Huge congrats, Dr. Alberti 🎉!

Congratulations, Alex 👏👏👏

Thank you so much, Lorenza :)

Thank you, Joe :)

Thank you, Isabel!

Thank you very much, Thibaut!

Thank you, Paula :)

thank you, Juan!

thanks a lot, Claus! :)

thank you, Dima!

There’s much more to explore in the paper—so dive in! It also opens exciting questions for future research: What is the role (if any) of loop extrusion in the formation of these structures? Are these loops dynamic across development/cell types? When did insulating sequence elements evolved?

This is our (current/tentative) model for the early evolution of animal chromatin architecture.

Finally, in unicellulars, chromatin architecture is “passively” defined by active/repressive chromatin states, without evidence of sequence elements or specific factor binding. See for example co-segregating repressive domains in Sphaeroforma, highly enriched in TEs:

In sponges we do not identify loops, despite the existence of distal enhancers. We hypothesize this could be explained by the relative proximity (<10Kb) of these enhancers to the closest TSS. What we do observe are prominent chromatin jets/fountains, as also recently described in other species.

In the cnidarian Nematostella, we observe multiple enhancer-promoter loops, including some very distal ones (1Mb). Interestingly, here loops show a characteristic one-sided stripe, which may suggest active extrusion (?).

In placozoans, we observed promoter-promoter hubs, highly conserved across two distantly related species.
Not all genes participate in these hubs, only those containing a sequence motif found in TIR sequences of a Mutator DNA transposon, with highly conserved insertions across all placozoans.

What proteins are involved in forming these loops? CTCF is absent in non-bilaterians. Using chromatin proteomics and DAP-seq, we identified two ctenophore-specific zf-C2H2 proteins that we called Ctenophore Tethering Element Proteins, which also cannot bind methylated sites.