Somatic hypermutagenesis in immunoglobulin genes. III. Somatic mutations in the chicken light chain locus.

We report a new approach based on the Monte Carlo method, to analyze gene conversion. With this, we have examined 235 somatic mutations in the chicken Vlambda gene and found that about 75% of somatic mutations significantly correlated with donor sequences in 25 pseudo Vlambda genes (set C) versus about 25% that did not (set N). The RGYW and TAA consensus sequences of mutational hotspots were earlier revealed in mammalian V genes. Analysis for correlation between somatic mutations in the Vlambda gene and the consensus sequences showed that the somatic mutations of set N were correlating with the consensus sequences (P(W < Wrandom) < 0.01) and the somatic mutations of set C were not. Based on further statistical analysis, we suggest that there must be at least two mechanisms responsible for somatic hypermutagenesis in the Vlambda gene: gene conversion and another, which accounts for the elevated frequencies of somatic mutations at the RGYW and TAA consensus sequences.