FUNCTION OF THE EVX-2 GENE IN THE MORPHOGENESIS OF VERTEBRATE LIMBS

Vertebrate gene members of the HoxD complex are essential for proper d evelopment of the appendicular skeletons, Inactivation of these genes induces severe alterations in the size and number of bony elements, Ev x-2, a gene related to the Drosophila even-skipped (eve) gene, is loca ted close to Hoxd-13 and is expressed in limbs like the neighbouring H erd genes. To investigate whether this tight linkage reflects a functi onal similarity, we produced a null allele of Evx-2. Furthermore, and because Hoxd-13 function is prevalent over that of nearby Herd genes, we generated two different double mutant loci wherein both Evx-2 and H oxd-13 were inactivated in cis, The analysis of these various genetic configurations revealed the important function of Evx-2 during the dev elopment of the autopod as well as its genetic interaction with Hoxd-1 3, These results show that, in limbs, Evx-2 functions like a Herd gene , A potential evolutionary scenario is discussed, in which Evx-2 was r ecruited by the HoxD complex in conjunction with the emergence of digi ts in an ancestral tetrapod.