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Oncogenic Nras has bimodal effects on stem cells that sustainably increase competitiveness.

Li Q, Bohin N, Wen T, Ng V, Magee J, Chen SC, Shannon K, Morrison SJ - Nature (2013)

Bottom Line: Nras(G12D) had a bimodal effect on HSCs, increasing the frequency with which some HSCs divide and reducing the frequency with which others divide.This mirrored bimodal effects on reconstituting potential, as rarely dividing Nras(G12D) HSCs outcompeted wild-type HSCs, whereas frequently dividing Nras(G12D) HSCs did not.Nras(G12D) caused these effects by promoting STAT5 signalling, inducing different transcriptional responses in different subsets of HSCs.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of Michigan, Ann Arbor, Michigan 48109, USA.

ABSTRACT
'Pre-leukaemic' mutations are thought to promote clonal expansion of haematopoietic stem cells (HSCs) by increasing self-renewal and competitiveness; however, mutations that increase HSC proliferation tend to reduce competitiveness and self-renewal potential, raising the question of how a mutant HSC can sustainably outcompete wild-type HSCs. Activating mutations in NRAS are prevalent in human myeloproliferative neoplasms and leukaemia. Here we show that a single allele of oncogenic Nras(G12D) increases HSC proliferation but also increases reconstituting and self-renewal potential upon serial transplantation in irradiated mice, all prior to leukaemia initiation. Nras(G12D) also confers long-term self-renewal potential to multipotent progenitors. To explore the mechanism by which Nras(G12D) promotes HSC proliferation and self-renewal, we assessed cell-cycle kinetics using H2B-GFP label retention and 5-bromodeoxyuridine (BrdU) incorporation. Nras(G12D) had a bimodal effect on HSCs, increasing the frequency with which some HSCs divide and reducing the frequency with which others divide. This mirrored bimodal effects on reconstituting potential, as rarely dividing Nras(G12D) HSCs outcompeted wild-type HSCs, whereas frequently dividing Nras(G12D) HSCs did not. Nras(G12D) caused these effects by promoting STAT5 signalling, inducing different transcriptional responses in different subsets of HSCs. One signal can therefore increase HSC proliferation, competitiveness and self-renewal through bimodal effects on HSC gene expression, cycling and reconstituting potential.

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NrasG12D (G12D/+) expression increased the reconstituting potential of CD150−CD48+LSK MPPs but did not affect the reconstituting potential of CD150+CD48+LSK, or CD150−CD48+LSK progenitors in irradiated micea) 10 donor MPPs, b) 25 CD150+CD48+LSK progenitors, or c) 100 CD150−CD48+LSK progenitors from Mx1-cre; NrasG12D/+ (G12D/+) or littermate control (con) mice at 2 weeks after pIpC treatment were transplanted into irradiated recipient mice along with 3×105 recipient bone marrow cells. Data represent mean±s.d. for donor blood cells in the myeloid (Gr-1+ or Mac-1+ cells), B (B220+), and T (CD3+) cell lineages. Two-tailed student's t-tests were used to assess statistical significance. None of the time points were significantly different between treatments. The data represent two independent experiments with 4 recipient mice per donor
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Figure 8: NrasG12D (G12D/+) expression increased the reconstituting potential of CD150−CD48+LSK MPPs but did not affect the reconstituting potential of CD150+CD48+LSK, or CD150−CD48+LSK progenitors in irradiated micea) 10 donor MPPs, b) 25 CD150+CD48+LSK progenitors, or c) 100 CD150−CD48+LSK progenitors from Mx1-cre; NrasG12D/+ (G12D/+) or littermate control (con) mice at 2 weeks after pIpC treatment were transplanted into irradiated recipient mice along with 3×105 recipient bone marrow cells. Data represent mean±s.d. for donor blood cells in the myeloid (Gr-1+ or Mac-1+ cells), B (B220+), and T (CD3+) cell lineages. Two-tailed student's t-tests were used to assess statistical significance. None of the time points were significantly different between treatments. The data represent two independent experiments with 4 recipient mice per donor

Mentions: To test whether NrasG12D expression influenced the reconstituting potential of MPPs we transplanted 10 donor CD150−CD48−LSK cells22 from the bone marrow of Mx-1-Cre; NrasG12D/+ or littermate control mice (2 weeks after finishing pIpC) into irradiated recipients along with 3×105 recipient bone marrow cells. Only one of 14 recipients of control MPPs exhibited long-term multilineage reconstitution by donor cells (Extended data Figure 4a). In contrast, 8 of 17 recipients of NrasG12D/+ MPPs were long-term multilineage reconstituted by donor cells. NrasG12D/+ MPPs were thus significantly (p<0.01 across three independent experiments) more likely to give long-term multilineage reconstitution than control MPPs.


Oncogenic Nras has bimodal effects on stem cells that sustainably increase competitiveness.

Li Q, Bohin N, Wen T, Ng V, Magee J, Chen SC, Shannon K, Morrison SJ - Nature (2013)

NrasG12D (G12D/+) expression increased the reconstituting potential of CD150−CD48+LSK MPPs but did not affect the reconstituting potential of CD150+CD48+LSK, or CD150−CD48+LSK progenitors in irradiated micea) 10 donor MPPs, b) 25 CD150+CD48+LSK progenitors, or c) 100 CD150−CD48+LSK progenitors from Mx1-cre; NrasG12D/+ (G12D/+) or littermate control (con) mice at 2 weeks after pIpC treatment were transplanted into irradiated recipient mice along with 3×105 recipient bone marrow cells. Data represent mean±s.d. for donor blood cells in the myeloid (Gr-1+ or Mac-1+ cells), B (B220+), and T (CD3+) cell lineages. Two-tailed student's t-tests were used to assess statistical significance. None of the time points were significantly different between treatments. The data represent two independent experiments with 4 recipient mice per donor
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Related In: Results  -  Collection

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Figure 8: NrasG12D (G12D/+) expression increased the reconstituting potential of CD150−CD48+LSK MPPs but did not affect the reconstituting potential of CD150+CD48+LSK, or CD150−CD48+LSK progenitors in irradiated micea) 10 donor MPPs, b) 25 CD150+CD48+LSK progenitors, or c) 100 CD150−CD48+LSK progenitors from Mx1-cre; NrasG12D/+ (G12D/+) or littermate control (con) mice at 2 weeks after pIpC treatment were transplanted into irradiated recipient mice along with 3×105 recipient bone marrow cells. Data represent mean±s.d. for donor blood cells in the myeloid (Gr-1+ or Mac-1+ cells), B (B220+), and T (CD3+) cell lineages. Two-tailed student's t-tests were used to assess statistical significance. None of the time points were significantly different between treatments. The data represent two independent experiments with 4 recipient mice per donor
Mentions: To test whether NrasG12D expression influenced the reconstituting potential of MPPs we transplanted 10 donor CD150−CD48−LSK cells22 from the bone marrow of Mx-1-Cre; NrasG12D/+ or littermate control mice (2 weeks after finishing pIpC) into irradiated recipients along with 3×105 recipient bone marrow cells. Only one of 14 recipients of control MPPs exhibited long-term multilineage reconstitution by donor cells (Extended data Figure 4a). In contrast, 8 of 17 recipients of NrasG12D/+ MPPs were long-term multilineage reconstituted by donor cells. NrasG12D/+ MPPs were thus significantly (p<0.01 across three independent experiments) more likely to give long-term multilineage reconstitution than control MPPs.

Bottom Line: Nras(G12D) had a bimodal effect on HSCs, increasing the frequency with which some HSCs divide and reducing the frequency with which others divide.This mirrored bimodal effects on reconstituting potential, as rarely dividing Nras(G12D) HSCs outcompeted wild-type HSCs, whereas frequently dividing Nras(G12D) HSCs did not.Nras(G12D) caused these effects by promoting STAT5 signalling, inducing different transcriptional responses in different subsets of HSCs.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of Michigan, Ann Arbor, Michigan 48109, USA.

ABSTRACT
'Pre-leukaemic' mutations are thought to promote clonal expansion of haematopoietic stem cells (HSCs) by increasing self-renewal and competitiveness; however, mutations that increase HSC proliferation tend to reduce competitiveness and self-renewal potential, raising the question of how a mutant HSC can sustainably outcompete wild-type HSCs. Activating mutations in NRAS are prevalent in human myeloproliferative neoplasms and leukaemia. Here we show that a single allele of oncogenic Nras(G12D) increases HSC proliferation but also increases reconstituting and self-renewal potential upon serial transplantation in irradiated mice, all prior to leukaemia initiation. Nras(G12D) also confers long-term self-renewal potential to multipotent progenitors. To explore the mechanism by which Nras(G12D) promotes HSC proliferation and self-renewal, we assessed cell-cycle kinetics using H2B-GFP label retention and 5-bromodeoxyuridine (BrdU) incorporation. Nras(G12D) had a bimodal effect on HSCs, increasing the frequency with which some HSCs divide and reducing the frequency with which others divide. This mirrored bimodal effects on reconstituting potential, as rarely dividing Nras(G12D) HSCs outcompeted wild-type HSCs, whereas frequently dividing Nras(G12D) HSCs did not. Nras(G12D) caused these effects by promoting STAT5 signalling, inducing different transcriptional responses in different subsets of HSCs. One signal can therefore increase HSC proliferation, competitiveness and self-renewal through bimodal effects on HSC gene expression, cycling and reconstituting potential.

Show MeSH
Related in: MedlinePlus