Take-home message: Antibody maturation is made possible through a dynamic, multiway chromatin hub that can be maintained without cohesin, and where SHM and CSR coexist. (9/10)

When we activated an IGH switch region (γ1), it was recruited into the hub. This is essential for CSR. Even without cohesin, this recruitment still occurred. So: loop extrusion isn’t required for enhancer-promoter contact or switch region activation. (6/10)

Using Tri-C, which maps multiway DNA contacts, we mapped the 3D folding of the human IGH locus during SHM. We discovered a multiway chromatin hub: The V region simultaneously contacts all its major enhancers, clustering them into one regulatory hub. (4/10)

Background: SHM introduces mutations into the V region of the IGH locus, fine-tuning antibodies for higher affinity towards antigens. CSR lets B cells change antibody isotypes (classes) and redirect immune signaling. (2/10)