LOCALIZATION OF TYPE-XII COLLAGEN IN NORMAL AND HEALING RABBIT CORNEABY IN-SITU HYBRIDIZATION

To identify the cell types responsible for type XII collagen synthesis in normal and healing rabbit cornea, a partial cDNA sequence of rabbi t type XII collagen, obtained from an adult rabbit cornea cDNA library , was used to develop highly specific oligonucleotide probes for North ern blot analysis and in situ hybridization. Approximately 2000 bases of a type XII collagen 2.2 kb cDNA clone were sequenced. Comparative s equence analysis of the bases showed a 74% identity with chick alpha 1 (XII) chain of type XII collagen. The deduced amino acid sequence indi cated a 72% identity with chick type XII collagen. Northern blot analy sis showed that cultures of cornea stromal and endothelial cells each contain two RNA species, greater than 10 kb, that hybridize to rabbit type XII collagen oligonucleotide probes. Although normal stromal cell s failed to show type XII collagen mRNA, normal endothelial cells cont ain mRNA for this collagen. These results indicate that endothelium of normal rabbit cornea has a potential to synthesize type XII collagen. During corneal wound healing, both endothelium-derived and stroma-der ived cells in the developing scar tissue contained type XII mRNA. In v iew of the known presence of type XII collagen in corneal stromas from chick and mouse, the distribution of mRNA in normal cornea is puzzlin g.