Protein tyrosine phosphatase–σ regulates hematopoietic stem cell–repopulating capacity
Mamle Quarmyne, Phuong L. Doan, Heather A. Himburg, Xiao Yan, Mai Nakamura, Liman Zhao, Nelson J. Chao, John P. Chute
Mamle Quarmyne, Phuong L. Doan, Heather A. Himburg, Xiao Yan, Mai Nakamura, Liman Zhao, Nelson J. Chao, John P. Chute
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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 3

Selection of PTPσ– CB cells enriches for human HSCs.

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Selection of PTPσ– CB cells enriches for human HSCs. (A) Mean expression...
(A) Mean expression of PTPRS in subsets of CB cells by qRT-PCR. *P < 0.0001; **P < 0.0001 (n = 3, t test). MNCs, mononuclear cells. (B) Flow cytometric analysis of PTPσ expression on CB cells and on CB CD34+CD38–CD45RA–lin– cells is shown. Numbers represent percentage of PTPσ levels. (C) Mean levels of human CD45+ hematopoietic cell and multilineage engraftment in the PB of NSG mice at 16 weeks following intrafemoral injection of human CB CD34+CD38–CD45RA–lin– cells (34+38–RA–), CD34+CD38–CD45RA–lin–PTPσ+ cells (34+38–RA–PTPσ+), or CD34+CD38–CD45RA–lin–PTPσ– cells (34+38–RA–PTPσ–). Percentage of human CD45+: *P = 0.0002, **P < 0.0001; percentage of CD13+: †P < 0.0001, ‡P < 0.0001; percentage of CD19+: §P = 0.0002, P < 0.0001; percentage of CD3+: #P < 0.0001, ††P < 0.0001 (n = 11–18/group, Mann-Whitney U test). (D) Flow cytometric analysis of human CD45+ cell and multilineage engraftment is shown at 16 weeks in the PB of mice transplanted with CB 34+38–RA– cells or 34+38–RA–PTPσ– cells. Numbers represent the percentages of donor lineage cells. (E) Mean levels of human CD45+ cell engraftment are shown over time after transplant in the PB of NSG mice with parent 34+38–RA– cells, 34+38–RA–PTPσ+ cells, or 34+38–RA–PTPσ– cells. Eight weeks: *P = 0.002 (PTPσ– vs. parent), †P < 0.0001 (PTPσ– vs. PTPσ+); 12 weeks: ‡P = 0.002, §P < 0.0001; 16 weeks: P = 0.0002, #P < 0.0001 (n = 11–18/group).