Deletion of the DQ52 element within the Ig heavy chain locus leads to a selective reduction in VDJ recombination and altered D gene usage

The process of V(D)J recombination that leads to the assembly of Ig gene se gments is tightly controlled during B cell differentiation. Two germline tr anscripts, one of which (mu (0)) originates from the promoter region of DQ5 2, may control the accessibility of the heavy chain locus. Here, we present the analysis of a mouse line in which the DQ52 gene together with its regu latory sequences is deleted by a Cre/loxP-based strategy. In F-1 (DQ52(+/-) ) mice, the use of the JH3 and JH4 elements in DJ or VDJ junctions of the D Q52(-) allele was strongly reduced in both the bone marrow pre-B and spleen cells, while the JH1 and JH2 elements were used with normal frequencies. I n addition, IgM(+) B cells of bone marrow and spleen used the DQ52(-) allel e less frequently. On DJ joints of the DQ52- allele, there was 2 times less processing of JH3 ends, which resulted in clearly increased addition of P nucleotides, Although the use of D elements in DJ joints was quite similar, an altered D repertoire was found in VDJ joints of the DQ52(-) allele. In splenic B cells of the DQ52(-/-) mouse the amino acid distribution of the C DR3 was skewed, probably to compensate for the altered processing of JH3 en ds. Thus, we have shown an interesting selective effect of the DQ52 region on controlling accessibility to 3 ' JH elements an the Ig locus, which also seems to influence the processing of DJ joints. We propose a model in whic h the DQ52 promoter region enhances the induction of secondary DJ rearrange ments. The Journal of Immunology, 2001, 166: 2540-2552.