians, which show preaxial dominance. Recent work shines light on the genetic differences between the two modes of limb development, suggesting that differences in 5'Hoxd expression, mediated by Gli3, may explain the switch in axial polarity.
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Affiliation(s)
- Samantha R Royle
- Department of Genetics, Balvatnik Institute, Harvard Medical School, Boston, MA 02115, USA; Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
| | - John J Young
- Biology Department, Simmons University, Boston, MA 02115, USA.
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4
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Trofka A, Huang BL, Zhu J, Heinz WF, Magidson V, Shibata Y, Shi YB, Tarchini B, Stadler HS, Kabangu M, Al Haj Baddar NW, Voss SR, Mackem S. Genetic basis for an evolutionary shift from ancestral preaxial to postaxial limb polarity in non-urodele vertebrates. Curr Biol 2021; 31:4923-4934.e5. [PMID: 34610275 DOI: 10.1016/j.cub.2021.09.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 06/30/2021] [Accepted: 09/03/2021] [Indexed: 11/24/2022]
Abstract
In most tetrapod vertebrates, limb skeletal progenitors condense with postaxial dominance. Posterior elements (such as ulna and fibula) appear prior to their anterior counterparts (radius and tibia), followed by digit-appearance order with continuing postaxial polarity. The only exceptions are urodele amphibians (salamanders), whose limb elements develop with preaxial polarity and who are also notable for their unique ability to regenerate complete limbs as adults. The mechanistic basis for this preaxial dominance has remained an enigma and has even been proposed to relate to the acquisition of novel genes involved in regeneration. However, recent fossil evidence suggests that preaxial polarity represents an ancestral rather than derived state. Here, we report that 5'Hoxd (Hoxd11-d13) gene deletion in mouse is atavistic and uncovers an underlying preaxial polarity in mammalian limb formation. We demonstrate this shift from postaxial to preaxial dominance in mouse results from excess Gli3 repressor (Gli3R) activity due to the loss of 5'Hoxd-Gli3 antagonism and is associated with cell-cycle changes promoting precocious cell-cycle exit in the anterior limb bud. We further show that Gli3 knockdown in axolotl results in a shift to postaxial dominant limb skeleton formation, as well as expanded paddle-shaped limb-bud morphology and ensuing polydactyly. Evolutionary changes in Gli3R activity level, which also played a key role in the fin-to-limb transition, appear to be fundamental to the shift from preaxial to postaxial polarity in formation of the tetrapod limb skeleton.
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Affiliation(s)
- Anna Trofka
- Cancer and Developmental Biology Laboratory, Center for Cancer Research, NCI, Frederick, MD, USA
| | - Bau-Lin Huang
- Cancer and Developmental Biology Laboratory, Center for Cancer Research, NCI, Frederick, MD, USA
| | - Jianjian Zhu
- Cancer and Developmental Biology Laboratory, Center for Cancer Research, NCI, Frederick, MD, USA
| | - William F Heinz
- Optical Microscopy and Analysis Laboratory, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | - Valentin Magidson
- Optical Microscopy and Analysis Laboratory, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | - Yuki Shibata
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver NICHD, Bethesda, MD, USA
| | - Yun-Bo Shi
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver NICHD, Bethesda, MD, USA
| | | | - H Scott Stadler
- Division of Skeletal Biology, Shriners Hospitals for Children, Portland, OR, USA; Department of Orthopaedics and Rehabilitation, Oregon Health & Science University, Portland, OR, USA
| | - Mirindi Kabangu
- Department of Neuroscience, Spinal Cord and Brain Injury Research Center, and Ambystoma Genetic Stock Center, University of Kentucky, Lexington, KY, USA
| | - Nour W Al Haj Baddar
- Department of Neuroscience, Spinal Cord and Brain Injury Research Center, and Ambystoma Genetic Stock Center, University of Kentucky, Lexington, KY, USA
| | - S Randal Voss
- Department of Neuroscience, Spinal Cord and Brain Injury Research Center, and Ambystoma Genetic Stock Center, University of Kentucky, Lexington, KY, USA.
| | - Susan Mackem
- Cancer and Developmental Biology Laboratory, Center for Cancer Research, NCI, Frederick, MD, USA.
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5
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Conserved Mechanisms, Novel Anatomies: The Developmental Basis of Fin Evolution and the Origin of Limbs. DIVERSITY 2021. [DOI: 10.3390/d13080384] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The transformation of paired fins into tetrapod limbs is one of the most intensively scrutinized events in animal evolution. Early anatomical and embryological datasets identified distinctive morphological regions within the appendage and posed hypotheses about how the loss, gain, and transformation of these regions could explain the observed patterns of both extant and fossil appendage diversity. These hypotheses have been put to the test by our growing understanding of patterning mechanisms that regulate formation of the appendage axes, comparisons of gene expression data from an array of phylogenetically informative taxa, and increasingly sophisticated and elegant experiments leveraging the latest molecular approaches. Together, these data demonstrate the remarkable conservation of developmental mechanisms, even across phylogenetically and morphologically disparate taxa, as well as raising new questions about the way we view homology, evolutionary novelty, and the often non-linear connection between morphology and gene expression. In this review, we present historical hypotheses regarding paired fin evolution and limb origins, summarize key aspects of central appendage patterning mechanisms in model and non-model species, address how modern comparative developmental data interface with our understanding of appendage anatomy, and highlight new approaches that promise to provide new insight into these well-traveled questions.
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6
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Hong Q, Li XD, Xie P, Du SX. All-trans-retinoic acid suppresses rat embryo hindlimb bud mesenchymal chondrogenesis by modulating HoxD9 expression. Bioengineered 2021; 12:3900-3911. [PMID: 34288810 PMCID: PMC8806522 DOI: 10.1080/21655979.2021.1940613] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In vertebrates, 5ʹ-Hoxd genes (Hoxd9), which are expressed in the hindlimb bud mesenchyme, participate in limb growth and patterning in early embryonic development. In the present study, We investigated the mechanisms by which ATRA regulates cultured E12.5 rat embryo hindlimb bud mesenchymal cells (rEHBMCs). Following exposure to ATRA over 24 h, mRNA and protein expression levels of HoxD9 were evaluated by reverse transcription-polymerase chain reaction (RT-PCR), quantitative real-time PCR (qPCR), and western blotting. Flow cytometry was used to detect apoptosis. ATRA inhibited the condensation and proliferation, and promoted the apoptosis rate of the rEHBMCs in a dose-dependent manner. Sox9 and Col2a1 in rEHBMCs were downregulated by ATRA in a dose-dependent manner at both mRNA and protein levels. Similarly, HoxD9 was downregulated by ATRA in a dose-dependent manner, in parallel with the cartilage-specific molecules Sox9 and Col2a1. Both qPCR and western blotting showed that both Shh and Gli3 were downregulated. Overexpression of HoxD9 reversed the effects of ATRA. These results demonstrate that ATRA suppresses chondrogenesis in rEHBMCs by inhibiting the expression of HoxD9 and its downstream protein targets, including Sox9 and Col2a1. This effect may also be correlated with inhibition of the Shh-Gli3 signaling pathway.
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Affiliation(s)
- Quan Hong
- Department of Orthopedics, Jieyang People's Hospital (Jieyang Affiliated Hospital, Sun Yat-sen University), Jieyang, Guangdong, China
| | - Xue-Dong Li
- Department of Orthopedics, Shenzhen Luohu Hospital Group Luohu People's Hospital (The Third Affiliated Hospital of Shenzhen University), Shenzhen, Guangdong, China
| | - Peng Xie
- Department of Orthopedics, Shenzhen Luohu Hospital Group Luohu People's Hospital (The Third Affiliated Hospital of Shenzhen University), Shenzhen, Guangdong, China
| | - Shi-Xin Du
- Department of Orthopedics, Shenzhen Luohu Hospital Group Luohu People's Hospital (The Third Affiliated Hospital of Shenzhen University), Shenzhen, Guangdong, China
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7
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Meyer A, Schloissnig S, Franchini P, Du K, Woltering JM, Irisarri I, Wong WY, Nowoshilow S, Kneitz S, Kawaguchi A, Fabrizius A, Xiong P, Dechaud C, Spaink HP, Volff JN, Simakov O, Burmester T, Tanaka EM, Schartl M. Giant lungfish genome elucidates the conquest of land by vertebrates. Nature 2021; 590:284-289. [PMID: 33461212 PMCID: PMC7875771 DOI: 10.1038/s41586-021-03198-8] [Citation(s) in RCA: 81] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Accepted: 01/06/2021] [Indexed: 01/29/2023]
Abstract
Lungfishes belong to lobe-fined fish (Sarcopterygii) that, in the Devonian period, 'conquered' the land and ultimately gave rise to all land vertebrates, including humans1-3. Here we determine the chromosome-quality genome of the Australian lungfish (Neoceratodus forsteri), which is known to have the largest genome of any animal. The vast size of this genome, which is about 14× larger than that of humans, is attributable mostly to huge intergenic regions and introns with high repeat content (around 90%), the components of which resemble those of tetrapods (comprising mainly long interspersed nuclear elements) more than they do those of ray-finned fish. The lungfish genome continues to expand independently (its transposable elements are still active), through mechanisms different to those of the enormous genomes of salamanders. The 17 fully assembled lungfish macrochromosomes maintain synteny to other vertebrate chromosomes, and all microchromosomes maintain conserved ancient homology with the ancestral vertebrate karyotype. Our phylogenomic analyses confirm previous reports that lungfish occupy a key evolutionary position as the closest living relatives to tetrapods4,5, underscoring the importance of lungfish for understanding innovations associated with terrestrialization. Lungfish preadaptations to living on land include the gain of limb-like expression in developmental genes such as hoxc13 and sall1 in their lobed fins. Increased rates of evolution and the duplication of genes associated with obligate air-breathing, such as lung surfactants and the expansion of odorant receptor gene families (which encode proteins involved in detecting airborne odours), contribute to the tetrapod-like biology of lungfishes. These findings advance our understanding of this major transition during vertebrate evolution.
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Affiliation(s)
- Axel Meyer
- Department of Biology, University of Konstanz, Konstanz, Germany.
| | | | - Paolo Franchini
- Department of Biology, University of Konstanz, Konstanz, Germany
| | - Kang Du
- Developmental Biochemistry, Biocenter, University of Würzburg, Würzburg, Germany
- The Xiphophorus Genetic Stock Center, Texas State University, San Marcos, TX, USA
| | | | - Iker Irisarri
- Department of Biodiversity and Evolutionary Biology, Museo Nacional de Ciencias Naturales (MNCN-CSIC), Madrid, Spain
- Department of Applied Bioinformatics, Institute for Microbiology and Genetics, University of Goettingen, Goettingen, Germany
| | - Wai Yee Wong
- Department of Neuroscience and Developmental Biology, University of Vienna, Vienna, Austria
| | | | - Susanne Kneitz
- Biochemistry and Cell Biology, Biocenter, University of Würzburg, Würzburg, Germany
| | - Akane Kawaguchi
- Research Institute of Molecular Pathology (IMP), Vienna, Austria
| | | | - Peiwen Xiong
- Department of Biology, University of Konstanz, Konstanz, Germany
| | - Corentin Dechaud
- Institut de Génomique Fonctionnelle, École Normale Superieure, Université Claude Bernard, Lyon, France
| | - Herman P Spaink
- Faculty of Science, Universiteit Leiden, Leiden, The Netherlands
| | - Jean-Nicolas Volff
- Institut de Génomique Fonctionnelle, École Normale Superieure, Université Claude Bernard, Lyon, France
| | - Oleg Simakov
- Department of Neuroscience and Developmental Biology, University of Vienna, Vienna, Austria.
| | | | - Elly M Tanaka
- Research Institute of Molecular Pathology (IMP), Vienna, Austria.
| | - Manfred Schartl
- Developmental Biochemistry, Biocenter, University of Würzburg, Würzburg, Germany.
- The Xiphophorus Genetic Stock Center, Texas State University, San Marcos, TX, USA.
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8
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Li M, Wang JF, Liu B, Wang XM. Homeobox B2 is a potential prognostic biomarker of glioblastoma. Rev Assoc Med Bras (1992) 2020; 66:794-799. [PMID: 32696872 DOI: 10.1590/1806-9282.66.6.794] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2019] [Accepted: 01/19/2020] [Indexed: 11/22/2022] Open
Abstract
SUMMARY OBJECTIVES HOXB2 is a new prognostic indicator for lung cancer. But it is unclear whether HOXB2 holds an effect in glioblastoma (GBM) progression. The purpose of this article was to probe the influences of HOXB2 on GBM pathogenesis. METHODS HOXB2 expression level and prognostic power in GBM patients were analyzed. Then the mRNA and protein expression levels of HOXB2 in GBM cell lines were tested by qRT-PCR and western blotting. Cell proliferation, invasion, and migration were determined by CCK8 and transwell assay, severally. The protein levels of PI3K/AKT-pathway associated proteins were analyzed by western blotting. RESULTS The results indicated that HOXB2 was distinctly overexpressed in GBM patients and high expression of HOXB2 was related to a poor prognosis. Moreover, the expression of HOXB2 was higher in all GBM cell lines U251, U-87MG, GOS-3 than that in HEB cells (normal control). Meanwhile, decreased expression of p-PI3K and p-AKT were identified after HOXB2 knockdown. CONCLUSIONS These data demonstrated that HOXB2 had a vital role in GBM progression and could serve as a promising target for GBM treatment.
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Affiliation(s)
- Ming Li
- Daqing Oilfield General Hospital, China
| | | | - Bo Liu
- Daqing Oilfield General Hospital, China
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9
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Woltering JM, Holzem M, Meyer A. Lissamphibian limbs and the origins of tetrapod hox domains. Dev Biol 2019; 456:138-144. [DOI: 10.1016/j.ydbio.2019.08.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 08/21/2019] [Accepted: 08/22/2019] [Indexed: 12/30/2022]
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10
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Purushothaman S, Elewa A, Seifert AW. Fgf-signaling is compartmentalized within the mesenchyme and controls proliferation during salamander limb development. eLife 2019; 8:48507. [PMID: 31538936 PMCID: PMC6754229 DOI: 10.7554/elife.48507] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 08/19/2019] [Indexed: 12/27/2022] Open
Abstract
Although decades of studies have produced a generalized model for tetrapod limb development, urodeles deviate from anurans and amniotes in at least two key respects: their limbs exhibit preaxial skeletal differentiation and do not develop an apical ectodermal ridge (AER). Here, we investigated how Sonic hedgehog (Shh) and Fibroblast growth factor (Fgf) signaling regulate limb development in the axolotl. We found that Shh-expressing cells contributed to the most posterior digit, and that inhibiting Shh-signaling inhibited Fgf8 expression, anteroposterior patterning, and distal cell proliferation. In addition to lack of a morphological AER, we found that salamander limbs also lack a molecular AER. We found that amniote and anuran AER-specific Fgfs and their cognate receptors were expressed entirely in the mesenchyme. Broad inhibition of Fgf-signaling demonstrated that this pathway regulates cell proliferation across all three limb axes, in contrast to anurans and amniotes where Fgf-signaling regulates cell survival and proximodistal patterning. Salamanders are a group of amphibians that are well-known for their ability to regenerate lost limbs and other body parts. At the turn of the twentieth century, researchers used salamander embryos as models to understand the basic concepts of how limbs develop in other four-limbed animals, including amphibians, mammals and birds, which are collectively known as “tetrapods”. However, the salamander’s amazing powers of regeneration made it difficult to carry out certain experiments, so researchers switched to using the embryos of other tetrapods – namely chickens and mice – instead. Studies in chickens, later confirmed in mice and frogs, established that there are two major signaling centers that control how the limbs of tetrapod embryos form and grow: a small group of cells known as the “zone of polarizing activity” within a structure called the “limb bud mesenchyme”; and an overlying, thin ridge of cells called the “apical ectodermal ridge”. Both of these centers release potent signaling molecules that act on cells in the limbs. The cells in the zone of polarizing activity produce a molecule often called Sonic hedgehog, or Shh for short. The apical ectodermal ridge produces another group of signals commonly known as fibroblast growth factors, or simply Fgfs. Several older studies reported that salamander embryos do not have an apical ectodermal ridge suggesting that these amphibian’s limbs may form differently to other tetrapods. Yet, contemporary models in developmental biology treated salamander limbs like those of chicks and mice. To address this apparent discrepancy, Purushothaman et al. studied how the forelimbs develop in a salamander known as the axolotl. The experiments showed that, along with lacking an apical ectodermal ridge, axolotls did not produce fibroblast growth factors normally found in this tissue. Instead, these factors were only found in the limb bud mesenchyme. Purushothaman et al. also found that fibroblast growth factors played a different role in axolotls than previously reported in chick, frog and mouse embryos. On the other hand, the pattern and function of Shh activity in the axolotl limb bud was similar to that previously observed in chicks and mice. These findings show that not all limbs develop in the same way and open up questions for evolutionary biologists regarding the evolution of limbs. Future studies that examine limb development in other animals that regenerate tissues, such as other amphibians and lungfish, will help answer these questions.
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Affiliation(s)
| | - Ahmed Elewa
- Cold Spring Harbor Laboratory, Cold Spring Harbor, United States
| | - Ashley W Seifert
- Department of Biology, University of Kentucky, Lexington, United States
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11
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Hirasawa T, Kuratani S. Evolution of the muscular system in tetrapod limbs. ZOOLOGICAL LETTERS 2018; 4:27. [PMID: 30258652 PMCID: PMC6148784 DOI: 10.1186/s40851-018-0110-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 09/04/2018] [Indexed: 05/16/2023]
Abstract
While skeletal evolution has been extensively studied, the evolution of limb muscles and brachial plexus has received less attention. In this review, we focus on the tempo and mode of evolution of forelimb muscles in the vertebrate history, and on the developmental mechanisms that have affected the evolution of their morphology. Tetrapod limb muscles develop from diffuse migrating cells derived from dermomyotomes, and the limb-innervating nerves lose their segmental patterns to form the brachial plexus distally. Despite such seemingly disorganized developmental processes, limb muscle homology has been highly conserved in tetrapod evolution, with the apparent exception of the mammalian diaphragm. The limb mesenchyme of lateral plate mesoderm likely plays a pivotal role in the subdivision of the myogenic cell population into individual muscles through the formation of interstitial muscle connective tissues. Interactions with tendons and motoneuron axons are involved in the early and late phases of limb muscle morphogenesis, respectively. The mechanism underlying the recurrent generation of limb muscle homology likely resides in these developmental processes, which should be studied from an evolutionary perspective in the future.
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Affiliation(s)
- Tatsuya Hirasawa
- Laboratory for Evolutionary Morphology, RIKEN Center for Biosystems Dynamics Research (BDR), 2-2-3 Minatojima-minami, Chuo-ku, Kobe, Hyogo 650-0047 Japan
| | - Shigeru Kuratani
- Laboratory for Evolutionary Morphology, RIKEN Center for Biosystems Dynamics Research (BDR), 2-2-3 Minatojima-minami, Chuo-ku, Kobe, Hyogo 650-0047 Japan
- Evolutionary Morphology Laboratory, RIKEN Cluster for Pioneering Research (CPR), 2-2-3 Minatojima-minami, Chuo-ku, Kobe, Hyogo 650-0047 Japan
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