title: Deleterious mutations of a claw keratin in multiple taxa of reptiles.
abstract: We have recently shown that homologs of mammalian hair keratins are expressed in the claws of the green anole lizard, Anolis carolinensis. To test whether reptilian hair keratin homologs are functionally associated with claws, we investigated the conservation of the prototypical reptilian hair keratin homolog, hard acidic keratin 1 (HA1), in representative species from all main clades of reptiles. A complete cDNA of HA1 was cloned from the claw-forming epidermis of the lacertid lizard Podarcis sicula, and partial HA1 gene sequences could be amplified from genomic DNA of tuatara, lizards, gekkos, turtles, and crocodiles. In contrast, the HA1 gene of the limbless slow worm, Anguis fragilis, and of two species of turtles contained at least one deleterious mutation. Moreover, an HA1 gene was undetectable in the softshell turtle, snakes, and birds. Mapping the presence and absence of HA1 onto the phylogenetic tree of sauropsids suggested that the HA1 gene has been lost independently in several lineages of reptiles. The species distribution of HA1 is compatible with the hypothesis of a primary function of HA1 in claws but also shows that the formation of reptilian claws does not strictly depend on this keratin.
authors.affiliation: Dipartimento di Biologia, University of Padova, 35121 Padova, Italy.
authors.forename: Luisa
authors.initials: L
authors.lastname: Dalla Valle
authors.forename: Francesca
authors.initials: F
authors.lastname: Benato
authors.forename: Chiara
authors.initials: C
authors.lastname: Rossi
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Alibardi
authors.forename: Erwin
authors.initials: E
authors.lastname: Tschachler
authors.forename: Leopold
authors.initials: L
authors.lastname: Eckhart
mesh_terms: D000489:Alligators and Crocodiles / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D006724:Hoof and Claw / Q000378:metabolism*; D007633:Keratins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D053530:Keratins, Type I / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008116:Lizards / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D012104:Reptiles / Q000145:classification / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014426:Turtles / Q000235:genetics
chemical_list: D053530:Keratins, Type I; D007633:Keratins