Related Experiment Videos
Influence of DNA replication inhibition on expression of cell growth and tissue-specific genes in osteoblasts and
Abstract:
Interrelationships between proliferation and expression of cell growth as well as bone cell-related genes were examined from two standpoints. First, the consequence of downregulating proliferation by DNA synthesis inhibition on expression of a cell cycle-regulated histone gene and genes associated with development of the bone cell phenotype (type I collagen, alkaline phosphatase, osteopontin, and osteocalcin) was investigated. Second, the requirement for stringent growth control to support functional relationships between expression of proliferation and differentiation-related genes was explored. Parameters of cell growth and osteoblast-related gene expression in primary cultures of normal diploid osteoblasts, that initially express proliferation-dependent genes and subsequently postproliferative genes associated with mature bone cell phenotypic properties, were compared to those operative in ROS 17/2.8 osteosarcoma cells that concomitantly express cell growth and mature osteoblast phenotypic genes. Our findings indicate that in both normal diploid osteoblasts and osteosarcoma cells, expression of the cell cycle regulated histone genes is tightly coupled with DNA synthesis and controlled predominantly at a posttranscriptional level. Inhibition of proliferation by blocking DNA synthesis with hydroxyurea upregulates a subset of developmentally expressed genes that postproliferatively support progressive establishment of mature osteoblast phenotypic properties (e.g., alkaline phosphatase, type 1 collagen, and osteopontin). However, the osteocalcin gene, which is expressed during the final stage of osteoblast differentiation when extracellular matrix mineralization occurs, is not upregulated. Variations in the extent to which inhibition of proliferation in normal diploid osteoblasts and in ROS 17/2.8 osteosarcoma cells selectively affects transcription and cellular levels of mRNA transcripts from bone cell-related genes (e.g., osteocalcin) may reflect modifications in proliferation/differentiation interrelationships when stringent growth control is abrogated.
Insights
Inhibiting DNA synthesis in bone cells upregulates some mature cell genes but not osteocalcin. Stringent growth control is crucial for normal bone cell gene expression and function.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Cell proliferation and differentiation are tightly regulated processes.
- Osteoblast gene expression is critical for bone formation and maintenance.
- Understanding the interplay between cell growth and differentiation is key to bone biology.
Purpose of the Study:
- To investigate the relationship between cell proliferation and the expression of bone cell-related genes.
- To determine the effect of inhibiting DNA synthesis on gene expression in osteoblasts.
- To explore the role of stringent growth control in maintaining functional relationships between proliferation and differentiation genes.
Main Methods:
- Comparison of gene expression in normal diploid osteoblasts and ROS 17/2.8 osteosarcoma cells.
- Inhibition of DNA synthesis using hydroxyurea.
- Analysis of cell cycle-regulated histone genes and bone cell-related genes (type I collagen, alkaline phosphatase, osteopontin, osteocalcin).
Main Results:
- Histone gene expression is coupled with DNA synthesis and regulated post-transcriptionally.
- Inhibition of proliferation upregulates genes like alkaline phosphatase, type 1 collagen, and osteopontin.
- Osteocalcin gene expression is not upregulated by proliferation inhibition, suggesting a distinct regulatory mechanism.
Conclusions:
- Proliferation inhibition selectively affects bone cell-related gene expression.
- Stringent growth control is essential for the coordinated expression of proliferation and differentiation genes.
- Aberrant proliferation may lead to altered bone cell function and gene expression patterns.