G Protein–Coupled Receptor APJ and Its Ligand Apelin Act Downstream of Cripto to Specify Embryonic Stem Cells Toward the Cardiac Lineage Through Extracellular Signal-Regulated Kinase/p70S6 Kinase Signaling Pathway
D'Aniello C, Lonardo E, Iaconis S, Guardiola O, Liguoro AM, Liguori GL, Autiero M, Carmeliet P, Minchiotti G
Cells used in publication:
Embryonic stem cell (ES), mouse
Tissue Origin: embryo
Murine msr1 cDNA was subcloned into the pEF1a vector (Clontech) to generate an msr1-V5 fusion protein and then cloned into the pallino (beta)A vector for expression in ESCs. Short hairpin (sh)RNAs vectors (pGIPZ lentiviral, pLKO vectors; OpenBiosystem) were used accordingly to the instructions of the manufacturer. Nucleofected into Mouse ES cells.
RATIONALE: Pluripotent stem cells represent a powerful model system to study the early steps of cardiac specification for which the molecular control is largely unknown. The EGF-CFC (epidermal growth factor-Cripto/FRL-1/Cryptic) Cripto protein is essential for cardiac myogenesis in embryonic stem cells (ESCs). OBJECTIVE: Here, we study the role of apelin and its G protein-coupled receptor, APJ, as downstream targets of Cripto both in vivo and in ESC differentiation. METHODS AND RESULTS: Gain-of-function experiments show that APJ suppresses neuronal differentiation and restores the cardiac program in Cripto(-/-) ESCs. Loss-of-function experiments point for a central role for APJ/apelin in the gene regulatory cascade promoting cardiac specification and differentiation in ESCs. Remarkably, we show for the first time that apelin promotes mammalian cardiomyogenesis via activation of mitogen-activated protein kinase/p70S6 through coupling to a Go/Gi protein. CONCLUSIONS: Together our data provide evidence for a previously unrecognized function of APJ/apelin in the Cripto signaling pathway governing mesoderm patterning and cardiac specification in mammals.
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