Rat Anti-Mouse Ighm Heterohybridoma [442.23]

A transcriptional enhancer, E mu, was defined in the IGH locus of the Pekin duck, Anas platyrhynchos. Regions of DNA from the JH to IGHM intron were cloned into reporter constructs containing the SV40 promoter and transiently transfected into chicken B and T lymphocytes. A strong transcriptional activity, of several hundred-fold greater than that of a reporter construct with the promoter alone, was localized to a 281 bp region that contains 2 E-box motifs, CAGCTG. This fragment showed enhancer activity in both orientations and was active in chicken B cells but not in T cells. When the activity of the enhancer was tested in constructs without a promoter, it showed high transcriptional activity in the forward orientation, but much less activity (by two orders of magnitude) when tested in the reverse orientation. This suggests that the fragment contains not only enhancer activity but may contain promoter activity analogous to that of the I mu promoter described in mammals. Thus it appears that the location, but not the fine structure, of the E mu enhancer was established before the evolutionary divergence of the avian and mammalian lineages some 300 Myr ago. (c) 2006 Elsevier Ltd. All rights reserved.

The number of immunoglobulin heavy chain (IGH) constant genes (IGHC) varies among mammals. To annotate the porcine IGHC genes, we sequenced the entire IGHC-containing genomic region from a single porcine haplotype. The resulting contiguous sequence included in 5' the IGH diversity (D) gene cluster and in 3' TMEM121, which flank the IGHC cluster in the human genome, suggesting that we had obtained the entire genomic region containing porcine IGHC. This region was about 190-kb long, in good agreement with those of other mammals. The porcine IGHC cluster contained 10 genes, IGHM, IGHD, six IGHG genes, IGHE and IGHA. The porcine IGHG genes formed a cluster between IGHD and IGHE, with IGHG3 considered as the most ancient IGHG gene, located at the beginning of the IGHG cluster. Furthermore, the porcine sequence contained two IGHG5 and two IGHG6 genes, but no IGHG genes for IgG2 and IgG4, suggesting flexibility within the IGHG cluster. We also recorded structural differences in the switch regions of the IGHC genes that may be important in their transcription. This haplotype can serve as a reference for future studies on other haplotypes and for functional analysis of porcine immunoglobulin (IG) isotypes. (C) 2012 Elsevier Ltd. All rights reserved.