Cloning and characterization of scale β‐keratins in the differentiating epidermis of geckoes show they are glycine‐proline‐serine–rich proteins with a central motif homologous to avian β‐keratins

The β‐keratins constitute the hard epidermis and adhesive setae of gecko lizards. Nucleotide and amino acid sequences of β‐keratins in epidermis of gecko lizards were cloned from mRNAs. Specific oligonucleotides were used to amplify by 3′‐ and 5′‐rapid amplification of cDNA ends analyses five specific gecko β‐keratin cDNA sequences. The cDNA coding sequences encoded putative glycine‐proline‐serine–rich proteins of 16.8–18 kDa containing 169–191 amino acids, especially 17.8–23% glycine, 8.4–14.8% proline, 14.2–18.1% serine. Glycine‐rich repeats are localized toward the initial and end regions of the protein, while a central region, rich in proline, has a strand conformation (β‐pleated fold) likely responsible for the formation of β‐keratin filaments. It shows high homology with a core region of other lizard keratins, avian scale, and feather keratins. Northern blotting and reverse transcriptase‐polymerase chain reaction (RT‐PCR) analysis show a higher β‐keratin gene expression in regenerating epidermis compared with normal epidermis. In situ hybridization confirms that mRNAs for these proteins are expressed in cells of the differentiating oberhautchen cells and β‐cells. Expression in adhesive setae of climbing lamellae was shown by RT‐PCR. Southern blotting analysis revealed that the proteins are encoded by a multigene family. PCR analysis showed that the genes are presumably located in tandem along the DNA and are transcribed from the same DNA strand like in avian β‐keratins. Developmental Dynamics 236:374–388, 2007. © 2006 Wiley‐Liss, Inc.