Previous studies showed that the vertebrate ABCA subfamily, one subgroup of the ATP-binding-cassette superfamily, has evolved rapidly in terms of gene duplication and loss. To further uncover the evolutionary history of the ABCA subfamily, we characterized ABCA members of two amphioxus species (Branchiostoma floridae and B. belcheri), the closest living invertebrate relative to vertebrates. Phylogenetic analysis indicated that these two species have the same set of ABCA genes (both containing six members). Five of these genes have clear orthologs in vertebrate, including one cephalochordate-specific duplication and one vertebrate-specific duplication. In addition, it is found that human orthologs of amphioxus ABCA1/4/7 and its neighboring genes mainly localize on chromosome 1, 9, 19 and 5. Considering that most of analyzed amphioxus genes have clear orthologs in zebrafish, we conclude these four human paralogous regions might derive from a common ancestral region by genome duplication occurred prior to teleost/tetrapod split. Therefore, the present results provide new evidence for 2R hypothesis.
"The 3 genes on scaffold 149 show close homology to the one on scaffold 152 and the two genes on scaffold 89 respectively, both in sequence and gene structure (Supplemental Table1). Since the B. floridae genome database contains sequences of two haplotypes (Li et al., 2007), we suggest that the 6 genes might represent different alleles of three independent genes. "
[Show abstract][Hide abstract] ABSTRACT: The secreted Wnt signaling inhibitor Dickkopf1 (Dkk1) plays key role in vertebrate head induction. Its receptor Kremen synergizes with Dkk1 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, BbDkk1/2/4 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, BbDkk1/2/4 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 Kremen1-4 and Kremen-like 1-3, respectively. In B. belcheri, Kremen1 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, BbDkk1/2/4 can strongly inhibit Wnt signaling, while BbDkk3, BbKremen1 and BbKremen3 can not. No co-operative effect was observed between amphioxus Dkk1/2/4 and Kremens, suggesting that the interaction between Dkk and Kremen likely originated later during evolution.
Journal of Genetics and Genomics 09/2010; 37(9):637-45. DOI:10.1016/S1673-8527(09)60082-5 · 3.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this study, we present a computational algorithm of self-excitation on BSN that is based both on the equations of two-dimensional disk model of beam, which include a spread of transverse component of electron velocities, and linear equations at the frequency W<sub>-1</sub> with variable coefficients.
Vacuum Electronics, 2003 4th IEEE International Conference on; 06/2003
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