Chicken immunoglobulin μ-chain gene: germline organization and tandem repeats characteristic of class switch recombination

Abstract

We have isolated the phage clones covering the region spanning from the heavy (H)-chain joining (J) region to the end of the μ-chain gene of the chicken immunoglobulin (Ig). The distance from J H to the first exon of the μ-chain constant (C) region is approximately 13 kb, and introns between the C region exons measure more than 3 kb. These distances are significantly larger than those of known μ-chain genes. We found a region cross-hybridizing to the switch regions of the mouse Cμ and Cα genes just in front of the first exon of Cμ. Partial nucleotide sequencing of this region revealed that this region consists of tandem repeats of pentamers ( C T )( C A ) CAG complementary to the mammalian switch repetitive region. These findings suggest that this region is a good candidate for a class switch region of the μ-chain gene of chicken Ig.