Expression of basic helix-loop-helix transcription factors in explant hematopoietic progenitors.
The basic helix-loop-helix (bHLH) transcription factors form heterodimers and control steps in cellular differentiation. We have studied four bHLH transcription factors, SCL, lyl-1, E12/E47, and ld-1, in individual lineage-defined progenitors and hematopoietic growth factor-dependent cell lines, evaluating mRNA expression and the effects of growth factors and cell cycle phase on this expression. Single lineage-defined progenitors selected from early murine colony starts and grown under permissive conditions were analyzed by RT-PCR. SCL and E12/E47 were expressed in the vast majority of tri-, bi-, and unilineage progenitors of erythroid, macrophage, megakaryocyte, and neutrophil lineages. Expression for E12/E47 was not seen in unilineage megakaryocyte and erythroid or bilineage neutrophil/mast cell progenitors. Lyl-1 showed a more restricted pattern of expression, although expression was seen in some bi- and unilineage progenitors. No expression was detected in erythroid, erythroid-megakaryocyte-macrophage, macrophage-neutrophil, macrophage, or megakaryocytic progenitors. Id-1, an inhibitory bHLH transcription factor, was also widely expressed in all bi- and unilineage progenitors; only the trilineage erythroid-megakaryocyte-macrophage progenitors failed to show expression. Expression of these factors within a progenitor class was generally heterogeneous, with some progenitors showing expression and some not. This was seen even when two sister cells from the same colony start were analyzed. Id-1, but not E12/E47, mRNA was increased in FDC-P1 and MO7E hematopoietic cell lines after exposure to IL-3 or GM-CSF. Id-1, E12, and lyl-1 showed marked variation at different points in cell cycle in isoleucine-synchronized FDC-P1 cells. These results suggest that SCL, lyl-1, E12/E47, and Id-1 are important in hematopoietic progenitor cell regulation, and that their expression in hematopoietic cells varies in response to cytokines and/or during transit through cell cycle.
Quesenberry
P J
PJ
Cancer Center, University of Massachusetts Medical Center, Worcester 01605, USA.
Iscove
N N
NN
Cooper
C
C
Brady
G
G
Newburger
P E
PE
Stein
G S
GS
Stein
J S
JS
Reddy
G P
GP
Pearson-White
S
S
D000818:Animals; D015152:Blotting, Northern; D002478:Cells, Cultured; D018507:Gene Expression Regulation, Developmental; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000378:metabolism; D006133:Growth Substances / Q000378:metabolism; D018257:Helix-Loop-Helix Motifs; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D006801:Humans; D007377:Interleukin-3 / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D006133:Growth Substances; D007377:Interleukin-3; D012333:RNA, Messenger; D014157:Transcription Factors; D016178:Granulocyte-Macrophage Colony-Stimulating Factor