Biomedical
Epidermal Differentiation Genes of the Common Wall Lizard Encode Proteins with Extremely Biased Amino Acid Contents
Karin Brigit Holthaus,
Attila Placido Sachslehner,
Julia Steinbinder,
Leopold Eckhart
Peer Reviewed
Abstract
The epidermal differentiation complex (EDC) is a cluster of genes that code for protein components of cornified cells on the skin surface of amniotes. Squamates are the most species-rich clade of reptiles with skin adaptations to many different environments. As the genetic regulation of the skin epidermis and its evolution has been characterized for only a few species so far, we aimed to determine the organization of the EDC in a model species of squamates, the common wall lizard (Podarcis muralis). By comparative genomics, we identified EDC genes of the wall lizard and compared them with homologs in other amniotes. We found that the EDC of the wall lizard has undergone a major rearrangement leading to a unique order of three ancestral EDC segments. Several subfamilies of EDC genes, such as those encoding epidermal differentiation proteins containing PCCC motifs (EDPCCC) and loricrins, have expanded by gene duplications. Most of the EDPCCC proteins have cysteine contents higher than 50%, whereas glycine constitutes more than 50% of the amino acid residues of loricrin 1. The extremely biased amino acid compositions indicate unique structural properties of these EDC proteins. This study demonstrates that cornification proteins of the common wall lizard differ from homologous proteins of other reptiles, illustrating the evolutionary dynamics of diversifying evolution in squamates.
Key Questions and Answers for "Epidermal Differentiation Genes of the Common Wall Lizard Encode Proteins with Extremely Biased Amino Acid Contents"
1. What is the epidermal differentiation complex (EDC) and what role does it play in reptiles?
The EDC is a cluster of genes involved in the terminal differentiation of epidermal cells. These genes encode structural proteins that are critical for the formation of the skin's outer protective layer, which is essential for protecting against mechanical stress and water loss in reptiles.
2. Why is the common wall lizard (Podarcis muralis) used as a model species for studying epidermal differentiation?
The common wall lizard is used as a model species because of its evolutionary diversification and adaptability to various habitats. This lizard has unique skin characteristics and has been studied in the context of tissue regeneration and skin biology.
3. What are the key findings about the EDC genes in the common wall lizard?
The study identified that the EDC of the common wall lizard underwent major rearrangements, leading to a unique order of ancestral EDC segments. It was also found that gene duplications expanded certain subfamilies, such as those encoding epidermal differentiation proteins (EDPCCC) and loricrins.
4. What makes the amino acid composition of the epidermal differentiation proteins (EDPCCC) and loricrins in the common wall lizard unique?
The EDPCCC proteins in the common wall lizard have cysteine contents higher than 50%, while loricrin 1 contains more than 50% glycine. This extreme bias in amino acid composition suggests unique structural properties of these EDC proteins, which may contribute to their role in skin differentiation.
5. How does the EDC of the common wall lizard compare to other reptiles in terms of amino acid content and structural properties?
The EDC of the common wall lizard differs significantly from that of other reptiles in terms of amino acid composition and structural properties. The study emphasizes that these differences highlight the evolutionary dynamics of skin adaptation and differentiation in squamates.
6. What is the importance of studying the EDC gene family in the context of reptilian evolution?
Studying the EDC gene family in reptiles, particularly squamates, helps in understanding the molecular basis of skin adaptation, cornification, and the evolutionary diversification of epidermal proteins in response to environmental pressures such as mechanical stress and water loss.
7. What are corneous beta-proteins (CBPs) and how do they function in the epidermis?
Corneous beta-proteins (CBPs) are characterized by beta sheet-forming segments that facilitate their dimerization and the formation of filaments. These proteins contribute to the structural integrity of the skin's outer layer, providing resistance to mechanical stress and water loss.
8. How do disulfide bonds and transglutamination contribute to the function of EDC proteins?
Disulfide bonds and transglutamination are essential for cross-linking EDC proteins, which strengthens the protein network in the skin. These chemical modifications enable the formation of a robust, protective epidermal barrier.
9. What evolutionary significance does the study of the EDC genes in the common wall lizard provide for squamate reptiles?
The study highlights the evolutionary dynamics of skin adaptation in squamates. It demonstrates how gene duplications, rearrangements, and amino acid composition contribute to the diversity of epidermal proteins in reptiles, influencing skin function and adaptation.
10. What is the broader significance of the findings related to the EDC of the common wall lizard for understanding vertebrate skin biology?
The findings provide new insights into the molecular mechanisms behind epidermal differentiation and the evolution of skin proteins in vertebrates. Understanding these processes can inform research on skin diseases, tissue regeneration, and the adaptation of animals to various environmental conditions.
