Expression of hox Genes and Genes Related to Limb Development During the Homeotic Transformation of Tails Into Limbs Induced by Vitamin A in the Anuran Rana ornativentris.

Anuran tadpoles regenerate their tails after amputation. However, when vitamin A is administered, some anuran species such as Rana ornativentris occasionally form ectopic limbs instead of tail. Few analyses of this phenomenon at the molecular level exist. To investigate the molecular mechanisms underlying ectopic limb development, we quantified the expression of genes related to normal limb positioning and development. We observed the downregulation of a posterior hox gene prior to the appearance of ectopic limb buds in the regenerating tail. This hox expression change also preceded the upregulation of pitx1, which is expressed in the earliest hind limb bud. These results suggest that Hox genes are involved in ectopic limb induction upstream of hind limb genes.