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new papers in Anatomical Record



These may be of interest - in the July issue; http://www3.interscience.wiley.com/cgi-bin/jhome/28243

Scale keratin in lizard epidermis reveals amino acid regions homologous with avian and mammalian epidermal proteins

Lorenzo Alibardi 1 *, Luisa Dalla Valle 2, Vania Toffolo 2, Mattia Toni 1
1Dipartimento di Biologia Evoluzionistica Sperimentale, University of Bologna, Bologna, Italy
2Dipartimento di Biologia, University of Padova, Padova, Italy
email: Lorenzo Alibardi (alibardi@biblio.cib.unibo.it)


*Correspondence to Lorenzo Alibardi, Dipartimento di Biologia Evoluzionistica Sperimentale, via Selmi 3, University of Bologna, 40126, Bologna, Italy
Fax: 39-051-2094286.
Funded by:
Universities of Bologna and Padova
Keywords
lizard • scales • -keratins • mRNA • amino acid sequence • keratin-associated proteins • evolution


Abstract
Small proteins termed -keratins constitute the hard corneous material of reptilian scales. In order to study the cell site of synthesis of -keratin, an antiserum against a lizard -keratin of 15-16 kDa has been produced. The antiserum recognizes -cells of lizard epidermis and labels -keratin filaments using immunocytochemistry and immunoblotting. In situ hybridization using a cDNA-probe for a lizard -keratin mRNA labels -cells of the regenerating and embryonic epidermis of lizard. The mRNA is localized free in the cytoplasm or is associated with keratin filaments of -cells. The immunolabeling and in situ labeling suggest that synthesis and accumulation of -keratin are closely associated. Nuclear localization of the cDNA probe suggests that the primary transcript is similar to the cytoplasmic mRNA coding for the protein. The latter comprises a glycine-proline-rich protein of 15.5 kDa that contains 163 amino acids, in which the central amino acid region is similar to that of chick claw/feather while the head and tail regions resemble glycine-tyrosine-rich proteins of mammalian hairs. This is also confirmed by phylogenetic analysis comparing reptilian glycine-rich proteins with cytokeratins, hair keratin-associated proteins, and claw/feather keratins. It is suggested that different small glycine-rich proteins evolved from progenitor proteins present in basic (reptilian) amniotes. The evolution of these proteins originated glycine-rich proteins in scales, claws, beak of reptiles and birds, and in feathers. Some evidence suggests that at least some proteins contained within -keratin filaments are rich in glycine and resemble some keratin-associated proteins present in mammalian corneous derivatives. It is suggested that glycine-rich proteins with the chemical composition, immunological characteristics, and molecular weight of -keratins may represent the reptilian counterpart of keratin-associated proteins present in hairs, nails, hooves, and horns of mammals. These small proteins produce a hard type of corneous material due to their dense packing among cytokeratin filaments. Anat Rec Part A, 288A:734-752, 2006. © 2006 Wiley-Liss, Inc.
Received: 30 November 2005; Accepted: 30 March 2006


Digital Object Identifier (DOI) 10.1002/ar.a.20342




Thoracic epaxial muscles in living archosaurs and ornithopod dinosaurs

Christopher Lee Organ 1 2 *
1Department of Paleontology, Museum of the Rockies, Bozeman, Montana
2Department of Cell Biology and Neuroscience, Montana State University, Bozeman, Montana
email: Christopher Lee Organ (corgan@oeb.harvard.edu)


*Correspondence to Christopher Lee Organ, Department of Organismic and Evolutionary Biology, Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, MA 02138
Fax: 617-495-5667
Funded by:
International Society of Biomechanics
Department of Paleontology
Museum of the Rockies
Department of Cell Biology and Neuroscience at Montana State University
Keywords
archosaur • dinosaur • ossified tendon • ornithischian • ornithopod • axial • epaxial


Abstract
Crocodylians possess the same thoracic epaxial muscles as most other saurians, but M. transversospinalis is modified by overlying osteoderms. Compared with crocodylians, the thoracic epaxial muscles of birds are reduced in size, disrupted by the synsacrum, and often modified by intratendinous ossification and the notarium. A phylogenetic perspective is used to determine muscle homologies in living archosaurs (birds and crocodylians), evaluate how the apparent disparity evolved, and reconstruct the thoracic epaxial muscles in ornithopod dinosaurs. The avian modifications of the epaxial musculoskeletal system appear to have coevolved with the synsacrum and notarium. The lattice of ossified tendons in iguanodontoidean dinosaurs (Hadrosauridae and Iguanodontidae) is homologized to M. transversospinalis in crocodylians and M. longus colli dorsalis, pars thoracica in birds. Birds have an arrangement of tendons within M. longus colli dorsalis, pars thoracica identical to that observed in the epaxial ossified tendons of iguanodontoid dinosaurs. Moreover, many birds (such as grebes and turkeys) ossify these tendons, resulting in a two- or three-layered lattice of ossified tendons, a morphology also seen in iguanodontoid dinosaurs. Although the structure of M. transversospinalis appears indistinguishable between birds and iguanodontoid dinosaurs, intratendinous ossification within this epaxial muscle evolved convergently. Anat Rec Part A, 288A:782-793, 2006. © 2006 Wiley-Liss, Inc.
Received: 19 October 2005; Accepted: 24 March 2006


Digital Object Identifier (DOI) 10.1002/ar.a.20341


-- ***************** Colin McHenry School of Environmental and Life Sciences (Geology) University of Newcastle Callaghan NSW 2308 Australia Tel: +61 2 4921 5404 Fax: + 61 2 4921 6925

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