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Razmadze D, Salomies L, Di-Poï N. Squamates as a model to understand key dental features of vertebrates. Dev Biol 2024; 516:1-19. [PMID: 39069116 DOI: 10.1016/j.ydbio.2024.07.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 06/11/2024] [Accepted: 07/23/2024] [Indexed: 07/30/2024]
Abstract
Thanks to their exceptional diversity, teeth are among the most distinctive features of vertebrates. Parameters such as tooth size, shape, number, identity, and implantation can have substantial implications for the ecology and certain social behaviors of toothed species. Despite decades of research primarily focused on mammalian dentition, particularly using the laboratory mouse model, squamate reptiles ("lizards" and snakes) offer a wide array of tooth types and dentition variations. This diversity, which includes differences in size, shape, function, and replacement capacity, provides invaluable opportunities for investigating these fundamental properties. The central bearded dragon (Pogona vitticeps), a popular pet species with well-established husbandry practices, is of particular interest. It features a broad spectrum of morphs and spontaneous mutants and exhibits a wide range of heterodont phenotypes, including variation in the size, shape, number, implantation, and renewal of teeth at both posterior and anterior positions. These characteristics position the species as a crucial model organism for developmental studies in tooth research and for gaining deeper insights into evolutionary patterns of vertebrate dentitions. In this article, we provide an overview of the current understanding of squamate dentition, its diversity, development, and replacement. Furthermore, we discuss the significant advantages offered by squamate species as model organisms for investigating the evolutionary and developmental aspects of vertebrate dentition.
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Affiliation(s)
- Daria Razmadze
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, 00014, Helsinki, Finland
| | - Lotta Salomies
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, 00014, Helsinki, Finland
| | - Nicolas Di-Poï
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, 00014, Helsinki, Finland.
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Eckhart L, Holthaus KB, Sachslehner AP. Cell differentiation in the embryonic periderm and in scaffolding epithelia of skin appendages. Dev Biol 2024; 515:60-66. [PMID: 38964706 DOI: 10.1016/j.ydbio.2024.07.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 05/10/2024] [Accepted: 07/02/2024] [Indexed: 07/06/2024]
Abstract
Terminal differentiation of epithelial cells is critical for the barrier function of the skin, the growth of skin appendages, such as hair and nails, and the development of the skin of amniotes. Here, we present the hypothesis that the differentiation of cells in the embryonic periderm shares characteristic features with the differentiation of epithelial cells that support the morphogenesis of cornified skin appendages during postnatal life. The periderm prevents aberrant fusion of adjacent epithelial sites during early skin development. It is shed off when keratinocytes of the epidermis form the cornified layer, the stratum corneum. A similar role is played by epithelia that ensheath cornifying skin appendages until they disintegrate to allow the separation of the mature part of the skin appendage from the adjacent tissue. These epithelia, exemplified by the inner root sheath of hair follicles and the epithelia close to the free edge of nails or claws, are referred to as scaffolding epithelia. The periderm and scaffolding epithelia are similar with regard to their transient functions in separating tissues and the conserved expression of trichohyalin and trichohyalin-like genes in mammals and birds. Thus, we propose that parts of the peridermal differentiation program were coopted to a new postnatal function during the evolution of cornified skin appendages in amniotes.
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Affiliation(s)
- Leopold Eckhart
- Department of Dermatology, Medical University of Vienna, Vienna, Austria.
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Sachslehner AP, Surbek M, Holthaus KB, Steinbinder J, Golabi B, Hess C, Eckhart L. The Evolution of Transglutaminases Underlies the Origin and Loss of Cornified Skin Appendages in Vertebrates. Mol Biol Evol 2024; 41:msae100. [PMID: 38781495 PMCID: PMC11152450 DOI: 10.1093/molbev/msae100] [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: 02/13/2024] [Revised: 04/11/2024] [Accepted: 05/20/2024] [Indexed: 05/25/2024] Open
Abstract
Transglutaminases (TGMs) cross-link proteins by introducing covalent bonds between glutamine and lysine residues. These cross-links are essential for epithelial cornification which enables tetrapods to live on land. Here, we investigated which evolutionary adaptations of vertebrates were associated with specific changes in the family of TGM genes. We determined the catalog of TGMs in the main clades of vertebrates, performed a comprehensive phylogenetic analysis of TGMs, and localized the distribution of selected TGMs in tissues. Our data suggest that TGM1 is the phylogenetically oldest epithelial TGM, with orthologs being expressed in the cornified teeth of the lamprey, a basal vertebrate. Gene duplications led to the origin of TGM10 in stem vertebrates, the origin of TGM2 in jawed vertebrates, and an increasing number of epithelium-associated TGM genes in the lineage leading to terrestrial vertebrates. TGM9 is expressed in the epithelial egg tooth, and its evolutionary origin in stem amniotes coincided with the evolution of embryonic development in eggs that are surrounded by a protective shell. Conversely, viviparous mammals have lost both the epithelial egg tooth and TGM9. TGM3 and TGM6 evolved as regulators of cornification in hair follicles and underwent pseudogenization upon the evolutionary loss of hair in cetaceans. Taken together, this study reveals the gain and loss of vertebrate TGM genes in association with the evolution of cornified skin appendages and suggests an important role of TGM9 in the evolution of amniotes.
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Affiliation(s)
| | - Marta Surbek
- Department of Dermatology, Medical University of Vienna, 1090 Vienna, Austria
| | | | - Julia Steinbinder
- Department of Dermatology, Medical University of Vienna, 1090 Vienna, Austria
| | - Bahar Golabi
- Department of Dermatology, Medical University of Vienna, 1090 Vienna, Austria
| | - Claudia Hess
- Clinic for Poultry and Fish Medicine, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine Vienna, 1210 Vienna, Austria
| | - Leopold Eckhart
- Department of Dermatology, Medical University of Vienna, 1090 Vienna, Austria
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Holthaus KB, Eckhart L. Development-Associated Genes of the Epidermal Differentiation Complex (EDC). J Dev Biol 2024; 12:4. [PMID: 38248869 PMCID: PMC10801484 DOI: 10.3390/jdb12010004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 12/28/2023] [Accepted: 01/10/2024] [Indexed: 01/23/2024] Open
Abstract
The epidermal differentiation complex (EDC) is a cluster of genes that encode protein components of the outermost layers of the epidermis in mammals, reptiles and birds. The development of the stratified epidermis from a single-layered ectoderm involves an embryo-specific superficial cell layer, the periderm. An additional layer, the subperiderm, develops in crocodilians and over scutate scales of birds. Here, we review the expression of EDC genes during embryonic development. Several EDC genes are expressed predominantly or exclusively in embryo-specific cell layers, whereas others are confined to the epidermal layers that are maintained in postnatal skin. The S100 fused-type proteins scaffoldin and trichohyalin are expressed in the avian and mammalian periderm, respectively. Scaffoldin forms the so-called periderm granules, which are histological markers of the periderm in birds. Epidermal differentiation cysteine-rich protein (EDCRP) and epidermal differentiation protein containing DPCC motifs (EDDM) are expressed in the avian subperiderm where they are supposed to undergo cross-linking via disulfide bonds. Furthermore, a histidine-rich epidermal differentiation protein and feather-type corneous beta-proteins, also known as beta-keratins, are expressed in the subperiderm. The accumulating evidence for roles of EDC genes in the development of the epidermis has implications on the evolutionary diversification of the skin in amniotes.
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Affiliation(s)
| | - Leopold Eckhart
- Department of Dermatology, Medical University of Vienna, 1090 Vienna, Austria
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Establishment of a culture model for the prolonged maintenance of chicken feather follicles structure in vitro. PLoS One 2022; 17:e0271448. [PMID: 36206252 PMCID: PMC9544018 DOI: 10.1371/journal.pone.0271448] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Accepted: 06/30/2022] [Indexed: 11/05/2022] Open
Abstract
Protocols allowing the in vitro culture of human hair follicles in a serum free-medium up to 9 days were developed 30 years ago. By using similar protocols, we achieved the prolonged maintenance in vitro of juvenile feather follicles (FF) microdissected from young chickens. Histology showed a preservation of the FF up to 7 days as well as feather morphology compatible with growth and/or differentiation. The integrity of the FF wall epithelium was confirmed by transmission electron microscopy at Day 5 and 7 of culture. A slight elongation of the feathers was detected up to 5 days for 75% of the examined feathers. By immunochemistry, we demonstrated the maintenance of expression and localization of two structural proteins: scaffoldin and fibronectin. Gene expression (assessed by qRT-PCR) of NCAM, LCAM, Wnt6, Notch1, and BMP4 was not altered. In contrast, Shh and HBS1 expression collapsed, DKK3 increased, and KRT14 transiently increased upon cultivation. This indicates that cultivation modifies the mRNA expression of a few genes, possibly due to reduced growth or cell differentiation in the feather, notably in the barb ridges. In conclusion, we have developed the first method that allows the culture and maintenance of chicken FF in vitro that preserves the structure and biology of the FF close to its in vivo state, despite transcriptional modifications of a few genes involved in feather development. This new culture model may serve to study feather interactions with pathogens or toxics and constitutes a way to reduce animal experimentation.
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Perry SM, Whitt JG, Reyna KS. The normal stages of development for the California valley quail. PLoS One 2022; 17:e0268524. [PMID: 35580090 PMCID: PMC9113606 DOI: 10.1371/journal.pone.0268524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Accepted: 05/02/2022] [Indexed: 11/19/2022] Open
Abstract
One challenge in avian embryology is establishing a standard developmental timetable, primarily because eggs incubated for identical durations can vary in developmental progress, even within the same species. For remedy, avian development is classified into distinct stages based on the formation of key morphological structures. Developmental stages exist for a few galliform species, but the literature is lacking a description of normal stages for California valley quail (Callipepla californica). Thus, the objective of this study was to stage and document the morphological and structural development of California valley quail. Over two laying seasons, 390 eggs were incubated at 37.8֯ C in 60% RH for ≤23 days. Eggs were opened every ≤6 hours to document embryonic development, including, blastoderm diameter, anterior angle of nostril to beak tip, and lengths of wing, tarsus, third toe, total beak, total foot, and embryo. California valley quail embryos were staged and compared to domestic chicken (Gallus gallus domesticus), the staging standard for galliformes, as well as Japanese quail (Coturnix japonica), blue-breasted quail (Synoicus chinensis) and northern bobwhite quail (Colinus virginianus). This study produced the first description of the 43 normal stages of development for California valley quail. Compared with other galliformes, the California valley quail has a different number of stages and displays developmental heterochrony in stages 1-24, and morphological and developmental differences in stages 25-hatch. The observed differences emphasize the importance of staging individual avian species instead of relying on poultry animal models or close relatives for developmental reference. This is extremely important in species-specific embryological studies that evaluate critical windows of development or evaluate the impacts of environmental change on avian development. This study also suggests that staging frequencies of ≤6 hours and egg transport protocols should be standardized for future staging studies.
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Affiliation(s)
- Shelby M. Perry
- The Quail Research Laboratory, Texas A&M University-Commerce, Commerce, Texas, United States of America
| | - Jeffrey G. Whitt
- The Quail Research Laboratory, Texas A&M University-Commerce, Commerce, Texas, United States of America
| | - Kelly S. Reyna
- The Quail Research Laboratory, Texas A&M University-Commerce, Commerce, Texas, United States of America
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Sachslehner AP, Surbek M, Lachner J, Paudel S, Eckhart L. Identification of Chicken Transglutaminase 1 and In Situ Localization of Transglutaminase Activity in Avian Skin and Esophagus. Genes (Basel) 2021; 12:1565. [PMID: 34680960 PMCID: PMC8535770 DOI: 10.3390/genes12101565] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 09/27/2021] [Accepted: 09/29/2021] [Indexed: 12/30/2022] Open
Abstract
Transglutaminase 1 (TGM1) is a membrane-anchored enzyme that cross-links proteins during terminal differentiation of epidermal and esophageal keratinocytes in mammals. The current genome assembly of the chicken, which is a major model for avian skin biology, does not include an annotated region corresponding to TGM1. To close this gap of knowledge about the genetic control of avian cornification, we analyzed RNA-sequencing reads from organotypic chicken skin and identified TGM1 mRNA. By RT-PCR, we demonstrated that TGM1 is expressed in the skin and esophagus of chickens. The cysteine-rich sequence motif required for palmitoylation and membrane anchorage is conserved in the chicken TGM1 protein, and differentiated chicken keratinocytes display membrane-associated transglutaminase activity. Expression of TGM1 and prominent transglutaminase activity in the esophageal epithelium was also demonstrated in the zebra finch. Altogether, the results of this study indicate that TGM1 is conserved among birds and suggest that chicken keratinocytes may be a useful model for the study of TGM1 in non-mammalian cornification.
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Affiliation(s)
- Attila Placido Sachslehner
- Skin Biology Laboratory, Department of Dermatology, Medical University of Vienna, 1090 Vienna, Austria; (A.P.S.); (M.S.); (J.L.)
| | - Marta Surbek
- Skin Biology Laboratory, Department of Dermatology, Medical University of Vienna, 1090 Vienna, Austria; (A.P.S.); (M.S.); (J.L.)
| | - Julia Lachner
- Skin Biology Laboratory, Department of Dermatology, Medical University of Vienna, 1090 Vienna, Austria; (A.P.S.); (M.S.); (J.L.)
| | - Surya Paudel
- Clinic for Poultry and Fish Medicine, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine Vienna, 1210 Vienna, Austria;
| | - Leopold Eckhart
- Skin Biology Laboratory, Department of Dermatology, Medical University of Vienna, 1090 Vienna, Austria; (A.P.S.); (M.S.); (J.L.)
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Alibardi L, Eckhart L. Immunolocalization of epidermal differentiation complex proteins reveals distinct molecular compositions of cells that control structure and mechanical properties of avian skin appendages. J Morphol 2021; 282:917-933. [PMID: 33830534 DOI: 10.1002/jmor.21357] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 04/02/2021] [Accepted: 04/07/2021] [Indexed: 11/09/2022]
Abstract
The epidermal differentiation complex (EDC) is a cluster of genes that encode structural proteins of skin derivatives with variable mechanical performances, from the scales of reptiles and birds to the hard claws and beaks, and to the flexible but resistant corneous material of feathers. Corneous proteins with or without extended beta-regions are produced from avian genomes, and include the largely prevalent corneous beta proteins (CβPs, formerly indicated as beta-keratins), and minor contribution from histidine-rich proteins, trichohyalin-like proteins (scaffoldin), loricrin, and other proteins rich in cysteine or other types of amino acids. The light-microscopic and ultrastructural immunolocalization of major and minor EDC-proteins in avian skin (feather CβPs, EDKM, EDWM, EDMTFH, EDDM, and scaffoldin) suggests that each specific appendage consists of a particular mix of these proteins in addition to the main proteins containing a peculiar beta-region of 34 amino acids, indicated as feather/scale/claw/beak CβPs (fCβPs, sCβPs, cCβPs, bCβPs). This indicates that numerous proteins of the EDC are added to the variable meshwork of intermediate filament keratins to produce avian epidermis with different mechanical and functional properties. Although the specific roles for these proteins are not known they likely make an important contribution to the final material properties of the different skin appendages of birds. The highest number of sauropsid CβPs is found in birds, suggesting a relation to the evolution of feathers, and additional epidermal differentiation proteins have contributed to the evolutionary adaptations of avian skin.
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Affiliation(s)
- Lorenzo Alibardi
- Comparative Histolab Padova and Department of Biology, University of Bologna, Bologna, Italy
| | - Leopold Eckhart
- Department of Dermatology, Medical University of Vienna, Vienna, Austria
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