Sequence analysis of non-expressed immunoglobulin heavy chain loci in clonally related, somatically mutated hybridoma cells.

The non-expressed, rearranged JH loci of two hybridoma cells, thought to be derived from a single B cell precursor were cloned and partially sequenced. Identical DJ rearrangements including N sequences at the DJ border were found, proving the common origin of the cells. The non-expressed loci lacked a rearranged VH gene and exhibited a single point mutation in a stretch of 1108 bp. This contrasts with 11 somatic point mutations in the 702 bp of the expressed VDJ regions. We discuss the possibility that the mechanism of somatic hypermutation may require V gene rearrangement.