Many thanks to the people who collaborated with us on this study! @charbel-alfeghaly.bsky.social @ireneaksoy.bsky.social Cloé Rognard @crougeulle.bsky.social @agneseloda.bsky.social @rougeulle-lab.bsky.social Anouk Necsulea @heardlab.bsky.social Pierre Savatier, Laura Villacorta, Michael Dong

The takeaway: regulatory elements can acquire function before becoming evolutionarily essential. They're complexity waiting to matter !

Using chromatin profiling and CRISPR, we identified enhancers, chromatin boundaries, and long non-coding RNAs controlling XIST, some conserved, others species-specific. The surprise: when we scanned these functional sequences for signatures of natural selection, most are evolving neutrally.

We often assume that if a DNA sequence does something functional, evolution must have preserved it. Our new study challenges this idea by investigated how the regulatory network of XIST, a gene essential for mammalian development, has evolved across marmosets, macaques, and humans.

We tile through ~300 ultra conserved elements 10bp at a time in 6 taxa (some alive, some extinct), to ask, are they the reason the two skulls below- separated by 160 million years of evolution - are so similar?

(image from former PhD student Laura Cook)