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MK Gordon, RA Hahn, P Zhou, A Kistler, DR Gerecke, M Koch; Structure of Collagen XXIV and its Expression in Cornea and Retina . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3207.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:The function of the cornea is dependent upon the expression and assembly of a unique set of extracellular matrix molecules. We have endeavored to identify new collagens that may be important contributors to the structure of the cornea. In particular, we are interested in those that modulate the properties of corneal collagen fibrils. Methods:A partial cDNA representing a potential fibrillar collagen was found in the database of expressed sequence tags; the clone was purchased and fully sequenced. A Clontech Marathon library was used to obtain overlapping cDNAs covering the full length mRNA. A synthetic peptide from a region of the N-peptide, near the triple helical domain, was used to generate polyclonal antibody for Western analysis. In situ hybridization was performed on paraffin sections of mouse eyes with an oligonucleotide probe from a unique region in the N-peptide coding sequence, close to the triple helix coding sequence. Results:We have cloned a new collagen chain, designated alpha 1(XXIV), containing a triple helical domain flanked by typical propeptide-like sequences. The C-propeptide (235 aa) is classic in structure; the N-peptide (547 aa) resembles those of the collagen V and XI subfamily, which are fibril diameter regulators. Like these molecules, the alpha 1 (XXIV) N-peptide contains a thrombospondin N-terminal-like domain and a region of charges and several tyrosine residues. The 930 amino acid residue triple helical domain is smaller than that of other fibrillar collagens. Unique aspects of the alpha 1(XXIV) structure make it unlikely that this new collagen polypeptide is another alpha chain of collagens V or XI. From the sequence, the predicted size of an alpha 1(XXIV) chain with propeptides is about 175 kDa. By Western analysis, the processed chain is about 145 kDa. In situ hybridization with an alpha 1(XXIV) oligonucleotide probe shows the presence of the mRNA in the cells of the corneal epithelium and stroma, and in the retinal photoreceptor cells. Conclusion:A new member of the collagen superfamily, type XXIV, appears to be a member of the fibrillar subfamily of collagens. The structure of the N-peptide suggests that collagen XXIV, like collagen V and XI, may regulate collagen fibril diameter. This is consistent with the expression of collagen XXIV in the cornea, where collagen fibril diameters are strictly controlled.
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