Dose-dependent effects of Runx2 on bone development

Shiqin Zhang, Zhousheng Xiao, Junming Luo, Nan He, Josh Mahlios, Leigh Quarles

Research output: Contribution to journalArticle

44 Citations (Scopus)

Abstract

Runx2 controls the commitment of mesenchymal cells to the osteoblastic lineage. Distinct promoters, designated P1 and P2, give rise to functionally similar Runx2-II and Runx2-I isoforms. We postulate that this dual promoter gene structure permits temporal and spatial adjustments in the amount of Runx2 isoforms necessary for optimal bone development. To evaluate the gene dose-dependent effect of Runx2 isoforms on bone development, we intercrossed selective Runx2-II+/- with nonselective Runx2-II+/-/ Runx2-I+/- mice to create compound mutant mice: Runx2-II +/-, Runx2-II+/-/Runx2-I+/-, Runx2-II -/-, Runx2-II-/-/Runx2-I+/-, Runx2-II -/-/Runx2-I-/-. Analysis of the different Runx2-deficient genotypes showed gene dose-dependent differences in the level of expression of the Runx2 isoforms. In addition, we found that Runx2-I is predominately expressed in the perichondrium and proliferating chondrocytes, whereas Runx2-II is expressed in hypertrophic chondrocytes and metaphyseal osteoblasts. Newborn mice showed impaired development of a mineralized skeleton, bone length, and widening of the hypertrophic zone that were proportionate to the reduction in total Runx2 protein expression. Osteoblast differentiation ex vivo was also proportionate to total amount of Runx2 expression that correlated with reduced Runx2 binding to the osteocalcin promoter by quantitative chromatin immunoprecipitation analysis. Functional analysis of P1 and P2 promoters showed differential regulation of the two promoters in osteoblastic cell lines. These findings support the possibility that the total amount of Runx2 derived from two isoforms and the P1 and P2 promoters, by regulating the time, place, and amount of Runx2 in response to changing environmental cues, impacts on bone development.

Original languageEnglish (US)
Pages (from-to)1889-1904
Number of pages16
JournalJournal of Bone and Mineral Research
Volume24
Issue number11
DOIs
StatePublished - Nov 1 2009

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Bone Development
Protein Isoforms
Chondrocytes
Osteoblasts
Core Binding Factor Alpha 1 Subunit
Genes
Social Adjustment
Chromatin Immunoprecipitation
Osteocalcin
Skeleton
Cues
Genotype
Bone and Bones
Cell Line

All Science Journal Classification (ASJC) codes

  • Endocrinology, Diabetes and Metabolism
  • Orthopedics and Sports Medicine

Cite this

Dose-dependent effects of Runx2 on bone development. / Zhang, Shiqin; Xiao, Zhousheng; Luo, Junming; He, Nan; Mahlios, Josh; Quarles, Leigh.

In: Journal of Bone and Mineral Research, Vol. 24, No. 11, 01.11.2009, p. 1889-1904.

Research output: Contribution to journalArticle

Zhang, Shiqin ; Xiao, Zhousheng ; Luo, Junming ; He, Nan ; Mahlios, Josh ; Quarles, Leigh. / Dose-dependent effects of Runx2 on bone development. In: Journal of Bone and Mineral Research. 2009 ; Vol. 24, No. 11. pp. 1889-1904.
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