The mouse mutation Pdn (Polydactyly Nagoya) is caused by the integration of a retrotransposon into the Gli3 gene.

Mutations in the Gli3 gene are associated with a preaxial polydactyly in several mouse mutants such as extra-toes (Xt). The semidominant mouse mutant Pdn (Polydactyly Nagoya) is characterized by a mild polydactyly on the anterior side of the hind limbs. Homozygous Pdn mice show a more severe polydactyly, additional skeletal malformations, and abnormal brain development. Herein, we report the molecular basis of Pdn, being the integration of an Early Transposon (ETn) into the Gli3 gene. As a consequence, several novel Gli3 mRNAs are generated by alternatively spliced transcripts.