HES1 inhibits cycling of hematopoietic progenitor cells via DNA binding.
Notch signaling is implicated in stem cell self-renewal, differentiation, and other developmental processes, and the Drosophila hairy and enhancer of split (HES) 1 basic helix-loop-helix protein is a major downstream effector in the Notch pathway. We found that HES1 was expressed at high levels in the hematopoietic stem cell (HSC)-enriched CD34+/[CD38/Lin](- /low) subpopulation but at low levels in more mature progenitor cell populations. When CD34+ cells were cultured for 1 week, the level of HES1 remained high in the CD34+ subset that had remained quiescent during ex vivo culture but was reduced in CD34+ cells that had divided. To investigate the effects of HES1 in human and mouse hematopoietic stem-progenitor cells (HSPCs), we constructed conditional lentiviral vectors (lentivectors) to introduce transgenes encoding either wild-type HES1 or a mutant lacking the DNA-binding domain (BHES1). We found that lentivector-mediated HES1 expression in CD34+ cells inhibited cell cycling in vitro and cell expansion in vivo, associated with upregulation of the cell cycle inhibitor p21(cip1/Waf1) (p21). The HES1 DNA-binding domain was required for these actions. HES1 did not induce programmed cell death or alter differentiation in HSPCs, and while short-term repopulating activity was reduced in HES1-transduced mouse and human cells, long-term reconstituting HSC function was preserved. Our data characterize the complex, cell context-dependent actions of HES1 as a major downstream Notch signaling regulator of HSPC function.
Yu
Xiaobing
X
The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Department of Oncology, Bunting-Blaustein Cancer Research Building, Room 2M44, 1650 Orleans Street, Baltimore, Maryland 21231, USA.
Alder
Jonathan K
JK
Chun
Jong Ho
JH
Friedman
Alan D
AD
Heimfeld
Shelly
S
Cheng
Linzhao
L
Civin
Curt I
CI
D000818:Animals; D018952:Antigens, CD34 / Q000378:metabolism; D017209:Apoptosis; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle; D002454:Cell Differentiation; D049109:Cell Proliferation; D003114:Colony-Forming Units Assay; D004247:DNA / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D005822:Genetic Vectors; D006085:Graft Survival; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000276:immunology / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D000072056:Transcription Factor HES-1; D014161:Transduction, Genetic
D018952:Antigens, CD34; D051792:Basic Helix-Loop-Helix Proteins; D004247:DNA; D018398:Homeodomain Proteins; D012333:RNA, Messenger; D000072056:Transcription Factor HES-1; C489734:Hes1 protein, mouse; C078493:HES1 protein, human