Identification of Chicken Transglutaminase 1 and In Situ Localization of Transglutaminase Activity in Avian Skin and Esophagus

Attila Placido Sachslehner,Leopold Eckhart,Marta Surbek,Julia Lachner,Surya Paudel

doi:10.3390/genes12101565

Attila Placido Sachslehner, Leopold Eckhart + Show 3 more

Open Access

https://doi.org/10.3390/genes12101565

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Abstract

Transglutaminase 1 (TGM1) is a membrane-anchored enzyme that cross-links proteins during terminal differentiation of epidermal and esophageal keratinocytes in mammals. The current genome assembly of the chicken, which is a major model for avian skin biology, does not include an annotated region corresponding to TGM1. To close this gap of knowledge about the genetic control of avian cornification, we analyzed RNA-sequencing reads from organotypic chicken skin and identified TGM1 mRNA. By RT-PCR, we demonstrated that TGM1 is expressed in the skin and esophagus of chickens. The cysteine-rich sequence motif required for palmitoylation and membrane anchorage is conserved in the chicken TGM1 protein, and differentiated chicken keratinocytes display membrane-associated transglutaminase activity. Expression of TGM1 and prominent transglutaminase activity in the esophageal epithelium was also demonstrated in the zebra finch. Altogether, the results of this study indicate that TGM1 is conserved among birds and suggest that chicken keratinocytes may be a useful model for the study of TGM1 in non-mammalian cornification.

Highlights

The outermost epidermal layer of amniotes consists of multiple layers of cornified keratinocytes
A large portion of the cornified envelope proteins is encoded by genes of the epidermal differentiation complex (EDC) which was originally identified in mammals [4,5,6]
To determine whether Transglutaminase 1 (TGM1) is conserved in the chicken, we searched the genome sequence assembly of the chicken for a chromosomal segment homologous to the locus of

Summary

Introduction

The outermost epidermal layer of amniotes (mammals, reptiles and birds) consists of multiple layers of cornified keratinocytes. A large portion of the cornified envelope proteins is encoded by genes of the epidermal differentiation complex (EDC) which was originally identified in mammals [4,5,6]. The cross-linking of epidermal proteins depends on disulfide bonds between cysteine residues and isopeptide bonds between glutamine and lysine residues [1,13]. The latter bond is formed under the control of transglutaminases (TGMs) [14]. TGM1, TGM3 and TGM5 are implicated in cornified envelope formation [15,16]

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