Protein tyrosine phosphatase–σ regulates hematopoietic stem cell–repopulating capacity
Mamle Quarmyne, … , Nelson J. Chao, John P. Chute
Mamle Quarmyne, … , Nelson J. Chao, John P. Chute
Published November 21, 2014
Citation Information: J Clin Invest. 2015;125(1):177-182. https://doi.org/10.1172/JCI77866.
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Brief Report Hematology

Protein tyrosine phosphatase–σ regulates hematopoietic stem cell–repopulating capacity

Abstract

Hematopoietic stem cell (HSC) function is regulated by activation of receptor tyrosine kinases (RTKs). Receptor protein tyrosine phosphatases (PTPs) counterbalance RTK signaling; however, the functions of receptor PTPs in HSCs remain incompletely understood. We found that a receptor PTP, PTPσ, was substantially overexpressed in mouse and human HSCs compared with more mature hematopoietic cells. Competitive transplantation of bone marrow cells from PTPσ-deficient mice revealed that the loss of PTPσ substantially increased long-term HSC-repopulating capacity compared with BM cells from control mice. While HSCs from PTPσ-deficient mice had no apparent alterations in cell-cycle status, apoptosis, or homing capacity, these HSCs exhibited increased levels of activated RAC1, a RhoGTPase that regulates HSC engraftment capacity. shRNA-mediated silencing of PTPσ also increased activated RAC1 levels in wild-type HSCs. Functionally, PTPσ-deficient BM cells displayed increased cobblestone area–forming cell (CAFC) capacity and augmented transendothelial migration capacity, which was abrogated by RAC inhibition. Specific selection of human cord blood CD34+CD38–CD45RA–lin– PTPσ– cells substantially increased the repopulating capacity of human HSCs compared with CD34+CD38–CD45RA–lin– cells and CD34+CD38–CD45RA–lin–PTPσ+ cells. Our results demonstrate that PTPσ regulates HSC functional capacity via RAC1 inhibition and suggest that selecting for PTPσ-negative human HSCs may be an effective strategy for enriching human HSCs for transplantation.

Authors

Mamle Quarmyne, Phuong L. Doan, Heather A. Himburg, Xiao Yan, Mai Nakamura, Liman Zhao, Nelson J. Chao, John P. Chute

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Figure 1

Deletion of Ptprs augments HSC-repopulating capacity.

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Deletion of Ptprs augments HSC-repopulating capacity. (A) Mean expressio...
(A) Mean expression of receptor PTPs in BM KSL cells by quantitative reverse-transcriptase PCR (qRT-PCR) (left) and expression of Ptprs within hematopoietic cell subsets (right) are shown. n = 3–9/group. *P < 0.0001 for each of the 3 comparisons. (B) Mean (± SEM) numbers of CFCs are shown for 12-week-old Ptprs–/– and Ptprs+/+ mice. *P = 0.002 (n = 6, Mann-Whitney U test). CFU-GEMM, CFU–granulocyte erythroid monocyte megakaryocyte; BFU-E, burst-forming unit–erythroid; CFU-GM, CFU–granulocyte macrophage. (C) Mean levels of donor CD45.2+ hematopoietic cell engraftment are shown in the PB of CD45.1+ mice at 16 weeks following competitive transplantation of 3 × 104 BM cells from Ptprs+/+ or Ptprs–/– mice. *P < 0.0001 (n = 15–18/group, Mann-Whitney U test). Multilineage engraftment of Mac-1/Gr-1+, B220+, and CD3+ donor cells is shown at right. **P = 0.008; †P = 0.0001; ‡P = 0.04 (Mann-Whitney U test). (D) Multilineage flow cytometric analysis of donor hematopoietic cell engraftment in the PB is shown from mice competitively transplanted with BM cells from Ptprs+/+ or Ptprs–/– mice at 16 weeks after transplant. Quadrant numbers represent the percentages of donor lineage cells. (E) In the upper panel, mean donor CD45.2+ cell engraftment in the PB is shown over time following transplantation of BM cells from Ptprs+/+ or Ptprs–/– mice in primary recipient mice. *P < 0.0001; **P = 0.0001; †P = 0.001; and ‡P < 0.0001 for engraftment at 4, 8, 12, and 16 weeks, respectively. In the lower panel, mean donor CD45.2+ cell engraftment in secondary transplanted mice is shown over time. *P = 0.004; **P = 0.01; †P = 0.005; and ‡P = 0.002 for engraftment at 4, 8, 12, and 16 weeks, respectively (n = 7–8/group, Mann-Whitney U test).