Gene and expression analysis of secretory mucins and trefoil factor(s) in the intestinal mucosa of chicken
Abstract
The mucosal epithelium in the gastrointestinal tract (GIT) produces an enormous amount of mucus that is comprised of high-molecular weight mucin glycoproteins and small trefoil peptides. These molecules, although belonging to distinct familial clusters, are secreted from a common cell linage and may also function cooperatively. The first two chapters outline the cloning and sequencing of chicken Mucin 2 (MUC2) and trefoil factor 2 (TFF2). MUC2 is the major secretory mucin found in intestinal mucus mass, and TFF2 is a key member in the trefoil peptide family. The major thrust of these experiments was to piece together MUC2 and TFF2 cDNAs, and then determine when and where these two genes are expressed in the GIT. In chicken MUC2, protein structure studies revealed the presence of conserved VWFD, C8 and CT domains in chicken MUC2, but the PTS region harboring variable numbers of imperfect tandem repeats was not able to be fully cloned by overlapping RT-PCR experiments. Two natural alternatively spliced variants of MUC2 were identified. Chicken TFF2 shares evolutionarily-conserved trefoil domains and demonstrates structural uniqueness which may contribute to functional divergence during evolution. Spatial-temporal transcript analysis of MUC2 and TFF2 indicated distinct patterns of expression along the GIT, as well as in embryonic and post-hatch development in the small intestine. The purpose of the third chapter was to investigate the interaction of nutrition and mucus compositional changes. A comparative study was conducted to evaluate mucus secretion and characteristics in responses to different grain sources and phenolic compounds fed to the chicken. The feeding trial showed a mucotrophic effect of fiber conferred by grain source, including directing mucin-producing goblet cell linage expansion and stimulating mucin secretion in the ileum. In addition, this was accompanied with diminished mucin hydration capacity and altered chemical characteristics. Supplemental carvacrol and thymol, two isomeric phenolic compounds, however, oppositely influenced mucin secretion, hydration capacity, and goblet cell cytokinetics. The MUC2 transcripts detected in the lower small intestinal mucosa did not differ significantly between grain sources but were induced by the presence of thymol in the diet. These observations may correspond to alterations in many molecular events governing mucin biosynthesis and expression such as glycosylation and alternative splicing.
Degree
Ph.D.
Advisors
Applegate, Purdue University.
Subject Area
Animal sciences
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