Sequence Analysis of 47 Low-abundance ESTs Expressed in Early Human Embryo

The availability of high quality cDNA libraries has proven essential to positional gene cloning efforts differential gene expression studies and EST sequencing/mapping projects.In order to isolate and identify new genes expressed during early human development a 3-week-old human embryo cDNA library was constructed and a pre-screening procedure was used to select cDNAs corresponding to low abundance mRNAs. 6 508 clones were hybridized with a mixture of cDNA probes. Approximately 1 677 clones (26%) did not hybridize with the cDNA probes and represent low abundance mRNAs as well as empty vectors.Partial sequences were generated from one or both end of 47 low abundance cDNA clones and the sequences comparisons with genetic databases revealed that 38.3% of them was annotated human genes 10.6% was highly similar to those from either human or other species 40.4% was partial sequence matched with ESTs that had already been detected and 8.5% of the cDNAs appeared to be unknown in the genetic databases.