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Alibardi L. Microscopic structure and immunolabeling of extremely overlapped scales in some scincid, anguid, and pygopod lizards. PROTOPLASMA 2025; 262:99-115. [PMID: 39212701 DOI: 10.1007/s00709-024-01982-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2024] [Accepted: 08/21/2024] [Indexed: 09/04/2024]
Abstract
Skink, anguid, and pygopod lizards possess an extremely flat skin, imparting a compact and solid body and shining surface that facilitates their slider and/or fossorial movements. The present morphological study, conducted using immunohistochemistry and electron microscopy, has analyzed the microscopical morphology of extremely overlapped scales in different lizards, including species with limb reduction (scincids such as Lerista bougainvilli, Scincella lateralis, Lampropholis delicata) or legless (pygopods such as Lialis burtonis and Delma molleri and the anguid Anguis fragilis). The outer surface of the epidermis shows different micro-structures of the Oberhautchen layer containing corneous beta-proteins (CBPs) with variable immunoreactivity for these proteins. The beta-layer is relatively thick in most of these species, probably in relation to the resistance against strong mechanical forces acting on scales during the movements on harsh substrates. The scincid and anguid lizards also possess and regenerate osteoderms that reinforce scales flatness and mechanical resistance during the serpentiform or fossorial movements of these reptiles. Osteoderms are absent in pygopods. Roundish cells with a granular content are detected in the deep hinge region of scales in Lerista and Lampropholis skinks. Whether these cells may secrete substances that facilitate scale anti-friction and also determine shining of the skin surface remains to be shown.
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Affiliation(s)
- Lorenzo Alibardi
- Comparative Histolab Padova, Padua, Italy.
- Department of Biology, University of Bologna, Via Selmi 3, 40126, Bologna, Italy.
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2
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Alibardi L. Scales of non-avian reptiles and their derivatives contain corneous beta proteins coded from genes localized in the Epidermal Differentiation Complex. Tissue Cell 2023; 85:102228. [PMID: 37793208 DOI: 10.1016/j.tice.2023.102228] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Revised: 09/25/2023] [Accepted: 09/25/2023] [Indexed: 10/06/2023]
Abstract
The evolution of modern reptiles from basic reptilian ancestors gave rise to scaled vertebrates. Scales are of different types, and their corneous layer can shed frequently during the year in lepidosaurians (lizards, snakes), 1-2 times per year in the tuatara and in some freshwater turtle, irregularly in different parts of the body in crocodilians, or simply wore superficially in marine and terrestrial turtles. Lepidosaurians possess tuberculate, non-overlapped or variably overlapped scales with inter-scale (hinge) regions. The latter are hidden underneath the outer scale surface or may be more exposed in specific body areas. Hinge regions allow stretching during growth and movement so that the skin remains mechanically functional. Crocodilian and turtles feature flat and shield scales (scutes) with narrow inter-scale regions for stretching and growth. The epidermis of non-avian reptilian hinge regions is much thinner than the exposed outer surface of scales and is less cornified. Despite the thickness of the epidermis, scales are mainly composed of variably amount of Corneous Beta Proteins (CBPs) that are coded in a gene cluster known as EDC (Epidermal Differentiation Complex). These are small proteins, 100-200 amino acid long of 8-25 kDa, rich in glycine and cysteine but also in serine, proline and valine that participate to the formation of beta-sheets in the internal part of the protein, the beta-region. This region determines the further polymerization of CBPs in filamentous proteins that, together a network of Intermediate Filament Keratins (IFKs) and other minor epidermal proteins from the EDC make the variable pliable or inflexible corneous material of reptilian scales, claws and of turtle beak. The acquisition of scales and skin derivatives with different mechanical and material properties, mainly due to the evolution of reptile CBPs, is essential for the life and different adaptations of these vertebrates.
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Affiliation(s)
- Lorenzo Alibardi
- Comparative Histolab Padova, Italy; Department of Biology, University of Bologna, Bologna, Italy.
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3
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Alibardi L. General aspects on skin development in vertebrates with emphasis on sauropsids epidermis. Dev Biol 2023; 501:60-73. [PMID: 37244375 DOI: 10.1016/j.ydbio.2023.05.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Revised: 05/02/2023] [Accepted: 05/25/2023] [Indexed: 05/29/2023]
Abstract
General cellular aspects of skin development in vertebrates are presented with emphasis on the epidermis of sauropsids. Anamniote skin develops into a multilayered mucogenic and soft keratinized epidermis made of Intermediate Filament Keratins (IFKs) that is reinforced in most fish and few anurans by dermal bony and fibrous scales. In amniotes, the developing epidermis in contact with the amniotic fluid initially transits through a mucogenic phase recalling that of their anamniotes progenitors. A new gene cluster termed EDC (Epidermal Differentiation Complex) evolved in amniotes contributing to the origin of the stratum corneum. The EDC contains numerous genes coding for over 100 types of corneous proteins (CPs). In sauropsids 2-8 layers of embryonic epidermis accumulate soft keratins (IFKs) but do not form a compact corneous layer. The embryonic epidermis of reptiles and birds produces small amount of other, poorly known proteins in addition to IFKs and mucins. In the following development, a resistant corneous layer is formed underneath the embryonic epidermis that is shed before hatching. The definitive corneous epidermis of sauropsids is mainly composed of CBPs (Corneous beta proteins, formerly indicated as beta-keratins) derived from the EDC. CBPs belong to a gene sub-family of CPs unique for sauropsids, contain an inner amino acid region formed by beta-sheets, are rich in cysteine and glycine, and make most of the protein composition of scales, claws, beaks and feathers. In mammalian epidermis CPs missing the beta-sheet region are instead produced, and include loricrin, involucrin, filaggrin and various cornulins. Small amount of CPs accumulate in the 2-3 layers of mammalian embryonic epidermis and their appendages, that is replaced with the definitive corneous layers before birth. Differently from sauropsids, mammals utilize KAPs (keratin associated proteins) rich in cysteine and glycine for making the hard corneous material of hairs, claws, hooves, horns, and occasionally also scales.
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Affiliation(s)
- Lorenzo Alibardi
- Comparative Histolab Padova, Italy; Department of Biology, University of Bologna, Bologna, Italy.
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Zhao T, Pan Y. An evaluation of the effect of hydrofluoric acid (HF) treatment on keratins. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART B, MOLECULAR AND DEVELOPMENTAL EVOLUTION 2023; 340:377-384. [PMID: 36002950 DOI: 10.1002/jez.b.23173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 06/26/2022] [Accepted: 07/28/2022] [Indexed: 06/09/2023]
Abstract
Hydrofluoric acid (HF) is commonly used in geological and paleontological research to extract organic fossils for morphological and chemical studies. However, during HF treatment, organic matter can also be altered, which raises concerns that HF-treated organic matter may not be representative of the original organic matter. To provide reference data for protein studies on fossils, herein, we use Fourier transform infrared (FTIR) spectroscopy to investigate the effect of HF (21.3 M) treatment on keratins, with treatment durations ranging from 2 to 48 h. Results show that the FTIR spectra of HF-treated samples are overall similar to that of the untreated sample, while curve fitting shows that HF treatment has led to alteration of the secondary structure in all the HF-treated samples and the effect is time-dependent. The 2- and 4-h treatment mainly reduced the content of the random coils, α-helix, and intermolecular β-sheet. From 8h onwards, the content of random coils greatly increased at the expense of other structures. Our results imply that for protein detection in fossils using FTIR spectroscopy, the negative effect of HF treatment is not substantial, as the bands characteristic of proteins, that is, amide A, amide B, amide I, amide II, and amide III, are still present after the 48-h treatment. If the target is a secondary structure, the effect of HF treatment should be considered. When HF treatment is necessary, limiting the treatment duration to less than 4h may be a choice.
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Affiliation(s)
- Tao Zhao
- State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Centre for Research and Education on Biological Evolution and Environment and Frontiers Science Center for Critical Earth Material Cycling, Nanjing University, Nanjing, China
| | - Yanhong Pan
- State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Centre for Research and Education on Biological Evolution and Environment and Frontiers Science Center for Critical Earth Material Cycling, Nanjing University, Nanjing, China
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Yenmiş M, Ayaz D. The Story of the Finest Armor: Developmental Aspects of Reptile Skin. J Dev Biol 2023; 11:jdb11010005. [PMID: 36810457 PMCID: PMC9944452 DOI: 10.3390/jdb11010005] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 01/06/2023] [Accepted: 01/11/2023] [Indexed: 01/31/2023] Open
Abstract
The reptile skin is a barrier against water loss and pathogens and an armor for mechanical damages. The integument of reptiles consists of two main layers: the epidermis and the dermis. The epidermis, the hard cover of the body which has an armor-like role, varies among extant reptiles in terms of structural aspects such as thickness, hardness or the kinds of appendages it constitutes. The reptile epithelial cells of the epidermis (keratinocytes) are composed of two main proteins: intermediate filament keratins (IFKs) and corneous beta proteins (CBPs). The outer horny layer of the epidermis, stratum corneum, is constituted of keratinocytes by means of terminal differentiation or cornification which is a result of the protein interactions where CBPs associate with and coat the initial scaffold of IFKs. Reptiles were able to colonize the terrestrial environment due to the changes in these epidermal structures, which led to various cornified epidermal appendages such as scales and scutes, a beak, claws or setae. Developmental and structural aspects of the epidermal CBPs as well as their shared chromosomal locus (EDC) indicate an ancestral origin that gave rise to the finest armor of reptilians.
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Haase E, Dybus A, Konieczna A, Kovalev A, Gorb S. Effects of a FCBP gene polymorphism, location, and sex on Young's modulus of the tenth primary feather in racing pigeons. Sci Rep 2022; 12:1785. [PMID: 35110587 PMCID: PMC8810990 DOI: 10.1038/s41598-022-05649-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 01/05/2022] [Indexed: 12/02/2022] Open
Abstract
Young's modulus (E) is a measure for stiffness of a material and a higher E means a higher stiffness. The respective polymorphism of the feather corneous beta-protein gene causes the replacement of glycine by cysteine. We looked for possible effects of the three FCBP genotypes on E in the 10th primaries of racing pigeons. However, we did not find a statistically significant difference of E between the genotypes, even within the sexes and/or within different locations under our test conditions. Our findings do not preclude the possibility that under other conditions (temperature, moisture) an influence of the glycine/cysteine polymorphism on E may exist. Compared to the more proximal locations of the rachis (base and middle) we observed lower values for E in the distal region (tip). The 10th primary constitutes the leading edge of the pigeon wing and this special function may require higher stiffness in the proximal parts of the shaft. We observed significantly higher values of E in females than in males, which result only from statistically significantly higher values in the middle region. The higher stiffness of female primaries may also contribute to the better results of hens compared to cocks in pigeon races.
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Affiliation(s)
- Eberhard Haase
- Department of Functional Morphology and Biomechanics, Zoological Institute of the University of Kiel, Am Botanischen Garten 1-9, 24118, Kiel, Germany
| | - Andrzej Dybus
- Department of Genetics, Faculty of Biotechnology and Animal Husbandry, West Pomeranian University of Technology in Szczecin, Aleja Piastów 45, 70-311, Szczecin, Poland.
| | - Aneta Konieczna
- Department of Functional Morphology and Biomechanics, Zoological Institute of the University of Kiel, Am Botanischen Garten 1-9, 24118, Kiel, Germany.,Department of Genetics, Faculty of Biotechnology and Animal Husbandry, West Pomeranian University of Technology in Szczecin, Aleja Piastów 45, 70-311, Szczecin, Poland
| | - Alexander Kovalev
- Department of Functional Morphology and Biomechanics, Zoological Institute of the University of Kiel, Am Botanischen Garten 1-9, 24118, Kiel, Germany
| | - Stanislav Gorb
- Department of Functional Morphology and Biomechanics, Zoological Institute of the University of Kiel, Am Botanischen Garten 1-9, 24118, Kiel, Germany.
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Lazarus BS, Chadha C, Velasco-Hogan A, Barbosa JD, Jasiuk I, Meyers MA. Engineering with keratin: A functional material and a source of bioinspiration. iScience 2021; 24:102798. [PMID: 34355149 PMCID: PMC8319812 DOI: 10.1016/j.isci.2021.102798] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Keratin is a highly multifunctional biopolymer serving various roles in nature due to its diverse material properties, wide spectrum of structural designs, and impressive performance. Keratin-based materials are mechanically robust, thermally insulating, lightweight, capable of undergoing reversible adhesion through van der Waals forces, and exhibit structural coloration and hydrophobic surfaces. Thus, they have become templates for bioinspired designs and have even been applied as a functional material for biomedical applications and environmentally sustainable fiber-reinforced composites. This review aims to highlight keratin's remarkable capabilities as a biological component, a source of design inspiration, and an engineering material. We conclude with future directions for the exploration of keratinous materials.
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Affiliation(s)
- Benjamin S. Lazarus
- Materials Science and Engineering Program, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, USA
| | - Charul Chadha
- Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Champaign, IL, USA
| | - Audrey Velasco-Hogan
- Materials Science and Engineering Program, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, USA
| | | | - Iwona Jasiuk
- Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Champaign, IL, USA
| | - Marc A. Meyers
- Materials Science and Engineering Program, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, USA
- Department of Mechanical and Aerospace Engineering, University of California San Diego, San Diego, CA, USA
- Department of Nanoengineering, University of California San Diego, San Diego, CA, USA
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8
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Alibardi L. Vertebrate keratinization evolved into cornification mainly due to transglutaminase and sulfhydryl oxidase activities on epidermal proteins: An immunohistochemical survey. Anat Rec (Hoboken) 2021; 305:333-358. [PMID: 34219408 DOI: 10.1002/ar.24705] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 03/27/2021] [Accepted: 05/04/2021] [Indexed: 02/06/2023]
Abstract
The epidermis of vertebrates forms an extended organ to protect and exchange gas, water, and organic molecules with aquatic and terrestrial environments. Herein, the processes of keratinization and cornification in aquatic and terrestrial vertebrates were compared using immunohistochemistry. Keratins with low cysteine and glycine contents form the main bulk of proteins in the anamniote epidermis, which undergoes keratinization. In contrast, specialized keratins rich in cysteine-glycine and keratin associated corneous proteins rich in cysteine, glycine, and tyrosine form the bulk of proteins of amniote soft cornification in the epidermis and hard cornification in scales, claws, beak, feathers, hairs, and horns. Transglutaminase (TGase) and sulfhydryl oxidase (SOXase) are the main enzymes involved in cornification. Their evolution was fundamental for the terrestrial adaptation of vertebrates. Immunohistochemistry results revealed that TGase and SOXase were low to absent in fish and amphibian epidermis, while they increased in the epidermis of amniotes with the evolution of the stratum corneum and skin appendages. TGase aids the formation of isopeptide bonds, while SOXase forms disulfide bonds that generate numerous cross-links between keratins and associated corneous proteins, likely increasing the mechanical resistance and durability of the amniote epidermis and its appendages. TGase is low to absent in the beta-corneous layers of sauropsids but is detected in the softer but pliable alpha-layers of sauropsids, mammalian epidermis, medulla, and inner root sheath of hairs. SOXase is present in hard and soft corneous appendages of reptiles, birds, and mammals, and determines cross-linking among corneous proteins of scales, claws, beaks, hairs, and feathers.
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Affiliation(s)
- Lorenzo Alibardi
- Comparative Histolab Padova and University of Bologna, Bologna, Italy
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Parry DAD. Structures of the ß-Keratin Filaments and Keratin Intermediate Filaments in the Epidermal Appendages of Birds and Reptiles (Sauropsids). Genes (Basel) 2021; 12:591. [PMID: 33920614 PMCID: PMC8072682 DOI: 10.3390/genes12040591] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 04/13/2021] [Accepted: 04/15/2021] [Indexed: 01/14/2023] Open
Abstract
The epidermal appendages of birds and reptiles (the sauropsids) include claws, scales, and feathers. Each has specialized physical properties that facilitate movement, thermal insulation, defence mechanisms, and/or the catching of prey. The mechanical attributes of each of these appendages originate from its fibril-matrix texture, where the two filamentous structures present, i.e., the corneous ß-proteins (CBP or ß-keratins) that form 3.4 nm diameter filaments and the α-fibrous molecules that form the 7-10 nm diameter keratin intermediate filaments (KIF), provide much of the required tensile properties. The matrix, which is composed of the terminal domains of the KIF molecules and the proteins of the epidermal differentiation complex (EDC) (and which include the terminal domains of the CBP), provides the appendages, with their ability to resist compression and torsion. Only by knowing the detailed structures of the individual components and the manner in which they interact with one another will a full understanding be gained of the physical properties of the tissues as a whole. Towards that end, newly-derived aspects of the detailed conformations of the two filamentous structures will be discussed and then placed in the context of former knowledge.
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Affiliation(s)
- David A D Parry
- School of Fundamental Sciences, Massey University, Private Bag 11-222, Palmerston North 4442, New Zealand
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Alibardi L. Development, structure, and protein composition of the corneous beak in turtles. Anat Rec (Hoboken) 2021; 304:2703-2725. [PMID: 33620157 DOI: 10.1002/ar.24604] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2020] [Revised: 01/06/2021] [Accepted: 01/24/2021] [Indexed: 01/28/2023]
Abstract
The beak or rhamphotheca in turtles is a horny lamina that replaces the teeth. Its origin, development, structure, and protein composition are here presented. At mid-development stages, the epidermis of the maxilla and mandible gives rise to placodes that enlarge and merge into laminae through an intense cell proliferation. In these expanding laminae, the epidermis gives rise to 5-8 layers of embryonic epidermis where coarse filaments accumulate for the initial keratinization of cells destined to be sloughed before hatching. Underneath the embryonic epidermis of the beak numerous layers of spindle-shaped beta-cells are produced while they are absent in other skin regions. Beta-cells contain hard corneous material and give rise to the corneous layer of the beak whose external layers desquamate due to wearing and mechanical abrasion. Beta-catenin is present in nuclei of proliferating keratinocytes of the germinal layer likely responding to a wnt signal, but also is part of the adhesive junctions located among beak keratinocytes. The thick corneous layer is made of mature corneocytes connected one to another along their irregular perimeter by an unknown cementing material and junctional remnants. Immunolabeling shows that the main components of the horny beak are Corneous Beta Proteins (CBPs) of 10-15 kDa which genes are located in the Epidermal Differentiation Complex (EDC) of the turtle genome. Specific CBPs, in addition to a lower amount of Intermediate Filament Keratins, accumulate in the horny beak. Compaction of the main proteins with other unknown, minor proteins give rise to the hard corneous material of the beak.
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Affiliation(s)
- Lorenzo Alibardi
- Comparative Histolab Padova and Department of Biology, University of Bologna, Bologna, Italy
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Parry DAD, Winter DJ. Keratin intermediate filament chains in tuatara (Sphenodon punctatus): A comparison of tuatara and human sequences. J Struct Biol 2021; 213:107706. [PMID: 33577903 DOI: 10.1016/j.jsb.2021.107706] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 01/27/2021] [Accepted: 01/28/2021] [Indexed: 11/19/2022]
Abstract
Determination of the sequences of the keratin intermediate filament chains in tuatara has shown that these are closely akin to the α-keratins in human and other vertebrates, especially in the central, coiled-coil rod region. The domain lengths within the rod are preserved exactly, both Type I and Type II chains have been recognised, and sequence identity/homology exists between their respective chains. Nonetheless, there are characteristic differences in amino acid composition and sequence between their respective head (N-terminal) domains and their tail (C-terminal) domains, though some similarities are retained. Further, there is evidence of tandem repeats of a variety of lengths in the tuatara heads and tails indicative of sequence duplication events. These are not evident in human α-keratins and would therefore have implications for the physical attributes of the tissues in the two species. Multiple families of keratin-associated proteins that are ultra-high cysteine-rich or glycine + tyrosine-rich in human and other species do not have direct equivalents in the tuatara. Although high-sulphur proteins are present in tuatara the cysteine residue contents are significantly lower than in human. Further, no sequence homologies between the HS proteins in the two species have been found, thereby casting considerable doubt as to whether any matrix-forming high-sulphur proteins exist in tuatara. These observations may be correlated with the numerous cysteine-rich β-keratins (corneous β-proteins) that are present in tuatara, but which are conspicuously absent in mammals.
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Affiliation(s)
- David A D Parry
- School of Fundamental Sciences, Massey University, Private Bag 11-222, Palmerston North 4442, New Zealand.
| | - David J Winter
- School of Fundamental Sciences, Massey University, Private Bag 11-222, Palmerston North 4442, New Zealand
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12
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Microbial enzymes catalyzing keratin degradation: Classification, structure, function. Biotechnol Adv 2020; 44:107607. [PMID: 32768519 PMCID: PMC7405893 DOI: 10.1016/j.biotechadv.2020.107607] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Revised: 07/29/2020] [Accepted: 07/30/2020] [Indexed: 12/11/2022]
Abstract
Keratin is an insoluble and protein-rich epidermal material found in e.g. feather, wool, hair. It is produced in substantial amounts as co-product from poultry processing plants and pig slaughterhouses. Keratin is packed by disulfide bonds and hydrogen bonds. Based on the secondary structure, keratin can be classified into α-keratin and β-keratin. Keratinases (EC 3.4.-.- peptide hydrolases) have major potential to degrade keratin for sustainable recycling of the protein and amino acids. Currently, the known keratinolytic enzymes belong to at least 14 different protease families: S1, S8, S9, S10, S16, M3, M4, M14, M16, M28, M32, M36, M38, M55 (MEROPS database). The various keratinolytic enzymes act via endo-attack (proteases in families S1, S8, S16, M4, M16, M36), exo-attack (proteases in families S9, S10, M14, M28, M38, M55) or by action only on oligopeptides (proteases in families M3, M32), respectively. Other enzymes, particularly disulfide reductases, also play a key role in keratin degradation as they catalyze the breakage of disulfide bonds for better keratinase catalysis. This review aims to contribute an overview of keratin biomass as an enzyme substrate and a systematic analysis of currently sequenced keratinolytic enzymes and their classification and reaction mechanisms. We also summarize and discuss keratinase assays, available keratinase structures and finally examine the available data on uses of keratinases in practical biorefinery protein upcycling applications.
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Goerner-Hu X, Scott EL, Seeger T, Schneider O, Bitter JH. Reaction Stages of Feather Hydrolysis: Factors That Influence Availability for Enzymatic Hydrolysis and Cystine Conservation during Thermal Pressure Hydrolysis. BIOTECHNOL BIOPROC E 2020. [DOI: 10.1007/s12257-019-0351-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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14
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Alibardi L. Development, structure, and protein composition of reptilian claws and hypotheses of their evolution. Anat Rec (Hoboken) 2020; 304:732-757. [PMID: 33015957 DOI: 10.1002/ar.24515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 06/23/2020] [Accepted: 07/10/2020] [Indexed: 11/06/2022]
Abstract
Here, we review the development, morphology, genes, and proteins of claws in reptiles. Claws likely form owing to the inductive influence of phalangeal mesenchyme on the apical epidermis of developing digits, resulting in hyperproliferation and intense protein synthesis in the dorsal epidermis, which forms the unguis. The tip of claws results from prevalent cell proliferation and distal movement along most of the ungueal epidermis in comparison to the ventral surface forming the subunguis. Asymmetrical growth between the unguis and subunguis forces beta-cells from the unguis to rotate into the apical part of the subunguis, sharpening the claw tip. Further sharpening occurs by scratching and mechanical wearing. Ungueal keratinocytes elongate, form an intricate perimeter and cementing junctions, and remain united impeding desquamation. In contrast, thin keratinocytes in the subunguis form a smooth perimeter, accumulate less corneous beta proteins (CBPs) and cysteine-poor intermediate filament (IF)-keratins, and desquamate. In addition to prevalent glycine-cysteine-tyrosine rich CBPs, special cysteine-rich IF-keratins are also synthesized in the claw, generating numerous SS bonds that harden the thick and compact corneous material. Desquamation and mechanical wear at the tip ensure that the unguis curvature remains approximately stable over time. Reptilian claws are likely very ancient in evolution, although the unguis differentiated like the outer scale surface of scales, while the subunguis might have derived from the inner scale surface. The few hair-like IF-keratins synthesized in reptilian claws indicate that ancestors of sauropsids and mammals shared cysteine-rich IF-keratins. However, the number of these keratins remained low in reptiles, while new types of CBPs function to strengthen claws.
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Structure and topology of the linkers in the conserved lepidosaur β-keratin chain with four 34-residue repeats support an interfilament role for the central linker. J Struct Biol 2020; 212:107599. [PMID: 32800921 DOI: 10.1016/j.jsb.2020.107599] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2020] [Revised: 07/10/2020] [Accepted: 08/07/2020] [Indexed: 11/20/2022]
Abstract
The β-keratin chain with four 34-residue repeats that is conserved across the lepidosaurs (lizards, snakes and tuatara) contains three linker regions as well as a short, conserved N-terminal domain and a longer, more variable C-terminal domain. Earlier modelling had shown that only six classes of structure involving the four 34-residue repeats were possible. In three of these the 34-residue repeats were confined to a single filament (Classes 1, 2 and 3) whereas in the remaining three classes the repeats lay in two, three or four filaments, with some of the linkers forming interfilament connections (Classes 4, 5 and 6). In this work the members of each class of structure (a total of 20 arrangements) have been described and a comparison has been made of the topologies of each of the linker regions. This provides new constraints on the structure of the chain as a whole. Also, analysis of the sequences of the three linker regions has revealed that the central linker (and only the central linker) contains four short regions displaying a distinctive dipeptide repeat of the form (S-X)2,3 separated by short regions containing proline and cysteine residues. By analogy with silk fibroin proteins this has the capability of forming a β-sheet-like conformation. Using the topology and sequence data the evidence suggests that the four 34-residue repeat chain adopts a Class 4a structure with a β-sandwich in filament 1 connected through the central linker to a β-sandwich in filament 2.
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Holthaus KB, Alibardi L, Tschachler E, Eckhart L. Identification of epidermal differentiation genes of the tuatara provides insights into the early evolution of lepidosaurian skin. Sci Rep 2020; 10:12844. [PMID: 32732894 PMCID: PMC7393497 DOI: 10.1038/s41598-020-69885-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Accepted: 07/09/2020] [Indexed: 11/20/2022] Open
Abstract
The tuatara (Sphenodon punctatus) is the phylogenetically closest relative of squamates (including lizards and snakes) from which it diverged around 250 million years ago. Together, they constitute the clade Lepidosauria. Fully terrestrial vertebrates (amniotes) form their skin barrier to the environment under the control of a gene cluster, termed the epidermal differentiation complex (EDC). Here we identified EDC genes in the genome of the tuatara and compared them to those of other amniotes. The organization of the EDC and proteins encoded by EDC genes are most similar in the tuatara and squamates. A subcluster of lepidosaurian EDC genes encodes corneous beta-proteins (CBPs) of which three different types are conserved in the tuatara. Small proline-rich proteins have undergone independent expansions in the tuatara and some, but not all subgroups of squamates. Two genes encoding S100 filaggrin-type proteins (SFTPs) are expressed during embryonic skin development of the tuatara whereas SFTP numbers vary between 1 and 3 in squamates. Our comparative analysis of the EDC in the tuatara genome suggests that many molecular features of the skin that were previously identified in squamates have evolved prior to their divergence from the lineage leading to the tuatara.
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Affiliation(s)
| | | | - Erwin Tschachler
- Department of Dermatology, Medical University of Vienna, Vienna, Austria
| | - Leopold Eckhart
- Department of Dermatology, Medical University of Vienna, Vienna, Austria.
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17
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Laurent CM, Dyke JM, Cook RB, Dyke G, de Kat R. Spectroscopy on the wing: Investigating possible differences in protein secondary structures in feather shafts of birds using Raman spectroscopy. J Struct Biol 2020; 211:107529. [PMID: 32416130 DOI: 10.1016/j.jsb.2020.107529] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 04/24/2020] [Accepted: 05/03/2020] [Indexed: 10/24/2022]
Abstract
The central shaft of a bird's flight feather bears most of the aerodynamic load during flight and exhibits some remarkable mechanical properties. The shaft comprises two parts, the calamus and the rachis. The calamus is at the base of the shaft, while the rachis is the longer upper part which supports the vanes. The shaft is composed of a fibrous outer cortex, and an inner foam-like core. Recent nanoindentation experiments have indicated that reduced modulus values, Er, for the inner and outer regions of the cortex can vary, with the Er values of the inner region slightly greater than those of the outer region. In this work, Raman spectroscopy is used to investigate the protein secondary structures in the inner and outer regions of the feather cortex. Analysis of the Amide I region of Raman spectra taken from four birds (Swan, Gull, Mallard and Kestrel) shows that the β-sheet structural component decreases between the inner and outer region, relative to the protein side-chain components. This finding is consistent with the proposal that Er values are greater in the inner region than the outer region. This work has shown that Raman spectroscopy can be used effectively to study the change in protein secondary structure between the inner and outer regions of a feather shaft.
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Affiliation(s)
- Christian M Laurent
- Aerodynamics and Flight Mechanics, University of Southampton, SO17 1BJ, UK; Ocean and Earth Science, National Oceanography Centre, SO17 1BJ, UK; Department of Biology and Geology, Babes-Bolyai University, Romania.
| | - John M Dyke
- School of Chemistry, University of Southampton, SO17 1BJ, UK.
| | - Richard B Cook
- nCATS National Centre for Advanced Tribology Southampton, University of Southampton, SO17 1BJ, UK
| | - Gareth Dyke
- Department of Biology and Geology, Babes-Bolyai University, Romania
| | - Roeland de Kat
- Aerodynamics and Flight Mechanics, University of Southampton, SO17 1BJ, UK; Faculty of Military Sciences, Netherlands Defence Academy, The Netherlands
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18
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Alibardi L. Immunolocalization of corneous proteins including a serine-tyrosine-rich beta-protein in the adhesive pads in the tokay gecko. Microsc Res Tech 2020; 83:889-900. [PMID: 32274891 DOI: 10.1002/jemt.23483] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 03/12/2020] [Accepted: 03/16/2020] [Indexed: 12/30/2022]
Abstract
Adhesive pads of geckos contain many thousands of nanoscale spatulae for the adhesion and movement along vertical or inverted surfaces. Setae are composed of interlaced corneous bundles made of small cysteine-glycine-rich corneous beta proteins (CBPs, formerly indicated as beta-keratins), embedded in a matrix material composed of cytoskeletal proteins and lipids. Negatively charged intermediate filament keratins (IFKs) and positively charged CBPs likely interact within setae, aside disulphide bonds, giving rise to a flexible and resistant corneous material. Using differernt antibodies against CBPs and IFKs an updated model of the composition of setae and spatulae is presented. Immunofluorescence and ultrastructural immunogold labeling reveal that one type of neutral serine-tyrosine-rich CBP is weakly localized in the setae while it is absent from the spatula. This uncharged protein is mainly present in the thin Oberhautchen layer sustaining the setae, although with a much lower intensity with respect to the cysteine-rich CBPs. These proteins in the spatula likely originate a positively charged or neutral contact surface with the substrate but the influence of lipids and cytoskeletal proteins present in setae on the mechanism of adhesion is not known. In the spatula, protein-lipid complexes may impart the pliability for the attachment and adapt to irregular surfaces. The presence of cysteine-glycine medium rich CBPs and softer IFKs in alpha-layers sustaining the setae forms a flexible base for compliance of the setae to substrate and improved adhesion.
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Affiliation(s)
- Lorenzo Alibardi
- Comparative Histolab Padova and University of Bologna, Bologna, Italy
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Alibardi L. Immunolocalization of corneous beta proteins of the Epidermal Differentiation Complex in the developing claw of the alligator. Ann Anat 2020; 231:151513. [PMID: 32229243 DOI: 10.1016/j.aanat.2020.151513] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 03/06/2020] [Accepted: 03/08/2020] [Indexed: 12/20/2022]
Abstract
Knowledge on the sharpness, mechanical and hydration resistance of the corneous material of claws requires information on its constituent proteins. The present immunohistochemical study has localized some of the main corneous beta proteins (CBPs, formerly termed beta-keratins) indicated to be present in alligator claws only by genomic data. Using specific antibodies we show the immunolocalization of representative claws CBPs of the Epidermal Differentiation Complex (Beta A1 group) during late stages of claw development in alligator. Intense but asymmetric proliferation, revealed by 5BrdU-immunolabeling, determines the formation of a curved dorsal part (unguis) and a linear ventral part (sub-unguis). The large beta-cells generated in the unguis and their packing into a solid corneous layer occur before thinner beta-cells appear in the sub-unguis. In the latter, CBPs are also immune-detected but with less intensity compared to the unguis, and corneocytes remain separated and desquamate. It is suggested that at the tip of the developing claw beta-corneocytes move downward into the initial part of the sub-unguis. This circular movement contributes to sharpen the claw as these cells fully cornify and are desquamated from the sub-unguis. Corneocytes of the unguis contain 10-16 kDa proline-serine-rich proteins that also possess high percentages of glycine, cysteine, tyrosine, valine and leucine. Cysteines likely give rise to numerous SS bonds in the constituent hard horny material, tyrosine contribute to packing proteins into a dense horny material while glycine, valine and leucine increase the hydrophobic property of claws in these water-adapted predators.
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Affiliation(s)
- Lorenzo Alibardi
- Comparative Histolab Padova and Department of Biology, University of Bologna, Italy.
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20
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Fraser RDB, Parry DAD. Lepidosaur ß-keratin chains with four 34-residue repeats: Modelling reveals a potential filament-crosslinking role. J Struct Biol 2019; 209:107413. [PMID: 31698074 DOI: 10.1016/j.jsb.2019.107413] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 10/16/2019] [Accepted: 11/02/2019] [Indexed: 10/25/2022]
Abstract
ß-keratin chains contain a characteristic and homologous 34-residue sequence, which is believed to adopt a twisted ß-sheet conformation that assembles in an antiparallel manner with a similar sheet in a second chain to form a ß-sandwich. These sandwiches are, in turn, related to one another by a left-handed four-fold screw axis to generate a helical structure that forms the core of the 3.4 nm diameter filaments observed by electron microscopy and deduced from X-ray fibre diffraction. Recently, it has been shown that one ß-keratin chain, with a molecular weight approximately twice that of the majority of ß-keratin chains, is conserved across the lepidosaurs (lizards, snakes and tuatara). Uniquely, it contains four 34-residue repeats. Although this chain is a minor component the observation that the entire chain shows a high degree of sequence conservation between species suggests an important structural/functional role in vivo. Modelling shows that only six families of structures are physically possible. In three of these the repeats exist within a single filament and might therefore act in a filament nucleation role. In the second three families the repeats exist in two, three or four filaments, implying that their function may be to act as an inter-filament crosslinker, thereby providing lateral reinforcement to the epidermal appendage. The favoured model is one in which the first two repeats form a β-sandwich in one filament and the second two repeats form a β-sandwich in a neighbouring filament. Links between alternating up- and down-pointing β-sheets would provide optimum connectivity.
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Affiliation(s)
- R D Bruce Fraser
- School of Fundamental Sciences, Massey University, Private Bag 11-222, Palmerston North, New Zealand
| | - David A D Parry
- School of Fundamental Sciences, Massey University, Private Bag 11-222, Palmerston North, New Zealand; Riddet Institute, Massey University, Private Bag 11-222, Palmerston North, New Zealand.
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21
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Parry DA, Fraser RB, Alibardi L, Rutherford KM, Gemmell N. Molecular structure of sauropsid β-keratins from tuatara (Sphenodon punctatus). J Struct Biol 2019; 207:21-28. [DOI: 10.1016/j.jsb.2019.04.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 04/06/2019] [Accepted: 04/08/2019] [Indexed: 02/08/2023]
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Skieresz-Szewczyk K, Buchwald T, Szybowicz M, Jackowiak H. Alpha-keratin and corneous beta protein in the parakeratinized epithelium of the tongue in the domestic goose (Anser anser f. domestica). JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2019; 332:158-166. [PMID: 31243896 DOI: 10.1002/jez.b.22892] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 04/16/2019] [Accepted: 05/22/2019] [Indexed: 12/14/2022]
Abstract
The parakeratinized epithelium is a common epithelium in the oral cavity in birds and is characterized by the presence of cell nuclei in the cells of the cornified layer. This epithelium covers almost the entire dorsal surface of the tongue in the domestic goose apart of the lingual nail and conical papillae. So far no study has identified the molecular proteins alpha-keratin (IF-keratin) and/or corneous beta protein (CBP), which are responsible for keratinization or cornification processes in the parakeratinized epithelium of domestic geese. The study was performed using immunohistochemical (IHC) methods to identify alpha-keratin. The innovative method of Raman microspectroscopy was used to determine the presence of CBP and specify their percentage in epithelial layers of the parakeratinized epithelium. The results revealed that alpha-keratin is present in the whole parakeratinized epithelium. A strong staining reaction was detected in the basal and intermediate layers and a less strong staining reaction in the cornified layer. Raman microspectroscopy analysis confirmed the presence of alpha-keratin and demonstrated that its percentage decreases from the basal layer to the cornified layer. The Raman microspectroscopy technique revealed the occurrence of CBP in the parakeratinized epithelium and demonstrated that the percentage of this protein increases from the basal layer to the cornified layer. Performed analysis determines that parakeratinized epithelium undergoes cornification. However, the lower percentage of CBP in the cornified layer of parakeratinized epithelium than in orthokeratinized epithelium points to the fact that parakeratinized epithelium has a weaker protective function.
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Affiliation(s)
- Kinga Skieresz-Szewczyk
- Department of Histology and Embryology, Faculty of Veterinary Medicine and Animal Science, Poznan University of Life Sciences, Wojska Polskiego, Poznan, Poland
| | - Tomasz Buchwald
- Institute of Materials Research and Quantum Engineering, Faculty of Technical Physics, Poznan University of Technology, Piotrowo, Poznan, Poland
| | - Mirosław Szybowicz
- Institute of Materials Research and Quantum Engineering, Faculty of Technical Physics, Poznan University of Technology, Piotrowo, Poznan, Poland
| | - Hanna Jackowiak
- Department of Histology and Embryology, Faculty of Veterinary Medicine and Animal Science, Poznan University of Life Sciences, Wojska Polskiego, Poznan, Poland
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Abstract
Ancient protein analysis is a rapidly developing field of research. Proteins ranging in age from the Quaternary to Jurassic are being used to answer questions about phylogeny, evolution, and extinction. However, these analyses are sometimes contentious, and focus primarily on large vertebrates in sedimentary fossilisation environments; there are few studies of protein preservation in fossils in amber. Here we show exceptionally slow racemisation rates during thermal degradation experiments of resin enclosed feathers, relative to previous thermal degradation experiments of ostrich eggshell, coral skeleton, and limpet shell. We also recover amino acids from two specimens of fossil feathers in amber. The amino acid compositions are broadly similar to those of degraded feathers, but concentrations are very low, suggesting that much of the original protein has been degraded and lost. High levels of racemisation in more apolar, slowly racemising amino acids suggest that some of the amino acids were ancient and therefore original. Our findings indicate that the unique fossilisation environment inside amber shows potential for the recovery of ancient amino acids and proteins.
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24
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Brunner MAT, Rüfenacht S, Bauer A, Erpel S, Buchs N, Braga-Lagache S, Heller M, Leeb T, Jagannathan V, Wiener DJ, Welle MM. Bald thigh syndrome in sighthounds-Revisiting the cause of a well-known disease. PLoS One 2019; 14:e0212645. [PMID: 30794648 PMCID: PMC6386255 DOI: 10.1371/journal.pone.0212645] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Accepted: 02/06/2019] [Indexed: 01/17/2023] Open
Abstract
Bald thigh syndrome is a common hair loss disorder in sighthounds. Numerous possible causes, including environmental conditions, trauma, stress, endocrinopathies and genetic components have been proposed, but only endocrinopathies have been ruled out scientifically. The overall goal of our study was to identify the cause of bald thigh syndrome and the pathological changes associated with it. We approached this aim by comparing skin biopsies and hair shafts of affected and control dogs microscopically as well as by applying high-throughput technologies such as genomics, transcriptomics and proteomics. While the histology is rather unspecific in most cases, trichogram analysis and scanning electron microscopy revealed severe structural abnormalities in hair shafts of affected dogs. This finding is supported by the results of the transcriptomic and proteomic profiling where genes and proteins important for differentiation of the inner root sheath and the assembly of a proper hair shaft were downregulated. Transcriptome profiling revealed a downregulation of genes encoding 23 hair shaft keratins and 51 keratin associated proteins, as well as desmosomal cadherins and several actors of the BMP signaling pathway which is important for hair shaft differentiation. The lower expression of keratin 71 and desmocollin 2 on the mRNA level in skin biopsies corresponded with a decreased protein expression in the hair shafts of affected dogs. The genetic analysis revealed a missense variant in the IGFBP5 gene homozygous in all available Greyhounds and other sighthounds. Further research is required to clarify whether the IGFBP5 variant represents a predisposing genetic risk factor. We conclude from our results that structural defects in the hair shafts are the cause for this well-known disease and these defects are associated with a downregulation of genes and proteins essential for hair shaft formation. Our data add important knowledge to further understand the molecular mechanisms of HF morphogenesis and alopecia in dogs.
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Affiliation(s)
- Magdalena A. T. Brunner
- Institute of Animal Pathology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
- DermFocus, University of Bern, Bern, Switzerland
| | | | - Anina Bauer
- DermFocus, University of Bern, Bern, Switzerland
- Institute of Genetics, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Susanne Erpel
- Nano Imaging Lab, SNI, University of Basel, Basel, Switzerland
| | - Natasha Buchs
- Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Sophie Braga-Lagache
- Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Manfred Heller
- Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Tosso Leeb
- DermFocus, University of Bern, Bern, Switzerland
- Institute of Genetics, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Vidhya Jagannathan
- Institute of Genetics, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Dominique J. Wiener
- Department of Veterinary Pathobiology, Texas A&M University, College Station, United States of America
| | - Monika M. Welle
- Institute of Animal Pathology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
- DermFocus, University of Bern, Bern, Switzerland
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25
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Pan Y, Zheng W, Sawyer RH, Pennington MW, Zheng X, Wang X, Wang M, Hu L, O'Connor J, Zhao T, Li Z, Schroeter ER, Wu F, Xu X, Zhou Z, Schweitzer MH. The molecular evolution of feathers with direct evidence from fossils. Proc Natl Acad Sci U S A 2019; 116:3018-3023. [PMID: 30692253 PMCID: PMC6386655 DOI: 10.1073/pnas.1815703116] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Dinosaur fossils possessing integumentary appendages of various morphologies, interpreted as feathers, have greatly enhanced our understanding of the evolutionary link between birds and dinosaurs, as well as the origins of feathers and avian flight. In extant birds, the unique expression and amino acid composition of proteins in mature feathers have been shown to determine their biomechanical properties, such as hardness, resilience, and plasticity. Here, we provide molecular and ultrastructural evidence that the pennaceous feathers of the Jurassic nonavian dinosaur Anchiornis were composed of both feather β-keratins and α-keratins. This is significant, because mature feathers in extant birds are dominated by β-keratins, particularly in the barbs and barbules forming the vane. We confirm here that feathers were modified at both molecular and morphological levels to obtain the biomechanical properties for flight during the dinosaur-bird transition, and we show that the patterns and timing of adaptive change at the molecular level can be directly addressed in exceptionally preserved fossils in deep time.
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Affiliation(s)
- Yanhong Pan
- Chinese Academy of Sciences Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing 210008, China;
| | - Wenxia Zheng
- Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695
| | - Roger H Sawyer
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29205
| | | | - Xiaoting Zheng
- Institute of Geology and Paleontology, Lingyi University, Lingyi City, 27605 Shandong, China
- Shandong Tianyu Museum of Nature, Pingyi, 273300 Shandong, China
| | - Xiaoli Wang
- Institute of Geology and Paleontology, Lingyi University, Lingyi City, 27605 Shandong, China
- Shandong Tianyu Museum of Nature, Pingyi, 273300 Shandong, China
| | - Min Wang
- CAS Key Laboratory of Vertebrate Evolution and Human Origins of the Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 100044 Beijing, China
- Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, 100044 Beijing, China
| | - Liang Hu
- Chinese Academy of Sciences Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing 210008, China
- College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, 100049 Beijing, China
| | - Jingmai O'Connor
- CAS Key Laboratory of Vertebrate Evolution and Human Origins of the Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 100044 Beijing, China
- Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, 100044 Beijing, China
| | - Tao Zhao
- Chinese Academy of Sciences Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing 210008, China
| | - Zhiheng Li
- CAS Key Laboratory of Vertebrate Evolution and Human Origins of the Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 100044 Beijing, China
- Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, 100044 Beijing, China
| | - Elena R Schroeter
- Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695
| | - Feixiang Wu
- CAS Key Laboratory of Vertebrate Evolution and Human Origins of the Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 100044 Beijing, China
- Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, 100044 Beijing, China
| | - Xing Xu
- CAS Key Laboratory of Vertebrate Evolution and Human Origins of the Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 100044 Beijing, China
- Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, 100044 Beijing, China
| | - Zhonghe Zhou
- CAS Key Laboratory of Vertebrate Evolution and Human Origins of the Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 100044 Beijing, China;
- Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, 100044 Beijing, China
- College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, 100049 Beijing, China
| | - Mary H Schweitzer
- Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695;
- North Carolina Museum of Natural Sciences, Raleigh, NC 27601
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Holthaus KB, Eckhart L, Dalla Valle L, Alibardi L. Review: Evolution and diversification of corneous beta‐proteins, the characteristic epidermal proteins of reptiles and birds. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2019; 330:438-453. [DOI: 10.1002/jez.b.22840] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Revised: 11/28/2018] [Accepted: 12/23/2018] [Indexed: 02/04/2023]
Affiliation(s)
- Karin Brigit Holthaus
- Department of DermatologyMedical University of ViennaWien Austria
- Dipartimento di Scienze Biologiche, Geologiche ed Ambientali (BiGeA)University of BolognaBologna Italy
| | - Leopold Eckhart
- Department of DermatologyMedical University of ViennaWien Austria
| | | | - Lorenzo Alibardi
- Dipartimento di Scienze Biologiche, Geologiche ed Ambientali (BiGeA)University of BolognaBologna Italy
- Comparative Histolab PadovaPadova Italy
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27
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Ng CS, Li WH. Genetic and Molecular Basis of Feather Diversity in Birds. Genome Biol Evol 2018; 10:2572-2586. [PMID: 30169786 PMCID: PMC6171735 DOI: 10.1093/gbe/evy180] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/13/2018] [Indexed: 12/16/2022] Open
Abstract
Feather diversity is striking in many aspects. Although the development of feather has been studied for decades, genetic and genomic studies of feather diversity have begun only recently. Many questions remain to be answered by multidisciplinary approaches. In this review, we discuss three levels of feather diversity: Feather morphotypes, intraspecific variations, and interspecific variations. We summarize recent studies of feather evolution in terms of genetics, genomics, and developmental biology and provide perspectives for future research. Specifically, this review includes the following topics: 1) Diversity of feather morphotype; 2) feather diversity among different breeds of domesticated birds, including variations in pigmentation pattern, in feather length or regional identity, in feather orientation, in feather distribution, and in feather structure; and 3) diversity of feathers among avian species, including plumage color and morph differences between species and the regulatory differences in downy feather development between altricial and precocial birds. Finally, we discussed future research directions.
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Affiliation(s)
- Chen Siang Ng
- Institute of Molecular and Cellular Biology & Department of Life Science, National Tsing Hua University, Hsinchu, Taiwan.,The iEGG and Animal Biotechnology Center, National Chung Hsing University, Taichung, Taiwan
| | - Wen-Hsiung Li
- The iEGG and Animal Biotechnology Center, National Chung Hsing University, Taichung, Taiwan.,Biodiversity Research Center, Academia Sinica, Taipei, Taiwan.,Department of Ecology and Evolution, University of Chicago
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28
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Trichocyte Keratin-Associated Proteins (KAPs). ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1054:71-86. [DOI: 10.1007/978-981-10-8195-8_7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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29
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Fraser RDB, Parry DAD. Structural Hierarchy of Trichocyte Keratin Intermediate Filaments. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1054:57-70. [PMID: 29797268 DOI: 10.1007/978-981-10-8195-8_6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Although trichocyte keratins (hair, wool, quill, claw) have been studied since the 1930s it is only over the last 30 years or so that major advances have been made in our understanding of the complex structural hierarchy of the filamentous component of this important filament-matrix composite. A variety of techniques, including amino acid sequence analysis, computer modelling, X-ray fibre diffraction and protein crystallography, various forms of electron microscopy, and crosslinking methods have now combined to reveal much of the structural detail. The heterodimeric structure of the keratin molecule is clear, as are the highly-specific modes by which these molecules aggregate to form functionally viable IF. The observation that hair keratin can adopt not one but two structurally-distinct conformations, one formed in the living cells at the base of the hair follicle in a reducing environment and the second in the fully differentiated hair in dead cells in an oxidized state, was unexpected but has major implications for the mechanism of hair growth. Insights have also been made into the mechanism of the uppermost level of hair superstructure, relating to the assembly of the IF in the paracortical and orthocortical macrofibrils.
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Affiliation(s)
- R D Bruce Fraser
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand.,, Tewantin, QLD, Australia
| | - David A D Parry
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand. .,Riddet Institute, Massey University, Palmerston North, New Zealand.
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Abstract
During the 1930s and 1940s the technique of X-ray diffraction was applied widely by William Astbury and his colleagues to a number of naturally-occurring fibrous materials. On the basis of the diffraction patterns obtained, he observed that the structure of each of the fibres was dominated by one of a small number of different types of molecular conformation. One group of fibres, known as the k-m-e-f group of proteins (keratin - myosin - epidermin - fibrinogen), gave rise to diffraction characteristics that became known as the α-pattern. Others, such as those from a number of silks, gave rise to a different pattern - the β-pattern, while connective tissues yielded a third unique set of diffraction characteristics. At the time of Astbury's work, the structures of these materials were unknown, though the spacings of the main X-ray reflections gave an idea of the axial repeats and the lateral packing distances. In a breakthrough in the early 1950s, the basic structures of all of these fibrous proteins were determined. It was found that the long protein chains, composed of strings of amino acids, could be folded up in a systematic manner to generate a limited number of structures that were consistent with the X-ray data. The most important of these were known as the α-helix, the β-sheet, and the collagen triple helix. These studies provided information about the basic building blocks of all proteins, both fibrous and globular. They did not, however, provide detailed information about how these molecules packed together in three-dimensions to generate the fibres found in vivo. A number of possible packing arrangements were subsequently deduced from the X-ray diffraction and other data, but it is only in the last few years, through the continued improvements of electron microscopy, that the packing details within some fibrous proteins can now be seen directly. Here we outline briefly some of the milestones in fibrous protein structure determination, the role of the amino acid sequences and how new techniques, including electron microscopy, are helping to define fibrous protein structures in three-dimensions. We also introduce the idea that, from the known sequence characteristics of different fibrous proteins, new molecules can be designed and synthesized, thereby generating new biological materials with specific structural properties. Some of these, for example, are planned for use in drug delivery systems. Along the way we also introduce the various Chapters of the book, where individual fibrous proteins are discussed in detail.
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Fraser RDB, Parry DAD. Filamentous Structure of Hard β-Keratins in the Epidermal Appendages of Birds and Reptiles. Subcell Biochem 2017; 82:231-252. [PMID: 28101864 DOI: 10.1007/978-3-319-49674-0_8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The structures of avian and reptilian epidermal appendages, such as feathers, claws and scales, have been modelled using X-ray diffraction and electron microscopy data, combined with sequence analyses. In most cases, a family of closely related molecules makes up the bulk of the appendage, and each of these molecules contains a central β-rich 34-residue segment, which has been identified as the principal component of the framework of the 3.4 nm diameter filaments. The N- and C-terminal segments form the matrix component of the filament/matrix complex. The 34-residue β-rich central domains occur in pairs, related by either a parallel dyad or a perpendicular dyad axis, and form a β-sandwich stabilized by apolar interactions. They are also twisted in a right-handed manner. In feather, the filaments are packed into small sheets and it is possible to determine their likely orientation within the sheets from the low-angle X-ray diffraction data. The physical properties of the various epidermal appendages can be related to the amino acid sequence and composition of defined molecular segments characteristic of the chains concerned.
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Affiliation(s)
- R D Bruce Fraser
- Institute of Fundamental Sciences, Massey University, Private Bag 11-222, Palmerston North, 4442, New Zealand
- , 28 Satinay Drive, Noosa Parklands, Tewantin, Qld, 4565, Australia
| | - David A D Parry
- Institute of Fundamental Sciences and Riddet Institute, Massey University, Private Bag 11-222, Palmerston North, 4442, New Zealand.
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Alibardi L, Michieli F, Dalla Valle L. Low-cysteine alpha-keratins and corneous beta-proteins are initially formed in the regenerating tail epidermis of lizard. J Morphol 2016; 278:119-130. [PMID: 27807871 DOI: 10.1002/jmor.20624] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2016] [Revised: 09/28/2016] [Accepted: 10/14/2016] [Indexed: 11/08/2022]
Abstract
During tail regeneration in lizards, the stratified regenerating epidermis progressively gives rise to neogenic scales that form a new epidermal generation. Initially, a soft, un-scaled, pliable, and extensible epidermis is formed that is progressively replaced by a resistant but non-extensible scaled epidermis. This suggests that the initial corneous proteins are later replaced with harder corneous proteins. Using PCR and immunocytochemistry, the present study shows an upregulation in the synthesis of low-cysteine type I and II alpha-keratins and of corneous beta-proteins with a medium cysteine content and a low content in glycine (formerly termed beta-keratins) produced at the beginning of epidermal regeneration. Quantitative PCR indicates upregulation in the production of alpha-keratin mRNAs, particularly of type I, between normal and the thicker regenerating epidermis. PCR-data also indicate a higher upregulation for cysteine-rich corneous beta-proteins and a high but less intense upregulation of low glycine corneous protein mRNAs at the beginning of scale regeneration. Immunolabeling confirms the localization of these proteins, and in particular of beta-proteins with a medium content in cysteine initially formed in the wound epidermis and later in the differentiating corneous layers of regenerating scales. It is concluded that the wound epidermis initially contains alpha-keratins and corneous beta-proteins with a lower cysteine content than more specialized beta-proteins later formed in the mature scales. These initial corneous proteins are likely related to the pliability of the wound epidermis while more specialized alpha-keratins and beta-proteins richer in glycine and cysteine are synthesized later in the mature and inflexible scales. J. Morphol. 278:119-130, 2017. ©© 2016 Wiley Periodicals,Inc.
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Affiliation(s)
- L Alibardi
- Comparative Histolab and Dipartimento di Bigea, Università di Bologna, Bologna, Italy
| | - F Michieli
- Dipartimento di Biologia, Università di Padova, Padova, Italy
| | - L Dalla Valle
- Dipartimento di Biologia, Università di Padova, Padova, Italy
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Alibardi L. Review: mapping epidermal beta-protein distribution in the lizard Anolis carolinensis shows a specific localization for the formation of scales, pads, and claws. PROTOPLASMA 2016; 253:1405-1420. [PMID: 26597267 DOI: 10.1007/s00709-015-0909-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 11/09/2015] [Indexed: 06/05/2023]
Abstract
The epidermis of lizards is made of multiple alpha- and beta-layers with different characteristics comprising alpha-keratins and corneous beta-proteins (formerly beta-keratins). Three main modifications of body scales are present in the lizard Anolis carolinensis: gular scales, adhesive pad lamellae, and claws. The 40 corneous beta-proteins present in this specie comprise glycine-rich and glycine-cysteine-rich subfamilies, while the 41 alpha-keratins comprise cysteine-poor and cysteine-rich subfamilies, the latter showing homology to hair keratins. Other genes for corneous proteins are present in the epidermal differentiation complex, the locus where corneous protein genes are located. The review summarizes the main sites of immunolocalization of beta-proteins in different scales and their derivatives producing a unique map of body distribution for these structural proteins. Small glycine-rich beta-proteins participate in the formation of the mechanically resistant beta-layer of most scales. Small glycine-cysteine beta-proteins have a more varied localization in different scales and are also present in the pliable alpha-layer. In claws, cysteine-rich alpha-keratins prevail over cysteine-poor alpha-keratins and mix to glycine-cysteine-rich beta-proteins. The larger beta-proteins with a molecular mass similar to that of alpha-keratins participate in the formation of the fibrous meshwork present in differentiating beta-cells and likely interact with alpha-keratins. The diverse localization of alpha-keratins, beta-proteins, and other proteins of the epidermal differentiation complex gives rise to variably pliable, elastic, or hard corneous layers in different body scales. The corneous layers formed in the softer or harder scales, in the elastic pad lamellae, or in the resistant claws possess peculiar properties depending on the ratio of specific corneous proteins.
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Affiliation(s)
- Lorenzo Alibardi
- Comparative Histolab and Department of Biology, Geology and Environmental Sciences, University of Bologna, via Selmi 3, 40126, Bologna, Italy.
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ALIBARDI LORENZO. Sauropsids Cornification is Based on Corneous Beta-Proteins, a Special Type of Keratin-Associated Corneous Proteins of the Epidermis. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2016; 326:338-351. [DOI: 10.1002/jez.b.22689] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2016] [Revised: 06/22/2016] [Accepted: 07/05/2016] [Indexed: 12/13/2022]
Affiliation(s)
- LORENZO ALIBARDI
- Comparative Histolab and Department of Bigea; University of Bologna; Italy
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Calvaresi M, Eckhart L, Alibardi L. The molecular organization of the beta-sheet region in Corneous beta-proteins (beta-keratins) of sauropsids explains its stability and polymerization into filaments. J Struct Biol 2016; 194:282-91. [DOI: 10.1016/j.jsb.2016.03.004] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2015] [Revised: 02/29/2016] [Accepted: 03/05/2016] [Indexed: 11/17/2022]
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Alibardi L. The Process of Cornification Evolved From the Initial Keratinization in the Epidermis and Epidermal Derivatives of Vertebrates: A New Synthesis and the Case of Sauropsids. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 327:263-319. [DOI: 10.1016/bs.ircmb.2016.06.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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The molecular structure of the silk fibers from Hymenoptera aculeata (bees, wasps, ants). J Struct Biol 2015; 192:528-538. [DOI: 10.1016/j.jsb.2015.10.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 10/09/2015] [Accepted: 10/24/2015] [Indexed: 11/22/2022]
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Holthaus KB, Strasser B, Sipos W, Schmidt HA, Mlitz V, Sukseree S, Weissenbacher A, Tschachler E, Alibardi L, Eckhart L. Comparative Genomics Identifies Epidermal Proteins Associated with the Evolution of the Turtle Shell. Mol Biol Evol 2015; 33:726-37. [PMID: 26601937 PMCID: PMC4760078 DOI: 10.1093/molbev/msv265] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The evolution of reptiles, birds, and mammals was associated with the origin of unique integumentary structures. Studies on lizards, chicken, and humans have suggested that the evolution of major structural proteins of the outermost, cornified layers of the epidermis was driven by the diversification of a gene cluster called Epidermal Differentiation Complex (EDC). Turtles have evolved unique defense mechanisms that depend on mechanically resilient modifications of the epidermis. To investigate whether the evolution of the integument in these reptiles was associated with specific adaptations of the sequences and expression patterns of EDC-related genes, we utilized newly available genome sequences to determine the epidermal differentiation gene complement of turtles. The EDC of the western painted turtle (Chrysemys picta bellii) comprises more than 100 genes, including at least 48 genes that encode proteins referred to as beta-keratins or corneous beta-proteins. Several EDC proteins have evolved cysteine/proline contents beyond 50% of total amino acid residues. Comparative genomics suggests that distinct subfamilies of EDC genes have been expanded and partly translocated to loci outside of the EDC in turtles. Gene expression analysis in the European pond turtle (Emys orbicularis) showed that EDC genes are differentially expressed in the skin of the various body sites and that a subset of beta-keratin genes within the EDC as well as those located outside of the EDC are expressed predominantly in the shell. Our findings give strong support to the hypothesis that the evolutionary innovation of the turtle shell involved specific molecular adaptations of epidermal differentiation.
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Affiliation(s)
- Karin Brigit Holthaus
- Research Division of Biology and Pathobiology of the Skin, Department of Dermatology, Medical University of Vienna, Vienna, Austria Dipartimento di Scienze Biologiche, Geologiche ed Ambientali (BiGeA), University of Bologna, Bologna, Italy
| | - Bettina Strasser
- Research Division of Biology and Pathobiology of the Skin, Department of Dermatology, Medical University of Vienna, Vienna, Austria
| | - Wolfgang Sipos
- Clinical Department for Farm Animals and Herd Management, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Heiko A Schmidt
- Center for Integrative Bioinformatics Vienna (CIBIV), Max F. Perutz Laboratories, Medical University of Vienna, University of Vienna, Vienna, Austria
| | - Veronika Mlitz
- Research Division of Biology and Pathobiology of the Skin, Department of Dermatology, Medical University of Vienna, Vienna, Austria
| | - Supawadee Sukseree
- Research Division of Biology and Pathobiology of the Skin, Department of Dermatology, Medical University of Vienna, Vienna, Austria
| | | | - Erwin Tschachler
- Research Division of Biology and Pathobiology of the Skin, Department of Dermatology, Medical University of Vienna, Vienna, Austria
| | - Lorenzo Alibardi
- Dipartimento di Scienze Biologiche, Geologiche ed Ambientali (BiGeA), University of Bologna, Bologna, Italy
| | - Leopold Eckhart
- Research Division of Biology and Pathobiology of the Skin, Department of Dermatology, Medical University of Vienna, Vienna, Austria
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Alibardi L. Immunolocalization of sulfhydryl oxidase in reptilian epidermis indicates that the enzyme participates mainly to the hardening process of the beta-corneous layer. PROTOPLASMA 2015; 252:1529-1536. [PMID: 25740419 DOI: 10.1007/s00709-015-0782-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2014] [Accepted: 02/16/2015] [Indexed: 06/04/2023]
Abstract
Reptilian skin is tough and scaled representing an evolutionary adaptation to the terrestrial environment. The presence of sulfhydryl oxidase during the process of hardening of the corneous layer in reptilian epidermis has been analyzed by immunocytochemistry and immunoblotting. Sulfhydryl oxidase-like immunoreactivity of proteins in the 50-65 kDa range of molecular weight is mainly observed in the transitional and pre-corneous layers of crocodilians, chelonian, and in the forming beta-layer of lepidosaurians. The ultrastructural localization of the enzyme by immunogold in lizard epidermis during renewal and resting stages shows that the labeling is mainly distributed in the cytoplasm and along the accumulating beta-packets of differentiating beta-cells while it appears very low to undetectable in differentiating alpha-cells of the lacunar, clear, mesos, and alpha-layers. The labeling however becomes absent or undetectable also in the fully mature beta-layer. The study shows that an oxidative enzyme is likely responsible of the cross-linking of the numerous cysteines present in the main proteins accumulated in corneocytes of reptilian epidermis, known as corneous beta-proteins (beta-keratins). This process of disulphide bond formation is probably largely responsible for the formation of hard beta-corneous layers in reptilian scales, a difference with alpha-corneous layers where substrate proteins of transglutaminase appear predominant.
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Affiliation(s)
- Lorenzo Alibardi
- Comparative Histolab and Department of Bigea, University of Bologna, Bologna, Italy.
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