CCCTC-binding factor is essential for the mouse hematopoietic stem cell maintenance and quiescence

Hematopoiesis is a series of lineage differentiation programs initiated from hematopoietic stem cells (HSCs) in the bone marrow (BM). To maintain lifelong hematopoiesis, the pool of HSCs is precisely maintained by diverse molecular mechanisms. CCCTC-binding factor (CTCF) is a DNA-binding zinc-finger protein which regulates its target gene expression by organizing higher order chromatin structures. Currently, the role for CTCF in controlling HSC homeostasis is unknown. By using a tamoxifen-induced CTCF conditional knockout mouse system, we demonstrate that CTCF is a critical regulator for the homeostatic maintenance of adult HSCs by retaining HSC cell cycle quiescence. Acute systemic CTCF ablation leads to a severe BM failure and rapid shrinkage of multiple c-Kithi progenitor populations, including Sca-1+ HSCs in adult mice. Similarly, a hematopoietic system-confined CTCF depletion elicits an acute loss of HSCs and highly increased mortality. Mixed BM chimeras reconstituted together with the supporting BM reveal that CTCF deficiency-mediated HSC depletion is a cell-autonomous effect. Although c-Kithi myeloid progenitors were severely reduced after ablating Ctcf gene, c-Kitint common lymphoid progenitors and their progenies were less affected by the lack of CTCF. Whole transcriptome analyses show that CTCF deficiency results in an enhanced expression of the cell cycle-promoting program and CTCF-depleted HSCs express higher level of reactive oxygen species (ROS). Importantly, in vivo treatment with the antioxidant partially rescued the c-Kithi population and their quiescence. We conclude that CTCF is a pivotal player in maintaining adult HSC pool likely through regulating ROS-dependent HSC quiescence.

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Kim TG, Kim S, Jung S, Kim M, Yang B, Lee MG, Kim HP