Published Book on Amphioxus Immunity

Research Project of Amphioxus Immune System

Introduction

Cephalochordate amphioxus is one of the closest extant relative of vertebrates and has been viewed as a “living fossil”. Although lancelets split from vertebrates more than 520 million years ago, their genomes hold clues about evolution, particularly how vertebrates have employed old genes for new functions.It is also a significant and promising research model in the study of the vertebrate evolution.

The anatomy of adult amphioxus.Lancelets grow up to about 5 centimetres (2.0 in) long, reaching 7 centimetres (2.8 in) at the longest. They have a translucent, somewhat fish-like body, but without any paired fins or other limbs. A relatively poorly developed tail fin is present, but they are not especially good swimmers. While they do possess some cartilage-like material stiffening the gill slits, mouth, and tail, they have no true skeleton.

Our Interest on Amphioxus Immune System
Since year 2000, our lab began to use amphioxus in comparative study, mainly focusing on comparative immunology. So far, eight cDNA libraries of different tissues and developmental stages have been constructed. More than 20,000 cDNA clones from these cDNA libraries have been sequenced and some of those crucial immune-related genes have been carefully studied. Recently, by taking advantage of the 454-pyrosequencing technology, we have sequenced approximately 400,000 EST from Chinese amphioxus, which lays a foundation for the upcoming Chinese Amphioxus Genome Project. We also participate in the Genome Project of amphioxus B. floridae and dedicate to the annotation of the immune gene repertoire. So far, we have established various primary technical platforms for amphioxus, including in situ hybridization, large scale sequencing, pathogen infection, microinjection, primary cell culture, protein expression and interaction and so on. Until now, we have obtained 4 patents and have published 11 SCI papers.

Research Areas---some interesting results

A comparison of the function and regulation of DR-mediated signaling pathways in Drosophila, amphioxus, and humans. We suggest that the original formation of the extrinsic apoptotic pathway in amphioxus was a result of the emergence of DRs that co-opted the FADD–caspase-8 complex from the ancestral IMD and Toll pathways, whereas the emergence of multifunctional TRADD provided the coordination between apoptosis and gene activation when invertebrates evolved into vertebrates. IKK, inhibitor of NF-kB kinase.

 A schematic comparison of TLR, NLR, RLH, and TNF pathways between vertebrates and amphioxus. Dashed lines indicate that the pathway has no functional evidence as yet. The colors used for different domains have no special meaning.

Transmission electron microscopic views of the lymphocyte-like cells in follicle-associated epithelium of amphioxus gill. (A) Follicleassociated epithelium cells in the gill contained follicle (F) rootlet (R), and cilia (C). Magnification 29000. (B) The lymphocyte-like cells contained large nuclei (N) with heterochromatin forming a peripheral rim adjacent to the nuclear envelope. Magnification 48000. (C) Under the FAE of normal amphioxus gill, lots of lymphocyte-like cells (L) were seen. The cells contained large nuclei (N) with heterochromatin forming a peripheral rim adjacent to the nuclear envelope. Magnification 5800. (D) At the same magnification, after the microbial challenge, the lymphocyte-like cells were bigger than those of normal cells.

 A schematic of the evolution of the complement system. (Solid line) The pathway has experimental evidence; (dashed lines) no experimental support; the existence of the item or pathway is not verified; (*) amphiMASP1/3 gene can produce two proteins, MASP1 and MASP3; (**) amphioxus contains the most abundant CCP domains, see Supplemental Table S1; (***) the human C1q proteins recognize antibody, while the lamprey C1q serves as a lectin.