biostudies-literatureBush ELU.S. Department of Health & Human Services | NIH | National Cancer Institute (NCI)U.S. Department of Health & Human Services | NIH | National Institute of General Medical Sciences (NIGMS)NSF | BIO | Division of Biological Infrastructure (DBI)NIAID NIH HHSNSF | Directorate for Mathematical & Physical Sciences | Division of Mathematical Sciences (DMS)U.S. Department of Health & Human Services | NIH | National Institute of Allergy and Infectious Diseases (NIAID)NCI NIH HHSNIGMS NIH HHS751https://www.ebi.ac.uk/biostudies/studies/S-EPMC12820099biostudies-literatureUnknown17(1)Dynamic genome folding is important for V(D)J recombination at the immunoglobulin kappa (Igκ) locus, which recombines Jκ and Vκ gene segments across a 3.2 Mb region in both deletional and inversional orientations. Chromatin loop extrusion and diffusion are considered two key mechanisms underlying Igκ locus folding, but how they coordinate remains unclear. Here we show that CTCF is a key regulator coupling loop extrusion and diffusion during Igκ V-J rearrangement, promoting recombination in both orientations across long genomic distances. Mechanistically, the CTCF N-terminus promotes long-range loop extrusion that facilitates distal Vκ usage by stabilizing cohesin against WAPL release, and also forms loop barriers enabling chromatin diffusion for inversional Vκ joining. In CTCF N-terminal-deficient B cells, defects in inversional Vκ joining are not restored by WAPL depletion but are instead largely rescued by a dCas9-blockade targeted to the Vκ-Jκ intergenic region, mimicking the CTCF barrier. Our findings thus highlight how CTCF coordinates distinct genome-folding mechanisms through its dual roles in cohesin stabilization and extrusion barrier formation to ensure the generation of a diverse Igκ repertoire.Nature communicationsCTCF couples long-range loop extrusion and diffusion to mediate a diverse Igκ repertoire.PMC12820099R35GM153479R01 AI155775DMS-2152011R35 GM153479DBI-1942143R01 CA247863R01AI155775R01CA247863Sun LHutchins KMYang JBerke-Reynolds BColon-Rosado JAZhang YChang FBush ELCurran JWang JYu XfalseCTCF couples long-range loop extrusion and diffusion to mediate a diverse Igκ repertoire.Dynamic genome folding is important for V(D)J recombination at the immunoglobulin kappa (Igκ) locus, which recombines Jκ and Vκ gene segments across a 3.2 Mb region in both deletional and inversional orientations. Chromatin loop extrusion and diffusion are considered two key mechanisms underlying Igκ locus folding, but how they coordinate remains unclear. Here we show that CTCF is a key regulator coupling loop extrusion and diffusion during Igκ V-J rearrangement, promoting recombination in both orientations across long genomic distances. Mechanistically, the CTCF N-terminus promotes long-range loop extrusion that facilitates distal Vκ usage by stabilizing cohesin against WAPL release, and also forms loop barriers enabling chromatin diffusion for inversional Vκ joining. In CTCF N-terminal-deficient B cells, defects in inversional Vκ joining are not restored by WAPL depletion but are instead largely rescued by a dCas9-blockade targeted to the Vκ-Jκ intergenic region, mimicking the CTCF barrier. Our findings thus highlight how CTCF coordinates distinct genome-folding mechanisms through its dual roles in cohesin stabilization and extrusion barrier formation to ensure the generation of a diverse Igκ repertoire.2025-01-01T00:00:00Z2025 Dec2026-06-30T03:32:16.374Z2026-06-30T03:22:20.755ZS-EPMC128200994138150010.1038/s41467-025-67438-5