Research Project of Amphioxus Immune
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
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.