Fig. 6.
The role of gelation in orchestrating ordered Igh locus rearrangement. (I) Igh locus harboring DH, JH, and VH regions in a germ-line configuration, in the absence of loop domains or crosslinks. (II) A chromatin loop domain containing DH and JH regions is formed, anchored by the CTCF sites flanking the DH elements and the CTCF sites in the super-anchor. (III) Weak crosslinks are established across the loop domain containing DH and JH regions. The resulting gel droplet, which is phase-separated from the rest of the locus, facilitates encounters between DH and JH elements and hinders encounters with VH elements. (IV) The CTCF sites are inactivated and crosslinks are dissolved; the mobility of DHJH segment is increased. (V) Chromatin loops containing DHJH and VH regions are formed, anchored by the CTCF sites within the VH-cluster and the CTCF sites in the super-anchor. (VI) Crosslinks across a loop are established, resulting in a de novo gel droplet to facilitate VH-DHJH encounters