Amplification of immunoglobulin λ constant genes in populations of wild mice

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Abstract
The λ immunoglobulin light chain (Igλ) locus of BALB/c inbred mice consists of two variable region gene segments (Vλ)1–3, and four constant region gene segments (Cλ)1,2,4,5. Each Cλ gene segment is associated with a unique joining segment (Jλ)2,4–7, and they are organized in two paired units, J3C3–J1C1 and J2C2–J4C4 (refs 4, 8). Using cDNA probes specific for Cλ1 and Cλ2 (ref. 9) we have analysed the genomic organization of the Cλ gene segments in wild-derived and inbred strains of mice. Although Southern blots of the genomic DNA of inbred mice show a constant pattern of hybridization, wild-derived mice show a high degree of variation in the number, size and intensity of hybridizing fragments. We have now found that, per haploid genome, mice of a Mus musculus musculus stock isolated from Sladeckovce, Czechoslovakia (CzII) have at least 12 Cλ segments, and mice of a Mus musculus domesticus stock ‘Centreville Lights’ from Centreville, Maryland (CL) have at least 8 Cλ segments. There appears to have been relatively recent amplifications of the Cλ gene segments in wild mice.