The secreted Wnt signaling inhibitor Dickkopfl （Dkkl） plays key role in vertebrate head induction. Its receptor Kremen synergizes with Dkkl in Wnt inhibition. Here we have carried out expression and functional studi...The secreted Wnt signaling inhibitor Dickkopfl （Dkkl） plays key role in vertebrate head induction. Its receptor Kremen synergizes with Dkkl in Wnt inhibition. Here we have carried out expression and functional studies of the Dkk and Kremen genes in amphioxus （Branchiostoma belcheri）. During embryonic and larval development, BbDkkl/2/4 is expressed in the posterior mesoendoderm, anterior somatic mesoderm and the pharyngeal regions. Its expression becomes restricted to the pharyngeal region on the left side at larval stages. In 45 h larvae, BbDkkl/2/4 is expressed specifically in the cerebral vesicle. BbDkk3 was only detected at larval stages in the mid-intestine region. Seven Kremen related genes were identified in the genome of the Florida amphioxus （Branchiostoma floridae）, clustered in 4 scaffolds, and are designated Kremenl-4 and Kremen-like 1-3, respectively. In B. belcheri, Kremenl is strongly expressed in the mesoendoderm during early development and Kremen3 is expressed asymmetrically in spots in the larval pharyngeal region. In luciferase reporter assays, BbDkkl/2/4 can strongly inhibit Wnt signaling, while BbDkk3, BbKremenl and BbKremen3 can not. No co-operative effect was observed between amphioxus Dkkl/2/4 and Kremens, suggesting that the interaction between Dkk and Kremen likely originated later during evolution.展开更多
基金supported by the grant from the Innovation Project of Chinese Academy of Sciences (No. KSCX2-YW-R-090)
文摘The secreted Wnt signaling inhibitor Dickkopfl （Dkkl） plays key role in vertebrate head induction. Its receptor Kremen synergizes with Dkkl in Wnt inhibition. Here we have carried out expression and functional studies of the Dkk and Kremen genes in amphioxus （Branchiostoma belcheri）. During embryonic and larval development, BbDkkl/2/4 is expressed in the posterior mesoendoderm, anterior somatic mesoderm and the pharyngeal regions. Its expression becomes restricted to the pharyngeal region on the left side at larval stages. In 45 h larvae, BbDkkl/2/4 is expressed specifically in the cerebral vesicle. BbDkk3 was only detected at larval stages in the mid-intestine region. Seven Kremen related genes were identified in the genome of the Florida amphioxus （Branchiostoma floridae）, clustered in 4 scaffolds, and are designated Kremenl-4 and Kremen-like 1-3, respectively. In B. belcheri, Kremenl is strongly expressed in the mesoendoderm during early development and Kremen3 is expressed asymmetrically in spots in the larval pharyngeal region. In luciferase reporter assays, BbDkkl/2/4 can strongly inhibit Wnt signaling, while BbDkk3, BbKremenl and BbKremen3 can not. No co-operative effect was observed between amphioxus Dkkl/2/4 and Kremens, suggesting that the interaction between Dkk and Kremen likely originated later during evolution.
