Identification of up-regulated genes in amphioxus neurula and the expression of AmphiFABP

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Amphioxus is a good model organism for understanding the origin and developmental mechanism of vertebrates owing to its important evolutionary position. During the developmental process of amphioxus embryo, the neurula is a crucial stage because of neural tube and notochord formation as well as somite emergence at this stage. In order to isolate genes up-regulated at the neurula stage, we constructed an 11-hour neurula subtracted cDNA library of amphioxus Branchiostoma belcheri and sequenced 204 ESTs representing 82 contigs. Comparative analysis revealed that 55% of those contigs were homologous to various known genes while 45% of them had no significant similarity to any known genes. Those observations imply that the un-identified ESTs might contain some new genes which are involved in the development of amphioxus neurula. Real-time quantitative PCR (RTqPCR) indicated that the expression levels of 14 genes are up-regulated after gastrulation among 20 assayed genes. Of those up-regulated genes, we further cloned and sequenced the full-length of fatty acid binding protein gene (AmphiFABP). The deduced protein sequence was similar to that of vertebrate brain FABP and heart FABP, and in situ hybridization displayed that AmphiFABP, similar to their vertebrate cognates, was expressed not only in nervous system but also in embryonic somite and gut, hinting a multifunctional property of AmphiFABP in amphioxus.