Atavisms in the avian hindlimb and early developmental polarity of the limb.

Background: The naturally occurring chicken mutant talpid (ta ), best known for its limb and craniofacial defects, has long served as a valuable tool for developmental biologists studying growth and patterning of craniofacial structures and the limb. The mutant provides a unique tool to examine the molecular and cellular processes regulating limb development.

Results: This mutant also provides unique insights into the evolution of developmental genetic programs. Previous work defined the appearance of atavistic dentition in ta embryos. Herein we describe the appearance of ancestral characters of the hindlimb in embryonic ta chicken embryos.

Conclusion: As the ta phenotype arises as a result of mutation in C2CD3 and disrupted cilia function, this mutant provides genetic and developmental insight into the causes of asymmetry in the limb and also a model for the evolution of the avian hindlimb.