Spatio-temporal expression patterns of Runx2 isoforms in early skeletogenesis

다국어 초록 (Multilingual Abstract)

Skeletogenesis occurs through either intramem-branous or endochondral ossification. In adition, some parts of the skeletal components maintain their cartilaginous characteristics throughout life without mineralization. Runx2 is known to be a cesses. In this study, we examined the expression patterns of two major isoforms of Runx2 in early skeletogenesis. During intramembranous bone for-mation, Runx2-type I (Runx2-I) was widely expres-sed in osteoprogenitor cels and active osteo-blasts, while Runx2-type II (Runx2-I) expression was stringently restricted to cels lining mineral-ized bones. Cels in permanent cartilage expressed colagen type II (Col-I) but never expresed Runx2 or Col-X. These permanent cartilages were wel Runx2-I was negative. In endochondral bone for-mation, 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 minerali-zation of cartilage. Collectively, both Runx2 iso-forms showed very similar expression patterns in active bone forming areas; however, Runx2-I has an exclusive role in the early comitment stage of intramembranous or endochondral bone form-ing processes or in cels surrounding permanent cartilage.