Genetic analyses in mouse fibroblast and melanoma cells demonstrate novel roles for PDGF-AB ligand and PDGF receptor alpha

Platelet Derived Growth Factor Receptor (PDGFR) signaling is a central mitogenic pathway in development, as well as tissue repair and homeostasis. The rules governing the binding of PDGF ligand to the receptor to produce activation and downstream signaling have been well defined over the last several decades. In cultured cells after a period of serum deprivation, treatment with PDGF leads to the rapid formation of dramatic, actin-rich Circular Dorsal Ruffles (CDRs). Using CDRs as a robust visual readout of early PDGFR signaling, we have identified several contradictory elements in the widely accepted model of PDGF activity. Employing CRISPR/Cas9 gene editing to disrupt the Pdgfra gene in two different murine cell lines, we show that in addition to the widely accepted function for PDGFR-beta in CDR formation, PDGFR-alpha is also clearly capable of eliciting CDRs. Moreover, we demonstrate activity for heterodimeric PDGF-AB ligand in the vigorous activation of PDGFR-beta homodimers to produce CDRs. These findings are key to a more complete understanding of PDGF ligand-receptor interactions and their downstream signaling consequences. This knowledge will allow for more rigorous experimental design in future studies of PDGFR signaling and its contributions to development and disease.