new papers in Anatomical Record

[Colin McHenry <cmchenry@westserv.net.au>]

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


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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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