A Preliminary Analysis of the Immunoglobulin Genes in the African Elephant ( Loxodonta africana)

Abstract

The genomic organization of the IgH (Immunoglobulin heavy chain), Igκ (Immunoglobulin kappa chain), and Igλ (Immunoglobulin lambda chain) loci in the African elephant ( Loxodonta africana) was annotated using available genome data. The elephant IgH locus on scaffold 57 spans over 2,974 kb, and consists of at least 112 V _H gene segments, 87 D _H gene segments (the largest number in mammals examined so far), six J _H gene segments, a single μ, a δ remnant, and eight γ genes (α and ε genes are missing, most likely due to sequence gaps). The Igκ locus, found on three scaffolds (202, 50 and 86), contains a total of 153 V _κ gene segments, three J _κ segments, and a single C _κ gene. Two different transcriptional orientations were determined for these V _κ gene segments. In contrast, the Igλ locus on scaffold 68 includes 15 V _λ gene segments, all with the same transcriptional polarity as the downstream J _λ-C _λ cluster. These data suggest that the elephant immunoglobulin gene repertoire is highly diverse and complex. Our results provide insights into the immunoglobulin genes in a placental mammal that is evolutionarily distant from humans, mice, and domestic animals.