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Recombination signal sequence-binding protein Jkappa alters mesodermal cell fate decisions by suppressing
Timm Schroeder1, Stuart T Fraser, Minetaro Ogawa
1GSF-National Research Center for Environment and Health, Institute of Clinical Molecular Biology and Tumor Genetics, Marchioninistrasse 25, 81377 Munich, Germany.
Abstract:
The transcription factor recombination signal sequence-binding protein Jkappa (RBP-J) is a key downstream element in the signaling pathway of all four mammalian Notch receptors that are critically involved in the control of embryonic and adult development. RBP-J-deficient mice display complex defects and die around day 9.5 postcoitum. Here, we investigate the function of RBP-J in the development of mesodermal cell lineages by using the OP9 stroma coculture system. RBP-J-deficient embryonic stem (ES) cells gave rise to cardiomyocytes, endothelial cells, and primitive and definitive hematopoietic cells. Thus, RBP-J-mediated signals are not required for generation of these cell types. However, when compared with parental RBP-J-expressing ES cells, cardiomyogenesis derived from RBP-J-deficient ES cells was increased. Repression over the cardiogenic pathway was restored by expressing RBP-J in RBP-J-deficient ES cells. Our data indicate that Notch signaling via RBP-J plays an important role for the correct specification of myocardial cell fates.
Insights
Recombination signal sequence-binding protein Jkappa (RBP-J) is crucial for development. While not essential for generating cardiomyocytes, endothelial, or hematopoietic cells, RBP-J normally represses cardiomyogenesis, ensuring proper cell fate specification.
Area of Science:
- Developmental Biology
- Cell Signaling
- Stem Cell Research
Background:
- The transcription factor RBP-J is a central mediator of Notch signaling, essential for embryonic development.
- RBP-J deficiency in mice leads to severe developmental defects and embryonic lethality.
- Understanding RBP-J's role in specific cell lineage development is critical.
Purpose of the Study:
- To investigate the function of RBP-J in the differentiation of mesodermal cell lineages.
- To determine if RBP-J signaling is required for the generation of cardiomyocytes, endothelial cells, and hematopoietic cells.
- To elucidate the role of RBP-J in regulating cardiomyogenesis.
Main Methods:
- Utilizing the OP9 stroma co-culture system for embryonic stem (ES) cell differentiation.
- Comparing differentiation outcomes from RBP-J-deficient ES cells versus parental RBP-J-expressing ES cells.
- Restoring RBP-J expression in deficient cells to assess functional rescue.
Main Results:
- RBP-J-deficient ES cells successfully generated cardiomyocytes, endothelial cells, and both primitive and definitive hematopoietic cells.
- RBP-J-mediated signals are not essential for the initial generation of these mesodermal cell types.
- Cardiomyogenesis was significantly increased in RBP-J-deficient ES cell cultures compared to controls.
- Restoration of RBP-J expression in deficient cells normalized the rate of cardiomyogenesis.
Conclusions:
- Notch signaling through RBP-J is not required for the generation of cardiomyocytes, endothelial cells, or hematopoietic cells.
- RBP-J acts as a repressor of the cardiogenic pathway, playing a vital role in the precise specification of myocardial cell fates.
- These findings highlight a critical regulatory function of RBP-J in preventing excessive cardiomyocyte formation and ensuring proper developmental trajectories.