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CDNA analysis predicts a cornea-specific collagen.

ABSTRACT: In the development of chicken corneal stroma, two or more collagens often interact, either as constituents of a single heterotypic fibril or as components of the fibril surface. The latter, fibril-associated collagens, may facilitate interactions between fibrils and the surrounding extracellular matrix or between fibrils themselves. In an effort to isolate putative nonfibrillar collagens that may have such a function, we screened a 13-day embryonic cornea cDNA library under reduced stringency conditions, using a cDNA probe for a collagenous domain of type XII collagen. We isolated a 4.2-kilobase (kb) cDNA that predicts a "collagenous" protein that has three unusual, if not unique, features. (i) The putative polypeptide encoded by this cDNA has a structural arrangement in which numerous stretches of Gly-Xaa-Yaa triplets, typical of collagens, are interrupted by non-Gly-Xaa-Yaa regions. One of the potential triple-helical domains is 246 amino acids long, but most are much smaller, consisting of 15-36 amino acids. Many are very rich in the helix-stabilizing imino acid proline. (ii) Northern blot analyses demonstrated strong cDNA hybridization to a 6.8-kb mRNA whose expression is restricted to the cornea. No hybridization was observed to mRNAs from the nine other tissues used in these analyses, even with extended exposure of the film. (iii) The cDNA contains a short (less than or equal to 425-base-pair) sequence in the 3' untranslated region of the 6.8-kb mRNA that hybridizes to a 7.8-kb mRNA that has a wide tissue distribution.

SUBMITTER: Marchant JK

PROVIDER: S-EPMC51059 | biostudies-other | 1991 Feb

REPOSITORIES: biostudies-other

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cDNA analysis predicts a cornea-specific collagen.

Marchant J K JK Linsenmayer T F TF Gordon M K MK

Proceedings of the National Academy of Sciences of the United States of America 19910201 4

In the development of chicken corneal stroma, two or more collagens often interact, either as constituents of a single heterotypic fibril or as components of the fibril surface. The latter, fibril-associated collagens, may facilitate interactions between fibrils and the surrounding extracellular matrix or between fibrils themselves. In an effort to isolate putative nonfibrillar collagens that may have such a function, we screened a 13-day embryonic cornea cDNA library under reduced stringency co ...[more]

PMID: 1705041

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Project description:Corneal collagen cross-linking (CXL) halts human corneal ectasias progression by increasing stromal mechanical stiffness. Although some reports describe that this procedure is effective in dealing with some infectious and immunologic corneal thinning diseases, there is a need for more animal models whose corneal thickness more closely resemble those occurring in these patients. To meet this need, we describe here high-intensity protocols that are safe and effective for obtaining CXL in rat corneas. Initially, a range of potentially effective UVA doses were evaluated based on their effectiveness in increasing tissue enzymatic resistance to dissolution. At UVA doses higher than a threshold level of 0.54 J/cm2, resistance to enzymatic digestion increased relative to that in non-irradiated corneas. Based on the theoretical threshold CXL dose, a CXL regimen was established in which the UVA tissue irradiance was 9 mW/cm2, which was delivered at doses of either 2.16, 2.7 or 3.24 J/cm2. Their dose dependent effects were evaluated on ocular surface morphological integrity, keratocyte apoptotic frequency, tissue thickness and endothelial cell layer density. Doses of 2.16 and 2.7 J/cm2 transiently decreased normal corneal transparency and increased thickness. These effects were fully reversed after 14 days. In contrast, 3.24 J/cm2 had more irreversible side effects. Three days after treatment, apoptotic frequency in the CXL-2.16 group was lower than that at higher doses. Endothelial cell losses remained evident only in the CXL-3.24 group at 42 days posttreatment. Stromal fiber thickening was evident in all the CXL-treated groups. We determined both the threshold UVA dose using the high-intensity CXL procedure and identified an effective dose range that provides optimal CXL with minimal transient side effects in the rat cornea. These results may help to provide insight into how to improve the CXL outcome in patients afflicted with a severe corneal thinning disease.

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CDNA analysis predicts a cornea-specific collagen.

Publications

cDNA analysis predicts a cornea-specific collagen.

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