![]() ![]() Genomic DNAs from homozygous mutant and wild-type animals were indistinguishable by Southern analyses using a variety of restriction enzyme digests and lgh probes. By contrast, the majority of the immunoglobulins of wild-type a2 rabbits are a2-positive and only a small percentage are a-negative. Adult homozygous ali/ali rabbits likewise have normal immunoglobulin levels resulting from increased production of a-negative immunoglobulins and some residual ability to produce the a2 allotype. In heterozygous a1/ali or a3/ali rabbits, serum immunoglobulins are almost entirely the products of the normal a1 or a3 allele and only traces of a2 immunoglobulin are detectable. Rabbits of the Alicia strain have a mutation (ali) that segregates with the immunoglobulin heavy-chain (lgh) locus and has a cis effect upon the expression of heavy-chain variable-region ( VH) genes encoding the a2 allotype. ![]() These results, and the fact that the 3' VH genes rearrange early in B-cell development, indicate that the 3' end of the VH locus probably plays a key role in regulation of VH gene expression. We suggest that this relatively small deletion affects a segment containing 3' VH genes with important regulatory functions, the loss of which leads to the ali phenotype. ![]() These fragments hybridized to probes both for VH and for a region of DNA a few kilobases downstream of the VH genes nearest the joining region. However, when digests with infrequently cutting enzymes were analyzed by transverse alternating-field electrophoresis, the ali DNA fragments were 10-15 kilobases smaller than the wild type. Altered phenotypic expression of immunoglobulin heavy-chain variable-region ( VH) genes in Alicia rabbits probably reflects a small deletion in the VH genes closest to the joining region.Īllegrucci, M Newman, B A Young-Cooper, G O Alexander, C B Meier, D Kelus, A S Mage, R G ![]()
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