Whole-mount RNA in situ hybridizations reveal expression domains of Fgf8 (A, B F, G), Fgf17 (C, H), and Shh (D, E, I, J) in wild-type and mutant embryos at stages E9.0 to E10.5. Only mild changes in the midfacial expression domains of these genes can be seen in homozygous mray mutants, suggesting an overall proper specification of the midface. The slightly smaller expression domains of all analyzed genes in the E9.0 and E9.5 mray/mray embryos correlate well with overall smaller size of these embryos. Particularly, at E10.5 the overall smaller size and developmental delay of the mutant embryos becomes apparent (G, J). In the mutant, considerably lower Shh expression along the ectodermal odontogenic line is probably due to general developmental delay and marked by asterisks in J. BA1, 2: branchial arch1, 2, FNP: frontonasal prominence, LNP: lateral nasal process, ML: midline, MP: mandibular process, MNP: medial nasal prominence, MX: maxillary process, NP: nasal pit, OL: odontogenic line, TV: telencephalic vesicle.