title: Spatio-temporal expression patterns of Runx2 isoforms in early skeletogenesis.
abstract: Skeletogenesis occurs through either intramembranous or endochondral ossification. In addition, some parts of the skeletal components maintain their cartilaginous characteristics throughout life without mineralization. Runx2 is known to be a pivotal transcription factor for all skeletogenic processes. In this study, we examined the expression patterns of two major isoforms of Runx2 in early skeletogenesis. During intramembranous bone formation, Runx2-type I (Runx2-I) was widely expressed in osteoprogenitor cells and active osteoblasts, while Runx2-type II (Runx2-II) expression was stringently restricted to cells lining mineralized bones. Cells in permanent cartilage expressed collagen type II (Col-II) but never expressed Runx2 or Col-X. These permanent cartilages were well circumscribed by Runx2-I positive cells, in which Runx2-II was negative. In endochondral bone formation, Runx2 expression temporarily disappeared in Col-II-positive proliferating chondrocytes, but a secondary surge of Runx2-I expression occurred in the prehypertrophic zone before the mineralization of cartilage. Collectively, both Runx2 isoforms showed very similar expression patterns in active bone forming areas; however, Runx2-I has an exclusive role in the early commitment stage of intramembranous or endochondral bone forming processes or in cells surrounding permanent cartilage.
authors.affiliation: Department of Biochemistry, School of Dentistry, Kyungpook National University, Daegu, Korea.
authors.forename: Kang-Young
authors.initials: KY
authors.lastname: Choi
authors.forename: Sang-Won
authors.initials: SW
authors.lastname: Lee
authors.forename: Mi-Hyun
authors.initials: MH
authors.lastname: Park
authors.forename: Yong-Chul
authors.initials: YC
authors.lastname: Bae
authors.forename: Hong-In
authors.initials: HI
authors.lastname: Shin
authors.forename: Soon- Hyeun
authors.initials: S
authors.lastname: Nam
authors.forename: Young-Jin
authors.initials: YJ
authors.lastname: Kim
authors.forename: Hyun-Jung
authors.initials: HJ
authors.lastname: Kim
authors.forename: Hyun-Mo
authors.initials: HM
authors.lastname: Ryoo
mesh_terms: D000818:Animals; D001846:Bone Development; D002356:Cartilage / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D050659:Core Binding Factor Alpha 1 Subunit; D005314:Embryonic and Fetal Development / Q000235:genetics; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D017403:In Situ Hybridization; D051379:Mice; D008813:Mice, Inbred ICR; D009363:Neoplasm Proteins; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; D009363:Neoplasm Proteins; D020033:Protein Isoforms; D014157:Transcription Factors