GSK3β regulates physiological migration of stem/progenitor cells via cytoskeletal rearrangement
Kfir Lapid, … , Massimo Zollo, Tsvee Lapidot
Kfir Lapid, … , Massimo Zollo, Tsvee Lapidot
Published March 8, 2013
Citation Information: J Clin Invest. 2013;123(4):1705-1717. https://doi.org/10.1172/JCI64149.
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Research Article Hematology

GSK3β regulates physiological migration of stem/progenitor cells via cytoskeletal rearrangement

Abstract

Regulation of hematopoietic stem and progenitor cell (HSPC) steady-state egress from the bone marrow (BM) to the circulation is poorly understood. While glycogen synthase kinase-3β (GSK3β) is known to participate in HSPC proliferation, we revealed an unexpected role in the preferential regulation of CXCL12-induced migration and steady-state egress of murine HSPCs, including long-term repopulating HSCs, over mature leukocytes. HSPC egress, regulated by circadian rhythms of CXCL12 and CXCR4 levels, correlated with dynamic expression of GSK3β in the BM. Nevertheless, GSK3β signaling was CXCL12/CXCR4 independent, suggesting that synchronization of both pathways is required for HSPC motility. Chemotaxis of HSPCs expressing higher levels of GSK3β compared with mature cells was selectively enhanced by stem cell factor–induced activation of GSK3β. Moreover, HSPC motility was regulated by norepinephrine and insulin-like growth factor-1 (IGF-1), which increased or reduced, respectively, GSK3β expression in BM HSPCs and their subsequent egress. Mechanistically, GSK3β signaling promoted preferential HSPC migration by regulating actin rearrangement and microtubuli turnover, including CXCL12-induced actin polarization and polymerization. Our study identifies a previously unknown role for GSK3β in physiological HSPC motility, dictating an active, rather than a passive, nature for homeostatic egress from the BM reservoir to the blood circulation.

Authors

Kfir Lapid, Tomer Itkin, Gabriele D’Uva, Yossi Ovadya, Aya Ludin, Giulia Caglio, Alexander Kalinkovich, Karin Golan, Ziv Porat, Massimo Zollo, Tsvee Lapidot

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Figure 1

GSK3β expression in HSPCs correlates with their physiological egress rates and is regulated by adrenergic signals.

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GSK3β expression in HSPCs correlates with their physiological egress rat...
(A) GSK3β expression levels in MFI units were compared between mature and immature BM populations: Lin+ cells, Lin– cells, Lin–cKit+ (LK) cells, Lin–Sca-1+cKit+ (LSK) cells, and CD34–Lin–Sca-1+cKit+ (CD34–LSK, i.e., phenotypic HSCs) (n = 4–6). **P < 0.01 compared with Lin+ cells, and #P < 0.05 compared with Lin– cells. (B–D) Mice were sacrificed at ZT5 (5 hours after initiation of light) and ZT13 (1 hour after initiation of darkness). (B) GSK3β expression (fold change) was determined by flow cytometry in total BM cells, LK cells, LSK cells, and CD34–LSK cells at ZT5 and ZT13 (n = 3–5). PB was obtained to measure circulating WBCs (C) and LSK cells, indicating HSPCs (D) (n = 6). (E–H) Mice were treated with 10 mg/kg NE or PBS and sacrificed after 1 hour. PB was then obtained to measure circulating WBCs (E) and LSK cells (F) (n = 5–8). (G) GSK3β expression was determined by flow cytometry in total BM cells, LK cells, LSK cells, and CD34–LSK cells 20 minutes after administration of NE (n = 4–6). (H) BM MNCs were obtained from PBS- or NE-treated mice and loaded into transwells. Migration toward 125 ng/ml CXCL12 was assessed for 2 hours. In addition, LK cells were measured among migrating BM MNCs (n = 3–5). *P < 0.05 and **P < 0.01 compared with control (or between ZT5 and ZT13 time points). Ctrl, control.