FIG. 2.

Af9 expression in embryogenesis detected by β-galactosidase staining of Af9LZ mouse embryos. Af9LZ heterozygous mice were mated with C57BL/6 mice, and staged embryos were removed from the uterus, prefixed in 4% PFA, and stained with X-Gal solution overnight. Wild-type embryos (+/+) and heterozygous littermates (+/−) were examined at E10.5, E11.5, E12.5, and E14.5. Activity of the Af9 gene, leading to expression of the β-galactosidase gene in the Af9LZ allele, is visible as blue staining. No staining by endogenous β-galactosidase was observed in the wild-type controls. Areas of precartilage primordium, such as the developing jaw, nose, and skull, as well as the limb buds, developing ribs, and vertebrae, exhibited Af9 expression, particularly at the later stages of development. At E14.5, the external ear and the vibrissae also exhibited strong Af9 expression. Strong staining was also observed in neural tissues, especially the caudal hindbrain, the midbrain-hindbrain junction, and the sympathetic ganglia, as well as in the heart tube, at E10.5.