Analysis and Comparison of the Mouse and Human Immunoglobulin Heavy Chain JH–Cμ–Cδ Locus

Abstract

We report here 23,686 bases of contiguous DNA sequences from the mouse germline immunoglobulin heavy chain (H) constant (C) μδ region. The sequence spans the joining (JH) regions, the μ constant region (Cμ), the δ constant region (Cδ) coding regions, a domain relic, the μ switch region (Sμ), seven blocks of simple sequence repeats, a large unique sequence inverted repeat, a large unique sequence forward repeat, and all of the intervening material. A comparison of this 23.7-kb region with the corresponding human Cμ/Cδ region reveals clear homology in the coding and introns of Cμ but not in the 5′ flanking J gene segments nor in the intergenic and Cδ regions. This mixed pattern of similarity between the human and the mouse sequences contrasts with high levels of similarity found in the T-cell receptor Cα/Cδ region and α and β myosin genes and the very low levels found in the γ-crystallin, XRCC1, and β-globin gene clusters. The human and mouse comparison further suggests the incorporation of novel sequences into expressed genes of IgD.