A preliminary analysis of the immunoglobulin genes in the African elephant (Loxodonta africana)

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.