Osteoadherin

The glycosylation profile of osteoadherin alters during endochondral bone formation.

"Osteoadherin (OSAD), a keratin sulphate (KS)-substituted small leucine-rich proteoglycan has been isolated from mineralized tissues and is considered to be a mineralized tissue-specific protein. This protein [is expressed] throughout mouse metatarsal long bone development, from the cartilage anlagen (E15) to the fully formed bone (Adult). OSAD was produced with the onset of mineralization and the formation of the ossification center.  Initial OSAD localization was restricted to the endosteal surfaces of the diaphysis and forming metaphysis. OSAD was substituted with varying patterns of glycosylation during bone development. OSAD lacked any KS chains throughout all development stages. Whereas, in the mineral bound fractions, with long bone maturation the substitution with KS became more apparent with development.  Different pools of OSAD are produced during endochondral bone formation and these may have specific roles in directing the mineralization process."

"During endochondral bone development DCN was not detected in bone whereas BGN{up} was located to developing growth plates"

"DCN has a principle role in collagen type I fibril formation, binds to calcium and regulates hydroxyapatite (HAP) crystal growth"

"DCN[KO] does not exhibit a skeletal phenotype"

"During endochondral ossification FMD was localized to the developing ossification center and LUM{up} detected in pre-osteogenic tissue"

"In bone, OSAD was localized to the primary spongiosa of bovine fetal rib growth plate, and OSAD [has a] similar distribution to BSP{up} in rat long bone and calvaria"

"OSAD mRNA has been detected within mature osteoblasts and a role has been proposed in the regulation of cell proliferation and migration"

"[OSAD has] a high affinity for HAP[hydroxyapatite] via the extended acidic C-terminal and in cell attachment via the integrin αvβ3"

NMR1 strain of mice: "embryonic (E) days 15, 18/19, new born (NB), 5 days (5d) and adult (Ad (> 3 months))."

OSAD levels were low in young tissues but very high in adult tissues.  BGN increased to day 5 but levels were reduced in adult.  There was no obvious trend with Decorin and FMD was extremely elevated in adult tissues.