At least five d_h genes of human immunoglobulin heavy chains are encoded in 9‐kilobase dna fragments

Abstract

The variable region of immunoglobulin (Ig) heavy chain is encoded by three separate genes: variable (VH), diversity (DH) and joining (JH) genes on the germ-line genome. In mice, most complementarity determining region (CDR) III of the heavy chains of myelomas and hybridomas sequenced so far can be assigned to one of the 12 already identified germ-line DH genes by the homology of nucleotide sequences of DH gene-coding regions although extranucleotides, the so-called N segments, are found at the boundaries between DH and JH as well as VH and DH. On the other hand, Siebenlist et al. (Nature 1981. 294:631) identified two DH gene families in human genome: DHQ52, located at 45 bp upstream of the JH gene cluster, and another family encoded at 9-kb regular intervals possibly between VH and JH gene clusters. However, the somatic DH sequences found in VH-DH-JH structure (the somatic DH segment being defined as the region which is not encoded either by germ-line VH or JH gene) are relatively long and apparently random, and do not seem to have the homology to any of the germ-line DH sequences. To explain the origin of high diversity in the CDR III of human Ig heavy chains, Siebenlist et al. predicted the presence of another mechanism, namely DH-DH joinings. In the present study, we identified five DH genes in one of the above 9-kb repeats. This suggests that the total number of germ-line DH genes is much higher in man than in mouse. The comparison between somatic DH sequences and germ-line DH sequences indicates that most somatic DH sequences in human Ig heavy chains are also produced by VH-DH and DH-JH joinings without the joining of multiple DH gene segments.

Relationship of the CD5 B cell to human tonsillar lymphocytes that express autoantibody-associated cross-reactive idiotypes.

“…5). Most clones have a segment within CDR3 that has a high degree ofsequence homology with a known germline D minigene (37)(38)(39)(40)(41) (Fig. 5).…”

Germline variable region gene segment derivation of human monoclonal anti-Rh(D) antibodies. Evidence for affinity maturation by somatic hypermutation and repertoire shift.

“…The remainder was run on a 1.8% agarose gel in Tris-acetate EDTA buffer, purified with GeneClean (BIO 101, Inc., Vista, CA) and the amplified DNA was end-filled, phosphorylated, ligated into Smal-cut dephosphorylated pUC18 vector, and used to transform DH5a-competent Escherichia coli (34). At (3,(54)(55)(56)(57)(58)(59)(60) using Bestfit and Gap programs. The JH genes were compared with the six JH segments (4).…”

Early human IgH gene assembly in Epstein-Barr virus-transformed fetal B cell lines. Preferential utilization of the most JH-proximal D segment (DQ52) and two unusual VH-related rearrangements.

“…Both strands of relevant restriction fragments were sequenced according to the methods of Maxam and Gilbert (16). Sequences were compared with Genbank human Ig sequences as well as additional recently available human D and VH sequences (14,(17)(18)(19)(20)(21)(22)(23)(24) using Microgenie IBM software.…”