The transcriptome of human CD34+ hematopoietic stem-progenitor cells.

Studying gene expression at different hematopoietic stages provides insights for understanding the genetic basis of hematopoiesis. We analyzed gene expression in human CD34(+) hematopoietic cells that represent the stem-progenitor population (CD34(+) cells). We collected >459,000 transcript signatures from CD34(+) cells, including the de novo-generated 3' ESTs and the existing sequences of full-length cDNAs, ESTs, and serial analysis of gene expression (SAGE) tags, and performed an extensive annotation on this large set of CD34(+) transcript sequences. We determined the genes expressed in CD34(+) cells, verified the known genes and identified the new genes of different functional categories involved in hematopoiesis, dissected the alternative gene expression including alternative transcription initiation, splicing, and adenylation, identified the antisense and noncoding transcripts, determined the CD34(+) cell-specific gene expression signature, and developed the CD34(+) cell-transcription map in the human genome. Our study provides a current view on gene expression in human CD34(+) cells and reveals that early hematopoiesis is an orchestrated process with the involvement of over half of the human genes distributed in various functions. The data generated from our study provide a comprehensive and uniform resource for studying hematopoiesis and stem cell biology.