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Sequence heterogeneity in Ig kappa transcripts from single B lymphocytes.
1Department of Immunology, National Jewish Medical and Research Center, 1400 Jackson St., Denver, CO 80206, USA.
Molecular Immunology
|September 23, 2000
Summary
Somatic hypermutation in kappa genes leads to sequence changes, suggesting rapid repair mechanisms. These findings offer insights into antibody gene diversification and mutation biases.
Area of Science:
- Immunology
- Molecular Biology
- Genetics
Background:
- Antibody variable (V) region genes undergo somatic hypermutation to generate diverse antibody responses.
- The mechanisms and sequence specificities of somatic hypermutation and subsequent repair are not fully understood.
Purpose of the Study:
- To investigate sequence heterogeneity and aberrant splicing in kappa cDNA from single B lymphocytes.
- To determine the origin of base changes and their relationship to somatic hypermutation and repair mechanisms.
Main Methods:
- Individual amplification of kappa cDNA from single B lymphocytes.
- Analysis of sequence heterogeneity, base changes, and splicing patterns.
- Comparison with beta2 microglobulin transcripts to rule out polymerase infidelity.
Main Results:
- Kappa cDNA revealed sequence heterogeneity and aberrantly spliced products, not attributable to polymerase errors.
- Base changes occurred in trinucleotide sequences disfavored by somatic hypermutation.
- Transcript alterations were absent from the kappa immunoglobulin (Ig) gene, suggesting rapid repair after limited transcription.
Conclusions:
- Somatic mutations may be acquired by the kappa gene and rapidly repaired, influencing observed mutation frequencies.
- Preferential repair of mutations in specific trinucleotide contexts could explain microsequence-specific biases in antibody V gene mutation rates.