| Summary: | 碩士 === 國立中山大學 === 海洋資源學系研究所 === 92 === The strategy of producing expressed sequence tags (ESTs) is greatly used for gene mining and analysis of gene expression. An EST is a partial and single-pass sequence generated from a complementary DNA (cDNA) library by random selection, and is typically about 400 to 600 bases. Here, we constructed and analyzed a brain EST library from 10-day-old (10-day posthatching) tilapia, Oreochromis mossambicus, to assist in investigating the relation between brain neural development and neuroendocrine and brain sexual differentiation during the critical period of sexual dimorphism by understanding brain gene expression, and, furthermore, to find genes that are important in brain but are unknown nowadays. A total 1,124 ESTs were in the 10-day-old tilapia brain EST library, and 1,092 ones were readable, and after discarding one that is too short (<200bp) or is totally vector sequence from the readable ESTs, 1,084 ESTs were assembled and then analyzed. 108 contigs from 261 ESTs, 20 kinds of similar sequences from 40 ESTs, and 783 singletons from the 1,084 ESTs were found, and after aligning in turn with the non-redundant (nr) protein database, nr nucleotide database and EST database dbEST supported by the National Center of Biotechnology Information (NCBI) using Basic Local Alignment Search Tool (BLAST) programs BLASTx (translated nucleotide-protein alignment) and BLASTn (nucleotide-nucleotide alignment) respectively, the results are as follows: 57 and 16 contigs including 146 and 37 ESTs matched with sequences in the nr protein and nr nucleotide databases respectively, and the rest 35 contigs including 78 ESTs were novel sequences; nine, one and two kinds of the similar sequences including 18, two and four ESTs matched with sequences in the nr protein, nr nucleotide and dbEST databases respectively, and the rest eight kinds of the similar sequences including 16 ESTs were novel sequences; 309, 52 and 47 singletons matched with sequences in the nr protein, nr nucleotide and dbEST databases respectively, and the rest 375 singletons were novel sequences. As a whole, the most functions of proteins that the contigs, similar kinds of sequences, and singletons from the 10-day-old tilapia brain EST library matched with were binding and transport activity. Recently, many researchers provide reasonable explanations for evolution, relation between genomic polymorphism and drug effects, and isoforms presentation of known proteins by collecting ESTs from open EST databases or from EST libraries they constructed, and we believe that this 10-day-old tilapia brain EST library can promote our ability to resolve questions about the topic we are researching in.
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