Similarities and differences in the regulation of HoxD genes during chick and mouse limb development [RNA-Seq]

Hoxd genes are important for limb development in all tetrapods examined thus far. In mouse, they are controlled by a complex bimodal regulation, which regulates first the proximal patterning, then the distal structure, allowing at the same time the formation of the wrist and ankle articulations. We analyzed the existence of this regulatory mechanism in chicken, i.e. in an animal where large morphological differences exist between fore- and hindlimbs. We report that while this bimodal regulation is globally conserved between mammals and avian, some important modifications evolved at least between these two model systems, in particular regarding the activity of specific enhancer and the position of the TAD boundary and the forelimb versus hindlimb comparative regulations. Some aspects of these regulations seem to be more conserved between chick and bats than with the mouse situation, which may relate to the extent to which forelimbs and hindlimbs of these various animals differ in their functions. RNA-seq analysis of limb tissues from mouse (E12.5) or chick (HH20 and HH30)