title: Occurrence in chick embryo vitreous humor of a type IX collagen proteoglycan with an extraordinarily large chondroitin sulfate chain and short alpha 1 polypeptide.
abstract: We have prepared a high buoyant density proteoglycan fraction from the vitreous humor of 13-day-old chick embryos. Using immunoblot analysis coupled with chondroitinase digestion, we demonstrate that the purified preparation is composed predominantly of type IX collagen-like chondroitin sulfate proteoglycan with an alpha 1(IX) chain Mr approximately 23,000 shorter than the known alpha 1 in cartilage type IX. Also different from cartilage type IX is the size of the chondroitin sulfate chain attached to the alpha 2(IX) polypeptide; its Mr is approximately 350,000 indicating that it is approximately 10 times larger in vitreous humor than in cartilage. Examination of vitreous bodies at different developmental stages indicates that a transition occurs in the size of alpha 1(IX) in a well defined temporal pattern; at about stage 31, a cartilage-type alpha 1(IX) of Mr 84,000 is the predominant species, whereas at stage 36 and thereafter, a Mr 61,000 species appears with a concomitant disappearance of the Mr 84,000 species. Immunostaining for type IX collagen followed by electron microscopic observation of 13-day-old chick embryo vitreous humor reveals a regular D-periodic arrangement of vitreous type IX collagen proteoglycan along thin fibrils. It seems possible that the chondroitin sulfate chains of extraordinarily high viscosity and high molecular weight may extend away from the fibrils, thus contributing to structural as well as functional properties of this unique matrix.
authors.affiliation: Institute for Molecular Science of Medicine, Aichi Medical University, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Yada
authors.forename: S
authors.initials: S
authors.lastname: Suzuki
authors.forename: K
authors.initials: K
authors.lastname: Kobayashi
authors.forename: M
authors.initials: M
authors.lastname: Kobayashi
authors.forename: T
authors.initials: T
authors.lastname: Hoshino
authors.forename: K
authors.initials: K
authors.lastname: Horie
authors.forename: K
authors.initials: K
authors.lastname: Kimata
mesh_terms: D053674:Aggrecans; D000818:Animals; D000936:Antigen-Antibody Complex / Q000032:analysis; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002356:Cartilage / Q000032:analysis; D002642:Chick Embryo; D011508:Chondroitin Sulfate Proteoglycans / Q000302:isolation & purification*; D002850:Chromatography, Gel; D003094:Collagen; D004591:Electrophoresis, Polyacrylamide Gel; D016326:Extracellular Matrix Proteins; D006023:Glycoproteins / Q000302:isolation & purification; D006025:Glycosaminoglycans / Q000302:isolation & purification; D007106:Immune Sera; D015151:Immunoblotting; D037181:Lectins, C-Type; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011509:Proteoglycans / Q000302:isolation & purification*; D014822:Vitreous Body / Q000032:analysis* / Q000648:ultrastructure
chemical_list: D053674:Aggrecans; D000936:Antigen-Antibody Complex; D011508:Chondroitin Sulfate Proteoglycans; D016326:Extracellular Matrix Proteins; D006023:Glycoproteins; D006025:Glycosaminoglycans; D007106:Immune Sera; D037181:Lectins, C-Type; D046911:Macromolecular Substances; D011509:Proteoglycans; D003094:Collagen