TEMPORAL EXPRESSION OF TYPE-XII AND TYPE-XIV COLLAGEN MESSENGER-RNA AND PROTEIN DURING AVIAN CORNEAL DEVELOPMENT

Using immunohistochemistry and competitive PCR for collagen types XII and XIV, we have followed the expression of these fibril-associated mo lecules during development of the avian cornea, By immunofluorescence histochemistry, both molecules are found in the acellular primary stro ma and are therefore presumably of epithelial origin. During formation and development of the secondary corneal stroma, which is populated b y mesenchymal cells, the molecules generally appear to be spatially se gregated from each other. Type XIV collagen is found throughout most o f the stroma, and therefore is predominantly a product of stromal fibr oblasts. During subsequent compaction of the cornea, an event necessar y for corneal transparency, the collagen XIV mRNA level increases dram atically, suggesting that this molecule may play a role in this event. Type XII collagen is more localized, occurring mainly in regions of t he secondary stroma where matrices interface, such as where Bowman's m embrane and Descemet's membrane abut the orthogonally layered collagen fibrils of the stromal matrix. These interfacial regions are highly s table areas of the cornea as determined previously by protease digesti on and thermal denaturation studies. Type XII collagen may be involved in this stabilization. (C) 1996 Wiley-Liss, Inc.