|Baldwin, Ransom - Randy|
Submitted to: Biochemical Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/1996
Publication Date: N/A
Interpretive Summary: The rumen is a large stomach in sheep and cows which enables the animal to digest grasses and then use the energy of the feed for productive purposes like making milk and growing muscles. The ruminal epithelium is one of the tissues which responsible for the absorption of nutrients but it also serves as a protective function. The ruminal epithelium is underdeveloped at birth and must change in order to perform its function adequately. We are interested in the way that this tissue develops and are looking for ways to evaluate the development of the tissue so that we can understand why and when it becomes mature. We found a two sequences of RNA, that encode proteins, that are present in maturing ruminal epithelium and not in the neonatal ruminal epithelium. These proteins appear to be important in the mature ruminal epithelium and because they are not expressed in the newborn, we can use these nucleotide sequences (cDNA Clones of the RNA) to investigate the process of epithelial maturation.
Technical Abstract: Small proline-rich proteins (SPRR) are markers associated with squamous cell differentiation. They have been proposed to be a novel group of precursor polypeptides for the cornified envelope in epidermal keratinocytes. In previous studies, a plus/minus screening procedure was used to identify cDNA clones expressed in mature but not in neonatal sheep ruminal epithelium. Two clones encoding SPRR were identified and are reported here. Clone 27 encodes an ovine SPRR corresponding to the human type II SPRR. Clone 26 encodes an ovine SPRR similar to human type II SPRR, but also contains an N-terminal His-Pro repeat similar to the paired repeats found in the Drosophila paired proteins. The combination of a paired domain and a SPRR has not been reported to this study. The tissue distribution indicates that specific expression of the genes corresponding to these two clones occurs in the epithelium of the ruminant forestomach, and to a lesser extent in skin epithelium. In situ hybridization demonstrated that the SPRR mRNA for both clones were localized in the stratum granulosum, in support of their putative physiological function, i.e. formation of the cornified envelope. Based on Northern blot analysis, mRNA complementary to the two clones appears in the ruminal epithelium by one week of age, corresponding to the formation of the stratum granulosum during epithelial development. The different patterns of changes in amount of mRNA corresponding to these clones during rumen epithelial development indicate that they play different roles in rumen epithelial development.