pdgfrb+ cells express pdgfrb (coding for PDGF receptor β; Pdgfrβ), and thus, are likely competent to respond to PDGF signals. We first analyzed the expression of the 6 zebrafish PDGF ligand-encoding genes by in situ hybridization (ISH). Transcripts of pdgfaa, pdgfab, pdgfba, pdgfc, ...