FIG. 2.

Absence of Nkx2.6 transcripts in homozygous mutant embryos. (A) Wild-type (+/+) and homozygous mutant (−/−) embryos at E9.5 were analyzed by whole-mount in situ hybridization using an Nkx2.6 probe containing the first and second exons. Note the complete absence of Nkx2.6 transcripts in the pharynx of the homozygous mutant embryo. Scale bar = 0.5 mm. (B and C) Tissue sections of wild-type (+/+) and homozygous mutant (−/−) embryos at E9.5 were hybridized with the Nkx2.6 probe. In the wild-type embryo, Nkx2.6 is strongly expressed in the third and fourth pharyngeal pouches. In contrast, no signals were detected in the homozygous mutant embryo. m, mandibular component of the first pharyngeal arch; III and IV, third and fourth pharyngeal pouches; a, atrium. Scale bars = 100 μm.