Developmental and Evolutionary Comparative Analysis of a Regulatory Landscape in Mammals and Birds

The study analyzed the regulation of Hoxd genes in murine vibrissae and chicken feather primordia, comparing them to the regulation during the elongation of the posterior trunk in amniotes. It found that different subsets of Hoxd genes in these skin appendages were contacted by lineage-specific enhancers, using an ancestral chromatin topology. In contrast, the regulation in the embryonic trunk of mice and chickens relied on conserved cis-regulatory elements (CREs), although many of these sequences had functionally diverged between the species. This suggested that transcriptional robustness was maintained despite significant divergence in CRE sequences, highlighting the role of 3D chromatin structures and CRE variations in transcriptional evolvability.