Related Experiment Video
Updated: Jul 5, 2026
Application of Retinoic Acid to Obtain Osteocytes Cultures from Primary Mouse Osteoblasts
Published on: May 13, 2014
Microarray analysis of thapsigargin-induced stress to the endoplasmic reticulum of mouse osteoblasts
Kazunori Hamamura1, Yunlong Liu, Hiroki Yokota
1Department of Biomedical Engineering, Indiana University-Purdue University, Indianapolis, IN 46202, USA.
Abstract:
Activating transcription factor 4 (ATF4) protein has a dual role in osteoblasts. It functions as a responder to stress to the endoplasmic reticulum (ER) as well as a transcription factor for bone formation. Little is known about molecular pathways that can potentially lead to stress-induced apoptosis or homeostasis of extracellular matrix (ECM) molecules. Based on microarray-derived mRNA expression data for mouse osteoblasts (MC3T3 E1 cells, clone 4), we analyzed the ER-stress responses in the presence of 10 nM Thapsigargin using two computational approaches: "Gene Set Enrichment Analysis (GSEA)" and "Ingenuity Pathways Analysis (IPA)." GSEA presented a strong linkage to an expression pattern observed in the responses to hypoxia, and IPA identified two molecular pathways: ATF4-unlinked connective tissue development and ATF4-linked organ morphology. Real-time polymerase chain reaction (PCR) and Western blot analyses validated eIF2alpha-driven translational regulation as well as ATF4-linked transcriptional activation of transcription factors and growth factors including FOS, FGF-9, and BMP-2. Consistent with the role of p38 MAPK in hypoxia, phosphorylation of p38 MAPK was activated in nonapoptotic osteoblasts under surviving ER stress. Furthermore, the level of phosphorylated PERK was elevated. These results support cross-talk between p38 MAPK and ER kinase, presenting a similarity to the responses to hypoxia as well as a pathway toward connective tissue development and organ morphology.
Insights
Activating transcription factor 4 (ATF4) responds to endoplasmic reticulum (ER) stress and aids bone formation. This study reveals ER stress activates pathways similar to hypoxia, influencing connective tissue and organ development in osteoblasts.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Activating transcription factor 4 (ATF4) has a dual role in osteoblasts, acting as an endoplasmic reticulum (ER) stress responder and a bone formation transcription factor.
- Limited knowledge exists regarding molecular pathways governing stress-induced apoptosis or extracellular matrix (ECM) homeostasis in osteoblasts.
Purpose of the Study:
- To analyze ER stress responses in mouse osteoblasts (MC3T3 E1 cells) using computational approaches.
- To identify molecular pathways linked to ER stress, ATF4, and their impact on osteoblast function and survival.
Main Methods:
- Microarray analysis of mRNA expression in MC3T3 E1 cells under ER stress (10 nM Thapsigargin).
- Computational analysis using Gene Set Enrichment Analysis (GSEA) and Ingenuity Pathways Analysis (IPA).
- Validation using real-time PCR, Western blot, and assessment of protein phosphorylation (p38 MAPK, PERK).
Main Results:
- GSEA indicated a strong link between ER stress response and hypoxia response patterns.
- IPA identified ATF4-unlinked connective tissue development and ATF4-linked organ morphology pathways.
- Validated eIF2alpha-driven translational regulation and ATF4-linked transcriptional activation of FOS, FGF-9, and BMP-2.
- Phosphorylation of p38 MAPK and PERK was elevated in non-apoptotic osteoblasts under ER stress, suggesting cross-talk.
Conclusions:
- ER stress in osteoblasts activates pathways similar to hypoxia responses.
- Identified molecular pathways involving ATF4 contribute to connective tissue development and organ morphology.
- Cross-talk between p38 MAPK and ER kinase is implicated in ER stress survival and osteoblast function.
