Tinkering with constraints in the evolution of the vertebrate limb anterior-posterior polarity.
Genes belonging to both HoxA and HoxD clusters are required for proper vertebrate limb development. Mice lacking all, or parts of, Hoxa and Hoxd functions in forelimbs, as well as mice with a gain of function of these genes in the early limb bud, have helped us to understand functional and regulatory issues associated with these genes, such that, for example, the tight mechanistic interdependency that exists between the production of the limb and its anterior to posterior (AP) polarity. Our studies suggest that the evolutionary recruitment of Hox gene function into growing appendages was crucial to implement hedgehog signalling, subsequently leading to the distal extension of tetrapod appendages, with an already built-in AP polarity. We propose that this process results from the evolutionary co-option, in the developing limbs, of a particular regulatory mechanism (collinearity), which is necessary to pattern the developing trunk. This major regulatory constraint imposed a polarity to our limbs as the most parsimonious solution to grow appendages.
Duboule
Denis
D
Department of Zoology and Animal Biology, University of Geneva, Sciences III, Quai Ernest Ansermet 30, 1211 Geneva 4, Switzerland.
Tarchini
Basile
B
Zàkàny
Jozsef
J
Kmita
Marie
M
D000818:Animals; D005075:Biological Evolution; D019521:Body Patterning; D019143:Evolution, Molecular; D005121:Extremities / Q000196:embryology* / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D053823:Hedgehog Proteins / Q000378:metabolism; D006801:Humans; D018878:Limb Buds; D051379:Mice; D008954:Models, Biological; D014714:Vertebrates
D053823:Hedgehog Proteins