RT Journal
A1 Huang, Shengfeng
A1 Yuan, Shaochun
A1 Guo, Lei
A1 Yu, Yanhong
A1 Li, Jun
A1 Wu, Tao
A1 Liu, Tong
A1 Yang, Manyi
A1 Wu, Kui
A1 Liu, Huiling
A1 Ge, Jin
A1 Yu, Yingcai
A1 Huang, Huiqing
A1 Dong, Meiling
A1 Yu, Cuiling
A1 Chen, Shangwu
A1 Xu, Anlong
T1 Genomic analysis of the immune gene repertoire of amphioxus reveals extraordinary innate complexity and diversity
JF Genome Research 
JO Genome Research 
YR 2008 
FD July 01 
DO 10.1101/gr.069674.107 
UL http://genome.cshlp.org/content/early/2008/06/18/gr.069674.107.abstract 
AB It has been speculated that before vertebrates evolved somatic diversity-based adaptive immunity, the germline-encoded diversity of innate immunity may have been more developed. Amphioxus occupies the basal position of the chordate phylum and hence is an important reference to the evolution of vertebrate immunity. Here we report the first comprehensive genomic survey of the immune gene repertoire of the amphioxus Branchiostoma floridae. It has been reported that the purple sea urchin has a vastly expanded innate receptor repertoire not previously seen in other species, which includes 222 toll-like receptors (TLRs), 203 NOD/NALP-like receptors (NLRs), and 218 scavenger receptors (SRs). We discovered that the amphioxus genome contains comparable expansion with 71 TLR gene models, 118 NLR models, and 270 SR models. Amphioxus also expands other receptor-like families, including 1215 C-type lectin models, 240 LRR and IGcam-containing models, 1363 other LRR-containing models, 75 C1q-like models, 98 ficolin-like models, and hundreds of models containing complement-related domains. The expansion is not restricted to receptors but is likely to extend to intermediate signal transducers because there are 58 TIR adapter-like models, 36 TRAF models, 44 initiator caspase models, and 541 death-fold domain-containing models in the genome. Amphioxus also has a sophisticated TNF system and a complicated complement system not previously seen in other invertebrates. Besides the increase of gene number, domain combinations of immune proteins are also increased. Altogether, this survey suggests that the amphioxus, a species without vertebrate-type adaptive immunity, holds extraordinary innate complexity and diversity.