Secreted nuclear protein DEK regulates hematopoiesis through CXCR2 signaling
Maegan L. Capitano, Nirit Mor-Vaknin, Anjan K. Saha, Scott Cooper, Maureen Legendre, Haihong Guo, Rafael Contreras-Galindo, Ferdinand Kappes, Maureen A. Sartor, Christopher T. Lee, Xinxin Huang, David M. Markovitz, Hal E. Broxmeyer
Maegan L. Capitano, Nirit Mor-Vaknin, Anjan K. Saha, Scott Cooper, Maureen Legendre, Haihong Guo, Rafael Contreras-Galindo, Ferdinand Kappes, Maureen A. Sartor, Christopher T. Lee, Xinxin Huang, David M. Markovitz, Hal E. Broxmeyer
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Research Article Hematology

Secreted nuclear protein DEK regulates hematopoiesis through CXCR2 signaling

Abstract

The nuclear protein DEK is an endogenous DNA-binding chromatin factor regulating hematopoiesis. DEK is one of only 2 known secreted nuclear chromatin factors, but whether and how extracellular DEK regulates hematopoiesis is not known. We demonstrated that extracellular DEK greatly enhanced ex vivo expansion of cytokine-stimulated human and mouse hematopoietic stem cells (HSCs) and regulated HSC and hematopoietic progenitor cell (HPC) numbers in vivo and in vitro as determined both phenotypically (by flow cytometry) and functionally (through transplantation and colony formation assays). Recombinant DEK increased long-term HSC numbers and decreased HPC numbers through a mechanism mediated by the CXC chemokine receptor CXCR2 and heparan sulfate proteoglycans (HSPGs) (as determined utilizing Cxcr2–/– mice, blocking CXCR2 antibodies, and 3 different HSPG inhibitors) that was associated with enhanced phosphorylation of ERK1/2, AKT, and p38 MAPK. To determine whether extracellular DEK required nuclear function to regulate hematopoiesis, we utilized 2 mutant forms of DEK: one that lacked its nuclear translocation signal and one that lacked DNA-binding ability. Both altered HSC and HPC numbers in vivo or in vitro, suggesting the nuclear function of DEK is not required. Thus, DEK acts as a hematopoietic cytokine, with the potential for clinical applicability.

Authors

Maegan L. Capitano, Nirit Mor-Vaknin, Anjan K. Saha, Scott Cooper, Maureen Legendre, Haihong Guo, Rafael Contreras-Galindo, Ferdinand Kappes, Maureen A. Sartor, Christopher T. Lee, Xinxin Huang, David M. Markovitz, Hal E. Broxmeyer

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Figure 2

Administration of rmDEK regulates hematopoiesis in vivo.

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Administration of rmDEK regulates hematopoiesis in vivo. (A–F) Dek–/– or...
(A–F) Dek–/– or littermate WT control mice were injected s.c. with 10 μg dialyzed rmDEK or vehicle once a day for 2 days (n = 3–5 mice/group). BM was harvested 48 hours after final injection. Immunophenotyping of LT-HSCs (A), ST-HSCs (B), and MPPs (C) was performed using flow cytometry. Data are mean ± SEM. (D–F) HPC numbers per femur were determined by CFU assay. Data are mean ± SEM of individually assessed mice per group plated in triplicate. *P < 0.05, **P < 0.01, ***P < 0.001 compared with WT vehicle control; ‡P < 0.05, ‡‡‡P < 0.001 compared with vehicle-treated Dek–/– mice. (G–I) C57BL/6 mice were given 10 μg rmDEK, drmDEK, or vehicle control as in A–F, then BM was harvested 24 and 48 hours after final injection. HPC numbers were determined. Data are mean ± SEM of 5 individually assessed mice per group plated in triplicate. **P < 0.01, ***P < 0.001 compared with WT vehicle control; ‡P < 0.05, ‡‡P < 0.01, ‡‡‡P < 0.001 compared with drmDEK group. (J) Engrafting efficiency of donor C57BL/6 BM cells collected 24 hours following final injection of vehicle or rmDEK (once a day for 2 days) in PB. Data are mean ± SEM of 8 host mice. (K) Engrafting efficiency of donor C57BL/6 BM cells collected 48 hours following final injection of vehicle or rmDEK (once a day for 2 days) in PB. *P < 0.05, **P < 0.01, ***P < 0.001 compared with vehicle-treated group at the same time point. For A–K, 1-way ANOVA with post hoc Tukey’s multiple-comparisons test was used.