Identification of a novel DNA sequence differentially expressed between normal human CD34+CD38hi and CD34+CD38lo...

We have applied the recently developed differential display method to extend the molecular characterization of the less mature CD34+CD38lo bone marrow progenitors in comparison with the CD34+CD38hi cells to better understand their functional differences. Immunomagnetic enrichment of CD34+ cells followed by flow cytometry was used to isolate CD34+CD38lo and CD34+CD38hi cells from human organ donor bone marrow. A limited set of the poly A+ RNA sequences present in these two cell populations was amplified by a combination of reverse transcription with an anchored oligo dT-based primer and polymerase chain reaction with the same oligo dT primer and arbitrary decamers. A radioactive tracer allowed these sequences to be displayed as a series of bands on a denaturing polyacrylamide gel. Eight bands were chosen that appeared in multiple displays to represent gene sequences differentially expressed between CD34+CD38hi and CD34+CD38lo cells. Comparison of the sequences with public DNA sequence databases available identified one sequence as myeloperoxidase. Two other clones matched sequence fragments of unknown function, whereas the remaining five are novel sequences not present in existing databases. The relative level of expression of all of the sequences was tested by an independent reverse transcriptase-polymerase chain reaction with sequence-specific oligonucleotide primers. The lower level of myeloperoxidase mRNA in CD34+CD38lo cells was confirmed, as was the higher expression of the novel sequence 345. Sequence 345 expression is highest in CD34+CD38- cells and decreases with increased CD38 expression. It is expressed in negligible amounts in hematopoietic cell lines and other sources of human tissue, suggesting it may have a functional role in normal hematopoiesis.