Immunoglobulin VH region genes of the mouse are organized in overlapping clusters

Abstract

Restriction fragment length polymorphism has been compared between the Igh loci of C57BL/6 and MOLF/EI (Mus musculus molossinus) mice utilizing probes which detect the C_γ2b gene and genes from nine V_H‐gene families. Distinct restriction site patterns were found for the CH genes and for V_H families PC7183, Q52 and X24. V_H families V31 and J558 showed identical patterns. Mixed patterns of identical and distinct bands were detected in V_H families S107, J606, V3660 and VGAM3.8. This indicates that a recombination took place involving the Igh loci of a M. m. molossinus and a progenitor of the C57BL/6 strain. The breakpoint of recombination maps to the chromosomal region carrying V_H families S107, J606, VGAM3.8 and V3660. V^H families PC7183, Q52 and X24 map 3′ to the recombination breakpoint and proximal to the D_H‐J_H‐C_H region, whereas V_H families V31 and J558 accordingly map 5′ to the recombination breakpoint and distal to D_H‐J_H‐C_H. This order of V_H families was confirmed by deletion mapping utilizing hybridomas which are haploid either for the Igh^b or for the Igh^a locus. The mapping data indicate that the V^H families of the mouse are organized in overlapping clusters. This notion is confirmed by demonstration of the physical linkage of V_H genes from families V31 and J558 in the Igh^a locus.