Figure 2.

Nm3768 is caused by a large deletion in Alx4. (A) Allele structure of the mouse Alx4 gene. Genotyping primer positions and southern blot probe positions are indicated. Blue and red boxes indicate the proximal and distal ends of the Alx4^lst-2J deletion (B), which was confirmed by sequencing. Allele-specific genotyping (C) confirms that severely affected mutant mice are homozygous for the deletion. Notably, some “unaffected” controls were shown to be heterozygous for the deletion, indicating the dominantly inherited short nose, single limb polydactyly phenotype is incompletely penetrant. Southern blot analysis (D) confirms the genomic structure of the deletion. The expected 3.8 Kb WT band from probe A is converted to a 8.4 Kb band in homozygous mutant animals, consistent with the predicted band size of the deletion, while no signal is detected in mutant mice for internal probe B.