Essential role for Ptpn11 in survival of hematopoietic stem and progenitor cells

Abstract

Src homology 2 domain-containing phosphatase 2 (Shp2), encoded by Ptpn11, is a member of the nonreceptor proteintyrosine phosphatase family, and functions in cell survival, proliferation, migration, and differentiation in many tissues. Here we report that loss of IntroductionHematopoiesis is maintained by a small number of multipotent long-term hematopoietic stem cells (LT-HSCs) with extensive self-renewal capability. These cells give rise to lineage-committed progenitors, which produce various types of mature blood cells. Cytokine and growth factor signaling is critical for the sustained production of HSCs and progenitors and directs cellular survival, migration, and differentiation. 1,2 Src homology 2 (SH2) domain-containing phosphatase 2 (Shp2) is a ubiquitously expressed nonreceptor protein-tyrosine phosphatase (PTP), encoded by the Ptpn11 gene, which regulates signaling networks and cell fates in many organisms. Shp2 is composed of 2 SH2 domains (N-SH2 and C-SH2), a PTP domain, a C-terminal tail with tyrosyl phosphorylation sites that modulate some RTK signaling pathways, and a proline-rich motif of unknown function. In multiple tissues, Shp2 positively regulates Ras/Erk signaling downstream of receptor tyrosine kinases (RTKs) and cytokine receptors. 3 Shp2 also appears to have cell-type-and/or agonistdependent effects on the activation of Akt, Jnk, NF-B, Rho, and Nfat. 3 Germline PTPN11 mutations underlie approximately 50% of Noonan syndrome, which is characterized by short stature, skeletal abnormalities, cardiac defects, learning disabilities, and a predisposition to hematologic abnormalities, particularly juvenile myelomonocytic leukemia. Somatic gain-of-function mutations in PTPN11 also are the most common cause of sporadic juvenile myelomonocytic leukemia. 4 Although Shp2 is required for normal Ras/Erk activation in many contexts, 3 the underlying mechanism shows great diversity and depends on the precise cell type and stimulus involved. Epistasis studies in Caenorhabditis elegans and Drosophila show that activated Ras/let-60/ras1 suppresses the effects of Shp2/ptp-2/ csw loss, 5,6 arguing that Shp2 acts upstream of Ras in these signaling pathways. However, in C elegans vulva development and Drosophila R7 photoreceptors and muscle precursors, Shp2/ptp-2/ csw appears to act downstream of Ras/let-60/ras1 in some contexts. 5,7-9 Furthermore, in the EGL-15/Egfr signaling pathway, ptp-2 may act parallel to let-60. 10 In mice, expression of activated Kras (Kras G12D ) does not completely restore defective lens proliferation and lacrimal gland development caused by the loss of Ptpn11. 11 Collectively, these results indicate that Shp2 can act upstream, downstream, or parallel to Ras in different systems, and imply that the consequences and the mediators of Shp2 action must be specifically delineated in particular biologic contexts.Homozygous inactivation of murine Shp2 results in early embryonic lethality 12-14 because of a critical role of Shp2 in trophoblast stem cell survival. 14 Loss of Shp2 also reduces...

Shp2 and Pten have antagonistic roles in myeloproliferation but cooperate to promote erythropoiesis in mammals

“…Shp2 acts to promote the Erk pathway and it may regulate the PI3K-Akt pathway positively or negatively in different cell types (30,31). Several groups generated mutant mouse lines with conditional deletion of Shp2 or Pten in the hematopoietic compartment, which confirmed a negative role of Pten and a positive role of Shp2 in hematopoiesis (8,9,11,12). Given the apparently opposite phenotypes of PKO and SKO mice in several aspects, we have interrogated a possible antagonizing effect between Pten and Shp2, by creating a new compound mutant mouse line (DKO) with both Shp2 and Pten removed in hematopoietic cells.…”

“…Consistently, selective deletion of Pten in blood cells resulted in short-term expansion and long-term decline of hematopoietic stem cells (HSC), as well as development of myeloproliferative neoplasm (MPN), defining a preventive role of Pten in myeloproliferative disorders (8,9). In contrast, Shp2 is an SH2-containing tyrosine phosphatase that plays a positive role in hematopoiesis, and ablating Shp2 suppressed HSC and progenitor cell self-renewal and differentiation in mice (10)(11)(12). Dominantly activating mutations were detected in Ptpn11/Shp2 in nearly 50% of Noonan syndrome patients (13)(14)(15)(16), who have higher risk of juvenile myelomonocytic leukemia (13,17,18).…”

Erk1 and Erk2 are required for maintenance of hematopoietic stem cells and adult hematopoiesis

“…SLAM-HSCs were isolated from control and Erk-mutant mice 10 days after pIpC treatment, and placed at 1 cell per well in a medium that preserves multipotency in vitro. 13,14 Mutant cells harvested at this time point all showed complete ablation of the appropriate Erk messenger RNA (supplemental Figure 2A- conditions, but deletion of both Erk isoforms leads to gross attrition of all hematopoietic lineages. Although Erk2 is known to play a crucial role in T-cell development and activation, 9,11 the role of Erk1 in T-lineage cells remains controversial.…”

Runx1 Phosphorylation by Src Increases Trans-activation via Augmented Stability, Reduced Histone Deacetylase (HDAC) Binding, and Increased DNA Affinity, and Activated Runx1 Favors Granulopoiesis

“…Plasmids-(Runx1) 4 TKLUC, CMV-␤Gal, pCEFL-Src(E381G), pBabePuro-Runx1-ER(T), CMV-CBF␤, CMV-FLAG-HDAC1, CMV-FLAG-HDAC3, CMV-HA-Cdc20, CMV-HA-Cdh1, pMIG, and pMIGC were previously described (4,16,23,26,27,30,31). CMV-HA-ubiquitin was obtained commercially (Addgene).…”