DNA rearrangement causes a high rate of spontaneous mutation at the immunoglobulin heavy-chain locus of a mouse myeloma cell line.

Abstract

The spontaneous mutation rate of immunoglobulin genes expressed in myeloma cells is well above that of other genes expressed in these or in other cell types. The nature of such mutations in one myeloma cell line, MPC11, was explored at the molecular level. Included in this study were MPC11 variants representing 24 independent and spontaneous mutations affecting immunoglobulin secretion. Of the mutants studied, 19 had ceased immunoglobulin heavy chain (IgH) production (nonproducers), and 5 produced from as little as 1/1,000 to as much as 1/10 the amount of immunoglobulin produced by MPC11 (low producers). Only one of the MPC11 mutants (a nonproducer) showed no evidence of DNA rearrangement in or near the expressed IgH gene. The formerly expressed gamma 2b gene had been deleted in 18 of the 19 nonproducers. All of the low producers had undergone DNA rearrangement in or near the expressed IgH gene, and three of them produced immunoglobulin of a new heavy chain class. The cause for reduced heavy-chain synthesis in the low producers is not yet known. However, in several of these mutants, the defect appeared to be posttranscriptional. In these cell lines, steady-state IgH mRNA levels were much lower than in the parent cell line, while the heavy-chain gene transcription rate remained unchanged.

Ectopic recombination within homologous immunoglobulin mu gene constant regions in a mouse hybridoma cell line.

“…Thus, these data suggest possible relationships between transcriptional activity, DNA sequence or accessibility, and immunoglobulin gene recombinations. It is also interesting that in both human and murine myeloma tumors as well as mouse myelomas and hybridomas in tissue culture, the rate of mutation in the chromosomal immunoglobulin heavy-chain locus is at least 100-to 1,000-fold higher than the rate of mutations in unlinked chromosomal loci (31,39,67). It is possible that both recombination and the high frequency of mutation reflect a common feature of the immunoglobulin genes.…”

T cell recognition of endogenous IgG2a expressed in B lymphoma cells

“…Hybridization was with yZa CH3, a plasmid containing sequences from the CH3 domain of the y2, heavy chain gene [28]. This probe hybridizes to yZa, but not to Y2b mRNA [29].…”

Unique Function for Carboxyl-Terminal Domain of Oct-2 in Ig-Secreting Cells

“…Cytoplasmic lysates were made for ELISAs, as previously described (49). For detection of ␥2b-H chains, ELISA plates (Dynatech Laboratories, Chantilly, VA) were coated with purified anti-mouse ␥2b (rat IgG1) (catalog 02041D; BD PharMingen, San Diego, CA).…”