Abstract
Trefoil factors are essential healing initiators participating in mucosal reconstitution and tissue morphogenesis, especially on the surfaces of the gastrointestinal tract. This family has been cloned and characterized predominantly from mammals and amphibians. Avian species ingest stone and grit to help digest food, which may expose their gut to severe physical conditions. To further the understanding of the function of the TFF gene family across species, we undertook this research to clone, sequence, and characterize the spatio-temporal expression patterns of chicken TFF2 (ChTFF2) cDNA. Bioinformatics analysis of the promoter region and deduced amino acid sequence demonstrated that ChTFF2 contained unique characteristics; specifically the chicken promoter has multiple start sites and the protein contains a series of Lys-Lys-Val repeats. Unlike mammals, where TFF2 is detected primarily in the stomach, and occasionally in the proximal duodenum, chicken TFF2 transcripts are found throughout the gastrointestinal tract, with major expression sites in the glandular and muscular stomach as well as evident expression in the colon, small intestine, cecal tonsil and crop. Temporal analysis of intestinal ChTFF2 transcripts by quantitative RT-PCR showed high levels in embryos and a trend of constant expression during embryonic and post-hatch development, with a reduction occurring around hatch. Phylogenetic analysis highlighted the conservation of TFF proteins and functional divergence of trefoil domains, which suggest a transitional role in the bird during evolution.
Highlights
The trefoil factors (TFFs) are a family of small (7–12 kDa in mammals) secretory protease-resistant peptides discovered in the 1980’s [1]
It has been suggested that this region is a consequence of gene duplication and exon-shuffling events during evolution [26][27]
Comparison of the chicken TFF2 promoter sequences with the human homologue revealed several conserved regions
Summary
The trefoil factors (TFFs) are a family of small (7–12 kDa in mammals) secretory protease-resistant peptides discovered in the 1980’s [1]. The highly-conserved trefoil motif ( known as the P-domain) consists of the following sequence: CX9–10CX9CX4CCX10C (where C represents cysteine and X represents any other amino acid), which forms three disulfide bonds in a unique 1–5, 2–4 and 3–6 of Cys-Cys linkage structure [2] This configuration differs from other similar protein domains such as the EGF-repeat family, which forms 1–3, 2–4 and 5–6 Cys-Cys bonds, and may allow TFFs to use distinct signaling cascades for their cellular functions, which include promoting cell migration [6]. TFF2 is abundant in gastric, pyloric and Brunner’s glands, but markedly lower in small intestine and colon [3][21] These species-specific expression patterns highlight the potential functional diversity of TFF genes across species. Analysis of TFF genes in nonmammalian model systems provides important contributions to better understand the functional importance of the TFF genes in wound healing in the gut, and deepens the evolutionary understanding of the biological function of TFF proteins in animal and human health
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