The order and orientation of mouse lambda-genes explain lambda-rearrangement patterns.

Mouse lambda-genes are rearranged in specific V lambda-JC lambda associations: V lambda 1 has only been found to rearrange with JC lambda 3 or JC lambda 1, whereas V lambda 2 mainly rearranges with JC lambda 2 and very rarely with JC lambda 1,3. In order to determine the physical basis for these associations we have cloned the respective lambda-genes and large portions of their flanking regions by chromosomal walking in a total of 141 kb of phage and cosmid clones. With the use of unique probes obtained from such clones, the order and orientation of the mouse lambda-gene segments were determined by analyzing patterns of DNA deletion associated with lambda-gene rearrangements in various cell lines. All V and C gene segments were found to be in the same transcriptional orientation, and V2 and V1 were found not to be next to each other, thus supporting the gene order V2-C2-C4-V1-C3-C1.