Roles for c-Myc in self-renewal of hematopoietic stem cells.
Notch and HOXB4 have been reported to expand hematopoietic stem cells (HSCs) in vitro. However, their critical effector molecules remain undetermined. We found that the expression of c-myc, cyclin D2, cyclin D3, cyclin E, and E2F1 was induced or enhanced during Notch1- or HOXB4-induced self-renewal of murine HSCs. Since c-Myc can act as a primary regulator of G(1)/S transition, we examined whether c-Myc alone can induce self-renewal of HSCs. In culture with stem cell factor, FLT3 ligand, and IL-6, a 4-hydroxytamoxifen-inducible form of c-Myc (Myc/ERT) enabled murine Lin(-)Sca-1(+) HSCs to proliferate with the surface phenotype compatible with HSCs for more than 28 days. c-Myc activated by 4-hydroxytamoxifen augmented telomerase activities and increased the number of CFU-Mix about 2-fold in colony assays. Also, in reconstitution assays, HSCs expanded by c-Myc could reconstitute hematopoiesis for more than 6 months. As for the mechanism of c-myc induction by Notch1, we found that activated forms of Notch1 (NotchIC) and its downstream effector recombination signal-binding protein-J kappa (RBP-VP16) can activate the c-myc promoter through the element between -195 bp and -161 bp by inducing the DNA-binding complex. Together, these results suggest that c-Myc can support self-renewal of HSCs as a downstream mediator of Notch and HOXB4.
Satoh
Yusuke
Y
Department of Hematology and Oncology, Osaka University Graduate School of Medicine, 2-2, Yamada-oka, Suita, Osaka 565-0871, Japan.
Matsumura
Itaru
I
Tanaka
Hirokazu
H
Ezoe
Sachiko
S
Sugahara
Hiroyuki
H
Mizuki
Masao
M
Shibayama
Hirohiko
H
Ishiko
Eri
E
Ishiko
Jun
J
Nakajima
Koichi
K
Kanakura
Yuzuru
Y
D000818:Animals; D002455:Cell Division; D019938:Cyclin D1 / Q000235:genetics; D006412:Hematopoietic Stem Cells / Q000502:physiology*; D018398:Homeodomain Proteins / Q000502:physiology; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D011401:Promoter Regions, Genetic; D016271:Proto-Oncogene Proteins c-myc / Q000502:physiology*; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface / Q000502:physiology; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000494:pharmacology; D014157:Transcription Factors / Q000502:physiology
C090460:HOXB4 protein, human; D018398:Homeodomain Proteins; C513262:Hoxb4 protein, mouse; C497761:NOTCH1 protein, human; C497762:Notch1 protein, mouse; D016271:Proto-Oncogene Proteins c-myc; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface; D014157:Transcription Factors; D013629:Tamoxifen; D019938:Cyclin D1; C016601:afimoxifene