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Lorenzo Alibardi - One of the best experts on this subject based on the ideXlab platform.
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Immunohistochemical detection of sulfhydryl oxidase in chick skin appendages and feathers suggests that the enzyme contributes to maturation of the corneous material
Zoomorphology, 2020Co-Authors: Lorenzo AlibardiAbstract:Maturation of the corneous material of feathers, scutate scales, claws and beak is a special case of hard cornification since it mainly derives from the accumulation of small feather corneous beta proteins (FCBPs) of 9–12 kDa with a central beta-pleated sheet region, formerly indicated as feather beta keratins. FCBPs contain a relatively high amount of cysteines that likely form numerous –S-S- in the corneous material of these skin appendages. The present immunocytochemical study shows that sulfhydryl oxidase and FCBPs are associated in the differentiating keratinocytes and corneous layers of the epidermis, scales, claws, beak and barb-barbule cells during chick development. The enzyme appears localized in pre-corneous and corneous layers and in differentiating barb-barbule cells where it likely determines formation of -S-S- bonds. This maturation transformation completed in corneous layers of scales, beak, claws and feathers determines increase of hardness and mechanical resistance that, in feathers, is needed for protection and sustaining flight. The process of cornification in chick skin appendages and feathers is discussed in relation to the general process of formation of hard corneous material in vertebrate skin appendages. This occurs by the association of intermediate filament proteins (IFKs, formerly indicates as alpha-keratins) and keratin-associated proteins (KAPs) or CBPs.
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Review: mapping epidermal beta-protein distribution in the lizard Anolis carolinensis shows a specific localization for the formation of scales, pads, and claws
Protoplasma, 2016Co-Authors: Lorenzo AlibardiAbstract: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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the molecular organization of the beta sheet region in corneous beta proteins beta keratins of sauropsids explains its stability and polymerization into filaments
Journal of Structural Biology, 2016Co-Authors: Matteo Calvaresi, Leopold Eckhart, Lorenzo AlibardiAbstract:The hard corneous material of avian and reptilian scales, claws, beak and feathers is mainly derived from the presence of proteins formerly known as Beta-Keratins but now termed Corneous beta-proteins of sauropsids to distinguish them from keratins, which are members of the intermediate filament protein family. The modeling of the conserved 34 amino acid residues long central beta-sheet region of Corneous beta-proteins using an ab initio protein folding and structure prediction algorithm indicates that this region is formed by four antiparallel beta-sheets. Molecular dynamic simulations and Molecular Mechanics/Poisson Boltzmann Surface Area (MM-PBSA) analysis showed that the disposition of polar and apolar amino acids within the beta-region gives rise to an amphipathic core whose stability is further increased, especially in an aqueous environment, by the association into a dimer due to apolar interactions and specific amino-acid interactions. The dimers in turn polymerize into a 3nm thick linear beta-filament due to van der Waals and hydrogen-bond interactions. It is suggested that once this nuclear core of anti-parallel sheets evolved in the genome of a reptilian ancestor of the extant reptiles and birds about 300 millions years ago, new properties emerged in the corneous material forming scales, claws, beaks and feathers in these amniotes based on the tendency of these unique corneous proteins to form stable filaments different from keratin intermediate filaments or sterical structures formed by other corneous proteins so far known.
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Comparative Genomics Identifies Epidermal Proteins Associated with the Evolution of the Turtle Shell
Molecular biology and evolution, 2015Co-Authors: Karin Brigit Holthaus, Lorenzo Alibardi, Bettina Strasser, Wolfgang Sipos, Heiko A. Schmidt, Veronika Mlitz, Supawadee Sukseree, Anton Weissenbacher, Erwin Tschachler, Leopold EckhartAbstract: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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Immunolocalization of alpha-keratins and associated beta-proteins in lizard epidermis shows that acidic keratins mix with basic keratin-associated beta-proteins
Protoplasma, 2014Co-Authors: Lorenzo AlibardiAbstract:The differentiation of the corneous layers of lizard epidermis has been analyzed by ultrastructural immunocytochemistry using specific antibodies against alpha-keratins and keratin associated beta-proteins (KAbetaPs, formerly indicated as Beta-Keratins). Both beta-cells and alpha-cells of the corneous layer derive from the same germinal layer. An acidic type I alpha-keratin is present in basal and suprabasal layers, early differentiating clear, oberhautchen, and beta-cells. Type I keratin apparently disappears in differentiated beta- and alpha-layers of the mature corneous layers. Conversely, a basic type II alpha-keratin rich in glycine is absent or very scarce in basal and suprabasal layers and this keratin likely does not pair with type I keratin to form intermediate filaments but is weakly detected in the pre-corneous and corneous alpha-layer. Single and double labeling experiments show that in differentiating beta-cells, basic KAbetaPs are added and replace type-I keratin to form the hard beta-layer. Epidermal alpha-keratins contain scarce cysteine (0.2–1.4 %) that instead represents 4–19 % of amino acids present in KAbetaPs. Possible chemical bonds formed between alpha-keratins and KAbetaPs may derive from electrostatic interactions in addition to cross-linking through disulphide bonds. Both the high content in glycine of keratins and KAbetaPs may also contribute to increase the hydrophobicy of the beta- and alpha-layers and the resistance of the corneous layer. The increase of gly-rich KAbetaPs amount and the bonds to the framework of alpha-keratins give rise to the inflexible beta-layer while the cys-rich KAbetaPs produce a pliable alpha-layer.
Mattia Toni - One of the best experts on this subject based on the ideXlab platform.
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evolution of hard proteins in the sauropsid integument in relation to the cornification of skin derivatives in amniotes
Journal of Anatomy, 2009Co-Authors: Lorenzo Alibardi, Luisa Dalla Valle, Alessia Nardi, Mattia ToniAbstract:Hard skin appendages in amniotes comprise scales, feathers and hairs. The cell organization of these appendages probably derived from the localization of specialized areas of dermal–epidermal interaction in the integument. The horny scales and the other derivatives were formed from large areas of dermal–epidermal interaction. The evolution of these skin appendages was characterized by the production of specific coiled-coil keratins and associated proteins in the inter-filament matrix. Unlike mammalian keratin-associated proteins, those of sauropsids contain a double beta-folded sequence of about 20 amino acids, known as the core-box. The core-box shows 60%–95% sequence identity with known reptilian and avian proteins. The core-box determines the polymerization of these proteins into filaments indicated as Beta-Keratin filaments. The nucleotide and derived amino acid sequences for these sauropsid keratin-associated proteins are presented in conjunction with a hypothesis about their evolution in reptiles-birds compared to mammalian keratin-associated proteins. It is suggested that genes coding for ancestral glycine-serine-rich sequences of alpha-keratins produced a new class of small matrix proteins. In sauropsids, matrix proteins may have originated after mutation and enrichment in proline, probably in a central region of the ancestral protein. This mutation gave rise to the core-box, and other regions of the original protein evolved differently in the various reptilians orders. In lepidosaurians, two main groups, the high glycine proline and the high cysteine proline proteins, were formed. In archosaurians and chelonians two main groups later diversified into the high glycine proline tyrosine, non-feather proteins, and into the glycine-tyrosine-poor group of feather proteins, which evolved in birds. The latter proteins were particularly suited for making the elongated barb/barbule cells of feathers. In therapsids-mammals, mutations of the ancestral proteins formed the high glycine-tyrosine or the high cysteine proteins but no core-box was produced in the matrix proteins of the hard corneous material of mammalian derivatives.
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Analysis of gene expression in gecko digital adhesive pads indicates significant production of cysteine- and glycine-rich Beta-Keratins
Journal of Experimental Zoology Part B: Molecular and Developmental Evolution, 2009Co-Authors: David L. Hallahan, Tanya Q Shang, Thaya Silke Ganzke, Mattia Toni, Luisa Dalla Valle, Natalie M. Keiper-hrynko, Lorenzo AlibardiAbstract:Microscopic bristles (setae) present on digital pads permit the adhesion and climbing of geckos. Keratins of setae of the lizard Gekko gecko (Tokay gecko) were analyzed by the isolation of expressed mRNAs and by the generation of an EST library. Of the 510 sequences determined, 268 (52.9%) were unique. Of these, 14 appeared to encode alpha- and 111 Beta-Keratins. Within the Beta-Keratins, we identified five groups based on nucleotide sequence comparisons. Of these, one contained the bulk of Beta-Keratins, with 103 EST members. The mRNAs within this major group, together with two singlets, encoded cysteine-proline-serine-rich proteins of 10-14 kDa (Ge-cprp). One of the smaller groups of transcripts encoded slightly larger glycine-proline-serine-rich proteins, of 14-19 kDa (Ge-gprp). The remaining group consisted of smaller (9 kDa) serine-tyrosine-rich Beta-Keratins (Ge-strp). Thus three classes could be distinguished by amino acid sequence alignment. Exact matches for some of the peptide sequences obtained from setal proteins by ms/ms sequencing occur within several of these clones. Most of the Beta-Keratins were basic and contained a core-box region of two beta-strand sequences, with high homology to core-boxes present in avian scale and feather Beta-Keratins. Core-boxes are beta-folded regions that are likely responsible for polymerization into the Beta-Keratin filaments. The two deduced alpha-keratins of 52.7 kDa are both acidic, and contain the typical central rod region with some homology to mammalian and avian alpha-keratins, with variable N- and C-terminal regions. Basic Beta-Keratins and acidic alpha-keratins may interact electrostatically to form the resistant corneous material of setae
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analysis of gene expression in gecko digital adhesive pads indicates significant production of cysteine and glycine rich beta keratins
Journal of Experimental Zoology, 2009Co-Authors: David L Hallaha, Natalie M Keiperhrynko, Tanya Q Shang, Thaya Silke Ganzke, Mattia Toni, Luisa Dalla ValleAbstract:Microscopic bristles (setae) present on digital pads permit the adhesion and climbing of geckos. Keratins of setae of the lizard Gekko gecko (Tokay gecko) were analyzed by the isolation of expressed mRNAs and by the generation of an EST library. Of the 510 sequences determined, 268 (52.9%) were unique. Of these, 14 appeared to encode alpha- and 111 Beta-Keratins. Within the Beta-Keratins, we identified five groups based on nucleotide sequence comparisons. Of these, one contained the bulk of Beta-Keratins, with 103 EST members. The mRNAs within this major group, together with two singlets, encoded cysteine–proline–serine-rich proteins of 10–14 kDa (Ge-cprp). One of the smaller groups of transcripts encoded slightly larger glycine–proline–serine-rich proteins, of 14–19 kDa (Ge-gprp). The remaining group consisted of smaller (9 kDa) serine–tyrosine-rich Beta-Keratins (Ge-strp). Thus three classes could be distinguished by amino acid sequence alignment. Exact matches for some of the peptide sequences obtained from setal proteins by ms/ms sequencing occur within several of these clones. Most of the Beta-Keratins were basic and contained a core-box region of two beta-strand sequences, with high homology to core-boxes present in avian scale and feather Beta-Keratins. Core-boxes are beta-folded regions that are likely responsible for polymerization into the Beta-Keratin filaments. The two deduced alpha-keratins of 52.7 kDa are both acidic, and contain the typical central rod region with some homology to mammalian and avian alpha-keratins, with variable N- and C-terminal regions. Basic Beta-Keratins and acidic alpha-keratins may interact electrostatically to form the resistant corneous material of setae. J. Exp. Zool. (Mol. Dev. Evol.) 312B:58–73, 2009. © 2008 Wiley-Liss, Inc.
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β-keratins of the crocodilian epidermis: composition, structure, and phylogenetic relationships
Journal of Experimental Zoology Part B: Molecular and Developmental Evolution, 2009Co-Authors: Luisa Dalla Valle, Mattia Toni, Alessia Nardi, Deena Emera, Carlotta Gelmi, Lorenzo AlibardiAbstract:Nucleotide and deduced amino acid sequences of three Beta-Keratins of Nile crocodile scales are presented. Using 5'- and 3'-RACE analysis, two cDNA sequences of 1 kb (Cr-gptrp-1) and 1.5 kb (Cr-gptrp-2) were determined, corresponding to 17.4 and 19.3 kDa proteins, respectively, and a pI of 8.0. In genomic DNA amplifications, we determined that the 5'-UTR of Cr-gptrp-2 contains an intron of 621 nucleotides. In addition, we isolated a third gene (Cr-gptrp-3) in genomic DNA amplifications that exhibits seven amino acid differences with Cr-gptrp-2. Genomic organization of the sequenced crocodilian Beta-Keratin genes is similar to avian Beta-Keratin genes. Deduced proteins are rich in glycine, proline, serine, and tyrosine, and contain cysteines toward the N- and C-terminal regions, likely for the formation of disulfide bonds. Prediction of the secondary structure suggests that the central core box of 20 amino acids contains two beta-strands and has 75-90% identity with chick Beta-Keratins. Toward the C-terminus, numerous glycine-glycine-tyrosine and glycine-glycine-leucine repeats are present, which may contribute to making crocodile scales hard. In situ hybridization shows expression of Beta-Keratin genes in differentiating beta-cells of epidermal transitional layers. Phylogenetic analysis of the available archosaurian and lepidosaurian Beta-Keratins suggests that feather keratins diversified early from nonfeather keratins, deep in archosaur evolution. However, only the complete knowledge of all crocodilian Beta-Keratins will confirm whether feather keratins have an origin independent of those in bird scales, which preceded the split between birds and crocodiles
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evolution of hard proteins in the sauropsid integument in relation to the cornification of skin derivatives
2009Co-Authors: Luisa Dalla Valle, Alessia Nardi, Mattia ToniAbstract:Hard skin appendages in amniotes comprise scales, feathers and hairs. The cell organization of these appendages probably derived from the localization of specialized areas of dermal–epidermal interaction in the integument. The horny scales and the other derivatives were formed from large areas of dermal–epidermal interaction. The evolution of these skin appendages was characterized by the production of specific coiled-coil keratins and associated proteins in the inter-filament matrix. Unlike mammalian keratin-associated proteins, those of sauropsids contain a double beta-folded sequence of about 20 amino acids, known as the core-box. The core-box shows 60%– 95% sequence identity with known reptilian and avian proteins. The core-box determines the polymerization of these proteins into filaments indicated as Beta-Keratin filaments. The nucleotide and derived amino acid sequences for these sauropsid keratin-associated proteins are presented in conjunction with a hypothesis about their evolution in reptiles-birds compared to mammalian keratin-associated proteins. It is suggested that genes coding for ancestral glycine-serine-rich sequences of alpha-keratins produced a new class of small matrix proteins. In sauropsids, matrix proteins may have originated after mutation and enrichment in proline, probably in a central region of the ancestral protein. This mutation gave rise to the core-box, and other regions of the original protein evolved differently in the various reptilians orders. In lepidosaurians, two main groups, the high glycine proline and the high cysteine proline proteins, were formed. In archosaurians and chelonians two main groups later diversified into the high glycine proline tyrosine, non-feather proteins, and into the glycine-tyrosine-poor group of feather proteins, which evolved in birds. The latter proteins were particularly suited for making the elongated barb/barbule cells of feathers. In therapsids-mammals, mutations of the ancestral proteins formed the high glycine-tyrosine or the high cysteine proteins but no core-box was produced in the matrix proteins of the hard corneous material of mammalian
Luisa Dalla Valle - One of the best experts on this subject based on the ideXlab platform.
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Ultrastructural localization of hair keratin homologs in the claw of the lizard Anolis carolinensis
Journal of morphology, 2010Co-Authors: Lorenzo Alibardi, Luisa Dalla Valle, Karin Jaeger, Leopold EckhartAbstract:The claw of lizards is largely composed of Beta-Keratins, also referred to as keratin-associated beta-proteins. Recently, we have reported that the genome of the lizard Anolis carolinensis contains alpha keratin genes homologous to hair keratins typical of hairs and claws of mammals. Molecular and immunohistochemical studies demonstrated that two hair keratin homologs named hard acid keratin 1 (HA1) and hard basic keratin 1 (HB1) are expressed in keratinocytes forming the claws of A. carolinensis. Here, we extended the immunocytochemical localization of the novel reptilian keratins to the ultrastructural level. After sectioning, claws were subjected to immunogold labeling using antibodies against HA1, HB1, and, for comparison, Beta-Keratins. Electron microscopy showed that the randomly organized network of tonofilaments in basal and suprabasal keratinocytes becomes organized in long and parallel bundles of keratin in precorneous layers, resembling cortical cells of hairs. Entering the cornified part of the claw, the elongated corneous cells fuse and accumulate corneous material. HA1 and HB1 are absent in the basal layer and lower spinosus layers of the claw and are expressed in the upper and precorneous layers, including the elongating corneocytes. The labeling for alpha-keratin was loosely associated with filament structures forming the fibrous framework of the claws. The ultrastructural distribution pattern of hard alpha-keratins resembled that of Beta-Keratins, which is compatible with the hypothesis of an interaction during claw morphogenesis. The data on the ultrastructural localization of hair keratin homologs facilitate a comparison of lizard claws and mammalian hard epidermal appendages containing hair keratins. J. Morphol., 2011. © 2010 Wiley-Liss, Inc.
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Isolation of a new class of cysteine–glycine–proline-rich beta-proteins (Beta-Keratins) and their expression in snake epidermis
Journal of anatomy, 2010Co-Authors: Luisa Dalla Valle, Alessia Nardi, Lorenzo AlibardiAbstract:Scales of snakes contain hard proteins (Beta-Keratins), now referred to as keratin-associated beta-proteins. In the present study we report the isolation, sequencing, and expression of a new group of these proteins from snake epidermis, designated cysteine–glycine–proline-rich proteins. One deduced protein from expressed mRNAs contains 128 amino acids (12.5 kDa) with a theoretical pI at 7.95, containing 10.2% cysteine and 15.6% glycine. The sequences of two more snake cysteine–proline-rich proteins have been identified from genomic DNA. In situ hybridization shows that the messengers for these proteins are present in the suprabasal and early differentiating beta-cells of the renewing scale epidermis. The present study shows that snake scales, as previously seen in scales of lizards, contain cysteine-rich beta-proteins in addition to glycine-rich beta-proteins. These keratin-associated beta-proteins mix with intermediate filament keratins (alpha-keratins) to produce the resistant corneous layer of snake scales. The specific proportion of these two subfamilies of proteins in different scales can determine various degrees of hardness in scales.
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evolution of hard proteins in the sauropsid integument in relation to the cornification of skin derivatives in amniotes
Journal of Anatomy, 2009Co-Authors: Lorenzo Alibardi, Luisa Dalla Valle, Alessia Nardi, Mattia ToniAbstract:Hard skin appendages in amniotes comprise scales, feathers and hairs. The cell organization of these appendages probably derived from the localization of specialized areas of dermal–epidermal interaction in the integument. The horny scales and the other derivatives were formed from large areas of dermal–epidermal interaction. The evolution of these skin appendages was characterized by the production of specific coiled-coil keratins and associated proteins in the inter-filament matrix. Unlike mammalian keratin-associated proteins, those of sauropsids contain a double beta-folded sequence of about 20 amino acids, known as the core-box. The core-box shows 60%–95% sequence identity with known reptilian and avian proteins. The core-box determines the polymerization of these proteins into filaments indicated as Beta-Keratin filaments. The nucleotide and derived amino acid sequences for these sauropsid keratin-associated proteins are presented in conjunction with a hypothesis about their evolution in reptiles-birds compared to mammalian keratin-associated proteins. It is suggested that genes coding for ancestral glycine-serine-rich sequences of alpha-keratins produced a new class of small matrix proteins. In sauropsids, matrix proteins may have originated after mutation and enrichment in proline, probably in a central region of the ancestral protein. This mutation gave rise to the core-box, and other regions of the original protein evolved differently in the various reptilians orders. In lepidosaurians, two main groups, the high glycine proline and the high cysteine proline proteins, were formed. In archosaurians and chelonians two main groups later diversified into the high glycine proline tyrosine, non-feather proteins, and into the glycine-tyrosine-poor group of feather proteins, which evolved in birds. The latter proteins were particularly suited for making the elongated barb/barbule cells of feathers. In therapsids-mammals, mutations of the ancestral proteins formed the high glycine-tyrosine or the high cysteine proteins but no core-box was produced in the matrix proteins of the hard corneous material of mammalian derivatives.
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analysis of gene expression in gecko digital adhesive pads indicates significant production of cysteine and glycine rich beta keratins
Journal of Experimental Zoology, 2009Co-Authors: David L Hallaha, Natalie M Keiperhrynko, Tanya Q Shang, Thaya Silke Ganzke, Mattia Toni, Luisa Dalla ValleAbstract:Microscopic bristles (setae) present on digital pads permit the adhesion and climbing of geckos. Keratins of setae of the lizard Gekko gecko (Tokay gecko) were analyzed by the isolation of expressed mRNAs and by the generation of an EST library. Of the 510 sequences determined, 268 (52.9%) were unique. Of these, 14 appeared to encode alpha- and 111 Beta-Keratins. Within the Beta-Keratins, we identified five groups based on nucleotide sequence comparisons. Of these, one contained the bulk of Beta-Keratins, with 103 EST members. The mRNAs within this major group, together with two singlets, encoded cysteine–proline–serine-rich proteins of 10–14 kDa (Ge-cprp). One of the smaller groups of transcripts encoded slightly larger glycine–proline–serine-rich proteins, of 14–19 kDa (Ge-gprp). The remaining group consisted of smaller (9 kDa) serine–tyrosine-rich Beta-Keratins (Ge-strp). Thus three classes could be distinguished by amino acid sequence alignment. Exact matches for some of the peptide sequences obtained from setal proteins by ms/ms sequencing occur within several of these clones. Most of the Beta-Keratins were basic and contained a core-box region of two beta-strand sequences, with high homology to core-boxes present in avian scale and feather Beta-Keratins. Core-boxes are beta-folded regions that are likely responsible for polymerization into the Beta-Keratin filaments. The two deduced alpha-keratins of 52.7 kDa are both acidic, and contain the typical central rod region with some homology to mammalian and avian alpha-keratins, with variable N- and C-terminal regions. Basic Beta-Keratins and acidic alpha-keratins may interact electrostatically to form the resistant corneous material of setae. J. Exp. Zool. (Mol. Dev. Evol.) 312B:58–73, 2009. © 2008 Wiley-Liss, Inc.
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evolution of hard proteins in the sauropsid integument in relation to the cornification of skin derivatives
2009Co-Authors: Luisa Dalla Valle, Alessia Nardi, Mattia ToniAbstract:Hard skin appendages in amniotes comprise scales, feathers and hairs. The cell organization of these appendages probably derived from the localization of specialized areas of dermal–epidermal interaction in the integument. The horny scales and the other derivatives were formed from large areas of dermal–epidermal interaction. The evolution of these skin appendages was characterized by the production of specific coiled-coil keratins and associated proteins in the inter-filament matrix. Unlike mammalian keratin-associated proteins, those of sauropsids contain a double beta-folded sequence of about 20 amino acids, known as the core-box. The core-box shows 60%– 95% sequence identity with known reptilian and avian proteins. The core-box determines the polymerization of these proteins into filaments indicated as Beta-Keratin filaments. The nucleotide and derived amino acid sequences for these sauropsid keratin-associated proteins are presented in conjunction with a hypothesis about their evolution in reptiles-birds compared to mammalian keratin-associated proteins. It is suggested that genes coding for ancestral glycine-serine-rich sequences of alpha-keratins produced a new class of small matrix proteins. In sauropsids, matrix proteins may have originated after mutation and enrichment in proline, probably in a central region of the ancestral protein. This mutation gave rise to the core-box, and other regions of the original protein evolved differently in the various reptilians orders. In lepidosaurians, two main groups, the high glycine proline and the high cysteine proline proteins, were formed. In archosaurians and chelonians two main groups later diversified into the high glycine proline tyrosine, non-feather proteins, and into the glycine-tyrosine-poor group of feather proteins, which evolved in birds. The latter proteins were particularly suited for making the elongated barb/barbule cells of feathers. In therapsids-mammals, mutations of the ancestral proteins formed the high glycine-tyrosine or the high cysteine proteins but no core-box was produced in the matrix proteins of the hard corneous material of mammalian
Roger H. Sawyer - One of the best experts on this subject based on the ideXlab platform.
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Genomic organization and molecular phylogenies of the beta (β) keratin multigene family in the chicken (Gallus gallus) and zebra finch (Taeniopygia guttata): implications for feather evolution
BMC Evolutionary Biology, 2010Co-Authors: Matthew J Greenwold, Roger H. SawyerAbstract:Background The epidermal appendages of reptiles and birds are constructed of beta (β) keratins. The molecular phylogeny of these keratins is important to understanding the evolutionary origin of these appendages, especially feathers. Knowing that the crocodilian β-keratin genes are closely related to those of birds, the published genomes of the chicken and zebra finch provide an opportunity not only to compare the genomic organization of their β-keratins, but to study their molecular evolution in archosaurians. Results The subfamilies (claw, feather, feather-like, and scale) of β-keratin genes are clustered in the same 5' to 3' order on microchromosome 25 in chicken and zebra finch, although the number of claw and feather genes differs between the species. Molecular phylogenies show that the monophyletic scale genes are the basal group within birds and that the monophyletic avian claw genes form the basal group to all feather and feather-like genes. Both species have a number of feather clades on microchromosome 27 that form monophyletic groups. An additional monophyletic cluster of feather genes exist on macrochromosome 2 for each species. Expression sequence tag analysis for the chicken demonstrates that all feather β-keratin clades are expressed. Conclusions Similarity in the overall genomic organization of β-keratins in Galliformes and Passeriformes suggests similar organization in all Neognathae birds, and perhaps in the ancestral lineages leading to modern birds, such as the paravian Anchiornis huxleyi . Phylogenetic analyses demonstrate that evolution of archosaurian epidermal appendages in the lineage leading to birds was accompanied by duplication and divergence of an ancestral β-keratin gene cluster. As morphological diversification of epidermal appendages occurred and the β-keratin multigene family expanded, novel β-keratin genes were selected for novel functions within appendages such as feathers.
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Beta-Keratin localization in developing alligator scales and feathers in relation to the development and evolution of feathers.
Journal of submicroscopic cytology and pathology, 2006Co-Authors: Lorenzo Alibardi, Loren W. Knapp, Roger H. SawyerAbstract:Beta-Keratins form large part of the corneous material of scales and feathers. The present immunocytochemical study describes the fine distribution of scale- and feather-keratins (Beta-Keratins) in embryonic scales of the alligator and in avian embryonic feathers. In embryonic scales of the alligator both scale-keratin and feather-keratin can be immunolocalized, especially in the subperiderm layer. No immunolabeling for feather keratin is instead present in the adult scale after the embryonic epidermis is lost. The embryonic epidermis of feather folds into barb ridges while subperiderm or subsheath cells are displaced into two barbule plates joined to the central ramus. Subperiderm cells react with an antibody against feather keratin and with lower intensity with an antibody against scale keratin. The axial plate is colonized by barb ridge vane cells, which surround subperiderm cells that become barb/barbule cells. The latter cells merge into a branched syncitium and form the micro ramification of feathers. The lengthening of barbule cells derives from the polymerization of feather keratin into long bundles coursing along the main axis of cells. Keratin bundles in feather cells are however ordered in parallel rows while those of scales in both alligator and birds are irregularly packed. This observation indicates a different modality of aggregation and molecular structure between the feather keratin of subperiderm cells versus that of barbule/barbs. Barb vane ridge cells among barbule cells degenerate at late stage of feather development leaving spaces that separate barbules. Barb vane ridge cells contain alpha-keratin and lipids, but not Beta-Keratin. Cells of marginal plates do not contain Beta-Keratin, and later degenerate allowing the separation of barbs. The latter become isolated only after sloughing of the sheath, which cells contain bundle of keratin not reactive for both scale- and feather-keratin antibodies. The study confirms morphological observations and shows that subperiderm or subsheath cells differentiate into barb and barbule cells. The morphogenesis of barb ridges has to be considered as an evolutionary novelty that permitted the evolution of feathers from a generalized archosaurian embryonic epidermis.
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Avian skin development and the evolutionary origin of feathers
Journal of experimental zoology. Part B Molecular and developmental evolution, 2003Co-Authors: Roger H. Sawyer, Loren W. KnappAbstract:The discovery of several dinosaurs with filamentous integumentary appendages of different morphologies has stimulated models for the evolutionary origin of feathers. In order to understand these models, knowledge of the development of the avian integument must be put into an evolutionary context. Thus, we present a review of avian scale and feather development, which summarizes the morphogenetic events involved, as well as the expression of the beta (beta) keratin multigene family that characterizes the epidermal appendages of reptiles and birds. First we review information on the evolution of the ectodermal epidermis and its beta (beta) keratins. Then we examine the morphogenesis of scutate scales and feathers including studies in which the extraembryonic ectoderm of the chorion is used to examine dermal induction. We also present studies on the scaleless (sc) mutant, and, because of the recent discovery of "four-winged" dinosaurs, we review earlier studies of a chicken strain, Silkie, that expresses ptilopody (pti), "feathered feet." We conclude that the ability of the ectodermal epidermis to generate discrete cell populations capable of forming functional structural elements consisting of specific members of the beta keratin multigene family was a plesiomorphic feature of the archosaurian ancestor of crocodilians and birds. Evidence suggests that the discrete epidermal lineages that make up the embryonic feather filament of extant birds are homologous with similar embryonic lineages of the developing scutate scales of birds and the scales of alligators. We believe that the early expression of conserved signaling modules in the embryonic skin of the avian ancestor led to the early morphogenesis of the embryonic feather filament, with its periderm, sheath, and barb ridge lineages forming the first protofeather. Invagination of the epidermis of the protofeather led to formation of the follicle providing for feather renewal and diversification. The observations that scale formation in birds involves an inhibition of feather formation coupled with observations on the feathered feet of the scaleless (High-line) and Silkie strains support the view that the ancestor of modern birds may have had feathered hind limbs similar to those recently discovered in nonavian dromaeosaurids. And finally, our recent observation on the bristles of the wild turkey beard raises the possibility that similar integumentary appendages may have adorned nonavian dinosaurs, and thus all filamentous integumentary appendages may not be homologous to modern feathers.
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Region-specific patterns of beta keratin expression during avian skin development.
Developmental dynamics : an official publication of the American Association of Anatomists, 1993Co-Authors: Loren W. Knapp, Rose B. Shames, George L. Barnes, Roger H. SawyerAbstract:The transient embryonic layers primarily composed of a periderm and subperiderm cover most regions of the chick embryo and are the first suprabasal cell layers covering the body ectoderm. This study presents evidence for regional vriation in the expression of beta keratin in the embryonic layers. Here we show that the embryonic layers covering the anterior metatarsal region of the chicken hindlimb (scutate scale forming region) produce several members of the beta keratin family of polypeptides, designated beta (β) 1–7. These specific polypeptides are later expressed in this region exclusively in the thick, cornified beta strata of mature scutate scales. In contrast to this sequence of events, the embryonic layers overlying the epidermis of the ventral foot pad (reticulate scale-forming region) and those covering the epidermis in apteric regions of the body produce beta keratin polypeptides β1–3 and β2,3, respectively, but no subsequent expression of these proteins occurs in the mature epidermises of these regions. Furthermore, we find that the embryonic layers of the skin overlying the anterior metatasal region of birds homozygous for the mutation “scaleless” (sc/sc), which completely lack scutate scales, produce the same members of the beta keratin family, β1–7, as the embryonic layers and beta strata of normal scutate scales. Thus, the accumulation of specific beta keratin polypeptides in the developing anterior metatarsal region appears to occur in two distinct phases; first, an early region-specific expression in cells of the embryonic layers followed by a second phase of expression which occurs in conjunction with appendage morphogenesis. The relationship between differentiation of embryonic skin and the expression of beta keratins is discussed. © 1993 wiley-Liss, Inc.
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Region‐specific expression of scutate scale type beta keratins in the developing chick beak
The Journal of experimental zoology, 1991Co-Authors: Rose B. Shames, Loren W. Knapp, Wayne Carver, Roger H. SawyerAbstract:This study shows that different patterns of scutate scale type beta keratins are accumulated in the three adjacent structures of the embryonic chick beak: periderm, egg tooth, and cornified beak. The cornified beak accumulates all of the beta keratins of scutate scale except pp2,3. The periderm, which is the outermost, multilayered covering of the whole embryonic beak, accumulates only beta keratins 2,3, and p2,3 of the scutate scale pattern. The egg tooth, which is the rounded elevation on the dorsal surface of the upper beak, and the embryonic claw accumulate greatly reduced levels of 2,3 and p2,3 compared to scutate scale. Like cornified beak, the claw does not accumulate pp2,3, but both tissues express a potentially new beta keratin, beta keratin 8. Neither the histidine rich “fast” proteins (HRPs), which are expressed in embryonic scutate scales and feathers, nor the avian cytokeratin associated proteins (cap-1 and cap-2), which are expressed in scutate and reticulate scales, are expressed in any of the embryonic beak structures or in the claw. The implications of these findings with regard to regulation of terminal differentiation of avian skin are discussed.
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Molecular characterization of alpha-keratins in comparison to associated beta-proteins in soft-shelled and hard-shelled turtles produced during the process of epidermal differentiation.
Journal of experimental zoology. Part B Molecular and developmental evolution, 2013Co-Authors: L. Dalla Valle, F. Michieli, Francesca Benato, Tatjana Skobo, Lorenzo AlibardiAbstract:The tough corneous layer in the carapace and plastron of hard-shelled turtles derives from the accumulation of keratin-associated beta-proteins (KAbetaPs, formerly called Beta-Keratins) while these proteins are believed to be absent in soft-shelled turtles. Our bioinformatics and molecular study has instead shown that the epidermis of the soft-shelled turtle Apalone spinifera expresses beta-proteins like or even in higher amount than in the hard-shelled turtle Pseudemys nelsoni. The analysis of a carapace cDNAs library has allowed the identification and characterization of three alpha-keratins of type I and of ten beta-proteins (Beta-Keratins). The acidic alpha-keratins probably combine with the basic beta-proteins but the high production of beta-proteins in A. spinifera is not prevalent over that of alpha-keratin so that their combination does not determine the formation of hard corneous material. Furthermore the presence of a proline and cisteine in the beta-sheet region of beta-proteins in A. spinifera may be unsuited to form hard masses of corneous material. The higher amount of beta-proteins over alpha-keratins instead occurs in keratinocytes of the hard and inflexible epidermis of P. nelsoni determining the deposition of hard corneous material. The study suggests that the hardness of the corneous layer derives not exclusively from the interactions between alpha-keratins with KAbetaPs but also from the different dynamic of accumulation and loss of corneocytes in the corneous layer of the hard shelled turtles where a prevalent accumulation and piling of corneocytes takes place versus the soft shelled turtle where a rapid turnover of the stratum corneum occurs. J. Exp. Zool. (Mol. Dev. Evol.) 320B: 428–441, 2013. © 2013 Wiley Periodicals, Inc.
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Distribution of Specific Keratin‐Associated Beta‐Proteins (Beta‐Keratins) in the Epidermis of the Lizard Anolis carolinensis Helps to Clarify the Process of Cornification in Lepidosaurians
Journal of experimental zoology. Part B Molecular and developmental evolution, 2012Co-Authors: Lorenzo Alibardi, A. Segalla, L. Dalla ValleAbstract:The epidermis of different scales in the lizard Anolis carolinensis expresses specific keratin-associated beta-proteins (Beta-Keratins). In order to localize the sites of accumulation of different beta-proteins, we have utilized antibodies directed against representative members of the main families of beta-proteins, the glycine-rich (HgG5), glycine–cysteine rich (HgGC3), glycine–cysteine medium-rich (HgGC10), and cysteine-rich (HgC1) beta-proteins. Immunoblotting and immunocytochemical controls confirm the specificity of the antibodies made against these proteins. Light and ultrastructural immunocytochemistry shows that the glycine-rich protein HgG5 is present in beta-layers of different body scales but is scarce in the oberhautchen and claws, and is absent in alpha-layers and adhesive setae. The cysteine–glycine-rich protein HgGC3 is low to absent in the oberhautchen, beta-layer, and mesos-layer but increases in alpha-layers. This beta-protein is low in claws where it is likely associated with the hard alpha-keratins previously studied in this lizard. The glycine–cysteine medium-rich HgGC10 protein is low in the beta-layer, higher in alpha-layers, and in the oberhautchen. This protein forms a major component of setal proteins including those of the adhesive spatula that allow this lizard to stick on vertical surfaces. HgC1 is poorly localized in most epidermis analyzed including adhesive setae and claws and appears as a minor component of the alpha-layers. In conclusion, the present study suggests that beta- and alpha-layers of lizard epidermis represent regions with different accumulation of glycine-rich proteins (mainly for mechanical resistance and hydrophobicity in the beta-layer) or cysteine–glycine-rich proteins (for both resistance and elasticity in both alpha- and beta-layers). J. Exp. Zool. (Mol. Dev. Evol.) 318B:388-403, 2012. © 2012 Wiley Periodicals, Inc.
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The epidermis of scales in gecko lizards contains multiple forms of Beta-Keratins including basic glycine-proline-serine-rich proteins.
Journal of proteome research, 2007Co-Authors: Mattia Toni, L. Dalla Valle, Lorenzo AlibardiAbstract:The epidermis of scales of gecko lizards comprises alpha- and Beta-Keratins. Using bidimensional electrophoresis and immunoblotting, we have characterized keratins of corneous layers of scales in geckos, especially Beta-Keratins in digit pad lamellae. In the latter, the formation of thin bristles (setae) allow for the adhesion and climbing vertical or inverted surfaces. alpha-Keratins of 55-66 kDa remain in the acidic and neutral range of pI, while Beta-Keratins of 13-18 kDa show a broader variation of pI (4-10). Some protein spots for Beta-Keratins correspond to previously sequenced, basic glycine-proline-serine-rich Beta-Keratins of 169-191 amino acids. The predicted secondary structure shows that a large part of the molecule has a random-coiled conformation, small alpha helix regions, and a central region with 2-3 strands (beta-folding). The latter, termed core-box, shows homology with feather-scale-claw keratins of birds and is involved in the formation of Beta-Keratin filaments. Immunolocalization of Beta-Keratins indicates that these proteins are mainly present in the beta-layer and oberhautchen layer, including setae. The sequenced proteins of setae form bundles of keratins that determine their elongation. This process resembles that of feather-keratin on the elongation of barbule cells in feathers. It is suggested that small proteins rich in glycine, serine, and proline evolved in reptiles and birds to reinforce the mechanical resistance of the cytokeratin cytoskeleton initially present in the epidermis of scales and feathers.