Published online
doi:10.1084/jem.20060750
The Journal of Experimental Medicine, Vol. 204, No. 4, 715-722
The Rockefeller University Press, 0022-1007 $30.00
© Tadokoro et al.
De novo DNA methyltransferase is essential for self-renewal, but not for differentiation, in hematopoietic stem cells
Yuko Tadokoro1,
Hideo Ema1,
Masaki Okano2,
En Li3, and
Hiromitsu Nakauchi1
1 Laboratory of Stem Cell Therapy, Center for Experimental Medicine, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan
2 Laboratory for Mammalian Epigenetic Studies, Center for Developmental Biology, Institute of Physical and Chemical Research (RIKEN), Kobe 650-0047, Japan
3 Novartis Institutes for Biomedical Research, Cambridge, MA 02139
CORRESPONDENCE Hiromitsu Nakauchi: nakauchi{at}ims.u-tokyo.ac.jp
DNA methylation is an epigenetic modification essential for development. The DNA methyltransferases Dnmt3a and Dnmt3b execute de novo DNA methylation in gastrulating embryos and differentiating germline cells. It has been assumed that these enzymes generally play a role in regulating cell differentiation. To test this hypothesis, we examined the role of Dnmt3a and Dnmt3b in adult stem cells. CD34–/low, c-Kit+, Sca-1+, lineage marker– (CD34– KSL) cells, a fraction of mouse bone marrow cells highly enriched in hematopoietic stem cells (HSCs), expressed both Dnmt3a and Dnmt3b. Using retroviral Cre gene transduction, we conditionally disrupted Dnmt3a, Dnmt3b, or both Dnmt3a and Dnmt3b (Dnmt3a/Dnmt3b) in CD34– KSL cells purified from mice in which the functional domains of these genes are flanked by two loxP sites. We found that Dnmt3a and Dnmt3b function as de novo DNA methyltransferases during differentiation of hematopoietic cells. Unexpectedly, in vitro colony assays and in vivo transplantation assays showed that both myeloid and lymphoid lineage differentiation potentials were maintained in Dnmt3a-, Dnmt3b-, and Dnmt3a/Dnmt3b-deficient HSCs. However, Dnmt3a/Dnmt3b-deficient HSCs, but not Dnmt3a- or Dnmt3b-deficient HSCs, were incapable of long-term reconstitution in transplantation assays. These findings establish a critical role for DNA methylation by Dnmt3a and Dnmt3b in HSC self-renewal.

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