日時：	2022年12月13日（火）16：00～17：00
場所：	京都大学医生物学研究所　医生研2号館1階セミナー室（104室） Seminar Room 104, 1st floor of No.2 Bldg. of LiMe Inst.
演者：	Dr. Ryo Morimoto Dept. Developmental Immunology, Max Planck Institute of Immunology and Epigenetics, Germany.
演題：	The evolution of adaptive immunity. A lesson from lamprey. Cytidine deaminase-based anticipatory antigen receptor assembly in jawless vertebrate.

講演要旨

Diverging 500 million years ago, jawed and jawless vertebrates independently evolved different adaptive immune systems. Comparative immunology has shown that, although differing in their molecular components, striking functional parallels can be drawn between the two clades. Lampreys also possess T- and B-lymphocytes, expressing and assembling their leucine-rich repeat-based receptors in a lineage-specific manner (VLRA and C in T cells, and VLRB in B cells). While B cells are abundant in the blood and typhlosole, T cells are most prevalent in structures of the gill basket. This region includes a thymus-like microenvironment (the thymoid) at the gill tips where maturation and repertoire selection are thought to take place.

The seminar focuses on the alternative adaptive immune system of lampreys in their evolutionary context, with particular emphasis on the genetic basis of development and evolution of lymphocytes and their microenvironmental requirements. With the possibility of in vitro fertilization and rearing of lamprey in the laboratory environment, the ontogeny of the events underlying the lamprey immune system was determined with precisely staged samples. In proof-of-principle experiments, the CRISPR/Cas9 system can be successfully employed to disrupt specific genes, such as cytidine deaminase 2 (CDA2), a member of AID/APOBEC family in jawless vertebrate. With direct genetic evidence, it has been shown that CDA2 mutants displayed no VLRB assembly, without compromising the survival of the larvae in the analyzed timeframe. CDAs are proven to be involved in lineage-specific VLR receptor assembly and therefore critical for lymphocyte development. These results suggest a way forward to dissect the cellular and molecular components of the unique lamprey immune system. Based on current observations, I discuss about the evolutionary trajectory of random assembly of anticipatory antigen receptors in vertebrate adaptive immune systems.

 

Contact: Masaki Miyazaki, Dept. Immunology

Institute for Life and Medical Sciences, Kyoto University

E-mail: mmiyazaki*infront.Kyoto-u.ac.jp（*を＠へ変えてください）