The possibility exists that in snakes and caecilians a similar mechanism is involved in changes in their body plan.
A recent report indeed shows that HoxA13 has specific amino acid substitutions in snakes and limbless lizards that seem to correlate with limbless taxa (Kohlsdorf et al., 2008).
As the sequences cloned by us do not correspond to full coding sequences, we have not been able to analyze them in detail for deviations from a normal conservation profile. When full length sequences become available, transgenic gain-of-function assays in mouse should reveal whether snake and caecilian Hox genes do indeed have different inducing properties from those of their mouse orthologs.