Definition of a third VLR gene in hagfish

• Authors: Jianxu Li, Emory University; Sabyasachi Das, Emory University; Brant Herrin, Emory University; Masa Hirano, Emory University; Max Dale Cooper, Emory University
• Journal Title: Proceedings of the National Academy of Sciences
• Volume: Volume 110, Number 37
• Publisher: National Academy of Sciences | 2013-09-10, Pages 15013-15018
• Type of Work: Article | Post-print: After Peer Review
• Publisher DOI: http://doi.org/10.1073/pnas.1314540110
• Subjects: Health Sciences, Pathology
• Keywords: adaptive immunity; molecular evolution; antigen receptor; agnatha

Abstract

The jawless vertebrates (hagfish and lampreys) possess an alternative adaptive immune system in which variable lymphocyte receptors (VLRs) constructed of leucine-rich repeats are used to recognize foreign antigens. Three VLR genes have been identified in lampreys (VLRA, VLRB, and VLRC), but only two (VLRA and VLRB) have been found in hagfish. Here, we identified and characterized a third hagfish VLR gene. Our analysis indicates that the third hagfish VLR is the ortholog of lamprey VLRA, while the previously identified hagfish “VLRA” is the counterpart of lamprey VLRC. The demonstration of three orthologous VLR genes in hagfish and lampreys suggests that this anticipatory receptor system evolved in a common ancestor of the two jawless vertebrate lineages ∼480 Mya.