INVERSIONS PRODUCED DURING V(D)J REARRANGEMENT AT IGH, THE IMMUNOGLOBULIN HEAVY-CHAIN LOCUS

Diversity in immunoglobulin antigen receptors is generated in part by V(D)J recombination. In this process, different combinations of gene e lements are joined in various configurations. Products of V(D)J recomb ination are coding joints, signal joints, and hybrid junctions, which are generated by deletion or inversion. To determine their role in the generation of diversity, we have examined two sorts of recombination products, coding joints and hybrid junctions, that have formed by inve rsion at the mouse immunoglobulin heavy-chain locus. We developed a PC R assay for quantification and characterization of inverted rearrangem ents of D-H and J(H) gene elements. In primary cells from adult mice, inverted DJ(H) rearrangements are detectable but they are rare. There were approximately 1,100 to 2,200 inverted DJ(H) coding joints and inv erted DJ(H) hybrid junctions in the marrow of one adult mouse femur. O n day 16 of gestation, inverted DJ(H) rearrangements are more abundant . There are approximately 20,000 inverted DJ(H) coding joints and inve rted DJ(H) hybrid junctions per day 16 fetal liver. In fetal liver cel ls, the number of inverted DJ(H) rearrangements remains relatively con stant from day 14 to day 16 of gestation. Inverted DJ(H) rearrangement s to J(H)4, the most 3' J(H) element, are more frequently detected tha n inverted DJ(H) rearrangements to other J(H) elements. We compare the frequencies of inverted DJ(H) rearrangements to previously determined frequencies of uninverted DJ(H) rearrangements (DJ(H) rearrangements formed by deletion). We suggest that inverted DJ(H) rearrangements are influenced by V(D)J recombination mechanistic constraints and cellula r selection.