Fig. 3. Pharyngeal arch defects in Foxd3^flox/-; Wnt1-Cre embryos. (A) β-galactosidase activity as detected by X-Gal staining in control and mutant mouse embryos at 9.5 dpc. PA1 and PA2 are present but smaller in Foxd3 mutants and there is a paucity of cells migrating into PAs 3-4 and into the developing cardiac region (arrowheads in enlarged view below). (B) Scanning electron micrographs of 10.5 dpc embryos showing PA deficiency. Embryos were matched for somite number. (C) Whole-mount antibody staining of neurofilament protein. Cranial nerves are present in mutants but smaller and slightly misdirected. In the trunk (lower panels), the mutant embryo has smaller dorsal root gangia (DRG) and thinner spinal nerves than the control. Note that these embryos have been cleared so that both left and right nerves are visible. (D) Whole-mount in situ hybridization of embryos for Sox10. In Foxd3 mutant embryos, Sox10 mRNA is not detected in the glossopharyngeal (IX) and vagus (X) ganglia, although it is detected at reduced levels in the trigeminal (V), facial (VII) and vestibulocochlear (VIII) ganglia. Sox10 signal is also missing in the foregut of mutants (arrowheads); signal in the otic vesicle (circled) is background. drg, dorsal root ganglion; v, trigeminal ganglion; vii, facial ganglion; viii vestibulocochlear ganglion; ix, glossopharyngeal ganglion; x, vagus ganglion; PA, pharyngeal arch; sn, spinal nerves.