Transient expression of type II collagen and tissue mobilization during development of the scleral ossicle, a membranous bone, in the chick embryo

Abstract

Development of the chick sclera1 ossicle was studied with respect to expression of various collagen types, cartilage matrix molecules, and osteoblastic cell surface antigens. The extra-cellular matrix of the scleral ossicle primordium of stage 35.5 chick sclera and the mesenchyme beneath the conjunctival epithelium was immunoreactive with anti-type I1 collagen antibody, giving the impression that certain materials and/or cell clusters surrounded by reactive matrix were descending from the epithelial-mesenchyma1 interface to the scleral ossicle primordium. In stage 37 embryos, type I1 collagen immunoreactivity was restricted to the bone matrix of the scleral ossicles, and persisted through stage 39. However, at stage 41, virtually no type I1 collagen was detected. In contrast, strong immunostaining of type I collagen was first detected in the developing scleral ossicle at stage 37, coinciding with the formation of mineralized bone matrix. Following the extensive accumulation of type I collagen in bone matrix, type XI1 collagen was detected at the surface of the bone; both type I and type XI1 collagen immunostainings then remained. By stage 37, immunoreactivity with a pre-osteoblastic cell surface marker was detected on cells of the scleral ossicle, and typical osteocytes were subsequently identified by both morphological and specific immunostaining techniques. Antibodies other than for type I1 collagen, specific to chondrogenic mesenchyme or cartilage matrix, never reacted with the scleral ossicle and its primordium during development. Taken together, these observations indicate that the scleral ossicle is a membranous bone, whose development may not require overt chondrogenesis. Implications of type I1 collagen distribution during the positioning of scleral ossicles and their early bone matrix formation are discussed with respect to the origin and evolution of endoskeletons in vertebrate animals.

Microarray Analyses of Gene Expression during Chondrocyte Differentiation Identifies Novel Regulators of Hypertrophy

“…Proteins of numerous molecular families have been implicated in the longitudinal growth of the skeleton including growth factors, e.g., bone morphogenetic proteins, fibroblast growth factor family members, insulin-like growth factor signaling components (Cancedda et al, 1995); extracellular matrix molecules, e.g., collagen II, aggrecan, link protein and cartilage oligomeric protein (Cheah et al, 1991;Watanabe et al, 1994;Fang et al, 2000;Tuckermann et al, 2000); and transcription factors, e.g., Sox9, Core-binding factor alpha (Cbfa1) and ATF-2. In particular, Sox9 has been shown to be required for chondrogenesis, ATF-2 controls cell cycle progression and proliferation, and Cbfa1/Runx2 is involved in hypertrophic differentiation (Reimold et al, 1996;Lefebvre and de Crombrugghe, 1998;Beier et al, 1999;Bi et al, 1999;Stricker et al, 2002).…”

Changes in Distribution of the Long Form of Type XII Collagen during Chicken Corneal Development

“…Such localization indicates that the long form of Type XII collagen mediates periodic interactions between collagen fibrils and other extracellular matrix components to stabilize them. In fact, Types I, II, III, IV, V VI, IX, XIV, and XVII collagen molecules were detected immunohistochemically in avian cornea (Conrad et al 1980;Linsenmayer et al 1984Linsenmayer et al ,1986Birk et al 1986;Fitch et al 1988Fitch et al ,1990Sugrue 1991;Chen et al 1993;Watanabe et al 1994;Gordon et al 1996Gordon et al ,1997Doane et al 1998). Among them, Types IX and XIV are associated with collagen fibrils, Type IX collagen forms a complex with Type II collagen in the primary corneal stroma (Fitch et al 1988Cai et al 1994), and structurally related Types XII and XIV collagen molecules also form complexes with Type I collagen (Koch et al 1995).…”