Marion K. Gordon

Temporal expression of types XII and XIV collagen mRNA 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 molecules during development of the avian cornea. By immunofluorescence histochemistry, both molecules are found in the acellular primary stroma and are therefore presumably of epithelial origin. During formation and development of the secondary corneal stroma, which is populated by mesenchymal cells, the molecules generally appear to be spatially segregated from each other. Type XIV collagen is found throughout most of the stroma, and therefore is predominantly a product of stromal fibroblasts. During subsequent compaction of the cornea, an event necessary for corneal transparency, the collagen XIV mRNA level increases dramatically, suggesting that this molecule may play a role in this event.

Synteny between the loci for a novel FACIT-like collagen locus (D6S228E) and α1(IX) collagen (COL9A1) on 6q12–q14 in humans

A 1.8-kb cDNA encoding portion of a novel collagenous chain was isolated from a human rhabdomyosarcoma cell line by cross-hybridization using a chicken type V collagen probe. Sequence analysis suggests that this chain belongs to the recently discovered group of collagens, termed the FACIT class of macromolecules. This cDNA was used to locate the corresponding gene (D6S228E) to chromosome 6, notably at position 6q12-q14. Interestingly, within this region of human chromosome 6 residues the alpha 1 (IX) collagen gene (COL9A1), a member of the FACIT group.

Avian Epidermis Expresses Collagen Types I and II but not Type IX in a Restricted Spatial Pattern during Feather Morphogenesis

Type I1 collagen, once thought to be exclusively a mesenchymally derived, “cartilagespecific” molecule, is also a component of a number of widely diverse, epithelially derived matrices of avian embryos. These include ectodermal derivatives such as the primary corneal stroma,’.’ neuroepithelial derivatives such as the primary vitreous:’’ and a variety of other ~ites.4.~ Since these various type I1 collagen-containing matrices differ structurally and in their developmental fates, they likely differ in their composition as well. One possible source of variation among these matrices could be the presence or absence of other “cartilage-specific ” molecules that might be coexpressed with type I1 collagen, such as type IX collagen. WeZz6 and others’ have observed that type IX collagen is present, along with type 11, in some of these matrices but not in others. Recently we were surprised to observe6 in developing skin a transitory subepidermal deposition of type I1 collagen that is restricted to the interpapillary region of feather buds, being absent within the buds themselves. This suggests an involvement of the molecule in feather morphogenesis. The subepidermal matrix of interpapillary feather-forming skin is an example of the deposition of type 11 collagen without type IX. By immunofluorescence histochemistry, type I1 collagen (FIG. la) was restricted to the subepithelial matrix between the feather buds and was absent at the roots of, and within, the feather buds themselves. Type IX collagen (FIG. 1 b) was absent. Type I collagen (FIG. lc), however, was abundant within the feather buds, in the subepidermal matrix between them, and in the deeper tissues as well. The negative control was Type X collagen (FIG. Id). To examine the source and regulation of these subepidermal collagens, we performed in situ hybridizations employing 32P-labeled cDNA probes for the collagens.