Identification, characterization, and mapping of expressed sequence tags from an embryonic zebrafish heart cDNA library

The generation of expressed sequence tags (ESTs) has proven to be a rapid a nd economical approach by which to identify and characterize expressed gene s. We generated 5102 ESTs from a 3-d-old embryonic zebrafish heart cDNA lib rary. Of these, 57.6% matched to known genes, 14.2% matched only to other E STs, and 27.8% showed no match to any ESTs or known genes. Clustering of al l ESTs identified 359 unique clusters comprising 1771 ESTs, whereas the rem aining 3331 ESTs did not cluster. This estimates the number of unique genes identified in the data set to be approximately 3690. A total of 1242 uniqu e known genes were used to analyze the gene expression patterns in the zebr afish embryonic heart. These were categorized into seven categories on the basis of gene function. The largest class of genes represented those involv ed in gene/protein expression (25.9% of known transcripts). This class was followed by genes involved in metabolism (18.7%), cell structure/motility ( 16.4%), cell signaling and communication (9.6%), cell/organism defense (7.1 %) and cell division (4.4%). Unclassified genes constituted the remaining 1 7.91%. Radiation hybrid mapping was performed for 102 ESTs and comparison o f map positions between zebrafish and human identified new synteny groups. Continued comparative analysis will be useful in defining the boundaries of conserved chromosome segments between zebrafish and humans, which will fac ilitate the transfer of genetic information between the two organisms and i mprove our understanding of vertebrate evolution.