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Khan PA, Crawford MJ. Regeneration and development. An amphibian call to arms. Dev Dyn 2020; 250:896-901. [DOI: 10.1002/dvdy.272] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 11/10/2020] [Accepted: 11/11/2020] [Indexed: 01/22/2023] Open
Affiliation(s)
- Paul A. Khan
- Department of Biomedical Sciences University of Windsor Windsor Ontario Canada
| | - Michael J. Crawford
- Department of Biomedical Sciences University of Windsor Windsor Ontario Canada
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2
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Yeung KWY, Zhou GJ, Hilscherová K, Giesy JP, Leung KMY. Current understanding of potential ecological risks of retinoic acids and their metabolites in aquatic environments. ENVIRONMENT INTERNATIONAL 2020; 136:105464. [PMID: 31926435 DOI: 10.1016/j.envint.2020.105464] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 12/13/2019] [Accepted: 01/02/2020] [Indexed: 06/10/2023]
Abstract
In animals, retinoic acids (RAs), one of the main derivatives of vitamin A, are crucial for a variety of physiological processes. RAs, including all-trans-RA, 9-cis-RA, 13-cis-RA, and their corresponding metabolites (i.e., all-trans-4-oxo-RA, 9-cis-4-oxo-RA and 13-cis-4-oxo-RA) can be excreted through urination from humans and animals. Sewage treatment plants (STPs) are a significant source of RAs and 4-oxo-RAs into aquatic environments. RAs and 4-oxo-RAs can be identified and quantified by use of liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). RAs and 4-oxo-RAs have been reported in various environmental matrices including rivers, lakes, reservoirs and coastal marine environments as well as in sewage effluents discharged from STPs. Greater concentrations of RAs and 4-oxo-RAs have been observed during blooms of cyanobacteria and microalgae, suggesting that cyanobacteria and microalgae are natural sources of RAs and 4-oxo-RAs in aquatic environments. These potential sources of RAs and 4-oxo-RAs raise concerns about their concentrations and risks in aquatic environments because excessive intake of these chemicals can result in abnormal morphological development in animals. Teratogenic effects were observed in amphibians, fish embryos, gastropods, mammals and birds when exposed to RAs. This review summarizes sources, concentrations, adverse effects and ecological risks of RAs and 4-oxo-RAs in aquatic environments. An interim, predicted no-effect concentration (PNEC) of RAs (in terms of at-RA) for freshwater environments was determined to be 3.93 ng/L at-RA equivalents. Based on limited data on concentrations of RAs in freshwater ecosystems, their hazard quotients were found to range from zero to 16.41, depending on the environmental conditions of receiving waters. Ecological risks of RAs in marine environments are yet to be explored due to the paucity of data related to both their concentrations in marine environment and toxic potencies to marine species. This review updates current knowledge of RAs and 4-oxo-RAs in aquatic environments and calls for more studies on their concentrations and fate in aquatic environments, especially estuarine and coastal marine environments with a view to enabling a comprehensive assessment of their ecological risks around the globe.
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Affiliation(s)
- Katie Wan Yee Yeung
- The Swire Institute of Marine Science and School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong, China
| | - Guang-Jie Zhou
- The Swire Institute of Marine Science and School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong, China.
| | - Klára Hilscherová
- RECETOX, Faculty of Science, Masaryk University, Kamenice 753/5, Pavilion A29, 625 00 Brno, Czech Republic
| | - John P Giesy
- Department of Veterinary Biomedical Sciences and Toxicology Centre, University of Saskatchewan, Saskatoon, SK, Canada; Department of Environmental Science, Baylor University, Waco, TX, United States
| | - Kenneth Mei Yee Leung
- The Swire Institute of Marine Science and School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong, China; State Key Laboratory of Marine Pollution (City University of Hong Kong), Tat Chee Avenue, Kowloon, Hong Kong, China.
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3
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Evans T, Wade CM, Chapman FA, Johnson AD, Loose M. Acquisition of germ plasm accelerates vertebrate evolution. Science 2014; 344:200-3. [PMID: 24723612 DOI: 10.1126/science.1249325] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Primordial germ cell (PGC) specification occurs either by induction from pluripotent cells (epigenesis) or by a cell-autonomous mechanism mediated by germ plasm (preformation). Among vertebrates, epigenesis is basal, whereas germ plasm has evolved convergently across lineages and is associated with greater speciation. We compared protein-coding sequences of vertebrate species that employ preformation with their sister taxa that use epigenesis and demonstrate that genes evolve more rapidly in species containing germ plasm. Furthermore, differences in rates of evolution appear to cause phylogenetic incongruence in protein-coding sequence comparisons between vertebrate taxa. Our results support the hypothesis that germ plasm liberates constraints on somatic development and that enhanced evolvability drives the evolution of germ plasm.
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Affiliation(s)
- Teri Evans
- School of Life Sciences, University of Nottingham, Nottingham, NG7 2UH, UK
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4
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Stopper GF, Wagner GP. Inhibition of Sonic hedgehog signaling leads to posterior digit loss in Ambystoma mexicanum: parallels to natural digit reduction in urodeles. Dev Dyn 2007; 236:321-31. [PMID: 17117438 DOI: 10.1002/dvdy.21025] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Molecular mechanisms patterning the tetrapod limb, including anterior-posterior axis determination involving Sonic hedgehog (Shh), have received much attention, particularly in amniotes. Anterior-posterior patterning in urodele amphibians differs radically from that of amniotes in that it shows a pronounced anterior-to-posterior sequence of digit development. In contrast, amniotes develop their digits almost simultaneously with a slight posterior-to-anterior polarity. Here we use cyclopamine, an inhibitor of the Hedgehog signaling pathway, to investigate the role of Shh in anterior-posterior patterning in the urodele limb. Inhibition of Shh signal transduction affects digit number long before their morphological appearance. In accordance with the apparently derived order of digit development in urodeles, exposure reproducibly removes digits in a posterior-to-anterior sequence, the inverse of their developmental sequence. This pattern of digit loss mimics the order of digit loss in natural variation. We suggest that variation in Shh expression and/or signal transmission may explain natural variation in digit number in urodeles.
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Affiliation(s)
- Geffrey F Stopper
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, USA.
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5
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Hutchison C, Pilote M, Roy S. The axolotl limb: a model for bone development, regeneration and fracture healing. Bone 2007; 40:45-56. [PMID: 16920050 DOI: 10.1016/j.bone.2006.07.005] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2006] [Revised: 06/30/2006] [Accepted: 07/04/2006] [Indexed: 11/18/2022]
Abstract
Among vertebrates, urodele amphibians (e.g., axolotls) have the unique ability to perfectly regenerate complex body parts after amputation. The limb has been the most widely studied due to the presence of three defined axes and its ease of manipulation. Hence, the limb has been chosen as a model to study the process of skeletogenesis during axolotl development, regeneration and to analyze this animal's ability to heal bone fractures. Extensive studies have allowed researchers to gain some knowledge of the mechanisms controlling growth and pattern formation in regenerating and developing limbs, offering an insight into how vertebrates are able to regenerate tissues. In this study, we report the cloning and characterization of two axolotl genes; Cbfa-1, a transcription factor that controls the remodeling of cartilage into bone and PTHrP, known for its involvement in the differentiation and maturation of chondrocytes. Whole-mount in situ hybridization and immunohistochemistry results show that Cbfa-1, PTHrP and type II collagen are expressed during limb development and regeneration. These genes are expressed during specific stages of limb development and regeneration which are consistent with the appearance of skeletal elements. The expression pattern for Cbfa-1 in late limb development was similar to the expression pattern found in the late stages of limb regeneration (i.e. re-development phase) and it did not overlap with the expression of type II collagen. It has been reported that the molecular mechanisms involved in the re-development phase of limb regeneration are a recapitulation of those used in developing limbs; therefore the detection of Cbfa-1 expression during regeneration supports this assertion. Conversely, PTHrP expression pattern was different during limb development and regeneration, by its intensity and by the localization of the signal. Finally, despite its unsurpassed abilities to regenerate, we tested whether the axolotl was able to regenerate non-union bone fractures. We show that while the axolotl is able to heal a non-stabilized union fracture, like other vertebrates, it is incapable of healing a bone gap of critical dimension. These results suggest that the axolotl does not use the regeneration process to repair bone fractures.
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Affiliation(s)
- Cara Hutchison
- Department of Biochemistry, Université de Montréal, Québec, Canada
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6
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Stopper GF, Wagner GP. Of chicken wings and frog legs: a smorgasbord of evolutionary variation in mechanisms of tetrapod limb development. Dev Biol 2005; 288:21-39. [PMID: 16246321 DOI: 10.1016/j.ydbio.2005.09.010] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2005] [Revised: 09/06/2005] [Accepted: 09/06/2005] [Indexed: 01/24/2023]
Abstract
The tetrapod limb, which has served as a paradigm for the study of development and morphological evolution, is becoming a paradigm for developmental evolution as well. In its origin and diversification, the tetrapod limb has undergone a great deal of remodeling. These morphological changes and other evolutionary phenomena have produced variation in mechanisms of tetrapod limb development. Here, we review that variation in the four major clades of limbed tetrapods. Comparisons in a phylogenetic context reveal details of development and evolution that otherwise may have been unclear. Such details include apparent differences in the mechanisms of dorsal-ventral patterning and limb identity specification between mouse and chick and mechanistic novelties in amniotes, anurans, and urodeles. As we gain a better understanding of the details of limb development, further differences among taxa will be revealed. The use of appropriate comparative techniques in a phylogenetic context thus sheds light on evolutionary transitions in limb morphology and the generality of developmental models across species and is therefore important to both evolutionary and developmental biologists.
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Affiliation(s)
- Geffrey F Stopper
- Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect Street, New Haven, CT 06520, USA.
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7
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Alsop DH, Brown SB, van der Kraak GJ. Dietary retinoic acid induces hindlimb and eye deformities in Xenopus laevis. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2004; 38:6290-6299. [PMID: 15597884 DOI: 10.1021/es049765n] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
This study investigated the effects of dietary retinoic acid (RA) on frog hindlimb development. Xenopus laevis (African clawed frog) tadpoles were fed a diet supplemented with 0, 1, 10, or 100 microg of RA/g of food for 2 or 5 d at different stages of metamorphosis. Hindlimb deformities were induced in the group fed 100 microg of RA/g of diet for 5 d. Exposures beginning at mid-hindlimb bud development induced bilaterally bent tibiafibula (bony triangles), while exposures later in hindlimb development induced deformities of the feet, including fusion of the 1st and 2nd clawed digits and reduced length of the 4th and 5th digits (due to reduced, missing, or misplaced phalanges). There were also cases of extra phalanges in the 5th digit. The eye was another target of RA exposure. In one experiment, 58% of the tadpoles fed 10 microg of RA/g had a smaller or absent right eye. Additionally, 11% of the tadpoles fed 100 microg of RA/g of diet developed a smaller or absent left eye. Waterborne heavy metals (Zn or Cu) modified RA effects on the hindlimb and eye. Co-exposure to metals and RA resulted in cases of unilateral bony triangles and reduced rates of smaller eyes. There were also cases of extra hindlimb digits in Zn-exposed animals. Dietary RA exposure in tadpoles can cause some deformities that differ from waterborne RA exposures in previous studies. RA also induced deformities that resemble those in affected wild frog populations (bony triangles), although the patterns of other deformities and missing segments (phalanges and metatarsals) are not similar to those documented in the wild.
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Affiliation(s)
- Derek H Alsop
- Department of Zoology, University of Guelph, Guelph, Ontario, Canada N1G 2W.
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8
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Tsonis PA, Vergara MN, Spence JR, Madhavan M, Kramer EL, Call MK, Santiago WG, Vallance JE, Robbins DJ, Del Rio-Tsonis K. A novel role of the hedgehog pathway in lens regeneration. Dev Biol 2004; 267:450-61. [PMID: 15013805 DOI: 10.1016/j.ydbio.2003.12.005] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2003] [Revised: 12/01/2003] [Accepted: 12/01/2003] [Indexed: 10/26/2022]
Abstract
Lens regeneration in the adult newt is a classic example of replacing a lost organ by the process of transdifferentiation. After lens removal, the pigmented epithelial cells of the dorsal iris proliferate and dedifferentiate to form a lens vesicle, which subsequently differentiates to form a new lens. In searching for factors that control this remarkable process, we investigated the expression and role of hedgehog pathway members. These molecules are known to affect retina and pigment epithelium morphogenesis and have been recently shown to be involved in repair processes. Here we show that Shh, Ihh, ptc-1, and ptc-2 are expressed during lens regeneration. The expression of Shh and Ihh is quite unique since these genes have never been detected in lens. Interestingly, both Shh and Ihh are only expressed in the regenerating and developing lens, but not in the intact lens. Interfering with the hedgehog pathway results in considerable inhibition of the process of lens regeneration, including decreased cell proliferation as well as interference with lens fiber differentiation in the regenerating lens vesicle. Down-regulation of ptc-1 was also observed when inhibiting the pathway. These results provide the first evidence of a novel role for the hedgehog pathway in specific regulation of the regenerating lens.
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Affiliation(s)
- Panagiotis A Tsonis
- Laboratory of Molecular Biology, Department of Biology, University of Dayton, Dayton, OH 45469-2320, USA.
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9
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Abstract
Larval and adult urodeles and anuran tadpoles readily regenerate their limbs via a process of histolysis and dedifferentiation of mature cells local to the amputation surface that accumulate under the wound epithelium as a blastema of stem cells. These stem cells require growth and trophic factors from the apical epidermal cap (AEC) and the nerves that re-innervate the blastema for their survival and proliferation. Members of the fibroblast growth factor (FGF) family synthesized by both AEC and nerves, and glial growth factor, substance P, and transferrin of nerves are suspected survival and proliferation factors. Stem cells derived from fibroblasts and muscle cells can transdifferentiate into other cell types during regeneration. The regeneration blastema is a self-organizing system based on positional information inherited from parent limb cells. Retinoids, which act through nuclear receptors, have been used in conjunction with assays for cell adhesivity to show that positional identity of blastema cells is encoded in the cell surface. These molecules are involved in the cell-cell signaling network that re-establishes the original structural pattern of the limb. Other systems of interest that regenerate by histolysis and dedifferentiation of pigmented epithelial cells are the neural retina and lens. Members of the FGF family are also important to the regeneration of these structures. The mechanism of amphibian regeneration by dedifferentiation is of importance to the development of a regenerative medicine, since understanding this mechanism may offer insights into how we might chemically induce the regeneration of mammalian tissues.
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Affiliation(s)
- D L Stocum
- Department of Biology, Indiana University Center for Regenerative Biology and Medicine, School of Science, Indiana University-Purdue University Indianapolis, 402 N. Blackford St., Indianapolis, IN 46202, USA.
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10
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Abstract
Cell signaling plays a key role in the development of all multicellular organisms. Numerous studies have established the importance of Hedgehog signaling in a wide variety of regulatory functions during the development of vertebrate and invertebrate organisms. Several reviews have discussed the signaling components in this pathway, their various interactions, and some of the general principles that govern Hedgehog signaling mechanisms. This review focuses on the developing systems themselves, providing a comprehensive survey of the role of Hedgehog signaling in each of these. We also discuss the increasing significance of Hedgehog signaling in the clinical setting.
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Affiliation(s)
- Andrew P McMahon
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
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11
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Abstract
Urodele amphibians have been widely used for studies of limb regeneration. In this article, we review studies on blastema cell proliferation and propose a model of blastemal self-organization and patterning. The model is based on local cell interactions that intercalate positional identities within circumferential and proximodistal boundaries that outline the regenerate. The positional identities created by the intercalation process appear to be reflected in the molecular composition of the cell surface. Transcription factors and signaling molecules involved in patterning are discussed within the context of the boundary/intercalation model.
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Affiliation(s)
- Holly L D Nye
- University of Illinois Department of Cell and Structural Biology and College of Medicine, B107 Chemical and Life Sciences Laboratory, Urbana, Illinois, USA
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12
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Roy S, Gardiner DM. Cyclopamine induces digit loss in regenerating axolotl limbs. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 2002; 293:186-90. [PMID: 12115913 DOI: 10.1002/jez.10110] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Axolotls, with their extensive ability to regenerate as adults, provide a useful model for studying the mechanisms of regeneration in a vertebrate, in hopes of understanding why other vertebrates cannot regenerate. Although the expression of many genes has been described in regeneration, techniques for gain and loss of function analyses have been limited. We demonstrated in a previous study that gain of function for secreted proteins was possible in the axolotl using the vaccinia virus to drive expression of the transgene. In this study, we used a pharmacological approach made possible by the existence of a naturally occurring compound that specifically blocks shh signaling, cyclopamine. The treatment of axolotls with cyclopamine during the process of limb regeneration caused a loss of digits similar to that described for the shh knockout mouse. Our results further demonstrate that shh signaling and function are conserved during limb regeneration in urodeles as in limb development in other vertebrates.
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Affiliation(s)
- Stéphane Roy
- Developmental Biology Center and Department of Developmental Cell Biology, University of California at Irvine, Irvine, California 92697, USA.
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13
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Hanken J, Carl TF, Richardson MK, Olsson L, Schlosser G, Osabutey CK, Klymkowsky MW. Limb development in a "nonmodel" vertebrate, the direct-developing frog Eleutherodactylus coqui. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 2001; 291:375-88. [PMID: 11754016 DOI: 10.1002/jez.1136] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Mechanisms that mediate limb development are regarded as highly conserved among vertebrates, especially tetrapods. Yet, this assumption is based on the study of relatively few species, and virtually none of those that display any of a large number of specialized life-history or reproductive modes, which might be expected to affect developmental pattern or process. Direct development is an alternative life history found in many anuran amphibians. Many adult features that form after hatching in metamorphic frogs, such as limbs, appear during embryogenesis in direct-developing species. Limb development in the direct-developing frog Eleutherodactylus coqui presents a mosaic of apparently conserved and novel features. The former include the basic sequence and pattern of limb chondrogenesis, which are typical of anurans generally and appear largely unaffected by the gross shift in developmental timing; expression of Distal-less protein (Dlx) in the distal ectoderm; expression of the gene Sonic hedgehog (Shh) in the zone of polarizing activity (ZPA); and the ability of the ZPA to induce supernumerary digits when transplanted to the anterior region of an early host limb bud. Novel features include the absence of a morphologically distinct apical ectodermal ridge, the ability of the limb to continue distal outgrowth and differentiation following removal of the distal ectoderm, and earlier cessation of the inductive ability of the ZPA. Attempts to represent tetrapod limb development as a developmental "module" must allow for this kind of evolutionary variation among species.
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Affiliation(s)
- J Hanken
- Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA.
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Bely AE, Wray GA. Evolution of regeneration and fission in annelids: insights from engrailed- and orthodenticle-class gene expression. Development 2001; 128:2781-91. [PMID: 11526083 DOI: 10.1242/dev.128.14.2781] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The recent explosion of information on the role of regulatory genes in embryogenesis provides an excellent opportunity to study how these genes participate in post-embryonic developmental processes. We present a detailed comparison of regulatory gene expression during regeneration and asexual reproduction (by fission) in the segmented worm Pristina leidyi (Annelida: Oligochaeta). We isolated three genes from Pristina, one homolog of engrailed and two homologs of orthodenticle, and characterized their expression in different developmental contexts. In situ hybridization studies on worms undergoing normal growth, regeneration and fission demonstrate that in all three processes, Pl-en is expressed primarily in the developing nervous system, and Pl-Otx1 and Pl-Otx2 are expressed primarily in the anterior body wall, foregut and developing nervous system. Our data reveal extensive similarities between expression during regeneration and fission, consistent with the idea that similar developmental processes underlie these two types of development. Thus, we argue that in these annelids fission may have evolved by recruitment of regenerative processes. Furthermore, by comparing our data to existing data from leech embryos, we find evidence that embryonic processes are re-deployed during regeneration and fission.
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Affiliation(s)
- A E Bely
- Department of Ecology and Evolution, State University of New York at Stony Brook, 11794-5245, USA.
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Capdevila J, Izpisúa Belmonte JC. Perspectives on the evolutionary origin of tetrapod limbs. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 2000; 288:287-303. [PMID: 11144278 DOI: 10.1002/1097-010x(20001215)288:4<287::aid-jez2>3.0.co;2-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The study of the origin and evolution of the tetrapod limb has benefited enormously from the confluence of molecular and paleontological data. In the last two decades, our knowledge of the basic molecular mechanisms that control limb development has grown exponentially, and developmental biologists now have the possibility of combining molecular data with many available descriptions of the fossil record of vertebrate fins and limbs. This synthesis of developmental and evolutionary biology has the potential to unveil the sequence of molecular changes that culminated in the adoption of the basic tetrapod limb plan.
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Affiliation(s)
- J Capdevila
- The Salk Institute for Biological Studies, La Jolla, CA 92037, USA.
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16
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Roy S, Gardiner DM, Bryant SV. Vaccinia as a tool for functional analysis in regenerating limbs: ectopic expression of Shh. Dev Biol 2000; 218:199-205. [PMID: 10656763 DOI: 10.1006/dbio.1999.9556] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Axolotls, with their extensive abilities to regenerate as adults, provide a useful model in which to study the mechanisms of regeneration in a vertebrate, in hopes of understanding why other vertebrates cannot regenerate. Although the expression of many genes has been described in regeneration, techniques for functional analysis have so far been limited. In this paper we demonstrate a new method for efficient overexpression of foreign genes in axolotls. Using vaccinia virus expressing beta-galactosidase microinjected into regenerating limbs, we show that vaccinia can infect both dividing and nondividing limb cells. The site of infection remains discrete and there is no secondary spread of infection to nearby cells. beta-Gal is expressed at high levels in blastema cells for about a week and in differentiated cells for longer. Blastemas that have been injected with vaccinia at different stages regenerate normally. As a test of the utility of vaccinia for functional analysis in regeneration, we constructed a virus expressing Shh and injected it into the anterior of regenerating limbs. Ectopic Shh expression caused extra digits, carpals, and tarsals in the hands and feet of regenerating limbs, suggesting that despite differences in the timing of expression and the eventual pattern, the function of Shh appears to be similar to that in the developing limbs of other vertebrates. Our results demonstrate that vaccinia virus is an excellent vector for ectopically expressing genes for secreted proteins and is a useful tool to study the function of signaling molecules during the process of regeneration in urodeles.
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Affiliation(s)
- S Roy
- Developmental Biology Center and Department of Developmental and Cell Biology, University of California at Irvine, Irvine, California 92697, USA
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Kierdorf U, Bartos L. Treatment of the growing pedicle with retinoic acid increased the size of the first antlers in fallow deer (Dama dama L.). COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PART C, PHARMACOLOGY, TOXICOLOGY & ENDOCRINOLOGY 1999; 124:7-9. [PMID: 10579642 DOI: 10.1016/s0742-8413(99)00038-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Unilateral injection of 10 mg of all-trans retinoic acid (RA) into the lateral portion of the growing pedicle of fallow bucks (n = 20) led to a significant (P = 0.033, Wilcoxon matched-pairs test) increase in first antler volume (median, 25.5 ml) as compared to the contralateral (control) side, injected with vehicle only (median, 21.5 ml). It is hypothesized that the RA treatment of the developing pedicle exercised a direct or indirect effect on the periosteal/perichondrial cells covering the growing cranial appendage, resulting in an increased proliferation rate of the cells of the antler perichondrium.
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Affiliation(s)
- U Kierdorf
- Institute of General and Systematic Zoology, Justus-Liebig-University of Giessen, Germany.
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