Smad family proteins are identified as intracellular signal mediators of the TGF-β superfamily.In this study,we identified two novel members of the Smad family,termed as AmphiSmad1/5/8 and AmphiSmad4,from Chinese amphioxus.Both AmphiSmad1/5/8 and AmphiSmad4 showed a typical domain structure of Smad proteins consisting of conserved MH1 and MH2 domains.Phylogenetic analysis placed AmphiSmad1/5/8 in the Smad1,5 and 8 subgroup of the R-Smad subfamily,and AmphiSmad4 in the Co-Smad subfamily.The spatial and temporal gene expression patterns of AmphiSmad1/5/8 and AmphiSmad4 showed that they may be involved in the embryonic development of notochord,myotome and alimentary canal,and may help to establish the specification of dorsal-ventral axis of amphioxus.Moreover,AmphiSmad1/5/8 and AmphiSmad4 showed extensive distribution in all adult tissues examined,suggesting that these two genes may play important roles in the morphogenesis of a variety of tissues especially notochord and gonad.
Vertebrate RACK1 plays a key role in embryonic development. This paper described the cloning, phy- logenetic analysis and developmental expression of AmphiRACK1, the RACK1 homologous gene in amphioxus. Phylogenetic analysis indicated that amphioxus RACK1 was located at the base of verte- brate clade. AmphiRACK1 expression in lithium-treated embryos was also examined. During embryonic development, AmphiRACK1 was expressed strongly in cerebral vesicles, neural tubes and somites. In lithium-treated embryos, the segmental expression of AmphiRACK1 in somites became blurry and decreased. Its expression in cerebral vesicles and neural tubes was also weaker or disappeared. In the adult animal, AmphiRACK1 transcripts were detected in the epithelium of midgut diverticulus and gut, wheel organ, gill blood vessels and testis.
HUANG XiangWei1, ZHANG Wei1, LI XinYi1, ZHANG XiaoHui1, LI BaoJun1, MAO BingYu2 & ZHANG HongWei1 1 Institute of Developmental Biology, College of Life Science
Amphioxus is an important animal model for phylogenetic analysis,including comparative immunology.Exploring the immune system in amphioxus contributes to our understanding of the origin and evolution of the vertebrate immune system.We investigated the amphioxus immune system using ultrastructural examination and in situ hybridization.The expression patterns of TLR1(toll-like receptor 1),C1Q(complement component 1,q subcomponent),ECSIT(evolutionarily conserved signaling intermediate in Toll pathways),SoxC,DDAHa(Dimethylarginine dimethylaminohydrolase a),and NOS(nitric oxide synthase) show that these genes play key roles in amphioxus immunity.Our results suggest that the epidermis and alimentary canal epithelium may play important roles in immune defense,while macrophages located in the coelom and so-called lymph spaces may also be crucial immune cells.
LIN YuShuangCHEN DongYanZHANG WeiCAI ZhaoPingCHEN ZhongKeZHANG NingMAO BingYuZHANG HongWei
Myocyte enhancer factor 2 proteins are members of MADS family of transcription factors, which can control the expression of muscle-specific genes in vertebrates. However, not all Mef2 genes are es-sential for muscle development in invertebrates. Here we have isolated a full-length cDNA from am-phioxus, designated AmphiMef2. The predicted amino acid sequence has highly conserved MADS and MEF2 domains, showing higher identity with the corresponding regions of its homologues in verte-brates than those in invertebrates. Results from whole-mount in situ hybridization show that the ex-pression of AmphiMef2 initially appears in the presomitic mesoderm at early neurula stage, then the transcripts are detected in both the somites and the unsegmented presomitic mesoderm. At 36 h larval stage, the expression is only detected in the posterior somites. By 48 h larval stage, the expression is shifted to the preoral pit (a homologous organ to the vertebrate adenohypophysis) and persists until at least 72 h larval stage. The results suggest that AmphiMef2 may be not only involved in the myogenesis but also the development or function of the preoral pit in amphioxus.
