Defects in pathfinding by cranial neural crest cells in mice lacking the neuregulin receptor ErbB4

Mouse embryos with a loss-of-function mutation in the gene encoding the rec eptor tyrosine kinase ErbB4 exhibit misprojections of cranial sensory gangl ion afferent axons. Here we analyse ErbB4-deficient mice, and find that mor phological differences between wild-type and mutant cranial ganglia correla te with aberrant migration of a subpopulation of hindbrain-derived cranial neural crest cells within the paraxial mesenchyme environment. In transplan tation experiments using new grafting techniques in cultured mouse embryos, we determine that this phenotype is non-cell-autonomous: wild-type and mut ant neural crest cells both migrate in a pattern consistent with the host e nvironment, deviating from their normal pathway only when transplanted into mutant embryos. ErbB4 signalling events within the hindbrain therefore pro vide patterning information to cranial paraxial mesenchyme that is essentia l for the proper migration of neural crest cells.