Fig. 2. Targeted disruption of the Shox2 gene in mice. (A) The mouse Shox2 genomic structure spans 8.3 kb, and contains 6 exons, as indicated by numbers. The targeting vector contains genomic fragments flanking the PGK-neo cassette which replaces exon 3 of Shox2 when correct homologous recombination occurs in ES cells. (B) Southern blot analysis of genomic DNA (digested with BamHI and probed with 3'-probe) derived from E11.5 embryos with different genotypes. (C) PCR analysis of DNA from DNA samples from yolk sac of embryos using W and M pairs of primers for wild-type and mutant alleles, respectively (see A). The W set of primers amplify the wild-type DNA fragment at the size of 520 bp, while the M set of primers amplify the mutant DNA fragment of 300 bp. (D) RT-PCR assays showing the absence of partial Shox2 transcripts in Shox2-deficient embryos.