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Published on: June 3, 2018
Hedgehog signaling induces cardiomyogenesis in P19 cells
Peter J Gianakopoulos1, Ilona S Skerjanc
1Department of Biochemistry, Medical Sciences Building, University of Western Ontario, London, Ontario N6A 5C1, Canada.
Insights
Sonic Hedgehog (Shh) signaling is crucial for heart development. Shh induces cardiomyogenesis in aggregated cells, specifying mesodermal cells into cardiac muscle lineages via Gli1/2 and BMP-4 pathways.
Area of Science:
- Developmental Biology
- Molecular Biology
- Stem Cell Biology
Background:
- Sonic Hedgehog (Shh) is a key signaling factor in embryonic development.
- Shh plays a role in specifying left-right asymmetry in the heart.
- Hedgehog signaling deficiency in mice delays cardiomyogenesis and Nkx2-5 expression.
Purpose of the Study:
- To investigate the role of Shh in cardiomyogenesis.
- To explore how Shh signaling influences cardiac muscle development using P19 cells.
Main Methods:
- Isolated P19 cell clones stably expressing Shh (P19(Shh) cells).
- Cultured cells in monolayer and aggregated formats.
- Analyzed gene expression of cardiac muscle markers (GATA-4, MEF2C, Nkx2-5), pathway components (Ptc1, Gli1, Gli2), and BMP-4.
Main Results:
- Shh pathway was functional in monolayer P19(Shh) cultures (Ptc1, Gli1 up-regulation) but did not induce cardiac markers.
- Cellular aggregation of P19(Shh) cells induced cardiomyogenesis, activating cardiac muscle factors (GATA-4, MEF2C, Nkx2-5).
- Gli2 and Meox1 also induced cardiomyogenesis in aggregated cells; Meox1 modulated Shh pathway components and BMP-4 expression.
Conclusions:
- Shh signaling, particularly through Gli1/2, can specify mesodermal cells into the cardiac muscle lineage.
- Cellular aggregation is a critical context for Shh-induced cardiomyogenesis.
- The Shh pathway interacts with bone morphogenetic protein (BMP) signaling, indicated by BMP-4 up-regulation.
Abstract:
Sonic Hedgehog (Shh) is a critical signaling factor for a variety of developmental pathways during embryogenesis, including the specification of left-right asymmetry in the heart. Mice that lack Hedgehog signaling show a delay in the induction of cardiomyogenesis, as indicated by a delayed expression of Nkx2-5. To further examine a role for Shh in cardiomyogenesis, clonal populations of P19 cells that stably express Shh, termed P19(Shh) cells, were isolated. In monolayer P19(Shh) cultures the Shh pathway was functional as shown by the up-regulation of Ptc1 and Gli1 expression, but no cardiac muscle markers were activated. However, Shh expression induced cardiomyogenesis following cellular aggregation, resulting in the expression of factors expressed in cardiac muscle including GATA-4, MEF2C, and Nkx2-5. Furthermore, aggregated P19 cell lines expressing Gli2 or Meox1 also up-regulated the expression of cardiac muscle factors, leading to cardiomyogenesis. Meox1 up-regulated the expression of Gli1 and Gli2 and, thus, can modify the Shh signaling pathway. Finally, Shh, Gli2, and Meox1 all up-regulated BMP-4 expression, implying that activation of the Hedgehog pathway can regulate bone morphogenetic protein signals. Taken together, we propose a model in which Shh, functioning via Gli1/2, can specify mesodermal cells into the cardiac muscle lineage.
