title: Visualization of looping involving the immunoglobulin heavy-chain locus in developing B cells.
abstract: The immunoglobulin heavy-chain (IgH) locus undergoes large-scale contraction in B cells poised to undergo IgH V(D)J recombination. We considered the possibility that looping of distinct IgH V regions plays a role in promoting long-range interactions. Here, we simultaneously visualize three subregions of the IgH locus, using three-dimensional fluorescence in situ hybridization. Looping within the IgH locus was observed in both B- and T-lineage cells. However, monoallelic looping of IgH V regions into close proximity of the IgH DJ cluster was detected in developing B cells with significantly higher frequency when compared with hematopoietic progenitor or CD8+ T-lineage cells. Looping of a subset of IgH V regions, albeit at lower frequency, was also observed in RAG-deficient pro-B cells. Based on these observations, we propose that Ig loci are repositioned by a looping mechanism prior to IgH V(D)J rearrangement to facilitate the joining of Ig variable, diversity, and joining segments.
authors.affiliation: Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093, USA.
authors.forename: Camil E
authors.initials: CE
authors.lastname: Sayegh
authors.forename: Camil
authors.initials: C
authors.lastname: Sayegh
authors.forename: Suchit
authors.initials: S
authors.lastname: Jhunjhunwala
authors.forename: Roy
authors.initials: R
authors.lastname: Riblet
authors.forename: Cornelis
authors.initials: C
authors.lastname: Murre
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology*; D002454:Cell Differentiation / Q000276:immunology*; D005803:Genes, Immunoglobulin; D007143:Immunoglobulin Heavy Chains / Q000235:genetics* / Q000276:immunology; D007135:Immunoglobulin Variable Region / Q000235:genetics; D051379:Mice
chemical_list: D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region