LOCALIZATION OF PDGF-A AND PDGFR-ALPHA MESSENGER-RNA IN XENOPUS EMBRYOS SUGGESTS SIGNALING FROM NEURAL ECTODERM AND PHARYNGEAL ENDODERM TO NEURAL CREST CELLS

In situ hybridization analysis of Xenopus laevis embryos reveals that mRNA encoding the platelet-derived growth factor alpha receptor (PDGFR alpha) is expressed in cephalic neural crest masses prior to migratio n from the future neural tube and during their migration into the visc eral arches. The analysis of fluorescently labeled neural crest tissue transplanted to unlabeled host embryos demonstrates that neural crest cells are the only detectable source of PDGFR alpha mRNA within visce ral arches. Transcripts encoding PDGF A are present in neural ectoderm , otic vesicle and pharyngeal endoderm. Their location suggests that P DGF A provides a signal, first from the neural epithelium and later fr om the otic vesicle and pharyngeal endoderm, to cephalic neural crest cells during their migration in the arch region.